Archive for the 'Roll Cake' Category

 

Roll Cake 3: The Build!

Oct 09, 2018 in Bots, Roll Cake

It’s time to put a robot together! This post covers the entire fabrication of Roll Cake 3 in the week or so before Dragon Con. The goal of the bot was primarily to try and drive better with an indirect drive brushless setup and also further refine the packaging and action of the flipper linkage. Will it do anything?! Hell if I know, that’s the fun part to discover!

Even as I was finishing up the design the weeks prior, I was pregaming getting parts. Basically as soon as I determined the C2028 motor would fit in the triangle behind the wheels, I went ahead and ordered 3 more since I only had 1 to start with.

I also ordered these OMG THE MOST ADORABLE LITTLE 0.8 MODULE PINIONS EVER THAT COST WAY TOO MUCH MONEY from SDP-SI. I had to go solely by what they sold for 2mm bores in these gears. I wanted an 8-tooth gear to achieve the 8:1 reduction I wanted to get with the wheel gears, but they only sold the 8-tooth with a 3mm bore. So my drivetrain reduction is going to end up more like 10.6:1, which is fine by me – the bot will be too fast no matter what.

The problem with these tiny gears? The 2mm bores were slip-fit, not press-fit! Certainly irritating, but not the end of the world. Already noted for a revision in the future is maybe transitioning to R/C model pinions, such as R/C car transmissions. Those typically come in 3mm or 1/8″ bores.

I used Loctite 609 to stuff the pinions onto the motors in the end – I tried to silver solder one of them to little success – while I’ve managed to solder or braze pinions before, it seems that the steel they used in this motor shaft is an unusually high chromium grade which didn’t want to take with any flux I had on hand.

That was before I melted the pinion completely. Ah well.

Completed drive motors refitted with their shafts, which was a minor press fit job. I also replaced the stock stainless steel prop-saver screws with drilled-out and re-tapped #4-40 set screws. Another minor point of trouble with these motors is that due to their length and the small shaft diameter, it was hard to get these things to spin entirely true again after resintalling the shaft. A shorter motor (more pancakey) will resolve this.

I put the gearbox parts on print in Onyx as soon as I finished the bot design. The two ring gears and main cam linkage (sticking off to the left) have hoops of carbon fiber; everything else just derives strength from a bunch of perimeters. On the very left are the two connecting links between the cam link and the arm. I also made two first-pass prints of the drive wheels, seen here with O-rings.

Frame parts freshly done and needing cleaning. I’d say this is the only irritating part of doing unibody bots for me – picking the support out of difficult crevices. There’s certainly orientations that I can print in for minimal support, but they sacrifice immense strength in the part itself.  Both of these frame halves were printed in the orientation shown to give continuous loops in the XY (flat) plane.

In Roll Cakes past, I’ve actually taken to making fiber laps around the frame in this orientation, but with the more recent-ish changes to Eiger, you can change the perimeter and fill with more flexibility such that I just stack on the perimeters.

Otherwise, pull out some injection-molded part design – relatively constant wall thickness and smooth transitions if you can manage it, using ribs and cavities versus just solid massive areas, etc. However, my habit with 3D printed frames is leaving a few bulky areas up front such that they remain somewhat hollow – this acts as a very effective energy absorbing medium. For instance, basically the front inch or so if this bot is solid in the model, which means it’s perimeter plus non-solid infill in real life.

 

Drive motor installed with some test fitting done on the wheels here. Most of the hardware on Roll Cake 3 is specified as plastic or metal threadforming screws. If you get really fancy, people like using heat-set or tanged flanged inserts in MarkForged prints. However, I like my expediency, so some fat #10 tri-lobe threads will do to hold the wheels on.

Here’s the final drive fitup. The 0.8 Mod (32-ish DP) gears printed perfectly fine. In my experience, this is about as small as you can print reliably because the nozzle diameter still is small enough to go in and out of tooth tips profiles.

 

Both sides now fitted with drives. The front binding screw is shown sticking out here.

…and now joined together. Already, this thing is way more rigid than last time side to side. Hell, I might as well just ditch the flipper and make it a pure drum :v

The screw length needed to do this assembly were compromises with what I had on hand, so the bot dimensions shifted a little to accommodate them. Roll Cake is in fact not a perfect circle, but slightly squished inwards to yield the rough double-D-flat shape.

I slid in the trigger piece (which has a cutout for the servo arm) first, then I slid the servo into the DMs.

Alrighty, all the easy 3D printed stuff is assembled now. I still have to make a drum and motor, so off to Taki-chan we go!

(Also, check out the waterjet-cut feeder wedges made from leftover Hardox 450 from Overhaul!)

First order of business: separate the motor magnet ring so I can stuff it inside the drum. This can’t always happen cleanly, depending on the motor’s construction. The Donkeys have a single-piece stamped steel rotor, so I simply chucked the shaft in and very carefully parted at the outside corner where the magnet ring area joins the endcap.

With a motor that has an aluminum endcap, it’s often scarier since the parts can separate and self-destruct.  Luckily, this operation went very smoothly with higher speed and gentler feed to keep the forces on the rotor low.

Next up is to rough the drum shape. Most of this was easy, but I had to make the dual-disk shape, so I had to cut a valley in the middle. I just went with multiple staggered parting tool cuts to nearly the right shape, then very very carefully and gently made really shallow passes side to side to clean the profile up. Very gentle. These insert tools really should not be taking any side forces. To do this without wallhacking, I’d have gotten a single wider custom-ground HSS tool or something.

 

Then I bored the drum interior. There’s three stepped diameters – one for the ring bearing, then the magnet ring of the motor, then the “doesn’t matter” internal diameter. For the output side “bearing-stem-gear” I just did a straight drill to 12.0mm since it did not have to be that precise.

Next up: stator holder.

With the aluminum parts roughed out, I decided to make the one odd piece, which is the gear-on-a-stick that will carry the drum energy into the gearbox. This was a pretty easy turning job, but remember, it’s also the other bearing of the whole drum. The center bore, then, had to be 1. a clearance, but not by much, and 2. very clean and precise.

I actually went out and bought a 8mm-plus-0.001″ …. yes, this exists in America…. reamer to make this bore. You read that correctly – it’s a 0.3159″ reamer.

The gear gets a cylindrical boss on both ends eventually. After I finished both sides, I actually had to take a wire brush on an angle grinder to it in order to deburr the gear tooth edges – there were many little burrs and swarf hanging on which would have prevented the gear mate from working.

Parts in the midst of preparation! The stator bore has been drilled and the stem gear keyed on the top surface seen.

Throwing it together for a quick test fit! Here’s where it’s clearly visible that the stem gear skewers the cam ring gear and the cam linkage.

The next task was to drill the tooth holes in the aluminum drum body. I no longer have my old indexing head that made guest appearances in many of my undergrad builds, since I donated it to MITERS years ago. So to make sure I’m able to place the teeth 180 degrees apart, I milled a very shallow flat, then rotated it to sit on that flat, then milled another one.

This ensured I can drill and tap both sides with relatively equal precision. The teeth are just 3/8″-16 alloy cap screws, so they thread right in.

After the drum body was fully fnished, I broached it for a 3mm key – the stem gear is shown here mated to it. The magnet ring pressed into position without much trouble.

Unfortunately, I didn’t have time to make a new set of cluster gears, so I had to take them out of Roll Cake 2. Sad, since I wanted to keep that bot fully operational if I could!

The thought has crossed my mind of hiring out a whole basket of little cluster gears to be made if I’m going to keep evolving this bot.

The catch with these compound planetary cluster-fuck gears is that they have to be assembled at specific angle, or phasing, since there’s a hard relationship between the number of gears and the relative tooth counts. I scratched alignment marks into them when I first put them together for Roll Cake 1, and still use them for reference.

The gray goop I have dripped all over the assembly is liquid bike chain wax. I’ve been avoiding using petroleum-based lubricants like common greases because I don’t want to risk damaging the nylon-based Onyx material from the solvent action. Grease would also add immensely to the no-load drag of the gearbox, which is already a lot happening for a weapon drive.

The planet carrier installs easily after the gears are properly phased in place. It looks from here that there’s a ton of stuff going on, but I guarantee you this is not the case :v

As I mentioned in the design post, this carrier now has its own bearing to support itself. This is a pretty odd (but still apparently some kind of standard) 8mm bore, 14mm OD bearing – very low profile.

The drum drops into place from the front. The service order of this thing is a little suboptimal – to service the drum, I have to disconnect it from the folding linkage, but the central pivot bolt doesn’t rise up out of the body’s central cavity…. so really I have to undo the bottom linkage anchor (those three screws in a row from the CAD model) first, then remove the arm hinge. At least I made sure to make it all serviceable with at most 2 tools this time!

After the drum and arm are mounted, it was time for electrical dressup.

Along with the feeder claws, I cut another insectweight top plate set out of this piece of 1/32″ blue spring steel shim. I bought like 10 feet of this shim some time during undergrad, and have slowly been generating robots out of it since. This thing made its first appearance all the way back in 2009 with Pop Quiz’s rebuild! I’m now on the very last 8-10″ of it after Roll Cake’s parts are accounted for!

For better or worse, picking the parts out of the mother material was one of the last things I did before absconding on  3-day long slow meander down to Atlanta for Dragon Con. On the way, I hit up the Blue Ridge Parkway, like I promised myself I’d do. I only brought Roll Cake and its suite of service tools and a box of parts I think I’d need (mostly electronics), and Overhaul for display. This Dragon Con was going to be a pretty clean show instead of scrambling to take care of a few robots – the reason for this is I was pretty much solo this time, as there was a lot of bad timing involved for the various startups and schemes my friends and I are all involved in.

So what’s better than finishing your bot in the airBnB room when you got into town? Not all that much. I pre-gamed some of the electronics wiring (like battery leads and the like) before I left, so installing the two drive ESCs (AfroESC 12A) and weapon ESC (Spider ZTW 40A with SimonK) was a quick affair. I was able to drive Roll Cake around on the floor to get a gauge for its handling – which is much, MUCH improved over the hub motor drive version.

It’s very quick, but much more maneuverably so than Roll Cake 2, which tended to twitch everywhere. I swear the twitching is better than it was! At least now I could predictably send the bot places, which is an improvement over before!

The flipper geartrain was very tight, though, because I hadn’t had the chance to run it fully in up until that point. It would take several minutes of just running the drum at maximum speed and also a while of keeping the linkage engaged to wear everything in.

Here’s Roll Cake 3 fully buttoned up!

And shown with the flipper linkage at full height. In the next episode, hopefully you’ll get to hear about what it did, if anything!

The Roll Cake that Won’t Die: Roll Cake 3.0

Oct 03, 2018 in Bots, Roll Cake

I still like to pretend that I build robots here on this website! So in preparation for the fall round of events I like to go to (Dragon Con, Franklin, and any MassDestructions we try to hold) I decided in August to try and keep making progress on my recent persistent itch – Roll Cake.

Roll Cake had never “done well” – really done much of anything – at a competition since my main focus each and every time is kind of getting the vision of the bot finally in physical form. Remember its origin story and how I’ve been meaning to build a kinetic flipper for years, but never quite gotten around to it. It’s a robot built around a vision of a exterior shape and layout I came up with more than a decade ago, so it’s almost suboptimal on purpose.

Roll Cake 1 was sort of the grand puking of the idea in which nothing really worked. Roll Cake 2 made the mechanism shine, but still had a deficient drive due to sacrificing drivability for space conservation. My goal with Roll Cake 3 was to improve its driveability while making the weapon much more aggressive; Roll Cake 2 had a rather light drum/flywheel being belt-driven by an undersized motor that frequently overheated or shed belts.

The story of Roll Cake 3 actually dates back to not long after the previous Franklin Institute event, to which I brought it in order to talk about Alternative Flippers with a few other builders – it didn’t compete.

After mulling life on the return trip, I began the design by throwing some parts at the version 2 frame CAD and seeing what stuck. The principal design goals for V3 were:

  1. Moving to indirect drive on the wheels – the direct drive, while workable, was obviously still not very controllable. I figured a very small motor could tuck in the wasted volume (there’s a lot of wasted volume on Roll Cake) behind the wheels and could get me a considerable reduction just with open spur gears alone.
  2. Moving, on the contrary, to DIRECT drive on the weapon. The little 22mm outrunner just wasn’t enough to drive the whole geartrain continuously while also spinning a weapon. I could, with the increased drum interior volume, actually have a beetle-class weapon (so, you know, if the flipper plan just falls off a quarry cliff and explodes, it will at least be just a spinner)
  3. And lastly, moving to a dead shaft instead of V2′s live weapon shaft. This was more or less driven by going to a hub motor weapon. I’ll talk more about the Implications of this design change a little further down.

