Archive for the 'Overhaul 2' Category

 

The Long, Cold Winter of No Posting Ends: Awaken the sadbot2019

Apr 16, 2019 in Bots, Overhaul 2, sadbot2016

Is this thing still running?

Needless to say I am a little less than proud of the longest post drought this site has ever seen. I’m still alive! Just preoccupied largely with getting the company product technology to a stage where I can at least be assured the tunnel will end eventually, even if I haven’t seen the light yet. Along with this gradual better-scoping of product tasks, it’s taken me a while to get used to not just working on dumb projects all the time in big blocks of work, but learning how to divide up tasks and think about their dependencies more, such that I can pick stuff up and drop it back off easily. I brought this up a bit in the preamble of the Great Mikuvan Engine Rebuild Scandal of yesteryear. Whatever, it just means hopefully I can get back to working on stuff, but until the day I exit the company and become a full time bad idea investor, the pace will inevitably be slower.

I believe the real world calls this “Adulting”.

Anyhow, adulting is dumb and robots are cool. Let’s revisit Sadbot, which was left kind of functioning last year some time before I sold the pokey dingle to a west coast team. Then, incrementally more parts started coming out of it until there wasn’t much left but Overhaul 1′s drive system and a steel box. With the coming of BattleBots season 4, I figured I had to at least work on something, and I should probably consider repairing my wreckage instead of creating new wreckage.

Oh, if you notice the timing of this post – I’m clearly not competing in Season 4 with Overhaul.


I mean, if I didn’t even clean the barbeque out of it yet….

Ultimately I didn’t think I could muster up the time and resources to do the bot justice, and enough of the team has split off to get real jobs (among other things, I mean) that i would have had to rally up a new crew. So, perhaps next year, and maybe it’s a blessing in disguise because now I’ll work on Sadbot out of FOMO and remorse, perhaps discovering something new about Overhaul in the mean time!

Next season, though. I promise I’ll be Bach.

So I set out to change up Sadbot in a fashion that would reflect the mods I want to make to Overhaul for next season. That in detail is itself an entire blog post for when Overhaul is modified for #Season5 one day, but in short…

  • Change the drivetrain to the 80mm “melon” motors – Sadbot being a single motor per side, it will 100% reflect the drivetrain setup I want Overhaul to have in the future, as in my post-season assessment the dual motor setup has not been as reliable as I wanted.
  • Using this opportunity to make sure the 12FET Brushless Rages weren’t actually trash, but were not utilized right the first time out. I had some more testing and changes I wanted to make after Season 3 that I hadn’t gotten around t
  • Finally doing the tractor pull contest between Sadbot and Overhaul which never happened. While the bot had “more” traction than Season 2, it wasn’t that much more, just more linear and predictable. I want more, something which I suspect is beyond the capabilities of my current bot architecture.

The first step is putting the damn thing together again. To do that, as usual, it has to come apart more first!

To retrofit the 80mm outrunners, I had to re-introduce Overhaul 1′s intermediate drive gear. The previous motors in Sadbot were 59mm SK3 outrunners running into Banebots P80 gearboxes, so the motors were already geared down and only needed the center sprocket.

To get the ratio I needed using a gearbox would have made the assembly too long to fit into the frame, so I needed to directly attach the motors to the face, needing the extra ~3:1 the intermediate gear provides.

I machined these gear-sprocket combos late last year. They’re waterjet-cut 12DP gears that are pinned into the sprocket face such that the assembly rotates on a dead shaft (pictured mounted in its former home). These were virtually identical to Overhaul 1′s (which were long disassembled or I’d have used them again!) but a different ratio.

New socket cap screw holes sunk into the drive plates – now featuring THREE bolt patterns! P80, 3″ Ampflow/Magmotor, and 80mm C-series outrunner.

Modules taken apart, cleaned, regreased/re-threadlocked, and reassembled.

At this point, the ‘skateboard’ of the bot weighed 163 pounds without batteries or the controller housing. This began my contemplation for bringing back the pokey dingle. I’d sold it because I didn’t like the design any more and someone else was going to incorporate it into another bot, so what better way to force me to start over?

Originally, Sadbot was going to be 220lb (nationwide Heavyweight class) without the pokey dingle, functioning only as a pusher/brick bot, and 250 pounds with it in order to simulate a BattleBots practice opponent. I was, after this weigh-in, now convinced I could make it close to 220lb even with a weapon, which would let it compete in the rising amount of “Heavyweight Sportsman’s” events around the country. Or at least I’d get it close enough that the laid-back nature of these events would make them take it anyway!

Next up, assembling the control deck. These were parts also designed and cut out last year – a basic polycarbonate tabbed box and nutstrips to make a second floor. Batteries will be mounted on the first level, and the aluminum plate mezzanine will house the brushless Ragebridges.

Originally, I wanted to use the Overhaul 1 batteries after being decomposed from the modules. However, they aged poorly and the cells have high internal resistance now, so I put together some of the Overhaul Season 3 batteries (Hobbyking Graphene bricks) instead. I greatly enjoyed how these worked in Overhaul, and while it packed four, I think two would have been plenty. Well, it’s time to test that!

