All Good (And Poorly-Maintained) Things Must Come To An End: The Great Project Purge of 2012

i swear to god i will fix this later

At some point, I need to stop telling myself that. It’s well known that my stuff isn’t exactly world-class in terms of reliability and Six Sigma class in quality, but even I can get sick enough of it to declare it a loss and start over. Over the past few months (and years) of neglect, quite a few of the robots and silly vehicles have become damaged and non-operational. I kept Swearing That I’ll Fix It Soon, Guys, but my shelf of stuff is long past overflowing with parts and project detritus and some of them contain good parts that I don’t want to keep buying. With my general shift of operations towards the newly opened IDC space just up the Z-axis from MITERS, tearing down some of the old derelicts and returning their parts to the Earth (/my storage bins) became more appealing – especially as I started collecting more stuff, most of it landing on my fresh new corner desk.

So it is with great sadness (and hidden catharsis) that I must announce the decomissioning of…

Cold Arbor

Cold Arbor never really worked – the frame was too flexible to accommodate the huge teeth of the saw. After Motorama 2010 and Dragon*Con’s Robot Battles ’10, CA pretty much only ventured off my shelf for the occasional demo – it illustrated, visually, what a “combat robot” was very well. Pretty much everyone’s first reaction at the word “Battlebot” is “You should put a saw on it to cut through the other robot!”, and CA is…. well, pretty much a saw. It never really stopped driving, but then the saw actuator broke so it couldn’t do the extending thing any more. Arbor, being the biggest lead weight I had on my shelf, was therefore the first to go.

But before I tore it totally down, I decided to use it still-functional and very smooth drive base as a test dummy.

Last year in the Austrailian robot fighting circle (did you know that Australia has a very active robot combat scene too?), one of the builders began to modify Hobbyking brushless controllers to act as H-bridges for DC drive motors, utilizing 2 of the 3 half-bridges available on the average BLDC controller. I’ve been advocating something like this for a while – use the cheap hardware base that is Chinese brushless motor controllers instead of custom-developing an expensive niche robot controller solution. The choices in robot controllers these days are either said niche and expensive but generally reliable controllers, or these one-tiny-FET-per-leg overfeatured doodads that I’ve literally had zero success rate with. Or you straight build your own and have them work, but I’ve also not successfully managed that yet. There’s nothing on the market right now which is just a bucket of large FETs like the old Victor 883s (which you can still buy, but they’re now a design so old it can almost drive).

That aside, I have also never bothered to schematic-trace the brushless ESC boards or learn & put up with enough raw Atmel C to reflash the microcontrollers (though I suppose I could have flashed Arduino onto them…). So, a ton of hot air rage on my end, but lots of action in the 40+page thread over on the Robowars forum, which has seen all of the cheap common ESCs reverse engineered and firmware implemented for – up to and including its own confusing beepy configuration menu.

They’ve now started selling them (when I say ‘they’, I really mean like one dude), and I took the chance to get some modified “85A” units based off this Hobbyking ESC.

First, I had to remove most of Arbor’s existing electronics. Okay, so my success rate with the Sabertooth controllers isn’t zero – Arbor runs two of the closely related SyRen controllers, but $75 for 25 amps is stupid these days, and I’m also royally undersizing their loads – one is running a little Speed 400 class motor and the other is running a drill type 550 motor which sees about a 10% duty cycle on raising and lowering the saw.

Way cleaner wiring and layout with the ESCheap85 in – I could easily see a robot with a whole rack of these next to eachother. The massive spam of SMT FETs technique used to great success by cheap Chinese controllers is an acceptable compromise, in  my opinion, between one-tiny-SMT-FET per leg used by the Sabertooth and Roboclaw and other most-likely-designed-by-newly-graduated-college-students controllers, and the one-huge-nice-FET approach I usually take. It keeps the board size down, too.

After hooking this up, Arbor was taken on several somewhat strenuous (and absurd) test drives.

None of it was very scientific, nor was there really enough space to seriously stress the bot out. I’m going to have to use these in battle myself before I’m fully sold on the idea, but based on the reports of the substantial number of Australian users, they’re pretty bulletproof, and a few American users have already run 18v DeWalt drills in drivetrains using them (the same motors that Clocker uses). The 85A type has been praised as a “Victor replacement”, but its more limited voltage range (30V fets and 35v capacitors) doesn’t quite convince me it can be swapped directly into a native 24v (up to 28v fully charged and more during dynamic braking) system. I fully agree with the concept, though, and for about $1 per amp I don’t have any complaints past my own reservations.