I had a Turnigy  C2028 motor model already, so I used it as a modeling guide for the positioning of the motor. I placed a Stance Stance Revolution motor, a Multistar pancake outrunner, in as a placeholder for the drum motor, though I wasn’t keen on using it. A motor that was a little more primitive seemed a better fit for the weapon.

To explore the space, I ordered some of the cheapest, shittiest motors you could buy on Hobbyking in the 35 to 45mm size range:

I love Hobbyking for having the sheer gall to sell you a motor that doesn’t have bearings. The Donkey line has bronze bushings and is seemingly made precisely to be the parts-recycling minimum viable products they are. A lot of builders have used them as foundations for their own weapon drives, and so will I!

I miss making motors, so this will be a fun distraction too.

I ended up selecting the Donkey 3511 motor for its stator size, but more importantly, the 12mm stator bore. The blue and silver “DT700″ motor had a thicker stator that I liked, but sadly only had an 8mm bore.

Why the bigger bore? I said earlier I was intending to move to a dead shaft for this iteration. Roll Cake historically has been rather tenuously held together side to side, with relatively small cross sections of material in the center due to the need to fit the flipper linkage. Moving to a dead shaft design allows me to use the shaft as an additional structural member of sorts up front.

The downside is I’d have to make a stator hub that the shaft presses into, and to do that, the stator needs to have a larger hole in the middle. I was intending on keeping the 8mm steel shaft that Roll Cakes have used for time immemorial (as in, literally the same one from v1 and v2), so that meant the stator needed at minimum, say, a 10mm center hole.

I pulled my usual motor designing tricks of making a hub for the stator to mount on, upon which a tpye 68xx ring bearing fits over. I sized this for a 6806 bearing, which has a 30mm bore. It’s a design balance between clearing shaft and wires versus simply being overly large and heavier.

I next generated a rough drum weapon shape that’s hollowed out in the middle. All of the dimensions and spacings were adjustable at this point – the final weapon would be a different width entierly. This just gets me something to start throwing into the CAD model so I can do the fitment of the gearset.

The teeth are, in typical beetle fashion, some big countersunk alloy steel cap screws.

With an eye for weight, I made some parametric adjustable cuts into the drum to turn it into more of a ‘dual disc’ configuration not unlike Witch Doctor and Hypershock. The final drum weight is tuned by just making the cuts smaller or larger.

Next up was the magical Roll Cake gearbox. I made some design changes to make it up to 1/4″ narrower to make the weapon itself occupy more of the front width. The clutch ring now has a single tooth and no longer its own outer support bearing – instead, it simply has a smooth shoulder inside to gently ride on the planet carrier. The carrier itself will have a 8mm thin-section bearing bored into it instead. There will be some extra friction from the technically bearing-less clutch ring, but the much more OP drum should more than make up for it.  I also got rid of an equivalent support bearing on the offset cam ring and it now only has a single bearing also in the center.

To pass power from the drum into the gearbox via the now dead shaft, I had to do something rather unconventional. There is now a lot of stuff going on here, so bear with me….

The distal endcap of the drum (opposite the motor end) is bored out to 12mm and has a key broached in it. A stem gear with a 8mm clearance bore has a keyway milled in one end and is inserted into the drum endcap with a key. The gear’s stem is 12mm OD and passes through the 12mm support bearing of the offset cam ring, and both transmits rotational torque and supports impact loads from the drum.

There is no “bearing” inside the stem gear in the conventional sense – there is only reamed steel on polished hardened steel with some oil in between.  Hey, if there’s one thing I learned from begrudgingly rebuilding an engine, it’s that steel on steel with a bit of oil in between is how every car works. What could go wrong!?

I knew going in I was betting a lot on this… technically a fluid bearing, but whatever…. working out. The friction would be higher than a ball bearing by far, but I was going to bank on the length of engagement making up for it with a light pressure resulting from the contact area.

Anyways, the gear end of the stem gear interfaces with the existing split-planetary gearbox and makes the thing go up and down.

One of the biggest challenges of Roll Cake has always been where to put the battery. When you scale robots down, you inevitably hit a “component Planck Length” of sorts – essentially, at some scale of robotting, the parts stop getting usably smaller. For me, the prismatic battery has always been troublesome for packaging inside a wedge-shaped robot. I played around with several methods, such as this one placing the battery forward and vertical…

…and including the unpalatable approach of splitting the battery up into two smaller ones. I really didn’t want to deal with the extra wiring and now squeezing on space for other components.

But one night I had a moment of come-to-Plastic-Jesus clarity – perhaps it is a reasonable compromise (it is – there ain’t no Perhaps, I’m just stubborn) to ditch the notion that the flipper has to span the whole width of the bot. At this point in the bot’s evolution, I should be thinking in terms of what makes the design work and what it actually needs, versus still trying to stick to my vision of “robot go flap-flap”.

In mulling over the compromise for the arm design, I also included a mockup of the new wheels, which will have a spur gear included on them to mate with a pinion on the motor.  I ended up just rolling with the C2028 motor and ordered a few from Hobbyking. Optimal? Maybe not. Fits back there and in stock? Hell yeah!

I decided to keep the battery arrangement shown – where the battery is placed widthwise in the bot, leaving the left half or so open to be used for the flipper linkage. This suddenly freed up a WHOLE LOT of volume inside the bot, and it was honestly a relief.

Before I went further with that design, I actually backed up and basically started over on another thought in my head about the design. There’s technically nothing stating Roll Cake had to be round. In fact, V1 was not round. Having the corners back could result in the difference between fitting in the battery vertically versus not, so I tried generating a square (chamfered octagon, I suppose) version of the frame to see if that was profitable.

Admittedly I did get pretty far along here – I found a vertical cavity for the battery and even was able to make space for mounting the drum motor. There wasn’t really anything preventing me from going with this design.

What swung me back the other direction was actually the sheer amount of usable space opened by repositioning the battery in the round design. I did want a Roll Cake in which trying to injection-mold ESCs and hyraulic press wires inside wasn’t even going to be an issue. From there, with an ideally working bot, I would make space optimizations as needed.

Well that does it for me. I returned to the round design and began cutting out cavities for everything. There’s gratuitous volume now to put things, and almost makes me wonder if Roll Cake could be a little smaller. However, for now, the final diameter was driven by giving the most space to the drive wheels and batteries while retaining an acceptable arm width that didn’t reduce it to just a stick.

Adding internal boss features to support the drum hub and drive motors now. I also made a crossing retainer for the battery – it sits in a neat little cavity and is prevented from bouncing around by the low wall and the eventual top plate. The geometry for the trigger pin is also taking shape.

Inside the left half of the bot, I made more space-filling features to mount the trigger servo. The dimensions did require cutting a hole of sorts in the underside to clear the servo cable. I moved the servo up as far as I thought was reasonable while still keeping the trigger pin on a radial path into the clutch ring gear.

Smaller but important features are now rolled up including the integrated wheel pegs and the arm pivot. The wheel pegs were going to be a machined piece, but gradually became so short there was no point in machining a part and using a mechanical attachment method. Instead, just printing the peg would do!

Notice how the bottom of the peg has a flat on it – to counteract the messy nature of homogenous-material support lattices in 3D printing which never really prints bottom-sides cleanly, I just made the peg a D-flat to give a single flat surface for the support to finish and the part to build. The eccentricity potential of the wheel from the bearing being on an incomplete circle is going to be negligible; worst case I’ll stuff a shim into the gap.

I put the arm pivot at the very front tip of the bot to make the arm as long as possible in order to get free height at the flipping end. This constraint would drive the arm shape and the placement of the linkages.

I made a first approximation of the arm after that. It had to start out higher than the bot’s upper slope surface in order to clear the cam and ring gears, which is why there’s a mild kink in it. You can see the cam ring passing through the arm here – I used this as a guide to make a cut that was just barely enough to clear it.

From there, it was relatively easy to make the linkage by fixing the cam linkage centered in the bot and fixing the arm in the lowered position. The lower anchor is a simple pin joint I modeled on the backside of the center crossing span of the bot, so all I really needed to do is adjust lengths and the position of the pin joint on the arm itself.

I tuned the linkage lengths to give me in the end around 4″ of rise. The end driving constraint was not hitting the crossing span in the middle when extended, but also when folded, not closing more than about 60 included degrees (or 30 per side measured from the centered cam link as a baseline).

At that point, which is my mental cutoff for “sensible linkage”, the orthogonal loading force from pulling the linkage open is twice the actual opening force, and just gets worse as you collapse the linkage more.

(This, kids, is why your elaborate scissor lifts never work in 2.007…. wait until you take 2.12 and understand the Jacobian matrix)

 

Here is that “JUST BARELY” cut I talked about – when the cam’s coming up, there’s only a few thousands of an inch of clearance as the arm goes up.

In real life, as I found out, the slop in the system actually made it such that the cam lifting shoved the arm upwards, helping the linkage get started out of the folded position. Sci………ence?

As a matter of habit when designing the smaller bots, I began adding hardware to make things more realistic for weight. On a bot that’s tight in space selectively like Roll Cake, I also wanted a sense of where fastener heads were going to go. So it turns out McMaster actually has intricately-cut models of their shitty sheet metal screws for download. I didn’t even know shitty sheet metal screws were 3D modeled, really. Either way, it was handy to see how much fastener head you actually need to clear.

The arm and linkages also get their dose of “Real-ification” by the addition of shoulder screws and properly sized counterbores, thru-holes, and tapped holes.

The linkage length allowed me to finally add one feature that Roll Cakes Past have never ever had: a rear structural link. There was enough leftover space to put a crossing span in the back with a bolt to tie it together! This might be the most structurally sound Roll Cake yet.

Space was tight enough that I needed to put the bolt model in and make sure I could still tighten a nut. The length of the righthand cavity was adjusted a little bit to be just barely longer than the bolt, so I can, you know, actually install it.

The three holes in a row above the rear crossing span? It’s a removable piece, serviced from the rear of the bot, so I can install and uninstall the arm linkage.

It’s a little hard to see what’s going on here. This is a counterbored, hidden cross screw which holds the front half of the bot together. It’s installable from the outside by squishing it past the O-rings in the wheels. You’d otherwise barely know it’s there!

This might be a better view of where it goes. It is sunk about an inch into the right hand (here, left side) half of the bot before the thread diameter begins, in order to put that much plastic in compression first.

I moved onto making some kibbles and bits for the bot – here are two little feeder fangs to try and get under someone and make sure the drum gets first punch. They’ll be waterjet-cut from some kind of leftover steel.

We’re getting awfully close with the CAD now. I took care of some more last details, such as the tiny half-round ears for if the bot gets flipped over to prevent the drum from hitting the ground. While Roll Cake can obviously drive upside down, the double-sided flipper was deprecated post v1, so it still has an “up” side. Maybe one day I will try bringing the double-sided flipper back.

I then made wire passthroughs and filleted corners and broke edges. This is the now-complete “unibody” frame.

I took snapshots of the side cavities and traced them in order to generate conforming top plates. The hole locations were patterned where I could and kind of freelanced where I couldn’t, at a fixed distance from the nearest profile curve.

To actually make the bot, the monolithic model had to split into three pieces – the two halves, plus a drum axle retainer for the non-motor side. I generated cutting surfaces for this operation. The split is not linear, but has a jog in the middle to accommodate convenient locations to begin and end the frame profile.

The cover plates are modeled from the sketch drawings individually. I suppressed the monolithic body and  imported all of the cut pieces and properly constrained them in order to yield the multi-piece modeled frame.

So that does it for Roll Cake 3′s design. In the next episode, I have to actually build the damn thing!

ORIGINAL CONTENT! The All-Around Robot Update: Roll Cake Rises Again; Dragon Con 2017 & Uberclocker

Oct 02, 2017 in Bots, Dragon Con, Events, Roll Cake

Whoa, what happened to this place? Everything’s so dusty and gross. Why is there a pile of circuit boards on the bench??