The batteries are secured on the bottom with a few acres of Dual-Lock – think gender neutral Velcro for the woke Millennial – and then pressure-retained downwards by the 1/8″ aluminum plate with the adhesive-back foam rubber pad.

I forgot how easy wiring a 3-motor robot was. That’s it! This is the whole wiring harness, minus the battery-side mating connectors.

The rest of the wiring was built up over basically one evening. I had two leftover Whyachi Switches, one which I’ll set aside for the New Pokey Dingle weapon and the other for the drive. This keeps the activation process similar to what’s expected for BattleBots and also just allows me to test one system or the other.

And that’s all, really! This build was quite short and pleasant, occurring over several nights in about a week and some. Sadbot at this point weighed just under 180 pounds, which only left me around 40 for the entirety of the New Pokey Dingle. Difficult, and I decided at this point that the 220lb max goal was probably not that important, but I’ll give it a try.

 

I knew the parts I wanted to use already – an Overhaul lift gearbox (Banebots BB220 16:1 and SK3 59mm 149kv motor), enough reduction to get to about 180:1 which is the same ratio as Overhaul, and that the end effector should still be the Harbor Freight “manual slide log splitter” / toe destroyer. Furthermore, last time I permanently welded the tool to the output shaft, but this time I intended to make the output a socket to potentially make interchangeable ends.

I started flowing plates around some initial component placements. The output sprocket was only going to be able to get so big, so I fixed that first (48 tooth) and gave it a position that had some clearance to the electronics box, some clearance to the ground, but high enough to allow the motor to tuck underneath with some semblance of an intermediate stage. The width was fixed by choice at “Between the Melons” – one of the things I didn’t like about the last Pokey Dingle was how wide it was for what it did, and I had some ideas which involved moving the sprockets around to make the while thing narrower.

Here’s roughly what that looks like. The chain stages are very short and all overlap. Technically, I could have made this just open gearing, but chain drive is more available and serviceable – all of these sprockets, save for the output, are off the shelf parts.

I was contemplating how to make interchangeable “manipulator” sockets compact enough to fit in the confines of the side plates. I played with a couple of ideas including welded machined parts, making it a live shaft again (but with a socket tube welded to the shaft, and so on. All of these ideas turned out to be either too wide or, after a moment of …. brilliance? too tacky and complex.

Why not just weld the damn square tube to the plate sprocket, using the bushing as a locating feature!? The  wall thickness of the tube certainly permitted any inserted attachments to not come in contact with the drive chain, so that was really all.

I also utilized a chain tensioning approach which I remembered, but couldn’t place where I learned it from. Typically with a slotted mounting system you’d place the slots parallel to the direction of tension needed, e.g. slide the motor away from the shaft perpendicularly if you need to adjust the chain/belt spacing.

However, this arrangement doesn’t resist the normal forces that chain tension plus torque puts on the sprockets, which tends to force them together and loosen things up. At least, not all that well unless you had massive fasteners. Instead, I angled the bearing mounting slots at 30 degrees from the perpendicular to the axis joining the sprocket centers. This means I move the sprocket more “up and down” relative to the other one, but there’s that 0.5x component introduced by the 30 degree inclination which adjust the actual tension, and also reduces the effect of the tension “attractive force” immensely.

The downside? I have to have two chain pitches (well, sqrt(3) / 2, so basically 2) of vertical free movement in the chain to gain that horizontal spacing. That’s not all that much when considered, so only a little geometric squishing was needed to get space for everything.

Initial positioning in the bot  yielded some more Geometric Squishing to get the parts to all clear. I went out of my way to make things actually parametric and geometrically related instead of hard-coding dimensions, enabling some click-and-drag placement.

The final assembly by itself modeled with shaft and bearings for a realistic weight. It looks like this thing will weigh a little over 40 pounds after all. I added some cutouts to remove material where it wasn’t really needed, but the final bot will still end up around 225lb.

About a week later, this showed up! I sent these out to a local shop which the company has built up some rapport with, and they laser cut it from 1/4″ regular-ass P&O steel. Nothing too high tech going on here, though I recommended they stock up on ARx00 steel for future robot seasons…

Because I wasn’t in control of the machine any more, I very liberally oversized all the slots and shrunk the tabs – I went 0.015″ oversize in X and Y for planar square slots, principally. This turned out to be a near perfect, slightly jiggly fit. Laser cutting generally has a less clean finish than waterjetting, plus I couldn’t order them to “move the laser inwards 5 thou” like I typically fudge nozzle offset distances when waterjetting personally.

 

The machined parts needed for this new Pokey Dingle was really just the output dead shaft/epic standoff. I used some 1″ precision ground shaft leftovers and end-tapped both sides.