That doesn’t mean I’m no longer going to attempt my own controllers – I have yet to successfully execute a small current-controlled vehicle H-bridge, of which robot controller is a simpler subset. But that’s for another post.

At the end of it all, here’s Arbor mid-scrapping:

Scrapping is such a negative word. It took me a while to crack open that weapon drive gearbox, since I sealed it up so well at the start – and some of the bolts were bent.

Here’s everything I ended up keeping from Arbor. All of the motors, pretty much all of the drive mechanics (especially those delicious custom gearboxes, which were one of my first good ones), and of course the saw and worm drive in case I rebuild it all. The VictorHVs and Sabertooth controllers were also kept and filed in my robot controllers bin.

prospect for rebuilding: slim

Arbor was a very complicated robot with lots of moving parts – it’s something which is more difficult to get right, and it’s usually more disappointing (to watch as well as to operate) when it doesn’t work. Arbor’s build was rather rushed and many details weren’t completely thought out. I’m more likely to build a 30lb bot that is either more plainly functional or spend alot more time to build a complex but well-designed and tested robot before trying to compete with it.

Going down the line, next I pulled out…

nuclear kitten 5

NK5 was heavily damaged last Robot Battles, and ever since then has been sitting on the shelf. However, the disc motor still works great – and I can make spare discs, so that’s definitely being reused on something. The controllers and motors were also potential salvage items.

NK5 was the last robot I built before I converted fully over to “T-nut” style construction, visible in pretty much all my stuff from 2009 onwards. The design actually dates from late 2008 – my first major t-nutted endeavor was the ill-fated 2.007 robot. The frame has these wonderful corner bars that I machined for this application, but it seems like now you can buy everywhere. I really liked these, so I went ahead and saved them. Tapping into real metal is way better than t-nuts at any rate.

Here’s NK’s remnants pile. The frame materials were just not worth keeping, but I kept the motors – the gearboxes are not stripped, but one of the pinions fell off (but is intact). They might become donor parts for future gearboxes. I am a fan of these little 25mm metal gearboxen: while they are not planetary, they’re big and chunky inside to make up for it, and fairly cheap at $10-15 each.

prospect for rebuilding: hell yeah

I can’t guarantee when, but D*C 2012 is likely because I pretty much have everything-minus-frame. The disc is up for some revision, though. Big tall vertical disc spinners are no longer in vogue, being replaced by small, low bricky drum things with built-in motors (of which there are now like 50).

Next up is my pride and joy,

test bot 4.5 MCE

Really? The bot that made it to real-deal-Battlebots-IQ, then Motorama 2008 and back? The first thing I ever worked on at MITERS? Yep, since its default parking spot since Moto 2008 has been in Clocker’s lifter when it’s not doing other things.

TB certainly has the most grime of any of the bots, and the lifter was pretty much utterly trashed – it took a direct from the vertical disc bot Igoo at Motorama 2008 (that video is slightly painful to watch).

This is one of my first drill motor hacks. I did a few in 2006 for the original TB version 4, but they were either terrible or dismantled very quickly. This thing predates my entire website, pretty much. The extension shaft with the pinion was added when I redesigned the lifter for Moto 2008. It had an additional outboard support, but since it was made of UHMW, the whole gearbox still flexed too much to keep the gears in mesh, and so the pinion stripped very quickly in battle.

After I took the damaged arm parts off, I realized that TB’s drive base was actually in very good mechanical shape. I still love those gearboxes, too: they are super special 12:1 drill box hacks that I made with mating the salvaged 18 tooth planet gear and 9 tooth pinion gear of the first stage of a drill motor with an intact output stage. Coupled with the extremely overvolted 9.6v drill motors, this made the bot have a rather zippy top speed of 14mph. The first version of this gearbox predates the website (again) – this version at least had the luck of being milled, so things actually lined up!

I briefly entertained throwing the BotBitz ESCs in the frame just to drive it around again, but decided against it for the time being. It’s sure been a long time since I’ve had a 4WD drill-powered box.

So I closed it right back up again. Only the damaged arm and wedge parts were scrapped – otherwise, I think I can put something interesting in this bot again, or at least give it a better sendoff at a serious combat event later on, as the most honorable fate for a combat bot is still, in my opinion, being thoroughly vaporized into a cloud of small particles.

prospect for rebuilding: not for Robot Battles

TB4’s design was optimized for “arena” combat which has more guaranteed smooth floors and a more pressing need for huge, thick angled armor. The RB stage is purposefully left fallow to discourage pure wedges – a passive aggressive attempt at encouraging more robot creativity, which I contend has been successful in the past few years even though it kind of locks me out from competing in 12lbers again there with this design. Maybe Motorama 2013….