*trips over Chibikart on the ground and dies*

Hey, remember: whenever I disappear for an unexplained period of time, it’s always because I’m working on something hilarious. This time it’s extra hilarious, I promise! Obviously I’m always itching to keep everything updated here on my latest, but just like the first BattleBots build season, externalities which if broken would make other people look like assholes prevent me from saying anything at the moment. See, I don’t mind me alone looking like an asshole…

Anyways, backing up a little in life, I decided to redesign Roll Cake from the ground up following my hub drive experiments earlier. MomoCon came and went, but the Hobbyking orders kept stacking up, so I decided to roll it all in with Überclocker’s changes for Dragon Con!

roll cake

It all begins with a wheel.

Doing the drive test with the SimonK ESCs and the Multistar 460kv motors convinced me that the hub motor direct drive would work out, at least better than the previous BS I tried to do. I went shopping for high pole-count, low Kv drone motors since they’re pancakey. The plan was just to approximate wrapping an O-ring as close as I could to the motor. I ordered a few of these AX4006 motors for their combination of weight, low Kv, and high pole count.

Roll Cake is a bot which faces some packaging difficulties, since the middle of the bot has to be left pretty open for the flipper linkage. It would actually be easier in a 12 or 30lb design, since ‘noise floor’ of part sizes is much smaller compared to the bot size. If I scaled this design up to a 30lber right now, those would basically be 6″ hub motors, which is unnecessarily large.

There’s other architectures and shapes for the bot which might alleviate this, but for the time being I decided to try and keep the cheese wedge shape but  make it a little more…

…round. Remember that the flat sided shape was just an attempt at vomiting my vision of a bot that I’ve had for a while now, not making sure it works. When you ditch the need for 6WD, things get a little simpler! Even this is technically unoptimal packaging since there will be a lot of wasted space in the narrower parts of the cheese wedge. I’m basically just reskinning Roll Cake v1 and using all the same parts, since the goal is to get it driving and flipping things reliably, albeit not spectacularly, before deciding what aspect of the design to improve.

Once I had the parts placed reasonably, I started generating frame features to accommodate, such as wheel cutouts and future bearing blocks. The chassis will no longer split in the middle – that required so much extra effort to get everything to line up. Instead, I’ll be splitting the rounded caps next to the bearings off as its own print in the future.

The previous image showed the old linear slider trigger, but packaging necessitated switching to a swinging style. This means Roll Cake won’t fire when upside-down with the drum running in reverse – I’d still have to ‘self right’ so to speak. That’s fine, since I’m also ditching the double-sided linkage due to it taking up the entire center of the bot from swing space. At least keeping the flipper single-sided lets it still have structure in the middle!

The chassis is now taking shape pretty well, showing the swing trigger’s backing and “drilled” bearing cap holes and the like. I’m designing this to print ‘upside down’ on the flat top face.

After defining critical part anchor locations, I hollowed things out to accommodate the flipper linkage and irritatingly rectillinear things like batteries. Seriously, if there’s one thing this design is sorely lacking, it’s a battery worth having. I much prefer this to be 4S, but can only fit a 3S pack of adequate capacity for now.

As I model the body, I can give components final homes constrained by mounting holes and then adjust the cutouts and spacings to fit. So there was a fair amount of tuning going on at this point, including a change of wheel size to be smaller in order to shift the wheels more rearward (to give me battery space!)

After that, the fun part became linkage design. The goal is to get a linkage design which travels as far up as I can manage using the roughly 1″ throw of the cam ring, and generally has no linkage interacting at more than 45 degrees starting angle.

My insistence on a “pull” action on the main cam linkage means I have to transform the motion through a bell crank (the bottom and right side short line) to become an upward motion. Strictly speaking, I could potentially accept a push action from the cam linkage and that can directly interface with the flipper arm and move it upwards, but it would need to be designed much more heavy to stand the compressive force instead of tension (pulling) force.

 

This bell crank itself went through a few revisions in order to minimize the impact it has on the middle of the bot, the large bulkhead that runs across the two sides.

Here, I’m comparing designed linkage travel with actual part placement, seeing how much of the middle of the bot has to be cut out. The bell crank center distances and topology have also changed. The previous design intruded on the center of the bot with its full height, whereas this “T” design means only the short leg of the T pokes through the center bulkhead.

Then I decided to wrap the bulkhead around the bell crank instead of hollowing it out pre-emptively. It’s all going to be 3D printed in 50% density anyway, so no need to pre-emptively deny myself cross sectional area (which is very important to 3D printed parts)

After I was satisfied with the bell crank geometry, I made a crude flipper arm model to start out with.

The linkages will have to fold into themselves a fair amount, so I pre-emptively carved space for them before doing anything else.

The intermediate linkage is a bit of an awkward shape – here it is taking form. It has to adapt the narrow bell crank to the wide flipper linkage. I decided to do it here, and reinforce the middle of this linkage with a big flange, instead of trying to flare the end of the bell crank wider due to my desire to print it flat and have fully un-interrupted perimeters to maximize strength.

Here, see the aforementioned flange in the center of the intermediate linkage. I’ve now hollowed the flipper arm, which will be top-skinned with hardened spring steel.

The armor for this bot is quite simple – primarily Onyx in massive hollow-ish sections for the crumple zone effect, and blue-temper spring steel covering the important parts and providing access hatches.

I added a little feeder leg next to a region with unused material thickness. This will be a machined piece which is captured with nuts and flat-headed screws.

Finished and ready for printing!

I had to split the geometry first into the printable sections. I extracted the bearing cap by making a 5-sided surface box in Inventor and using a split body by surface function. Only one was needed – the other was disposed of. Other sections such as the mostly empty tail were cut off also in order to reach the print volume, and they were designed to be bolted back on.

A day later… Her’s the frame finished, printed in 3-perimeter 50% density Onyx. Ought to be plenty!  You can see where I cut the end of the wedge off and have modeled in a few tappable holes to hold them on.

Here’s a pretend-o-bot to make sure the dimensions all fit. The bearing cap was something I was particularly nervous about. I didn’t design clearances into the linkage parts to save design effort (read: I’m too lazy to make proper constraints) so some filing was needed to get them sliding freely.

Hardware installation time! I made sure to make little access ports for the motor wires, because wouldn’t that be embarrassing?

We move now to my old high school workbench down in Atlanta, which is somehow still there and in operation (maybe being 16 feet long has something to do with it). I got all the mechanical hardware installed before leaving, and decided to save the wiring for the Dirty South.

Pictured in the foreground is my new best friend: the itty-bitty-baby-offset-screwdriver-bit-ratchet. It’s McMaster part number 52725A31, and it’s positively adorable AND the only way some screws on Roll Cake are accessible at all. I designed it this way, so it’s legit, right!?

 

As usual with this thing, wiring is a disaster. The ESCs of choice are the Afro 30 Race with SimonK set up to do reversing with my usual tricks. They’re small, but not THAT small. I decided to keep the ESCs on the same side of the bot as their motors in order to reduce the amount of long wiring runs, so there’s two on the right side of the bot and one on the left.

All the motor connections have now been made, and I left one task for last before I soldered the 3-pin signal wires to the receiver….

I had to program the SimonK firmware to activate reversing and braking and my preferred goodies. I planned ahead and made this servo to tiny-clippy-jiggle breakout cable which I’ve termed “The Simonator 2.0″ in order to grip the signal wires of the ESCs. While I could have programmed them all beforehand when the servo conectors were all still there, I decided I needed this cable regardless just in case I had to change something in the field, post-installation.

I brought the finished bot to one of the robot panels at Dragon Con. Sadly this year I fell off the bus and did not host any panels, but I’ll make sure that changes next time! I’m glad that recently, my Makers presentation hasn’t really been needed – in the most recent years I delivered it, the percentage of the audience who’ve experienced CAD or soldering LEDs together, etc. has grown immensely, in my opinion greater than the rate of self-selection for these things.

Here’s the linkage fully opened! Note the preponderence of little shoulder screws forming the joint pins – I standardized all of these to the same length to save myself from my historic habit of making my robots all shoulder screw nightmares.

….and now announcing my new 6lb multibot entry??? This is the head of Lucy‘s Mei cosplay, the freeze-ray dispensing Snowball. overwatch has ruined my life run away now

I’ll post some of the test videos of Roll Cake soon – I was happy enough with its performance in the garage in terms of drivability and flipping, even if it won’t prove that impressive in the box due to being repackaged test rig parts.

überclocker

We now move onto good ol’ Clocker, which has looked like this since Motorama…

Pretty depressing, eh? In the final rumble of the 30lbers, I burned out one of the SK3 4240 drive motors, so I was on the hunt for replacements, and Hobbyking didn’t have stock in that size at the time.

What they did have is a sale on their new NTM line, which had a similar size motor:

So I scored a couple of these – they were physically the same dimension, but unfortunately these motors were slightly faster again, so I was facing the very real prospect of Clocker hitting 25mph without much provocation, which could be a liability on the Dragon Con stage.

I emptied the bag of Clocker remnants to see what I could salvage and what I’d have to remachine – the answer was really basically everything minus the motor output gear :p

Good thing Clocker is legal in the new 30lb Sportsman’s Class rules enacted FRESH AND NEW this year for the Franklin Institute event in 3 weeks!

To extricate the motors, I had to disassemble the frame, which proved a little…. challenging after Glasgow Kiss gave it a once-over. There were some special extraction techniques I had to use here on this machined corner!

From the spare Clocker parts bin I extracted another section of the 1/2″-10 leadscrew and flanged bronze nut that fit it. I’d bought a few spares last year in anticipation of needing to machine them eventually, and here we are.

The bronze nut gets machined all the way down to be smashed into the bore of the modified Vex Pro spur gear. When the gear spins, the leadscrew gets sucked in and out of the nut, and its own reaction forces are taken up by the bronze bushings surrounding it. All solid, all friction, all the time, but it gets the job done.

I’d like to eventually rebuild Overhaul’s actuator in this way, except with preloaded tapered roller bearings, for #season3 whenever it ends up being :’(

 

Mate this up with new waterjetted plates that I drilled and tapped and we have a new actuator. The drill gearbox was reassembled from stock pieces from my giant decade-old (…) bag of Chinese cordless drill parts, using the original shaft which was not damaged in the fight. I have enough pieces now to straight up make two whole actuators, which is nice.

After that, I repaired the bottom plate of the bot by stitching new holes in between the hole ones. I’m not sure if I’d use #4 screws like this anywhere in a loadbearing path (which the top and bottom plates do count as) if I redesigned Clocker again, since the indirect shock loads from the 30lb Featherweight class alone (in the form of getting socked by a spinning weapon) is much higher than Sportsmans. One of the corner hits from Glasgow Kiss sheared off a half dozen of my bottom plate screws just by momentarily bowing out the frame enough.

 

While I was in there, I swapped in the spare wheels made from 60A Mystery McMaster Urethane (actually OEM’d by Forsch Polymer, the most 1997 company extant in 2017). The white Smooth-on Simpact wheels had worked well enough, so I wanted to see how these would do.

Well, everything is technically ready for reassembly!

I rememberd a much better way of taking the entire top off Clocker. Previously, it involved trying to drive the center lift shaft out through ALL of the components that were shaft collar’d onto it. This was patently painful. Unlike Overhaul’s unboltable lift towers, Clocker has solid ones built into the frame rails. It turns out if I just unbolt the outer and inner frame rail on one side as a unit (9 screws), there’s enough room to wiggle the shaft out of the bearings and pop the whole thing off.

 

Clocker was the last thing I wanted to put the Brushless Rage test units in before shipping them off for production. The severely under-geared high-Kv motors will be a good stress test for the architecture, since on the Dragon Con stage I’ll mostly be driving at low speeds and turning/reversing often.

Check out that little Onyx bracket I made to hold the units. I wanted to place them flat against the frame rail behind them here, but this arrangement kept the wiring cleaner and away from the outrunner motors.

A new waterjet-cut gear and some quality Taki-time later, and everything is now back together. I did some drive testing outside, which showed me that the Brushless Rages were working great even under duress – the gearing on the motors is low enough that the bot has trouble turning in place on a high traction floor. So here I was hoping that it would be even able to turn at all on the Dragon Con stage carpet! But once it takes off… boy does it want to keep going.

the charles and the dragon con

Welcome to Dragon Con! Have a van.