It was then used as a welding fixture. The P&O (pickled and oiled hot roll) steel was very clean from the get-go, not needing the intense sanding/brushing typical of A36/A514 hot roll or tubing products.  So it was literally just 10 minutes of MIG blasting here.

I modified the Harbor Freight Robot Tallywacker this time by cutting off the heavy punch weight at the back – it’s just a 2″ steel billet chunk. Previously I drilled a 1.25″ hole into it and welded it to the output shaft. This time, the 1.5″ main body section is more interesting, since it will be cross-drilled and bolted to the tube socket.

 

I then proceeded to get carried away.

It started out innocently enough wanting to paint the frame of the New Pokey Dingle my signature Overhaul Miku Blue – and then I discovered I had a Miku Magenta can I never used!

Yeah, well, this is what you’re getting now. aestheticbot9001

I was also tempted to paint the frame itself a light pastelly purple, but by this point didn’t want to disassemble the thing again.

Marking and drilling the front mounting holes for the NPD which brace the thing against the massive C channel section of the front of the bot. Another reason I didn’t like the old NPD – it only was bolted to the bottom of the the bot, meaning a hard enough hit and it will probably just bend. The New Pokey Dingle acts as a truss structure to past the center of the bottom plate – hopefully this will yield substantially more rigidity.

Drilling the holes themselves was an adventure. It was too heavy to put on a drill press, and too tall for the Bridgeport. So hand marking and drilling we go!

I’m rather fond of step drills. For hand drilling in steel, twist drills are almost inevitably too aggressive and tend to either spin in the drill or catch and throw you halfway across the room. Step drills feed more controllably and never dig and then slam the drill into your kidneys.

I machined a small donut piece to bridge the gap between the shaft bushing and the plate sprocket’s 2″ bore.

The same annular cutter I used for the original Pokey Dingle (as well as Overhaul’s gear holes and a lot of other parts) was used to put in the 1.25″ bushing hole. Really that was the only operation needed here! Just a single, albeit massive, cross hole.

Then you clean the parts and MIG-smash them together!

Here’s how it is going together. Since I don’t really care about the precise alignment of the socket tube, all the bushing has to do is center it. I put a few tack welds around that end first and more solidly welded the other side (carrying most of the load) – welding too much around these bushings would deform them due to the lower melting point of pressed-together bronze particles (not to mention sweat oil everywhere!)

Installation was simple, with just a few shim washers needed to space everything out.

Well, I ended up taking the whole bot apart again anyway, so maybe I should have painted the frame purple. But here’s how the New Pokey Dingle elevator machinery bolts in – a line of nuts on the bottom, and the four big bolts on the front.

I broke into the electronics enclosure again to add the 3rd Brushless Rage. I ran out of production-spec boards at this point, though, having packed the majority of them already for product shipment and BattleBots, so I pulled out one of the previous version power boards (The signal board is the same production-spec one though, just an older power end revision).

The 1″ UHMW top lid had to be modified a little to clear the new sprocket placement, which was a simple jigsaw job with drilled holes at the vertices to turn the saw around.

And here it is put together! The final weight? 226.5 pounds (with the top plate, which isn’t on here). I could probably knock 6 pounds out of it somewhere, but that’s not really the point.

So that’s where Sadbot sits now! It drives great withe dual 80mm “melon” drive, but I haven’t fought it against Overhaul yet or otherwise substantially battle-loaded it. In between the first photo and now, we actually moved shops again, and Sadbot is still hiding behind a few pallets. So, watch for both a post about the #NewVapeShop(tm) as well as some more testing and driving videos.

The Overhaul Design and Build Series, Part 5: “Don’t you have to ship this on Wednesday, dude?”

May 31, 2018 in BattleBots 2018, Bots, Events, Overhaul 2

Yes, yes I do. STOP REMINDING ME OR YOU’RE HELPING MACHINE THINGS.

Well here we are, after the airing of the Overhaul vs. Sawblaze fight which will be on Science Channel’s website and other streaming service soon! I have a full writeup I need to do on the lead-in and post-match analysis for that one! That will come after the conclusion of the build series in this post.

We rejoin our heroe…. dumbasses in the 2nd-into-3rd week of March. March 21st was the latest ship date available for east coast teams in order for everything to make it there on time (or so we were told!?). Luckily, Overhaul was actually not in a bad position, at least compared to Season 2 when the extra long days really started kicking in. All I really had to do at this point was a final assembly, then work on remaining spare assemblies.

After the Week of #WeldingGoneWild, it was actually very easy to do a fitting of the whole front of the bot.

That’s about it. The only thing which wasn’t added in this photo was the clamp actuator itself.

I’m much more a fan of this design already. Once the whole thing is loosely assembled, there is a degree of “elastic averaging” *ahem* that goes on as all the bolts get tightened down, but after that, the arms are rock solid.

The drivetrain is being assembled more now. Check out the Markforged nylon engine timing chain style guides! The front chain was still a bit loose after this so (at the event) I ended up making a different set, to be shown.