Finally, a project that I hate to see get tossed so early, but…

razer revolution

It’s lived a decadent life of being a demo attention whore as well as occasionally coming in handy when Melonscooter was on blocks, and has seen 4 different motor controllers (Double DEC’er, Melontroller, Tinytroller, and Jasontroller!), but recently RazEr Rev has become kind of a wreck.

I donated the front end to another MITERS scooter effort after the new battery got 2 dead cells after only a few weeks – definitely a case of bad initial conditions. Since then, it’s been sort of chilling in a corner, slowly being eroded away by the tides of cruft and dead power supplies that ebbs and floes around the shop.

The Jasontroller works great, the battery can be surgically corrected (I’m literally going to scalpel/X-acto knife the dead cells out and make it into a 10S pack), and the Dual Non-Interleaved Razermotor is a little rattly in the bearings but otherwise functional.

So that’s pretty much all I kept. Oh, and the extra heavy duty generation 2 Razor handlebar, after they moved away from welded-to-frame folding joint but before cost cutting made the joint like 24 gauge steel. This front hinge is massive – the steel is something like 0.13″ thick.

The reason I decided to scrap RREV now is because I’ve become dissatisfied with the frame design. It uses a design which I now consider inferior to other similar scooters in the way it’s put together. Starting over with the frame will be a great way to optimize the design towards less material use (like giant plates of 1/4″ aluminum) and make it simpler to assemble in addition to making dedicated space for the battery and Jasontroller, both of which were “aftermarket” additions. It should end up lighter for the same performance, but I don’t see it getting any smaller. Sorry Jamo, but Razor Wind is a little on the small side for my tastes now.

All this talk of what I’m gonna do means the

prospect for rebuilding: immediate

I already ordered some more giant aluminum plates (…sigh) and will probably be redesigning the frame this week. I’ve already got the changes planned out – they’ll just need execution. Like NK5, it will just be a matter of moving old parts over to a new chassis – there’s otherwise not much about RREV that I’m unhappy about. It’s definitely going to get a stock fender.

other stuff

I didn’t take any pictures, but all the Chuckranoplans have been parted out and recycled too. I’m probably not going to be touching this for a while until I stop being afraid of foam so I can build meaningful scale models. 3D printer models were fun for design practice, but are too heavy to work.

Alright, now that I’ve eaten half my offspring, I can start considering rebirthing them again!

Dragon*Con 2010: The Real Wrapup…Finally.

hey charles, don’t you owe all of us a dragon*con 2010 event report or something?

Yeah, yeah. The beginning of term, lack of motivation, and the lackluster (but entertaining) run of the robots at Robot Battles meant that I just Haven’t Gotten Around to writing up D*C2010. But I seem to be on a streak of making up for missed writing assignments this week with all the site updates, so… here we go.

Welcome to Dragon*Con. If you missed my description of it last year, don’t worry. It hasn’t changed a bit. The atmosphere is still as eclectic as ever, and the crowds just as dense. Actually, they were probably denser. D*C is one of the biggest conventions in the continental United States.

But I’m not a fan enough of anything to really enjoy the con for most of its con…tent. So let’s move onto the robots.

Also, I like girls with big guns.

Right. Anyways, robots.

Like last year (and years past), Southern Polytechnic rolled out their VEX robotics kits and sponsored an open build-off on Saturday. The participation was pretty intense, with young children showing up strongly. At the end, there was a ball-gathering competition.

sunday sunday sunday

Time to stop diddling. The “Microbattles” event is held on Sunday, before the big competition. NK hasn’t been here since 2008… in fact, when this version was first built.  So NK is running 2 years behind the development curve. How have its opponents evolved since then?


The robot caliber this year is seriously advanced compared to years past – alot of it, in my opinion, due to the fact that the other Southeastern builders that I used to smash robots with have also now advanced to college machine shops and have become spoiled like me.

I mean, except Thomas up there, who’s just magic.

Cake, from the Georgia Tech crew – another one of the high-caliber machined and fabricated bots.

On the other end of the spectrum are things like this, which are built by people who are just out to have some fun and entertain the crowd.