I would have loved to bring VANTRUCK instead this year, as it has been now impeccably reliable after its lobotomy and subsequent headcrab installation, but could not even begin to justify the 9 miles per gallon each way. It’s beginning to dawn on me that the kind of person who would have bought one of these things new, never ever thought about the cost of fueling and ownership. I’m not quite to that level in life yet.

Overall, this con worked out a lot differently than some of my past Dragon Cons. See, I wasn’t scrambling to finish a robot every day for once – Roll Cake’s finishing work and testing occurred before the con started. Instead of trucking around a giant transforming mechanical prop, Cynthia instead prepared a bunch of pieces for the Dragon Con art show (which as I found out was nontrivial to get into)

On top of that, it’s become more of a yearly reunion for some of the BattleBots competitors and friends who have moved around the country & world. For example, I found Lisa Winter!

The cotton candy committee has arrived.

I attempted to replicate her tattoos in the middle of talking at a panel. Nailed it!?!

And for the first time in probably over 10 years, I actually played in a gaming tournament. There was an Overwatch ruined my life run away now tournament being hosted at the convention gaming center, and a few of us essentially set up #BattleBotsPlaysOverwatch.

The house equipment was sub-par, though, so we didnt’ do too well – people who have clearly been to more than one tournament brought their own mice, keyboards, headsets, and pillows and stuff. Now that’s pro.

 

HELLO FOR I AM MECHANICALLY THEMED VIDEO GAME GANDER AT MY CURATED ARRANGEMENT OF MECHANICALLY THEMED ITEMS

Alright, you know how Dragon Con goes down. Let me spare you the details and get to some robots!

MicroBattles has grown to the point where it has to be single eliminations only and running across two arenas to keep up. I’m glad that it’s a good problem to have! However, it does mean you’re pretty much one-and-done.

There wasn’t much to do with Roll Cake beforehand except get some driving in. I decided to move the tail on the flipper downwards one mounting bolt such that it was more likely to rest on the floor – otherwise, the bot tipped abouts its wheels a little. However, it kept weight on the feeder wedge, so that was a plus.

Robot Battles features mostly local builders who kind of keep to that series of events around the Southeast. It’s refreshing to see bots which haven’t been forced to become the small monolithic dense bricks that most competitions have forced them into being. These two, for instance, are hand-bent sheet metal from Home Depot, with a hand-soldered custom motor driver inside. I honestly miss these kinds of builds.

Pool noodle wheels were fully in fashion this year, made popular by the Dale robot Noodles. Hey, they’re totally not entanglement devices. The wheels aren’t supposed to come off, just incidentally if you hit them with your spinning thing! Wink wink. I suspect this kind of thing might get roundabout-banned somehow, but on the other hand, it’s 2017 – get a reversible ESC on your weapon already!

Sheet metal everything, down to the weapon! Now this is robot fighting.

Other builders who had too much time on their hands chose to adorn their robots in….. creative ways. That’s hand trimmed and applied fake wood veneer vinyl on Margin of Safety here…

I was pretty eager to fight Noodles since it’s high ground clearance and invertibility would have made for a whole match of flips with Roll Cake.

Besides the wacky builds, you had your usual array of kit-bots and modified kit-bots.

Roll Cake was matched with Margin of Safety first, obviously a fight that I was hard pressed to win. Aaron put on the miniature vertical drum module for the match, so we went head to head trading blows. Margins having the the smaller drum advantage,  Roll Cake got flipped over and I spent a while trying to self-right, but at the time didn’t have any skids on top of the bot, so I trundled it around a few times trying to get him to flip me back over.

See the two little hex nuts sticking up from the top? That was added after this match so I could get flipped over in the rumble and maybe get back up. With the drum bouncing off the ground, it wasn’t going to get enough momentum to roll it self back over, so after a while of trying, I decided to save the effort for the rumble.

In said rumble, the drum promptly threw the rubber o-ring belt and jammed as soon as it started. Well bugger me with a #1/2-20 tap, that sure didn’t come up in testing! So I spent the whole time running around like an idiot.

I suspect that spinning up quickly made the belt stretch enough (since rubber cord doesn’t have a tension element in the middle like fibers) to jump out out of the pulley enough to get grabbed by the drum. In Roll Cake 1, the pulley spacing was far enough apart that it would have just fallen off, but this time I had to move the drum closer and so there is a lot of overlap with the drum iself.

Hey, all things considered, I walked out with a working bot. It’s now time to get serious with Roll Cake. I’m extremely confident in the mechanism now, and so it’s time for it to stop being a test jig on wheels. The weapon motor is severely undersized – if there was one design which should have a motor-in-drum setup, it’s this one! And, furthermore, freeing up the space occupied by the weapon motor might mean I could use more conventional drive motors. The hub drive worked well enough, but I still prefer the positive feel of a geared motor.

And now it’s Monday!

 

With the return of all the robotty TV shows, we’ve seen a serious and sustained rise in the audience count. The room filled up to this level well before matches began, and the line continued out the door the entire day.

An entry being finished in the pit area before matches begin! How quaint.

Lisa brought itty-bitty Tento, weighing about 8 pounds, and entered it in the 12lb class for fun. This thing was built as a “how to build a robot” demo piece. Unfortunately, it suffered a gearbox failure literally right before matches began and it was of a type that nobody else was using, so spares couldn’t be located. Sad day – maybe next time!

Clocker just needed battery charging (and the replacement of a chain tensioner block) this whole event, so I’m quite pleased.

I only ended up having two matches – one against this giant purple thing (which had radio problems at the end – notice us both running onstage to disarm it), and the second against Dale’s Pushy Grabber. This thing has been sweeping RB events (literally) with the lynchpin strategy of wiggling under your bot almost no matter what. Now, normally I offer at least some resistance to Dale, but this thing I had to approach either at a very specific angle or risk getting plowed off the stage almost instantaneously. We had 4 total matchups, in the middle of which Dale had to reattach one of the rollers and I had to replace a chain tensioner block which finally decided to wear through and fall off.

This event really showed that, much like my arena-optimzed Test Bot v4 days in the Late Aughties, wide ground-hugging wedge surfaces really are more of a liability on the stage than an asset. Notice how in the final Pushy Grabber matchup, I tried executing the same strategy, but got hung up on the edge just long enough to become vulnetable. The only weakness of Pushy Grabber right now is a long-reach forked robot like Nyx with the lifter attachment – Clocker did not have enough “stickout” to really get a good handle on it – nor did it really on other bots.

Unlike version 2 and 3 where the clamp arm reached all the way to the end of the forks, this one for the sake of looking more like Overhaul has the ‘grab point’ more inwards, so I had a harder time getting opponents into the clamp in the first place unless I took a straight run at them with some velocity – upon which I would often run into the stage edges.

I stuck around for Rumble #1 which I won by virtue of trying to get around the damn stage and mostly ignoring opponents…. and in Rumble #2, I just took the wedges off and ran around like an idiot some more, accidentally handing the win to the purple thing after doing some kind of J-turn rocket jump off the stage. Oops.

This event was also the final straw for me in terms of gearing down the drive motors more. I’ve been threatening to go to 2-stage gearboxes for the drive, and now it’s more necessary than ever. Clocker v3 was geared for 19mph and was already a rocket, and there was barely any need for it on the stage. I’ll probably move to 11:1 2-stage P60s and use smaller 35mm drive motors.

Yes, this kind of thing is legal here, with a catch: It doesn’t exceed either 500 RPM, or 20 ft/s edge speed.  It’s driven by a geared motor, so it will more lift your bot up and chew at it.

 

Replicas of BattleBots entries are the in thing right now! This is Tuskin Raider, a 12lb Razorback-alike that Jamison built. It got all the way to the 12lb finals.

This is a 12lb shell spinner.

And here we have the assembled Power Rangers shot of all the scale models. Hey, we can film #season3 right now if we just get all the cameras up really close. I keep bugging Jamison about why he didn’t make Tuskin a 30lber instead of a 12lber.

So that’s it for Dragon Con! Two working robots remaining, shenigans abound, and…. no van adventures. Wow, when did my life become routine? Obviously it’s time for another all-vans update soon….

Brushless Hipsterism Intensifies: Returning to Brushless Rage. Brushless Mini-Rage!? And Trying Hub Motor Drive in a Beetleweight

May 12, 2017 in Motor Controllers, Reference Posts, Roll Cake

Oh, Brushless Rage… how far you’ve fallen. It’s been standing idle since late last year when I got the first version running. Thereafter, it began having some rather obdurate power supply problems that I couldn’t resolve with a few different attempts, and with #season3 still unknown (TO. THIS. DAY. UUUUUUGGGGGGGGGGGH.) and having to pick up and move shops, I lost motivation. Now, with the spring and summer silly go-kart season coming up, me really wanting to pregame getting Overhaul back in shape ( *cries deeply* ), and my comrades over at Robot Wars screaming for assistance, it’s time to put my robes and wizard hat again.

The last time I really worked on Brushless Rage was in October. After tuning out the first one, I went ahead and made a 2nd one. I wanted to get Sadbot running on them for a few test drives.

Here’s my innovative housing for the two controller! Bolted back-to-back with drilled holes in the Ragebridge shipping box.

And that was all! It was retained by a few zip ties running through the bottom ‘breadboard’ baseplate. I didn’t take much test video of Sadbot running on them, unfortunately;really the only one that exists within easy reach is, uhh, this one. While it doesn’t show them getting whipped, they definitely don’t not work! Yay!

But not for long. I soon lost both of the units in further off-bot tuning of settings. They didn’t blow up, but simply failed to ever power on, with the LM5017 regulator simply sitting there getting hot. The only “fix” was replacing the regulator, and I say “fix” because that really didn’t fix anything, and they would die again within minutes or even seconds.

No problem… maybe it’s just an issue with the two boards. I’ll just try another one of the five total I ended up making….

Nope. Nothing. They died one by one, all to the same symptom. I tried redoing my math for the regulator for the 4th time, thinking maybe  I made a mistake somewhere. I even tried mimicking the reference design to try and get something running. I literally never do that.

At this point, I figured it must have been something incredibly dumb and simple I missed. But why would the first two have worked at all, even for a little while?! Convinced the solution might just suddenly invent itself, I stopped thinking about it.

And so here we are, a few weeks ago, when I’m slowly building up a new rev of the logic board that fixes up some trace routing problems and Little Blue Wire problems. Again, the logic regulators kept exploding, some times dramatically taking out the input trace like seen above. The little light is strapped across the 15V gate drive supply to give me a visual indication of it being on.

What is with me and being unable to use switching regulators!? I recalled the Ragebridge Diode Debacle of 2015, and decided to take one last Hail Mary run through the datasheet along with friends to carefully cross-check each other for boneheaded mistakes and…….

TI, you assholes.

So here’s what’s going on. The Vcc pin of this chip allows you to power it from its own output voltage, which is often fairly low, so it prevents a lot of heat dissipation in the chip since otherwise it would have to derive its own power from the voltage input (up to 95V). But what I missed is this only works up to 13 volts. My gate drive supplies were 15 volts by design.

Beyond that? Who knows?! It might work, it might not. I’m guessing my first two were just high enough in manufacturing overhead that they worked for a little while. Subsequent statistics were not on my side.

Okay, whatever. I cut off the 11.3kohm feedback resistor and threw on a 9.1kohm to drop the voltage from 15V to about 12.5V and let’s see what happens.

Ah, it wakes right up.

Of course it does.

So I decided to respec the gate drive for 12.5V. Why do this instead of go for the full 15+ volts? Because I’m really aiming to make this design work at high-for-robots voltages of 36-48v, possibly up to 60V nominal with a different power stage, so I’d like to save the power dissipation in the chip’s onboard logic power supply.

The change in drive voltage will slightly affect the drive characteristics and switching time. For now, I’ll keep all the power stage parts unchanged, but I’ll probably tune the gate resistor values later.

 

To get rid of the noisy ripples on the feedback network and to stabilize the switching frequency, I added some more bypass capacitance to the chip. This was not included in the design at first, since I figured my large ceramic input and output caps were nearby, but it really really wants its own little private capacitor on Vcc. Gee, I thought I was a princess at times.