The one on the right between the two motors is a little ridiculous. We were running so tight on time that I wasn’t going to get the #35 half-links of chain in on time, or at least too close to risk not being able to drive test. So I invented the stupidest possible chain -pincher for the intermediate drive chain – it was gonna wear out very fast with its profile, but would at least let me get some test driving in.

Closing up the other drive side. The design for serviceability that I did 2 years ago is really coming back to help me here. Remember, my team this year is scattered – Paige is working a real job across the country, Cynthia is occupied full-time and could only help on a limited basis with set-up operations, and I only had Allen’s help briefly with welding too. Most of the photos taken in this build series was work done by myself solely.

Here’s the first test-fitment of the entire bot with all hardware installed. I’m really liking all the design changes to the steel parts. In person, the new clamp and forks look better proportioned to the bot. At least to me, way better than OH2 for 2016.

(Fun game: See how many dumb project artifacts you can spot in the background of this and other photos. Chibi-Mikuvan currently resides under my desk.)

 

I spent an evening just pounding out spare parts for the incipient shipment. For one, I was short on drive motors now, but with a shipment of new HobbyKing Sk3 6374-192s waiting, I needed to key the shafts and secure the hardware. It was easier to pop the shafts out en masse and set up the mill properly.

This and more! I went through….. zero 2mm endmills, somehow. Still a harrowing operation.

It was now the weekend before, and I realized that I wasn’t going to be able to get my last round of waterjet-cut parts in time. These days, I get to be in the back of the line for MIT shop waterjetting – which I think is a very reasonable voluntary position to be in, as I have no official involvement any more with the institute. But dangit Sawblaze, you guys still do!

The electrical deck could conceivably just be drilled from a plate of aluminum, so that is what I ended up having to do. Out comes the TERRORISM. I just cut a chunk of 1/4″ aluminum plate out and started marking holes like high school Charles would have done, and he is always right.

Please do not ever, ever, ever do this. This is how you die. This photo is for illustrative purposes only and should never be attempted, building a robot is dangerous, etc. If you do, use the finest tooth blade you can get and have someone else pump WD-40 or cutting fluid constantly. Or you will die.

 

In the middle of the process. All the small holes are #4-40 tapped for Brushless Rages. Notice how I put six holes in some positions? This will be important later.

 

I’m loading up the bot with electrical deck hardware and wiring now. The shock mounts are in (and secured from the bottom) and some of the battery harness is visible.

The wiring for Overhaul this time was…… ad hoc, to say the least. I said I would dispense with the carefully cultivated greenhouse of busbars. The fanout occurs at the master switch terminals this time, with 8 gauge main leads splitting into multiple 12-gauge intermediate cables to the Brushless Rages. Single 6-AWG conductors handle the “fan-in” from the 4 batteries to the master switches.

The octopus taking shape, with ESCs installed.

Remember those 6-hole patterns? I had to temporarily use the 6-FET models for drive, keeping the 12-FETs for lifting and clamping.

What, are they magic or something? In actuality far underrated from their published specs?!

No, but I accidentally sold my entire product line – which is great – leaving ME with no remaining 12-FET units – which isn’t great. I had to dig into all my pre-production units here to even complete Overhaul at all. What is stock tracking even??

I wasn’t running off a cliff without a drone backpack, by the way. A month earlier, I had placed the assembly order for a new batch of Brushless Rages, but they wouldn’t get in until the Monday of the ship week and I was not taking any chances.

With the octopus wired in, the drive base is live for the first time. Check out the motor-on-a-stick I used to simulate having a clamp motor.

 

Overhaul prior to its first indoor test drive! At this point, I’d fight in 20 minutes if I had to. I think I was actually ahead of the curve here by a distressing amount.

 

I cleaned up and routed more wires into loom in order to un-nest the wiring some. This is inconceivably ugly to me, like a steaming fresh pile of partly-regurgitated dog squeeze smeared across a sidewalk by multiple unassuming passerby. I would never ship this in a consulting project. Yet some of y’all at the event said this was the cleanest wiring in a bot ever? What the actual hell is wrong with you?

(After seeing inside everyone’s bots, I’m not inclined to disagree. Sorry not sorry.)

 

Monday came, and hey! Look what’s here! More Brushless RageBridge units for all! I’d end up assembling 25 12-FET units and packing them with me to the event (not including my own spares, which were 4x for drive plus another 4x for spare overhead)

One of the put-off things was welding the wedges together beyond just tacking, so I spent much of Tuesday doing this. The plan was to take the tacked units to MIT to use one of the MIG welders I have access to and really smash them out quickly.  Using the bot itself as a welding jig made for expedient alignment of all my wooden dinosaur puzzle pieces.

DETHPLOW ™ was tacked together in the same fashion, by actually mounting all the pieces to the bot and locally squeezing with clamps.

For completion purposes, I fully TIG welded one set of pointy-wedges and mounted them on the bot in their final positions. TIG welding is truly the wrong technique to use for bitey pointy robot parts, in my opinion, since it takes so much time compared to MIG in an application where the sensitivity is not really reflected in the end product.