Speaking of the crowd…

The Robot Battles events seem to always have outstanding attendance no matter what. The International ballroom has a seating capacity of several hundred (the exact number escapes me). At several points during the event, it was standing room only in the back of the room. And at least once, who I can only presume was the Hyatt Regency’s fire code liaison came booming over the room intercom instructing everyone who was standing to leave.

Disappointing, but oh well.

NK made a run through the tournament bracket before being Caked in the winner’s bracket finals. Cake, being a lower hitter, won every collision. I originally was going to forfeit any matches involving the high-energy weapon bots since I was more interested in maintaining NK’s operational status, but hell, it was the finals.

So I went for it. Overall, NK came out pretty undamaged for the amount of ass-kicking Cake dished out throughout the tournament.  No prizes this year, but the finals match was stunning.

Here’s NK’s highlights for the Microbattles tournament.

clocker and arbor

The day after was the big robot tournament.

Dragon Con is my annual robot party, since it’s precisely at the end of summer and represents the last bit of fun I’m allowed to have before flying back for the academic term. So I spend all summer building or upgrading the robots, among other activities, and bash it all up at the end.

This year, I brought both Arbor and Clocker. It’s been a while since I’ve run a 2-robot tournament, but with Robot Battle’s more laid back atmosphere, it wasn’t nearly as stressful as Motorama. In fact, I rather liked it.

Most of the usual suspects were back, with hacks, mods, and upgrades aplenty. Here’s (Big Blue Saw Presents) Jaws. Also back in the mix was Dale, Evil Robotics, MH, Found Objects, and others.

But this year also saw quite a few newcomers. The Armed Robotic Critters, for one, came with a whole fleet of critter-themed 12lb and 30lbers. Overall, attendance this year was back above pre-2009 levels. 2009 was sort of a bad year for the competition due to several builders having to skip the competition.

Then you have Sporkinok.

Really it’s not even an antweight, but Seth brought it (and a 12lber) anyway. Just for Grins and Chuckles™.

Only at Robot Battles…

….does this kind of stuff happen. You know what’s really hard to catch when you’re a 12 pound robot? A 1 pound robot.

I really can’t say enough about the level of audience energy at Robot Battles. The Regency 6 and 7 ballrooms combined sat over 1000 people….and again, during the event, was reduced to standing room only. The event also encourages the audienec to participate by helping start, end, and occasionally judge matches.

Yeah – you don’t come here for SRS BIDNESS TERNAMINT. You come here to put on a show.

Clocker did great for a while, but then immediately suffered another left-side drive failure. What the hell?

A quick examination revealed that the left gearbox output shaft was poorly assembled (read: did not press hard enough) and slipped its interference fit. Now, what was really weird was that shifting the whole shaft axially some times caused it to re-engage just enough to give the robot differential traction. So Clocker ran sporadically, but was crippled at other times. When the drive disengaged, I just threw on a Zip Tie Ratchet.

Here’s Clocker’s highlights video from the competition. I managed to execute another Robocopter spin with Jaws around a minute and some in.

That’s the move I designed Clocker to perform, and it did so admirably. Unfortunately, the clamp motor was unresponsive, so I couldn’t throw Jaws off the stage. As close as it turned out to the camera guys, this was probably for the better.

Oh, Cold Arbor.

As nice as the upgrades I made were, it still didn’t stop the saw from just catching and binding. I pretty much expected that to happen again, since this milling blade was made for multi-ton machines – not a 30 pound robot. Arbor was visually very impressive and garnered alot of audience applause, but ultimately it suffered two losses because it just couldn’t do anything.

If Arbor is to be actually competitive, I’d have to rethink the whole concept of the robot. Right now, it comes down to an issue of severe uncurable positive feedback – the forces of cutting are squarely directed into jamming the saw further into anything it contacts.

If you observe a regular cold saw or even power miter saw in action, you’d notice the saw’s swing is more vertical than horizontal. In other words, the tangential force of cutting is directed perpendicular (or nearly so) to the direction of saw motion.

Arbor’s movement is very horizontal – made even worse by pivoting the saw at the base of the robot. Therefore, the force of cutting is directed downwards and back into the robot, which is the same force vector I’d generate by cranking downwards on the saw with a pry bar. The net result is that any impact of the blade has to be compensated with massive torque inputs – realistically, more than the worm gear output can probably handle or anything short of an Etek can generate.