So now this thing is pretty much bombproof. Here’s a video of it throwing around one of the 30-pound old MIT CityCar prototype motors (which I inherited 4 of after the project was dismantled):

In that video, it’s running from 36 volts. I tested it with a smaller motor all the way up to 50V input before getting too scared for my power supply’s life; I’ll need to try it on a larger high-for-robots voltage power system later, but nothing smelled imminently unhappy!

With the regulator death issue apparently behind me (again) I decided to push another board revision. This time, I added all the necessary bypass caps and changed the layout of the logic power supply, as well as take out some parts I decided were superfluous.

The logic power supply got a little smaller and more electrically optimal. The whole thing is just less messy now. I like it – it takes up around 1/3rd square inch of PCB space on one side. At the behest of a professional PCB engineer friend, I turned the inductor 90 degrees and joined it with the LM5017′s switching node with a small trace instead of a larger groundplane. This would prevent the switching node (a source of huge voltage swings in microsecond timescales) from broadcasting as much noise.

Besides some other minor trace chasing, what’s going on down below on the board is also something experimental:

That there is a bidirectional optoisoated I2C bus for transmitting data between two microcontrollers which should never meet directly. I had a single-direction opto input on the board revisions so far, but this prevents updating of settings via the SimonK/BLHeli type bootloaders. That means tuning the settings require busting out my chip socket every time, which is annoying. I reviewed a couple of bidirectionally isolated bus schematics and decided to try this one out first, since it involved diodes only, not transistors.

The problem is, the I2C bus is a open-drain configuration with pullup resistors and ’1′ bits transmitted by pulling the line down to 0v. I kind of wanted to try keeping the opposite polarity, so to speak (even though SimonK supports an inverted input setting) just because I’m used to thinking about things this way. So I tried flipping the circuit over…. pullup resistors became pulldowns, and common-emitter became common-collector, and so on.

It makes sense in my head, but I’m sure excited to see this work!

On the board, this is the layout. It doesn’t consume much more space than my previous 1-direction optocoupler setup, and can be bypassed for testing with 2 wires if needed. That’s the nice thing about keeping things upright signal-wise.

So before I sent this board revision out, I stopped for a moment to think who would really be wanting to use Brushless Rage. I’d designed the 12-FET board to effectively replace Overhaul’s 250A DLUX controllers (with more realistic ratings, mind you). I’d say the majority of people who would buy such a thing won’t be running motors that big.

Recently, the thought of a “Half-Rage” has been coming up in my mind as something worth pursuing. This would be a board with about half the footprint of a RageBridge 2 and supporting about 1/2 of the amperage. As some curious question-askers had innocently drilled into my mind, this would be an Actually More 30lber-Sized controller.

> mfw "When are you going to make a 30lber/12lber version of RageBridge?

 

With this in mind, I decided to make a copy of the power stage and began downsizing the hell out of it.

Step 1: Reap what I sow when it comes to the sheer number of vias I deposited under the FETs.

After bunching the FETs together, I referenced one of the earlier abandoned Brushless Rage layout ideas for the output wires. This board is now short enough that I’m comfortable pulling the phase outputs all the way to the right with the power. Keeping all my wires on one side is something I prefer.

Somewhat final routing of the fat bus traces here. I had to move a few gate drive traces, as there was no longer an opportunity to swap sides in the middle of the FET bank. Power+ runs straight from the bottom right corner, through the bus capacitors, into the high-side FET. Power- emerges from the current shunts and then has 3 paths to return to the buscaps before being slurped up by by the wire hole on the upper right.

Here’s an overlay of the signal board design on the power stage, showing roughly the size of things. The final power stage is 2″ x 2.75″. Not the tiniest thing, but I have more capacitors than you!

This board shares a lot of thermal characteristics with RageBridge, so I’m pretty comfortable calling this a 50A continuous class controller. 50 real under-partial-throttle amps, so that’s what, like 1,200 Hobbyking Amps?

In all likelihood, this controller will be able to handle an average 63mm SK3 motor in continuous duty applications like a silly go-kart. Robot-wise, it will probably be stressed handling the same in bidirectional drive mode.

Fast forward a few days and….

OhmygoditssocuteIjustwanttohugit and then make it run a 80mm outrunner on 12S violently. I’ve ordered parts to make a handful of these, and two are going on Sadbot ASAP to be driven until something blows up!

Direct Outrunner Hub Drive for Your Little Bot

Next up, something even smaller!

So I’ve long been a connoisseur of fine handcrafted hub motors. I got curious recently on using direct-drive small outrunner motors in an ant or beetle after thinking a while on the redesign of Roll Cake. Version 1 of Roll Cake was honestly just a braindump of a vision I’ve had for years for the shape of the bot, and everythng else came second to that. On the beetle scale, the multi-pulley serpentine pulley drivetrain simply had too much friction for the Fingertech motors (which were severely underpowered for the task) to overcome.

For the next version, I’m ditching the triangular cheese wedge shape for something more straightfoward. The cheese wedge will be back for a heavier weight class. Roll Cake’s design really wants to have the middle of the bot kept clear for the flipper linkage. I’m sure I could work around it with low-mounted drive motors and similar, but this was an excuse to play with brushless things!

I based my thoughts off Jamison’s mini-gimbalbot which used camera gimbal motors for drive with a small Hobbyking R/C car ESC. It drove “okay”, certainly capable of a weapon delivery platform. So naturally, I wanted to put some SimonK-capable controllers on it and see how the handling would change. I got a small selection of motors: A pair of DYS and Quanum 28mm motors as well as a pair of Multistar “HV” 460kv motors. 460 RPM/V is reeeeeally slow for that size of motor that isn’t a gimbal motor, so I was quite interested in them.

These are the gimbal motors. I like them for their pancakeyness – the Quanum motor is more 30mm and has a bigger stator.

Playing around in the CAD model a little for component placement. At this point was when I realized Roll Cake in this incarnation might end up looking a lot like The Dentist :P

I designed up a few hubs that bolt to the face of the motors and have a tapped middle hole to sandwich a wheel. The wheels are spare 1.625″ BaneBots wheels that I originally bought for Candy Paint & Gold Teeth.

Shown with those motors is a ZTW Spider 18A controller. My typical SimonK ESCs, the Afro series, were out of stock when I placed this order, so I took recommendations from people on what I should use. The Spider series are fairly popular these days among small bot folks.

The issue is, they come with BLHeli firmware, the other other open source drone racing / vaping rig development path. It’s a newer effor than SimonK and has a more polished interface. I’d read about it before, but not worked with personally. Other builders have said it doesn’t run robot drivetrains as well due to being much more optimized for propellers. So hell, why not – this was a chance to explore that side of things.

Here’s some real life CAD layout, featuring the Multistar motors.

I really wanted to use the gimbal motors, but they disappointed me in bench testing sufficiently that I didn’t even end up installing them. Basically, they can’t draw enough current to make torque at typicall little-bot voltages. With phase resistances of 10-20 ohms, they can really only draw ~ 1amp or so. I mounted one in a vise and could stop the motor with my pinky finger at full radio stick input.

These motors might be better at 6S and up, but for the time being, since all of my small-bot batteries are 3S, I decided to pursue making a test platform using the Multistar 460kv motors.

 

The platform of choice was…… one of Candy Paint’s spare weapon pulleys. I literally spilled my “preformed robot spares” bin on the ground and tried to see what was good to use as a base. Hey, it’s round and has convenient wheel holes in it already! All I needed to do was quickly whip up some motor mounts (3D printed) and I was in business.

 

Here’s everything hooked up. That nut is for a counterweight on the front to add some friction against the ground while turning. Otherwise, it had a tendency to keep spinning and spinning if you even thought about turning.

Communicating with the ZTW Spiders was a hell of an adventure in its own right, and I am putting this post under Reference Posts because I’m 99% I will need it again or someone else will randomly find it while needing the information. If there was any industry that continually pisses me off with how undocumented and tribal-knowledge focused it is, it’s the R/C anything industry.

So, here’s how everything went down. I lost my AfroESC USB communicator, so I purchased the Spider SPLinker advertised as working with the controllers. I also bought one of these stupid things:

That’s a “SimonK/BLHeli compatible” dongle called the ESCLinker. It allegedly can talk to either kind of ESC, but there was nothing remotely resembling a manual or operating guide; all of the search results for this brilliant device were people complaining that there was no manual.

So I’m writing the manual now: This thing does not want to talk to KKMulticopter Tool (my go-to for flashing SimonK ESCs). It will only talk to BLHeli Suite. As a matter of fact, I couldn’t get the Spider SPLinker to talk to ANYTHING. For all of my tuning here on, I used the ESCLinker tool.

Here is BLHeli Suite, which is hosted on the sketchiest possible website that is one tier above compiling it from the Git repository yourself.

Notice how I’m connected to the ZTW Spider now. The ESCLinker (and SPLinker) install as virtual COM ports.  The necessary baud rate is 38400 baud, not 19200 (Afro/Turnigy USB dongles, to my knowledge)

By the way, once I realized this, I tried to talk to the SPLinker and ESCLinker on KKMulticopter Tool again using 38400 baud; no dice.

Further investigation revealed that the ESCLinker needs these options to communicate to the ESC – both options 2 and 3 will work. So if you’re listening, people mystified by the ESCLinker: Talk to it on 38400 Baud and ask it to communicate to your ESCs with BLHeli/SimonK 4-way-if bootlader.

Ugh. One of my selfish reasons for wanting Brushless Rage is so it’s one known quantity and I never have to dick around with other people’s open-source bullshit again.

So with all that behind me, I decided to try out BLHeli drive on the little pulleybot. I went with intuitive settings based on my SimonK advice, which included “Damped Light” mode, a fancy euphemism for synchronous rectification/complementary PWM, medium to low timing and maximum start power. BLHeli also has a “demag compensation” feature which appears to delay commutation to compensate for current decay in the windings. Who knows!? I wasn’t given the imprssion that its users actually understood what it meant, nor does the manual really say anything useful.

I found that Demag Compensation turned all the way up gave the best performance, along with maximum start power. However’ it still couldn’t compare with my SimonK experience. It seems like even maximum start power is much weaker than what SimonK permits you to do.

Here’s the final test drive I made with the BLHeli Spider ZTWs:

I’m honestly not very impressed. I think BLheli is very much optimized towards multirotors and helicopters (hmm, maybe it’s even called BrushLessHeli for a reason!) and the settings are more high-level and mask the underlying mechanicals of the firmware. I think this makes it much more accessible to hobbyists, though. In the end, I’m not very enamored by it.

These were my final settings:

For a direct comparison, I decided to replace the ESCs with my old SimonK Afro 30 amp units. These have been on quite a few bots now, starting with the original Stance Stance Revolution, and they were completely beat up. But they still worked!

A direct replacement into the existing wiring harness later… we have SimonK!

I found myself in the awkward position of using KKMulticopter Tool to compile a customized SimonK formware, then uploading it via BLHeli Suite because my USB dongles didn’t talk to KKMulticopter Tool; I’d lost my AfroESC USB dongle a long time ago.  BLHeliSuite doesn’t seem to have a firmware editor window that I’ve found yet.

Here it is. I found the SimonK version so much more responsive that I actually needed more counterweight on the front. So, a non-fitting bolt gets zip tied to the nut! Now the bot’s a lot more controllable:

I like it a lot. It might even be worth doing 4WD to give me more yaw damping, or I’d have to design the bot to be well balanced enough on front skids, or something. I used my typical SimonK parameters: complementary PWM, maximum braking power, maximum braking ramp speed, and adjusted start PWM limits to something like 50%.

I’m aiming to get Roll Cake and maybe Colsonbot running for this year’s MomoCon in a couple of weeks, so hopefully I’ll post up some design news soon!

 

Baking the Roll Cake, and How I Failed to Save Private Überclocker This Time: The Dragon Con 2016 Adventures

Sep 11, 2016 in Bots, Dragon Con, Events, mikuvan, Roll Cake, Überclocker 4

Oh hello everybody! It’s a few days after Dragon Con and I’ve finally woken back up. Where the hell am I?! What is this metallic coating all over my face? Why have I gained 20 delicious pounds?

Here it is, the Post Dragon Con 2016 recap. I didn’t get a change to put out another update before leaving for Atlanta, and then it was a mad pre-convention dash. So this update will cover all of the construction of Roll Cake, as well as get started on the Bot that Charles Forgot – Überclocker 4.0, a.k.a “I Can’t Believe It’s Not Overhaul!”.