As I mentioned previously, it ended up pissing us off so much we immediately bought a MIG welder after we all got back from the event.

This, for instance, is DETHPLOW all MIG-welded together, a process which took only 15 minutes or so once it was jigged up. I designed all these pieces to be MIG-filled anyway. Here I am doing some TIG touchup on areas which I fell a little short with the wirefeed or missed, or had a gap that I couldn’t bridge as the fitup wasn’t 100% perfect. This is a fine state of affairs for me – blitzing and then fine tuning if needed.

One thing which occurred over the weekend was crate setup. I decided to just spent money this time to get an elegant and reusable SINGLE. PALLET. solution. As someone who’s had two double-pallet crates wrecked over two BattleBots seasons for reasons unknown, I decided I was much better off with a tall single pallet. U-Line came to the rescue with this 4′ x 4′ x 6′ tall snap-together crate,which I modified by adding some removable side-in shelving levels. The bot with its lift table and large tool chests/boxes was to fill the bottom floor, and more containerized accessory suitcases in the middle, along with the pictured Markforged gear – Markforged went ahead and lent me a 2nd printer for the event.

The top level would contain the loose large parts such as the frame rails and spare welded assemblies.

You know all those spare-everythings I was cutting and machining? They ended up in a tote which contained all the important mechanical bits of the bot. I’d prepped a full set of drive and lift motor spares, along with a few mor prepared motors. There was also enough cut tube sections to weld up a new clamp at the event if it came to be.

 

And here it is, Overhaul and all of its support equipment and tools plus spare parts, all ready to load up into….

 

Vantruck??????????????

 

THE PLOT THICKENS! During the week prior to shipment, a few of us NE builders came together to ally ourselves against the forces of time.

You see, Team Forge & Farm was planning to road trip across the country with their bot in tow. For a nominal fee of a few spare RageBridges, they were willing to also bring Overhaul along.

This effectively bought me an extra 4 days to work on the bot – in fact, the electrical work and spare welding photos you see were done after the 21st. On the Monday following shipdate, I picked up HUGE along the way and ended up in southern New Jersey.

 

…where, under the cover of darkness, we packed Earl’s truck up with our bots and his alike.

So… what’s in the crate? Well, there was still the lift cart and all of the already-completed spares, the printer, the mechanical tote, and other support equipment like the battery chargers and power supplies, and a few doen Ragebridges of various flavors. I handed off the radio suitcase and both of my event toolboxes off with the robot.

 

There were still a few kibbles I had to take care of after the bot went out but before I did. So, how do you jig up pieces for welding with you don’t have a robot???

You 3D print an imitation of the robot! This is an Onyx print with the same hole spacings and offsets as an Overhaul front frame rail. I used it to tack the pieces together quickly (as to not melt anything) before removing them.

And with that, the build of Overhaul 2 for the new BattleBots concludes. To be entirely honest, I found this build season pretty stress-free, largely because I didn’t have to build a new bot from scratch and was making only well-scoped changes I had anticipated in advance. In the position I am in now working on a new company with my friends, I don’t think I could have pulled off the record build of OH2 for Season 2 in 2016. My (and my friends’) experiences in this build and competition season of BB – without going into NDA details of the show – has really shown me that I have to move back to a “When it’s ready” format like I had to do during my busiest times at MIT trying to vaguely graduate on time. I have a lot of thoughts on the show as a whole and the direction I’d like to move in (and the show should/shouldn’t move in) that are much better reserved until after the entire show airs.

But for now, hang out here a bit for the event report and a SawBlaze vs. Overhaul post-match!

And now a word from our sponsors!

HobbyKing – Somehow still loves me and enthusiastically supportive of my efforts to abuse R/C model parts for unintended applications! I’m running a HobbyKing radio (9XR Pro) and batteries (Graphene 6000 65C 6S packs, times 4), motors (SK3 63-series), BECs, and a whole lot of wiring and connectors. Not to mention the Reaktor battery chargers and who knows what other HK kibbles have made it into my tools and accessories. I like to think that I had a large role to play in the commoditization of silly electric vehicles using R/C parts also.

MarkForged – from the days when I knew 50% of the company to today when half the new marketing and sales staff go “Who is…. Professor Charles?”, they’ve provided me with high-strength printed parts for a lot of different projects, both on this site and off. Introducing them to the robot fighting community via Jamison’s and my efforts pretty much made MarkForged printed-unibodies the competitive standard in the 1 and 3lb classes, and trying to find new niches in the bigger weight classes is one of my goals. This time, Overhaul’s drive wheel hubs and casting molds are printed from Onyx, and there are also plenty of smaller chain glides and tensioners and accessory parts.