Neither a win, nor a fail. I went to the event to put on a show (since there’s really nothing to win), and I think the bots did that just fine. I’m still keen on the concept of an actual working saw bot, however, so don’t expect Arbor to just disappear into MITERS. It will be rethought (possibly while I make sure Clocker’s gearboxes don’t let loose ever again, EVER).

Dragon*Con 2010: It’s a wrap

cold arbor

First, I would like to say that I finished Ninjabridge.

It looks like this:

Yup. Back to a relay.

Ninjabridge worked briefly after extensive noise-reduction and ground loop prevention surgery. Sadly enough, it suffered a gate drive failure and subsequent Epic Shoot-Through at almost full saw speed. Nothing was particularly happy.

And so with the sun rising yet again, I pitched together this 12v SPDT relay assembly. It’s triggered by the previously mentioned R/C switch.

At least the saw works. Some more drive testing confirmed that my fears about the saw’s startup and running current pulling down the entire system were unfounded. Here’s a video of Arbor nibbling on some wood.

And a “pre-event” picture (not that D*C is a destructive enough event to warrant it, but hey.)


After putting all the screws on Arbor, I turned my attention back to Clocker to address one last detail that hasn’t proven fatal, but isn’t very healthy to ignore.

The bot’s drive chains have been getting increasingly looser as matches passed. The left side, in fact, has become so loose that the chain hits the ground on the bottom side of the frame. This is just begging to get snagged on something, or to make the chain walk right off the sprocket.

I’ve been meaning to put a chain tensioner on the drive since I built the bot, but never got around to it until now. The tensioner is just some simple bits of milled Delrin that has holes for perpendicularly tapped screws. I freehanded the vertical holes with a cordless drill, which brought back memories of before I was saved from a life of meager tools and hand fabrication. It was a heartwarming moment.

With the tensioners, the drive is substantially quieter. I would also venture as far as to say the bot is a little more responsive, too, since before the tensioners, the front wheels could spin 30 or more degrees before engaging.

If the chains ever get looser (Robot Jesus forbid) the Delrin sections can be milled more to compensate.

So now it’s time for a Clocker photo – I cheated a bit here, and actually took the picture before adding the tensioners.

And an everyone shot:


No, not that boxxy.

This year, I’m going to be shipping down the bots ahead of time – which really explains why I’m working on them now and not, say, next weekend. Last year, taking Überclocker and support equipment as baggage cost me a cool $90 or so for overweight, oversize, over-the-top baggage fees. For essentially the same price, courier services will ground-ship an excessively large “package” from here to Atlanta in about 3 to 4 days.

Now, I’m defining “package” as “giant 2-foot wooden cube weighing 135 pounds and loaded with two (and a tenth) deathbots”, which might be stretching the definition some. But here’s the wooden box.

It’s made of some cheap Home Depot plywood (the same plywood, in fact, that Arbor was nibbling on. That panel became the bottom.

This time, I have enough overhead such that I’m actually bringing SPARE PARTS.

The bots go out in several hours and will hopefully arrive Thursday…

Nuclear Kitten 5.1: Start to Finish

Something that very few people (myself included) have seen is the inside of NK’s weapon motor. About the time I built it in 2008, my camera decided to consume itself. So all I had from that time were grainy cell phone pictures because I’m compulsed to post build reports, but those pictures didn’t really show anything worthwhile.

NK’s motor was the third hub motor that I’ve ever built, period (after the original RazEr motor and the second iteration). It is also hands-down the most cleanest wound and carefully terminated motor I’ve built. This was back when I actually had patience for making motors. All the winding layers are clean and the termination is perfectly symmetric like a LRK should be.

After this, it all went to hell because I just stopped caring about how neat my motors looked… or even how concentric and wobble-free the cases were because it was fine as long as it could MOVE, dammit.

In International Crazy R/C Airplane Guy Notation, this motor is a 5205-14D. 52mm diamter stator, 5mm stack, and wound 14 turns per tooth in Delta termination.

I bought replacement magnets from Superdupermagnetgeorge to fill back in the 25% or so of the rotor that had become detached. The original magnets appeared to have been retained solely by superglue.

That’s kind of not legit at all.

In recent days, MITERS was given several large jugs of epoxy and hardener. While cleaning out a back shelf for the new EPOXY section, I found alot more adhesive accessories from years ago. Of most immediate interest was several cans of epoxy filler in different flavors in types. There was a can of West System 403 fiberglass-based filler, a bucket of phenolic microspheres, and wood flour.