Amazingly enough, there were no van shenanigans on the way down. I’m staying in Atlanta a few days later again, so the return trip is still clouded in the ether, but at this time (Boston to Atlanta and now a few hundred miles locally) there are no issues to report.

Alright, I lied a little – at some point a few weeks (months???) ago, the rearmost portion of the exhaust pipe decided to fall off. It had a hanger at the very back of the frame, so did not fall completely off, but just rattled haplessly.

I think it was due to the bend passing over the rear axle being repeatedly struck by said axle when Mikuvan is loaded heavy – such as the trip to Detroit Maker Faire. So anyway, all it manifested in was things being a little louder, but at times due to the exhaust being trapped under the body and in my 3-mile-long wake vorticies, exhaust smell would creep into the cabin. This is not something I wanted to deal with for the long trip down, so I repaired in the best WEEABOO REDNECK way possible:

None of this BEER CAN bullshit… only the best Ramune bottles will be used for MY hoodrat repairs!

This held all the way until South Carolina. When I rolled into town, one of my pre-convention stops was the local Advance Auto Parts to pick up a patch pipe. The whole system is definitely in need of replacement, though. Who wants to hook me up with D U A L   F L O W M A S T E R S?

Anyways, without further ado, here are the sections of this roman noir de robots:

  1. Finishing and testing Roll Cake
  2. Designing and building Überclocker 4
  3. Robot Battles and Dragon Con recap

 

Icing on the Roll Cake

So this is where we build up to that ‘preview picture’ I posted last time.  One of the first things I did as soon as I put the frame pieces printing on the Mark Two was go and do basically the only machining thing, which was make the drum.

For this, I brought back an old friend. One of my first major tool purchases was this little indexing head, which made its first appearance here in a LOLioKart build report. It became my most prized possession for some time thereafter, but I left it in the shop when I mostly scuttled off to main campus and upstairs into the IDC for graduate school nonsense. With my departure, it began becoming decrepit under usage by random newbies. One of the dividing plates was lost, and one of the tilting locks was also lost after someone cranked the locking bolt too tight and sheared it off.

Every once in a while, someone does find it again and use it, so I knew it was still operational. I gave it a once-over cleanup and adjustment before starting here.

The drum blank was carved out on New MITERlathe before being transferred to the indexing head for feature drilling. I originally specified 6 bolt holes. But as it turns out, 8 holes is easier to use the indexer for, since it didn’t involve going in partial circles using the dividing plates. Just 5 cranks of the handle… So, 8 holes it is.

Next up, putting the big 1/2″-13 threads in for the cap screw “teeth”.

One tricky operation was broaching the 8mm bore for a 2mm keyway. Since Roll Cake is being built from Banebots P80 parts, so it must be compatible with an 8mm keyed shaft. I could not get a 8mm bushing & 2mm broach in time – nor did i want to spent dozens of dollars for the honor. So I did what, I guess, I would do, and carefully hacked at it with a 1/16″ endmill until I got a 2mm slot with a bit of radius at the end.

Precision! Craftsmanship! Finesse! We strive to be the opposite of this at Big Chuck’s Robot Warehouse. Zero sigmas, guaranteed, or I’m keeping your damn money anyway.

 

The frame parts have finished printing from the new Onyx material!

Well, hold up a little… These are extremely hollow prints that were solely to test for dimensional correctness. Things like “Does the motor fit in this hole?” and similar.

Here is a mock fit with some of the parts. I used a paint marker to pinpoint locations which needed rework – generally increasing slop or tolerances in the CAD model to get a better fit in real life.

Another arrangement of “DO NOT USE THESE FOR REAL” parts, which all had X marked on them so I was not tempted.

The two main frame halves are actually made from regular nylon for the most part, with carbon fiber loops in the center of the bot to strengthen the area. Otherwise, the regular nylon is tough and a bit flexible, which will hopefully help against some impacts.

A little pile of wheels with grommet-tires installed…

I next synthesized these planet gears from spare P80 4:1 and 3:1 planet gears. The 4:1 gears were bored out and cut to half a normal pinion length. Then the 3:1 gears were machined down for half their length, and then promptly shoved into the 4:1 hollow half-gears. The shoving first involved lining one tooth with one valley between teeth on each gear. As mentioned in the design post, these compound gears require the correct phasing of teeth to be assembled succesfully. I was probably off by some fractions of a degree on each gear.

THAT’S WHY WE HAVE A PLASTIC RING GEAR

The ring gear itself has also been reprinted in carbon fiber back Onyx (a material we came to call RMCC – Reinforced MarkForged Carbon-Carbon). I made the number of engagement dogs lower to guarantee the servo being able to reach between them.

Assembly for realsies begins with the bolting together of the sides. On each side, three #4-40 cap screws with washers and nuts retain the sides to the center U, and at the very rear, a #4-40 threaded rod with 4 nuts provides last-ditch backup if those front fasteners fail.

The ‘flaps’ are waterjet-cut 6061 aluminum 1/16″ thick sheet, which are bent up at the edges like so:

Well, that’s how it’s supposed to work. I really need to watch some tutorials on how to use a box-and-pan metal brake correctly, because I clearly can’t do so, ever – and it probably doesn’t help that I make sheet metal parts infrequently enough that the shared machinery is never in the same condition twice (or some times working at all), so I have no clue how it’s supposed to behave. Anyways, no two bends on this thing are alike in location and alignment. One side is workable, the other side is very twisted… Oh well, we’ll fix it in post.

Time to solve the never-quite-solved wiring problem. I made access tunnel paths for the hypothetical wiring through the back end of the U-bracket that makes the center of the bot, but physically doing it was another whole issue. “Haphazard” and “ad-hoc” are two words that each don’t quite describe Roll Cake’s wiring on their own.

I basically had to make three long cables, fish them through the two wire tunnels, and then wire everything in-place at the ends and cut them to length. These cables were the main battery, left side drive motor, and firing servo cables. The right side drive motor also passed through the right tunnel, so really it was 4 cables.

For this purpose, I used the thinnest wire I could find for the drive motors, which was some 30 gauge blue wirewrapping wire.

Everything in the bot could run directly off 11.1v – the drive ESCs (VEX controllers), even the Hobbyking TR6Av2 receiver believe it or not – you can run basically every new receiver from battery voltages since they have onboard regulators for the microcontrollers. However, the firing servo still needs 5 volts to not go crazy and burn out.

Therefore, I made a super small in-line 5V regulator from two Chinese’d  LM1117 parts.

Don’t give me no “that’s racist” bullshit – you and I know this happens on a regular basis.

This 5V line then feeds the receiver, and the servo cable is a 3-pin custom cable which comes from that. Essentially as if I were to plug it in without hacking anything.

After the electronics are installed, I made the orange roundbelts and started closing everything up. The round belts are measured using the hypothetical pitch line in the belt circle drawing in the CAD model, then shortened about 10% to accommodate stretching.

The final act is to install the linkages. This is done using long M3 bolts cut down such that their unthreaded shoulder acted as the joint pin, but I could still put a locknut on the end.

Here is the finished bot from the flappy end.

And a photo from the ‘business end’.

So how does this thing work? Well, it doesn’t really.  The serpentine roundbelt drive has too much friction for the Fingertech motors to overcome. While Stance Stance Revolution used two 22:1 Fingertech motors, they were direct driving small wheels. Each pulley adds some friction, since the belts need to be tight to transmit torque and the pulleys do not have rolling bearings, just nylon on shoulder screws. Roll Cake therefore could not move at all. I’ve built some pretty damn immobile bots, but this is literally the most immobile thing I’ve ever made!

You can hear the motors strain to move, slipping on the belt, and occasionally it scoots forward a fraction of an inch. That’s about it. In doing this, I actually burned out one of my 22:1 motors.

I began making arrangements to get some 33:1 motors from fellow competitors down in Atlanta, which should help the torque problem, and also began the search for small timing belts. MXL and 2mm timing belts come in 1/8″ wide / 3mm wide, so I could redesign the pulleys to that tooth profile. Then, the matter becomes if the Mark Two can hold the kind of tolerances needed for the tooth geometry to work out. I decided to leave that to Atlanta.

While the driving test was a bust, I did get a few flipper tests in with the drum going full speed. I’m glad to say that this part seems to work great. The servo engagement is clean and predictable. Here’s a test against a roughly 3.5 pound empty toolbox. Note that I don’t have anything springy or elastic that’s preferentially loading the linkage closed, so it depends on good firing servo timing to bring it back down.

That was actually the second test. The first test was against a heavier (4.5 pound) aluminum rail – coincidentally, the unmachined blank frame rail for Uberclocker 4. On this test, the deceleration of the drum was severe enough that the bot rotated forward against the linkage… causing the drum to strike the ground and hilarity to ensue.

Well, truth be told, that was the part of the bot I cared about. I packed all of the parts up for Roll Cake anticipating needing to do some re-engineering once I was on site. Just prior to leaving, I ordered two sizes of timing belts from SDP-SI based on the existing pitch length and what was closest to it – two 155 tooth 1/8″ wide MXL belts, and two 160 tooth ones. At least one of these will be close enough after I redesign the pulleys to be timing belt profiles with roughly the same pitch circle.

 

Überclocker 4.0

No fake-outs with wheels this time! This is the real deal now.

I’d been MEANING to retire Clocker version 3 (Überclocker Advance) since after Motorama 2015. Then came Dragon Con 2015…and then Franklin Institute 2015. After it won handily at FI, I decided to force myself to retire it, leaving the broken actuator unrepaired. Clocker 4.0, which has no witty Engrish name, was meant to be designed much earlier in the summer, post #season2.

Well that clearly didn’t happen… I actually started working on the design on and off in mid-July, but some contract work was keeping me entertained at the time – so designing didn’t start in earnest until August. That’s one side of being “funemployed” is that the work you do pick up is often stuff you like to do, meaning you adopt it as your own, meaning certain death if you have zero time management ability like me.

The first thing I designed up was actually the custom cast wheels that I talked about last time. I decided to use Clocker 4 as a smaller-scale experiment to try out the technique and different materials without wasting a bunch of money. The wheels were made with a 3/4 hex hub, which Clocker 3 uses and which I intend to carry over to the new bot. They were made in two sizes – 3 inch and 2 inch – to reflect the needs of the new bot.

So let’s go through the design of the bot now! Keep in mind through all of this that the principal design constraint was “Is this dimension about 50% of what it would be on Overhaul 2?” and is definitely a departure from my usual tactic of letting the part placement drive the robot. In fact, you could argue that both Roll Cake and Clocker 4 represent me trying to “design to look like something first” – Roll Cake being an old robot vision from years ago, and Clocker 4 being a scale model of Overhaul.

Just like with Overhaul 2, I began with a sanity check sketch to make sure the dimensions aren’t impossible. In this picture, the only things fixed are the wheel sizes and chassis height. Much like OH2′s design phase, I was going to let the length of the frame be malleable in order to fit components. But it should end up somewhere around 30″ in the ideal case.

I focused a little more on the pontoons first. The rectangles shown are a size of wubbie that is the closest to 50% scaled down from the type used in OH2.   While their final shape and dimensions is not settled by this sketch, I just wanted to factor them in to get an idea of the size boundaries.

Bringing in more geometry into the mix now by playing with lifting fork lengths and the height of the arm towers.

Probably the terminal stage of The One Sketch has the 2.5″ square DeWut motor profiles imported, the length of the frame adjusted, and the first pass at the upper clamp arm also drawn. Most dimensions line up with OH2 within 10% or so, which is fine. Nothing truly scales directly in robotworld, and I figure so long as the visual is complete, nobody else but me will notice!

The beginnings of the 3D design went much the same way as with most of my bots,  Overhaul included, with the generation of frame rails. You have to start somewhere, so I usually start with the back or left side, and everything sort of grows off that.

I imported the One Sketch and aligned it with the bot as a reference.

Moving on ahead a little bit, here is a more complete drive side. The front wheel is inset significantly into the plane of the front endcaps which hold the rubber shock mounts. I wanted to do this to maximize the wheelbase. Previous Clockers have had the “reactive outriggers” up front to maintain front traction when an opponent gets picked up. This version is relying solely on the rubber shock mounts deflecting, and it will be riding on the front edge of the pontoons thereafter. To maximize the chances of retaining traction in that scenario, I wanted to push the front wheels as far forward as I could.