SSAB – I find it interesting that the company’s full name is SSAB AB – Svenskt Stål AB AB, or Swedish Steel Company Company, but these days the lettering is the whole company name so that’s actually not true. This year, I’m working with one of their North America regional distributors and all of the armor steel on Overhaul – including the entire clamp arm, top plates, and new wedgelets and DETHPLOW™ are Hardox 450. Hardox is the easily-obtained ARx00 of Europe and other regions worldwide, and bots overseas have used it for years, but it’s not really had a foothold here in our scene compared to the number of AR-spec steel products in the US. So hopefully I can help with advancing that brand too!

BaneBots – I was called an edgelord for even thinking about using P80 gearboxes in a modern Battlebot. I always thought they were under-loved after the FIRST Robotics Competition quality issues of the late noughties, and had used them otherwise in several projects including consulting projects before shoving shorty Ampflow motors into them for Overhaul 1 in 2015. And you know what!? They’re great! Overhaul 2 ran them exclusively for Season 2, and now for Season 3, OH is sporting the new BB220 series with much stronger planetary output stages for the lifter.

Equals Zero Designs – Yeah, umm, I don’t know much about those assclowns.

The Overhaul Design & Build Series, Part 4: Do You Want to be Gooey?

May 13, 2018 in BattleBots 2018, Bots, Events, Overhaul 2

Wasn’t that an insane season premier episode!? If you missed it, it even seems like they’re distributing the episodes in more creative ways this time, up and including Prime Video. That’s good news, including for me, who can’t be buttsed to TV like 99.5% of people near my age group and lower, and so can barely watch his own damn TV show. I’m fairly confident Overhaul will first be on the 3rd episode, so I think it will time well with the conclusion of this series.

The bulk of the physical construction took place around the first and second weeks of March. Actually, let me rewind the clocker just a little bit, back to the last weekend of February.

I got another shipment of stuff from Markforged, which is returning this season as one of the team sponsors. First, a bunch of Onyx filament to print wheel hubs with, as well as two large molds made on the Mark X series machines which have a bigger build volume. The Mark Two is limited to around 5″ in the width dimension, and guess what has 5″ wheels?! I printed a pair of 3″ front wheel molds in-house from Nylon, since that’s much smaller than the build volume limit.

Printing each pair of large wheel cores actually takes an entire day (22 hours, anyway) so it’s kind of a long process to make a dozen wheels. However, it was easy to pipeline everything once I got the prints going, as the polyurethane also happens to want about a day before demolding.

The resin of choice was Smooth-On Reoflex 60. I had plenty of good experiences with Reoflex 50 in Überclocker, but thought it wore a little fast and that Overhaul’s overpowered drivetrain would make that worse. So I elected to move up on the durometer rating, and 60A is similar to Colson wheels.  I got a small pack from the local distributor around here, Reynolds, to test my process and also the amount of liquid pigment needed. See, the native color of the Reoflex resin is a pleasant poop brown color, which is actually too dark to turn MIKU BLUE. So whatever, black wheels it is.

I’ve gotten a lot of questions on how the hell these wheels are supposed to demold. The molds are one-piece with zero draft, so it should be some kind of physical impossibility…. but then you realize that is what the screwy tread profile does!

I went light on the mold release here, and subsequent wheels actually popped out easier than that. Have I mentioned it’s also awkward trying to hold a camera at the same time as keeping yourself upright AND applying several Torques to something? At least a few torques.

They didn’t all work out though. The first center wheel mold I got from Markforged seemed to have some extrusion problems for the exposed surfaces, leaving them porous. We figured I’d just try slathering on the mold release as they reprinted it.

Nah, this one was stuck for good. Later on, I actually cut this mold open and discovered the resin had seeped entirely down through the floor of the mold and even through the inner walls due to its porosity… Yup, not unscrewing this one.

The reprinted mold was fine.

The problem with a robot with much larger wheels…. is that little sample pack pretty much only lasted those three initial wheels. So guess who now owns an entire gallon of goo? There is no intemediate size between the small trial-size and the full gallon.

These buckets are kind of crappy to use without dispensing equipment setup, but luckily I managed to get the workflow down for pouring them, and only got everything slightly gooey.

All of the frame rails now have brace plate holes-to-be-tapped drilled into them, so frame reassembly can begin in parallel with the remaining operations on new drivetrain and clamp/fork parts.

The first things to go back together are the liftgear and new lift motors.

One assembled front 3″ wheel… I’m liking these already.  The tread adhesion is outstanding – I can’t begin to tear the sidewall away from the face of the wheel. That and the mechanical over-molded interface means short of getting these things cut off, I’m not going to lose the tread.

A little bit more progress on reassembly, now with added drive motors.

Going on in parallel with the wheel casting and reassembly was lots and lots of welding. This damn thing almost has too much welding on it. I also know that I only say that because during this build, we didn’t have a MIG welder, only a TIG.

Here’s why – TIG welding is a very slow, methodical process which gives the welder maximum control over the weld composition. For the things we’ve been doing for “work” and consulting projects, this has been great! What it’s not good at is making large amounts of obnoxious fat welds quickly, for things which are only meant to run into each other over and over. Really, a lot of what you’ll see in the arms was designed for MIG welding, but I couldn’t gain access to my usual one back at MIT until nearly the very end of the build season. Putting Overhaul’s arms together, and Brutus’ wedges and plows, were processes which took up an entire day, or days.