I decided to do something that every other custom motor builder seems to do – fill in all the gaps and seams in the magnet ring with some hybrid epoxy. Adding filler gives the glue volume and more bonding area to the magnets. The fiberglass-based filler came out rough and lumpy, so I tried mixing up a cup of phenolic microballoon epoxy. It came out looking sort of like epoxy-flavored Nutella.

Now those magnets shouldn’t be going ANYWHERE.

weapon pod pivot

One of the gimpiest parts of NK5 is the weapon pod’s rear pivot. The disc is mounted on an assembly that can swing up and down, letting the bot drive inverted if necessary. The issue is that I made the last pivot in like 5 minutes. It was just a piece of sandpaper-cleaned Home Depot aluminum tubing and some roughly cut spacers. It flexed all over the place, and by the time D*C2008 was over, the tubing had crumpled from the impacts.

This was inexcusable. And so, in the middle of the night, I hopped on the lathe and just started making something. Above is the first 100% designed on the fly part I’ve made in a very long time. On one end, a snap ring groove. And on the other side, a 1/2″-28 thread machined so a thin panel nut can thread onto it. It basically functions as a very complicated but specialized bolt, holding the two halves of the bot together with some preload.

Originally I had intended to pick a random snap ring from the hardware bin, but a bit of digging around located me these weird e-clip-like things. A bit of research on McMaster showed me that they’re called “poodle rings”, presumably because of the big ears.

They had a much large diameter and thus potential contact area, so I remachined the groove slightly to fit them.

I also recut the UHMW spacers (using the same stick of UHMW) so they fit better and were also much large in diameter. The larger in diameter they are, the better they can resist side forces.

The old disc was warped from NK faceplanting into the steel arena bumper at full throttle. As a result, I dug out the spare disc I cut in 2008 and gave it the heat-to-orange-and-dump-in-oil treatment. It’s a crude method of heat treating, but it gives decent hardness for 4130 in bulk (don’t try this with a tube frame…) Afterwards, I reassembled the weapon motor and gave the teeth a touch up on the grinder.

With the important part of the robot done again, I begin refilling the internals. Pictured is the 1.3Ah Li battery I bought as a replacement for the old 2008 battery, now featuring a very dead cell. I actually got two because they’re too cheap for their own good.

And here’s the beauty shot:

While I had the lid open, I added a green LED next to the blue. Because funky colors are totally a priority.

NK handles just as well as I remember it from 2008. The right side drive motor is making some weird noises, but it doesn’t skip or feel crunchy. Regardless, I should probably get some replacement motors and have them dropped in Atlanta for next week.

Total robots finished: 2.999999999996842178 / 3

Dragon*Con 2010: Überclocker is Done, Cold Arbor in the Mix, and the Nuclear Kitten 5.1 Blitz

In 2008, I had a Pre-Dragon*Con Botgasm. Last year, with only Überclocker, I didn’t have enough robots on deck to be finished in order to properly botgasm. Therefore, this year, I’m going to have to make up for it with now three bots that need completion!

Well, let me interrupt myself before I even start: Überclocker is done. I closed the bot up (well, minus battery cover, which I physically lost some time in the past 6 months) this afternoon and have been driving it around relentlessly trying to uncover hidden driveline mechanical flaws that could come and bite me in two weeks.  With Clocker asymptotically functional, I set it back up on the shelf and am now turning my attention to Cold Arbor…and a a revival of the Nuclear Kitten.


Two days ago, I left the FrankenWalt gearboxes about 95% finished. I made both gear cases, both sets of ring gears, both motor mounting plates, even both output stub-shafts… but only one output spindle. I just didn’t feel like machining the teeth off another gear that night.

But I returned later, having re-educated myself on the importance of finishing robots, and attacked that last remaining part.

Now here’s the reassembled drive base of the robot. I essentially took apart the entire outer metal structure, cleaned everything, then put it back together with the motors in place. Significant amounts of dirt, arena grunge, and metal chunks and flakes (!) made it into the corners of the robot, so as long as I had it in the open, I might as well clean it all out.

The outer chains have experienced some pretty serious stretching, and I expect that I’lll need to make a tensioner for them soon, lest they snag on something.

A couple more screw later, and the fork structure is remounted. While I had the fork apart, I took the time to make a few minor tune-ups and adjustments; mostly line items on the laundry list of upgrades that I keep intending to do (since they would technically take little time), but never get off my ass to do so. Such as:

…grinding the tips off the fork shaft set screws. These were formerly normal cup-pointed set screws, but I was dissatisfied with the way the cup point was gouging and digging into the flat on the (relatively) soft aluminum lifter shaft.