This does open up a gap in the otherwise fully constrained tab of the frame rail, so here’s hoping that spamming the region with cap screws will make up for it.

Frame rail service for Clocker will also be a little harder harder than Overhaul. In this design, to pull the left frame rail, the pontoons and three of the six shock mounts have to be removed, and there is now more than 1 bit driver size needed. However, you could argue that OH2 also needed two bit sizes – 7/32 for the pontoon screws and 5/16 for the frame bolts.

Cloning stuff to the other side…

A very difficult step came afterwards. I now had to fit the DeWuts from Clocker 3 into this frame (I SOLEMNLY PROMISE DEWUTS WILL BE BACK IN STOCK SOON) . This presented a very serious problem, which is well summarized by NO.

You see, the average Featherweight, full-contact 30lber is generally much smaller than the Sportsman class bots, since they’re built denser with thicker materials to take KE weapon impacts. Clocker 3 is very large for a 30lb bot to begin with, at 20″ wide and 27″ long end to end, it’s almost the footprint of some of the denser 250lbers like Poison Arrow.

In order to make weight, as well as stay roughly true to Overhaul’s dimensions, Clocker 4 needs to be around 16″ wide. However, this utterly precludes the use of the DeWuts. I would need to make the bot at least 18″ wide to use them. That means proportionally more weight to cover the additional width of the bot, as well as a lot of inside space that’s kind of wasted lengthwise since more components would be able to fit next to the motors. This isn’t a bad thing by itself, but two DeWuts back to back kind of forces a different shape robot than what I was pursuing.

So I began working on the inevitable: going brushless with the drivetrain to save volume. I studied a few options which all revolved around a handful of AXi motors I picked up a few months ago (get yours today!). I borrowed a BaneBots P60 model since Jamison had already played with mounting P60s to the AXi motors. I also investigated stuffing the AXi motors into my spare P80s from Overhaul.

In the name of expediency – namely, that I had the spare P80 drive motors on hand, the AXi + P80 combination won. The 4:1 Overhaul P80s combined with the AXi motors at 7S (26v) ought to give a top speed of about 17mph, which is plenty.

The downside is extra weight. While the P80 and AXi combo weighs less than the DeWut, it weighs more than the P60 equivalent which would handle the motor power just fine. For Robot Battles where I won’t need extensive armor, I figured that letting the drive motors have 2 more pounds is fine.

However, I might actually swap these out before FI 2016 for modified P60s, since having the armor weight back would be nice.

Now importing more components – the space inside the bot is filling up fast!

I devised this quickly-3D-printable-from-Onyx mounting bracket for the AXi motor. A new pinion with a 6mm bore will be crafted out of spare 4:1 planet gears, which have 4mm bores I can hollow out.

So the AXi drive will solve the issue of width in the bot. I’m now toying with placement of the internal components. To start with, I’ll be using two of the spare DLUX 160A controllers I took out of Overhaul before the Season 2 tournament began, with a possible upgrade to Brushless Rage later using a 6-FET board (think Brushless HalfRage)

I settled for the two DLUX controllers up front mounted to a (not yet modeled) non-structural interior bulkhead, and the RageBridge in the rear corner to handle lift and clamp, also with a yet-unmodeled bracket.

Let’s begin on the fork tines now. I traced out the basic shape of Overhaul’s fork, but unlike Overhaul which uses a dead (fixed) lift shaft, I’m keeping the live life shaft of Clocker 3 since it’s fairly easy to attach to. The force transmission will be using clamp shaft collars made into hubs. There won’t be a central tube structure in the fork – both will just be held together with standoffs. The forks should, like in Overhaul, never be taking direct impacts unless I messed up horribly.

After I imported the quick fork model, which is still missing specific details like standoff mounting, I also began playing with the clamp actuator. I imported a few older Clocker actuators to check size and placement.

For this edition, I really wanted to move back to a full 550 motor actuator. This should actually give the bot a clamping force of several hundred pounds, which I wanted to have since most Featherweight class bots have negligible top armor.

The issue wasn’t so much weight (it would weigh around 1 cheap drill motor) as space. It had to fit in between the side plates of the clamp arm, first of all, and then anchor itself in a useful location that won’t impede the fork travel much. Overhaul has some issues with this which I would like to remedy for #season3 – so in a way, this is once again using the small bot to pilot something for the big one.

More details have been modeled into the fork plates now. The cross holes will have standoffs like good ol’ Clocker, not just to hold the fork sides together, but keep them level between arms. Overhaul has no such crossing feature near the tip of the arms, only the base. This was the cause of the forks becoming cockeyed during the Beta match when it got a good boop in on one of them, and I’d definitely like to solve this problem.

I decided to pursue the full 550 motor actuator at all costs, so I made one similar in construction to Clocker 3′s final actuator. The motor and gearbox? Just a 12 O’Clocker spare motor! The gears will be purchased from Vex, then modified – one to a 12mm bore, the other bored out to shove an Acme nut into.

Not shown in the above image is an “anti-buckle” MarkTwo printed piece that bridges the two thin plates and cradles the leadscrew for more of its travel. The actuator sides are in tension when clamping, but will be subject to sudden compression shock if the bot lands upside-down or I try reversing out of a grab, so I didn’t want to count on JUST 1/8″ aluminum plates.

Here it is loaded in place and showing placement. The upper anchor point was open to negotiation because the clamp arm sides hadn’t been designed yet. The lower anchor point for the leadscrew will just be a pin that is shoved through the first hole in the fork side plates, closest to the pivot point. The neat thing is this is somewhat adjustable for leverage ratios if I choose to use another hole instead.

I generated the fork side plates based on the dimensions of the One Sketch. It, too, will be held together by a bunch of standoffs – no welding here. This drawing shows some possible standoff positions. I was going to alternate inside and outside circles as I moved from left to right, like so:

The standoffs used are just some big McMaster-Carr 5/8″ hex aluminum standoffs, which for some reason are almost half the price of the neighboring sizes.

Actuator placement was a compromise between “How far does the motor stick out the top?” vs. “How far does the motor stick into the grabbing region?” since I could make the leadscrew as long or short as I pleased.

About this time, I threw Clocker 3 into the CAD model. The size different is almost comical, and at this point I wondered if Clocker 4 could pick up anything at all without falling on its face. Definitely will have trouble with the average 30SC sized bot, but again, 30lb Featherweights are smaller in general.

Anyways, moving on.

One of the next mods I want to make to Overhaul is what I call the “Anti-Cobalt System” – in other words, putting something between the frame rails so this doesn’t happen again. For Overhaul, I’ve been mentally designing it as a top and bottom plate fastened together in the middle, to close off the box and transfer sideway forces more rearward in the bot.

Since Clocker will now be competing in a high-energy class, I decided to implement the ACS for the most part on the bottom of the bot. This also acts to keep the drive chains above the plate, so they’ll be less vulnerable. I could still see this having a failure mode where in a very energetic sideways hit, the frame rails will deform in a parallelogram between the ACS plate on the bottom and the angled endcap on the top.

I’m now in the stage of generating top and bottom plates as well as random spacers. MarkForged spacers for everybody!

The single tooth will be made from some left over 1/2″ AR500 steel – good enough for the task.

I began the process of making the armor pontoons using the same method as on Overhaul. I made a master 2D sketch that represents the front face, and then a series of 3D Sketches thereafter, then defined surfaces using the sketch lines as their bounds.

The geometry for Clocker 4 is a lot simpler. There are no vertical forward-facing or side-facing wubbies, just the six widely spaced ones on the angled face. In a future revision I may consider adding forward-facing ones like Overhaul, if this decision comes back to bite me.

One major difference with these? They ride a lot closer to the ground than Overhaul’s. In fact, I will most definitely have to finish-grind the bottom edge to get enough clearance to not get hung up on them.

This is a good thing, because it resolves the other weakness of Overhaul that was clear during the beta match – the pontoons were simply up too high to be helpful, being designed to take a whomping instead of be good foot-in-the-door implements.

An overhead view of the bot basically done – you can see the standoffs between each pair of fork plates, the tie bar between the forks, and the tube which acts as the anchor for the leadscrew.

I added tabs and slots the same way as on Overhaul to prepare the pontoons for cutting and welding.

Here’s the finished bot minus cat ears!

The ears don’t seem to be necessary on Clocker 4, but it just doesn’t look right, man. I will probably design a pair up to be printed in RMCC which will bolt to the topmost hole in the clamp arm.

I left design of the internal brackets as an exercise to be done in Atlanta, since by this point I was running up on the last week available for fabrication. Hot off the CAD presses and into real life we go!

Man, it’s been a LONG TIME since I’ve done a one-shot epic waterjetting session to pop out a robot. Pictured above is the “Clocker kit”… or some 10 gauge mild steel, 1/4″ 1/2″ and 3/4″ aluminum, and some 1/16″ FR-4 laminate.

Sadly, in my cruftiness, waterjetting is no longer free – this is probably around $400 of machine time.

To prevent the FR-4 from delaminating, I brought back one of my tricks of cutting the outer profile only, and using another material as a template. So here’s how this part went – I routed the parts manually to ensure it does all the interior holes first, then the outer profile.

I laid a piece of plywood in the machine first and had it cut only the holes. Then I clamped the FR-4 on top of the plywood and continued the toolpath to cut only the profile. The 1/2″ plywood pieces then become drilling templates for conventional drilling of the holes later, which otherwise might (WILL) delaminate since they’re piercing close to the edges.

While the design was slow-cooking to completion, I continued casting wheels, making 4 of each total. I’ve basically gotten this process down, so the next step is to try out different materials.

Here, I’m readying the frame rails for countersinking and counterboring. It’s built in the same style as Overhaul, and also many 30lbers and 12lbers. The frame rails will need machining to key into each other slightly too.

One of the last operations I was able to pull off before having to depart for Atlanta was the coring of the large lift gear. This was done using MITERlathe and like 5 different tools. MITERS didn’t have a spoon-type boring bar to make a plunging face cut easy, so I had to make do using a few different types of insert cutters, switching left-hand and right-hand tools to clean out the blind pocket.

Sadly, Monday the 28th of August was upon me. I actually spent more time in the week preceding finishing Roll Cake, since I cared a lot more about perfecting that mechanism, so Clocker 4 fell by the wayside. Clocker traveled to Atlanta in kit form, shown above. I needed to do some (lol) work on it in Atlanta, such as milling the frame slots, before it could be assembled.

And that’s the bot half of the story. Next, what about the convention!? I came this far for something, I think. Whatever is causing all that noise next to the robot events, dammit!

Robot Battles & Dragon Con 2016

So before we get to the convention proper, let me interject with a proud announcement that…

…I finally got pulled over for speeding.

You didn’t think it was physically possible, right?

I’d like to thank my parents, uhh… Boston area highways…. and, of course and Smooth Automotive for the Accidental Engine Rebuild of 2015 which has restored Mikuvan’s former power so much that I legitimately now can speed. I mean, it takes a little while to get there, and no hills please, but otherwise, I can cruise at 75mph all day – just enough to get in trouble in Virginia when the speed limit drops to 60mph for an upcoming work zone and I ABSOLUTELY, POSITIVELY MUST PASS THIS ONE LAST MOTHERFUCKER ON THE RIGHT HERE and… Dammit.

He got me fair and square. In fact, he didn’t even mention how I Boston’d someone immediately before the orange construction barrel forest began. So thank you in that way, Virginia State Trooper. I’m not even going to look at this ticket until I’m back in town now, because Virginia sucks.

Alright, enough of that. As I mentioned at the beginning, there were no van shenanigans to be had. I got into town around 4:30PM Wednesday, and immediately began plotting robot finishing tactics. The first order of business was getting Roll Cake its timing belt setup, which I designed quickly once I settled in and put on print. What?

Yes, I dragged the Mark Two provided by my lovely sponsor MarkForged along. Hey guys, how’s about some hot and humid weather testing?!

The SDP-SI timing belt order arrived on Thursday afternoon, so I could test the fit immediately. More importantly, though, on Thursday…

I busted into Dale‘s shop like the good ol’ days and basically took over his entire workbench. On deck were finishing some milling and turning parts for Clocker 4. I machined the axles, finished off the wheel hubs, and made the motor pinions, among other unfinished business.

The big rear chamfer for the frame rails was also cut by tilting the head of his CNC mill 30 degrees.