The combined builds of Brutus and Overhaul made us go out and buy a MIG welder because of how bad it was. So that obviously won’t be a problem again, since now we have a Millermatic 211 in the arsenal.

However, I will begin with pointing out that a TIG welder is great for performing an act of terror I learned during my MIT career: TIG bending. Hey, it creates a highly localized heat region! By gliding the torch over a line scribed into some metal, you can very easily get it up to formability temperature. The upside is also a smaller HAZ than (in my experience) with an oxy-acetylene torch.

To make these bends in Overhaul’s future ears, I simply dumped 200 amps of TIG into them for a minute or so and then quickly threw them in the brake press. The welded-like appearance is actually very superficial and was a result of the metal surface liquefying somewhat.

The clamp side plates required some cleaning and standoff tubes machined. I actually didn’t have to buy any new tubing for this clamp design – all of it was either from some other tubular object on Overhaul, or could be slightly machined to the needed diameter. The machined tubes were advantageous since I could control the width of the assembly precisely using the turned shoulder.

SSAB’s Hardox comes with a paint-like coating instead of the heavy hot-rolled mill scale that I see a lot on generic AR grade steel. It comes off very quickly with a flap disc, whereas last season involved several hours of grinding with a solid wheel to get the material to clean weldable state.

Other weld prep included fitting the new lift hub pieces together – some diameters had to be cleaned up and shoulders turned once again.

I had to do a rather hilarious setup on the ears which connect to the clamp actuator in order to clean up the internal bore. Yep, that’s 4 out of 6 jaws.

Here I am doing the first assembly tacks on the lift hub. I have a very strange welding habit: I like doing my setup with the TIG welder, then switching to MIG to finish out. This is solely because I have no patience whatsoever for TIG.

Remember those little flats that were cut into the actuator ears and endcaps? Check out the parallels on the bottom – they help align everything so there is no complex fixturing needed.

Blah blah blah… welder and paint, grinder I ain’t, etc.

Because the clamp arm’s aluminum pivot rings still need to go over these, I had to clean the endcap welds up on the lathe afterwards.

A finished lift hub with endcaps threaded and with bearings made of oil impregnated nylon. I actually found a blank that I had machined most of to the correct dimensions, so making more was easy. I had more unfinished blanks which I machined new arm bushings for from also.

It was now Pi day, and New England greeted us with like the 3rd winter storm in 3 weeks. But the build must go on! Never give up, never surrender (seriously kids, don’t ever move up here. it’s not worth it. it’s expensive, shitty, and cold). I set out to Mid-City Steel which was able to quickly supply plasma-cut Hardox 450 parts on short notice and for very low ruble. Combined in this order are more parts for Brutus.

With this order came the first DETHPLOW (out of 2 – I entered a 2nd supplementary order for more spares) and all the arm parts too.

Plot twist: The arms are mild steel.

Yes, yes, finally obtain mythical Hardox sponsorship, end up making lifter forks from goopy mild. I was ready to design the arms to be made from HX450 also, but couldn’t help thinking if the arms were extremely rigid, that something happening to them would just take out everything upstream – the lift hub, main shaft, etc. which are decided not very Hardy or Ox-y.

Therefore, mild steel arms it is. Depending on how they perform in the season, this might be changed down the line.

Setting up the arms for welding was a similar process to everything else – chop and turn some tubes, and clamp it all together. I for one don’t mind if we bought a CNC plasma cutter. Before these industrial processes (which themselves are rather “old school” and established) were “discovered” by the robot community, welding a frame together was a much bigger deal and required much more setup and skill. This was the environment I grew up in, so that’s why it took me so long to learn and appreciate welding.

Here I am putting the arms together with our Miller 200 amp TIG in the foreground.

Hey, wait… That’s not actually me! That’s…

Allen, a new team mate for this season, who is a ‘graduated duckling’ of my involvement with New York Maker Faire and the Power Racing Series. These days, he’s a mechanical engineering student at Stony Brook. I stole him for their spring break and basically trained him from-scratch on TIG welding, upon which he somehow dumped the entire tank of argon over the course of the week.

First of all, it was a lot of welding, if I haven’t made myself clear on this front. But I do think the regulator was set up for too much gas in general, since at one point the flowmeter had something heavy run into it and did not work properly, and we set it up by listening to it. Sigmas! We have none!

(We do now have a new flowmeter)

 

Allen put together essentially everything you see in this build report that wasn’t the lift hub. This is a photo of the two Overhaul heads under construction. It was jigged up using the lift hub on one end and the spacers for the tooth on the other.

Your Godfather horse-head moment for this build.

Connecting all of the welded bits together was actually very painless this time. Think this means I’m getting better at design-for-welding! This is a test-fitted complete lifter assembly. Not pictured are the spare set of long arms and pair of finished short T-Rex arms. And the other lift hub. And D E T H P L O W.