One way to resolve this is to just make a more legitimate power transmission medium, such as a keyed hub. But we can’t have that, since I’m lazy and therefore always vigilant for hackarounds. To obtain a wider contact surface with the aluminum shaft, I ground the tips off. Now, the contact circle is much closer to the 1/2″ screw diameter.

It won’t prevent gouging, but it should increase the shock torque handling ability of the fork a little more.

I kept the electronic bays intact, so dropping the Victors back in was a quick job. Since most of the wiring was on connectors, I didn’t have to rewire much from scratch.

Bonus: There is something very, very bad in the above picture. First one to name it wins….

… something. For what it’s worth, I fixed it.

A quick power-on confirms that the system is still functional.

Well, functional to the degree that I somehow managed to solder both drive motors in backwards.

Oh yeah – also on the list of stupid hacks I never get to is rearranging the actuator layout of the robot. Historically, Clocker has ran with the clamp actuator slung under the clamp arm itself. This location protected the motor itself from direct impact from opponents and also made the wiring path simple.

However, it severely constrained how far up the clamp could move, because the way the linkage is set up, the motor would just back itself into the aluminum fork hubs. This essentially limited Clocker to gripping opponents less than 8 inches tall.

I’ve toyed with the idea of flipping the actuator around so the motor is mounted above the clamp. This arrangement gains the bot another 2 or 3 inches of “grip” and also helps the leadscrew clear the truss that forms the forward portion of the clamp arm, which means the clamp can close to just over 1″ gap.

The only downside is that the motor is now open to damage. I’ll make an aluminum plate cover for it or something, but I think I’ll keep this setup.

All of this said and done, here’s some test driving video of Clocker, chasing Twitch, Jr. Everything goes well until the robots collide head on.

Hint: The robot that weighs three times as much and is essentially an uparmored Humvee in terms of structural durability fared better. Sorry Twitch :<

However, test driving revealed a critical flaw in the right side FrankenWalt – the first one I made. When I hard reverse planted Clocker into a corner, the right side completely lost coupling. I was completely unsure of what it could be, since the whole thing was made of Beast Fits and Loctite. As it turned out, the second stage ring gear’s press fit was in fact not a press fit at all. I probably only thought it was because I was pushing through burrs. The gear was actually pretty free to spin inside the gearcase. Solution: Drill down into the ring gear through the aluminum case just deep enough to insert a dowel pin. I used a #14  drill at 0.182″ diameter to make a gouge for a 3/16″ pin.

And by pin I mean lathe tool stock. Hey, it’s hardened steel and polished. Give me a break.

(The pin was cut flush with the gearbox surface and ground smooth, just for the record.)

It’s good that I found this out now and not, say, Monday morning of the con.

Overall, that does it for Clocker. I still need to cut out a replacement battery cover, since it being a nondescript cut-up-looking chunk of black plastic, it probably fell on the floor and got tossed during a shop sweep. At this point, Überclocker weighs 27 pounds – more than it did originally, but not surprising after the addition of the much bigger drive motors.

I’ll actually be making the replacement battery cover out of some very thick steel just to use up the last 3 pounds and push the robot’s CG back another millimeter.

cold arbor

Arbor has reached its own apex of entropy – after this point, I should be putting the robot back together more than taking it apart. Hopefully – I still haven’t addressed the drive motor issue yet. I kind of don’t want to make another two FrankenWalts, but I doubt I’ll be able to use the 24:1 gearboxes any more.

The designed parts of yesterweek have materialized into 1/4″ and 1/8″ aluminum plate. I managed to find a good deal on 2024 aluminum panels on eBay several weeks ago, and the 1/4″ parts here are made of that plate. Featured above are the new claws, the new saw motor mount, and new actuator mounting points for both front and rear actuators.

A little bit of sanding later and the rear actuator mount is in place. This is a very visible use of “thickness buffers” in the art and science of T-nutting. The original 1/4″ aluminum struts were 1.75″ apart, but the saw actuator is 2 inches. So between the back of the bot and the saw actuator, the spacing needed to widen up an eighth inch on each side and still had to hold T-nuts at the back.

So the solution is to stack two 1/8″ plates: one part which is purely a T-nut anchor, and another which is identical in that regard but also has the actuator mounting points – and make sure it’s on the outside of the stack.

The mounting plate is bolted to the thickness buffer plate using a handful of 6-32 cap screws. I thought about riveting it, but I couldn’t find our rivet gun.