Friday bot work was mostly done at the GT Invention Studio. I primarily worked on Roll Cake, doing the final installation and tuning of the timing belt drive:

The pulleys were sized by how close they were to the pitch line defined in my belt loop sketch. The difference was then made up by changing the motor pulley tooth count until the tension was reasonable (just going from 21 tooth to 18 tooth in one try was enough).

This worked….. a little. Roll Cake’s movement was still extremely strained. There was no binding of the drivetrain anywhere I could see, just that there’s too many moving things for the 22:1 Fingertech motors. It moved slowly and quite arduously, and still could not turn.

Well, there wasn’t much else I could do to alleviate this problem except swap to the 33:1 gearmotors which I was able to pick up day-of MicroBattles from Mike Jeffries. Before the event started, I went ahead and did the motor transplant.

Operating sheets and all! This was so I didn’t get any abrasive/metallic grunge into the bot while cutting down the motor shafts.

The end result? I got Roll Cake to move somewhat reliably on the floor, so I went ahead and decided to put it in its first match anyway…. against Kurtis’ Black Adder.

Dammit, Kurtis.

Unfortunately, in the arena, it moved all of 18 inches or so before farting out again. It at least managed to flip Black Adder over with a chance collision. At this point, I stopped caring, since watching the mechanism test fire was more important to me than the rest of the bot, so I just kept flapping until the end.

Poor Roll Cake. It had such a bright future.

 

Okay, not really.

So the flipper mechanism kept working up until the end, even though I technically never got a direct shot at Black Adder.

That’s okay – I’m already out to rebuild this thing correctly such that it’s mobile. Roll Cake 2 will just have two brushless gimbal motors for drive, as hub motors, with the same Afro30 SimonK-enabled controllers driving them. It will have 2 larger wheels up front like a classic drumbot, not this 6WD business. Since Stance Stance Revolution could basically drive upside-down on its two discs, I’m much more confident in this setup working.

So that’s it for Roll Cake. Now back to your regularly scheduled Überclocker:

In the same work session as finishing out Roll Cake, I assembled all of the modules within Überclocker – the actuator, both drive motors, wheels, and the DeWut for the liftgear.

On Sunday afternoon, I returned to Dale’s shop to make a mess one more time. This time, to carve out the giant pocket that is in the back frame rail, formerly solid 6061 aluminum. Final weight estimates showed that I did need around 1.2 pounds out of the frame rail, so I calculated the pocket size needed, gave it some more oversize for weight tolerances, and went to town.

The next operation in Dale’s shop was putting some pilot holes into the end-tapped frame rails. I figured I could run with 1 bolt in each frame rail for now, and then drill them later once I had access again to a large drill press back at Artisan’s Asylum or MIT.  This let me put most of the frame together on Sunday evening.

After I went back home, I did what I could using the remains of my high school workbench, which contained a small 10″ drill press, hand drill, and jigsaw, plus the hand tools and cordless tools I brought down, and a few kibbles of tooling that I didn’t take up to Boston with me originally.

The above was…. basically all that I could do. Mount the shaft collar to the big lift gear using a counterbore I brought. I didn’t even have any clamps left, and by the time I got back home, all of the hardware stores and home improvement stores were closed for Sunday night. I tried drilling and tapping a few of the frame screws by hand, which was an arduous procedure. I basically called it quits around 6AM Monday after trying to work on putting it together all night, and not getting much further than 10 or so drilled holes.

Basically the most important part of having tools is having consistent tools. Maybe these tools were enough for me during high school, but I also built bots in completely different ways to accommodate them (e.g. making things from UHMW plastic). Designing for tools that are not consistently available, or totally unavailable, will just end in disappointment. I realized no matter what, I could only hack Clocker so far in the remnants of my parents’ garage if it depended on a full service shop to be put together.

So here is the assembled husk of Clocker 4 next Overhaul at Robot Battles on Monday, showing what could have been if I didn’t kick my own ass… or as Will Bales puts it, Will Balesing.

By the way, shoutouts to Matt and Dan of Chaos Corps for taking the pieces of the pontoons from me on Friday and returning them completely welded on Saturday. Not just welded, but all ground and wire brushed. I owe you guys a small water balloon filled with argon!

But wait! The story doesn’t end there!

I also brought 12 O’Clocker along, figuring that I’d be able to run something in the Monday event at least. 12 O’Clocker was working fine after Momocon, so I basically packed it right back up with some spare motors. The clamp motor on it was a little baked, so I reached out to the group for spare Kitbots/1000rpm-style motors.

It actually got a few matches in and entertained the audience immensely.

In the rumble, the lift sprocket got bent hard enough to pop the lift chain off. Otherwise, 12 O’Clocker takes no damage once again! Gosh, maybe I should just scale this thing UP instead of Overhaul DOWN, right?

So no prizes this year, and not a very good Dragon Con for robots. I’m going to continue finishing Clocker 4 in the interest of Franklin Institute Robot Conflict 2016, where I hopefully will get to play with some of the big energy bots. I never had a strategy for Overhaul against vertical weapons like drums and discs (e.g. Hypershock, Witch Doctor) – besides Don’t Get Owned, I mean. I hope the Featherweight class, which is full of vertical spinners, will let me fine tune how to approach bots like that better for #season3.

By the way, there was a trip to the new Atlanta McMaster-Carr warehouse to pick up last-minute hardware. This place is

…kinda big.

Okay, REALLY REALLY BIG. Douglasville and the surrounding west Atlanta area is kind of a new target for development, and besides industrial plazas and The McMastergon, there were plenty of housing developments. What could be better than stumbling out of bed and over to Will-Call to pick up your last night’s blurrily-assembled orders? Or hell, just wheel the robot over and work on it in the Will Call parking lot. It’s like working on your shitty car in an Advance Auto Parts parking lot! Who the hell’s ever done that… not me! Nope, never.

So wait… wasn’t there an ENTIRE CONVENTION going on besides just me working on robots? Absolutely… so let’s see how that went.

As usual, I’m too lazy to put together a worthwhile costume, so I went lazily all days as “me”. Just the Overhaul team shirt, and also wearing the Axent Wear headphones around.

I got stopped way more times than I expected.

Shown above is the crew of Jamison, Cynthia, Hannalin, and Lucy, formerly all of JACD last season. This year’s group is Overwatch. Overwatch is a video game. I haven’t played a video game with any degree of seriousness since Descent II Vertigo. I assume this is all legit. Wait until you see the construction Cynthia put into the giant bow…

There was a massive Overwatch photo gathering which took us an hour or more to get out of. Pictured above in the group are Pizoobie and Bonnie.

I generally haunt costumes which have had a lot of work put into them, especially very large and unwieldy ones. I swear at some point I will make an overly complex and elaborate costume. You could argue that Overhaul is in fact such a prop.

This was cool, too. These guys were cruisingly slowly around the convention. P I P E S

Okay, I don’t even know what’s going on any more. Overwatch players, I assume this is something you’d understand.

Alright, I usually don’t give a spare minute for Kantai Collection because it’s utterly destroyed my favorite genre. But I will make exceptions for well done ones. Behold, the U.S.S. Iowa.  I watched her being “assembled” on the spot, and before that, I followed the ant trail of battleship parts being carried high overhead down the packed street by her pit crew. Her drydock workers?

Good ol’ Kancolle, ruining “girls & machinery” since 2013.

If you know who this U.S.S Iowa is, let me know and I will gladly add links and creedits.

Now here’s how to properly do it. Besides Overwatch, Cynthia, Lucy and Hanna also teamed up for something else. Shamelessly stolen from the BattleBots Instagram, it’s….

BattleBots cosplay at @dragoncon with Lucy, Hanna and Cynthia. Zachary Ernst

A photo posted by BattleBots (@battlebots) on

I’m telling you all, #season3 will be one big weeb convention. Everything is falling into place, exactly according to keikaku. Cynthia is the designer of Haru-Chan, so it was only natural that she also sketched up plans for Sawblaze and Road Rash.

Now for the event recap!

MicroBattles this year was bigger than ever. With the insect classes (1s and 3s) being the easiest and cheapest to start in, the newbie and first timer proportion this year was immense. We ended up getting over 40 robots!

Sadly I actually missed a lot of the action getting Roll Cake prepared, but here are some of my favorites.

Here we have the wild Killer Colsonbot, which is believed to have evolved from escaped Domestic Colsonbots.

That’s Pvt. Slicer, or what happens when Mike gets ahold of the Colsonbot CAD. The cage is made of layers of waterjet-cut 4130 steel carefully welded together. It had friction drive reliability issues, but it somehow won 2 matches as round pushybot. When the cage met a vertical spinner, it died.

Representing the “meh” department of Dale’s Homemade Robots, this is Noodles, a 4wd pushybot. Besides all brushless drive, steering gyro, and a crafty urethane-sheet-mounted steel plow, it has pool noodle wheels which caused a bit of controversy because in the final a piece of them came off and jammed Black Adder’s drum.

Now, unintentional entanglement is allowed in the rules for the precise reason of a part inadvertantly coming off and getting stuck in something (as opposed to intentionally throwing things into a weapon to jam it), but there was still a fair bit of “Who do you think won this match?” talk.  I actually think repeatedly hitting the ceiling against Black Adder and coming back each time is a mark against the effectiveness of Black Adder’s weapon in this match.

It’s big bot time! After being forced to run 12 O’Clocker only, I had more time to go around and appreciate the 12s and 30s. The newbie count was great at this event also – I think probably 25% first or second events.

Pictured above, The Magical Lipo-Fire or…. something or other. The build looked great! Sadly only one match however, and fortunately did not live up to its name.

First time 30lb entry “STICK A FORK IN IT!” which was having some DeWut clutch issues this event. Hey, people, read the manual! Tighten down your DeWut clutches before using!

Team JACD Season 1  principal cheerleader Andrew brings Pusheen-Bot, a pushy-bot. It’s laser-cut out of wood, so naturally it faced a chainsaw first match.  This thing actually has two 50mm outrunners in it. It’s basically BurnoutChibi in a 30lb bot, so-illustrated by Andrew riding the bot around the room before (and during…) the event.

Another new 30lber with some heavy inspiration from Clocker and megaRon (under whichever moniker Jamison decides to run it at Robot Battles…)

There were obviously a lot of bots that I skipped, and you kind of get the idea. With the return of BattleBots to a mass audience, so the hobby grows! Robot Battles, fortunately, is one of the lowest barriers-to-entry competitions there is.

12 O’Clocker all set up and with spare clamp motor installed, ready for its first match. I had immense fun in its match with Dingleframus – it was the hardest physical driving match I’ve had in a little while, and in the end, a missed charge basically caused it to hover off the stage.

Here’s “Metric Brushless Hipster 12 O’Clocker” LiftLord, a Xo creation but shown with optional interchangeable Aaron module.

12 O’Clocker ready for its first match against Abrasive Personality, a design I really want to see more of – it has a belt sander running the length of the bot, with a backstop and all. I think this kind of design needs exploring. Putting more horsepower behind it and using a super gritty belt might actually result in some serious unconventional damage.

So what the hell are those blue things on the stage that have been appearing in every video so far?

They’re my secret weapon: 3D printed model set screws. I printed about a dozen, then another dozen or so followed me to Atlanta courtesy of RocketProps. Some local folks contributed a few more…. and suddenly, a stage full of giant set screws. Robot Battles: serious business since 1967 or whatever.

Not sure what I was doing here – probably double checking the chain drive after the rumble where it was derailed due to the main sprocket being physically bent. 12 o’clocker went 1/1 plus hanging around during the rumble, which was hugely entertaining.

Well look who’s on display!  I’m told that Witch Doctor & Hypershock were also going to be present. Lies! I didn’t see any of y’all this whole weekend, so Overhaul had to have all the fans to itself. Such a sad day.

That’s a wrap for Dragon Con 2016. Once again, I’m staying a few days extra in Atlanta, and will diffuse back up north some time this week. On deck for robot work is finishing Clocker and a quick revamp of Roll Cake before FI in about 1 month. Otherwise, I’ll be hopefully creating more problems for myself with van work soon, since I want to re-winterize a few spots before things get cold (e.g. in 2 months or so). Some of my earliest rust repair is starting to come apart finally, and I have better weaponry against it now. Further down the line is word about # s e a s o n 3 and starting Overhaul….overhaul…. work in earnest. This will ideally occur over the coming winter.

 aaayyyy