The actuator drops in place like so. The only thing changing on this part of the robot is the leadscrew, which I’ll remake using a longer piece of Acme rod stock.

electr(on)ic mayhem

One of the downsides of possibly running two robots in the same class is that they might have to fight eachother in the tournament. If this happens, you either have to make sure you’re awesome at dual-joystick driving two robots at the same time, or have two radio transmitters.

I don’t. I only have my (outdated and obsolete) Spektrum DX6 radio. The same type that I ran back in 2007, when DSM1 was still in style. I have multiple BR6000 receivers for the transmitter, but only one Tx, and I don’t intend to get more obsolete equipment.

So what do I do? A real Spektrum rig is going to cost me another $2-300, which I could swing, but it would be kind of a waste of money given that term is about to start.

Luckily, like every other problem I have, Hobbyking has a solution.

On the left is my Spektrum DX6 (not even the i version). On the right is the HK-T6A 2.4Ghz 6 channel radio.

It costs all of $25, and includes a receiver. However, it also comes with no displays whatsoever (it’s the most bare-ass radio I’ve ever seen with more than 4 channels), no onboard switches for calibratoin, and the worst, buggiest we-made-this-with-a-trial-version-of-VB6 calibration software ever. Oh, and you can technically only get 5 of 6 channels working at any one time if you enable V-tail (& elevon, Delta wing, etc.) mixing for single-stick robot driving.

What it does have, though, is an established userbase and numerous “upgrade” hacks and replacement calibration software, such as Digital Radio.

The most important thing, though is that IT WORKS. For $25, I can deal with some shortcomings and rough edges. I’m tempted to tell Horizon Hobbies to just fuck off, but I also understand that HK is playing with alot of home field advantages, and would still spring for a real Spektrum rig any day.

The bottom line is that Arbor is getting its own radio for the con and for future events. This receiver setup has been determined to output “Bot-safe” signals i.e. none at all when the radio link is lost, so Arbor ought to still pass every failsafing test there is.

For what it’s worth, here’s a slightly junky shot of the inside. The difference for me between Chinese equipment and “established” well known manufacturers is that I never feel bad tearing into the former without even using it beforehand. Usually, I know that at least some kind of engineering has gone into the latter, and that me picking at it is only going to make things worse. So I satiate my curiosity on cheap parts and equipment.

The main MCU in the radio is an Intel 8051 knockoff that appears to share the same instruction set and pinout. Otherwise, the radio module itself is a bit more sophisticated, and features a 2.4G Taiwanese transceiver (Amicom A7105) and some kind of custom ASIC from Flysky (FS8004, which I can’t find a datasheet for anywhere).

My first mod to this radio is to make the left stick (throttle) spring-return to run the saw and clamp actuators. I didn’t have the correct part, but I chopped a spring lever out of a dead DX6 transmitter and sanded it down until it fit in the same slot. I also used the spring from the dead Tx.

There you have it – for $25, which is something like the cost of two burgers from Five Guys or how much Mountain Dew money I run through per week, you can get a 2.4Ghz 5.2387 channel radio that is essentially intereference-free, does not require channel crystal diggling, and has all the features you might need to control a basic robot. A word to robot n00bs: it did not use to be this easy. Get building.

nuclear kitten 5.1 surround sound edition

It’s back!

NK5 has been sitting idle on my robot shelf since Dragon*Con 2008 after it was first built. I’ve practically not looked at it, since I assumed it had taken significant damage at DC08 and was essentially not worth repairing.

After some egging by friends, I found out that I was pretty wrong.

Here’s the robot after I stripped everything down to prepare for rework. The overall appraisal:

  • The two drive gearboxes I thought were destroyed are actually working fine. No stripping or weird noises
  • The motor is functional, doesn’t have crunched bearings, or shorts in the windings. It just needs some magnets replaced.
  • The weapon pod swingarm is pretty heavily damaged and will need rebuilding to a beefier specification.
  • The 3S 1.3Ah lithium polymer battery is toast. D’oh.
  • Why the hell did I use 12 gauge wire on a beetleweight?

I’ve ordered replacement magnets and two replacement lithium packs from Hobbyking. Hopefully, with the magic of express shipping, they will arrive next week. NK fundamentally needs maybe two or three hours of work to be back to competition-spec.

How long will it actually last? I have no clue. It’s built to barely 2008 spec, and the brushless masculinity contest has grown in magnitude sine then by far. But, expect NK5.1 at Robot Microbattles on Sunday.