Mechanical re-integration of the bot progressed quickly from this point. Check back in next week for more original content!

The Overhaul 2018 Design and Build Series, Part 3: When Your Supply Chain is Missing a Half-Link

May 04, 2018 in BattleBots 2018, Bots, Events, Overhaul 2

It’s fab time! The following story takes place in the last week of February to the first week of March – yep, that’s just over 3 weeks, reaching into 2 weeks, until the bot had to be in the crate! In fact, a lot of the earlier photos here were concurrent with finishing out the drivetrain changes and electronics module, since the mechanical modifications were first priority.

Alright, the first thing to do after two years of stagnation and one entire shop move is to take inventory. Some of Overhaul’s parts had wandered off into other projects or been repurposed, and others had been sold to needy builders elsewhere. Oh, and some things instead were to be deprecated and thrown out.

I was first out to ascertain how many good drive motors I had remaining. I originally built a whole bunch of spares and only ended up using two or three. But the lift motors at the time were low on stock at Hobbyking, so I only had four lift motors total – one of which was burnt out and the other had a severely damaged gearbox from (likely) the rumble and post-season shenanigans.

There were also other parts being counted – sprockets and drive hubs, and hardware relevant to the liftgear which I only had a few of to begin with.

By the end of the day, I had a good idea of what needed to be ordered from McMaster the following Monday, as well as what parts to ask HobbyKing for!

 

I began the stripping down of the bot during this process. Poor Overhaul – it’s mostly been living on a lift cart behind my work area, usually causing me to run into it in some way on a regular basis, causing a pattern of injuries on my leg which would have been highly suspicious during high school.

Breaking the bot down was important since I would want to start over with all new fasteners and ascertain the status of all of the parts, such as where a frame rail might need to get cleaned up or if this or that drive hub was about to let go anyway. There were also quite a few parts which were going to receive lightening in my efforts to make weight for DETHPLOW. Basically everything above in blue is being replaced completely, and a lot of parts which went into the now-previous design head will have to be deprecated.

 

Ah, the sad electrical box. Overhaul hasn’t been operational since a year and a half ago when I sold the DLUX 250 reflashed ESCs to Ellis for Robot Wars. To my surprise, this damn thing still powered on. There is a single brushed RageBridge inside to run the former clamp motor, an A23-150 sized Ampflow motor, as well as a BEC module.

Oh well – everything which caught fire is considered automatically sketchy in my book, and this box had an entire unassembled spare if I somehow needed another one – so I salvaged the bus bars and some intact wiring harness parts and unceremoniously chucked the rest.

Overhaul is probably my current masterpiece in terms of design-for-assembly and design-for-service. I put more thought into how things go in and out into this bot than probably every other project I’ve ever made, combined. It’s actually very easy to knock down as one person, since the majority of the bot is supposed to be serviceable by 2 people in under 5 minutes. It takes on average only 2 minutes to release a set of drive motors and under 60 seconds to separate the upper and lower halves of the bot at the arm towers, after which the set of lift motors comes out with only 4 bolts.

The revisions will see some of this go away – for instance, the frame rail brace plate would add a dozen bolts and a different tool to the process. However, I was fine with this – at BattleBots with the current format, you usually have several hours of notice before fighting, if not days. It gets tighter around the playoffs and finals obviously, but the quickest turnaround I’ve witnessed was still on the order of 2-3 hours. If I was scrambling to replace frame rails that hard, it means I’m doing pretty damn well.

On the plus side, the actuator and upper clamp retainment strategies have been changed to be more easy to service.

Well, when you get down to the basics, Overhaul is just a series of gears.

 

All said and done – this is what my table and bench area looks like. I sorted the remaining spare frame rails by type, since each type needed a different kind of surgery or modification.

Chibikart makes a cameo in this photo.

There was about 8 pounds to lose in the frame, spread across a few parts. Overhaul weighed in at 247.0 on the event scale during Season 2, so I used that as a cross-reference to the CAD weight of 240 pounds. To make sure DETHPLOW took me up to the same physical end weight in replacing the separate heavy wedges, and also taking into account the new frame brace plates, I had to get the bot down to around 230 pounds. The rest of the ‘missing weight’ was to be made up in the battery and ESC assembly being smaller and lighter.

Above, I use an annular cutter (also some times called trepanning cutters) to empty out some of the interior of the Epic Lift Gear. If you’ve never used these before, they’re like specialized high-precision hole saws for metal, and can cut a large hole very cleanly and quickly. They used to be very expensive and specialized, but you can find Chinesium sets now that work fine for under $100.  This one was driven in low-gear on Bridget.

The arm towers themselves also lose a bit of meat, with each side getting 1/4″ removed. In a mild perversion of their use, I actually used the same 2″ diameter annular cutter to make the circular boss by simply leaving the interior portion and machining the rest away.

It was now the first week of March, and life suddenly got much more exciting.

I had been scouring the country for a more consistent source of the 4mm AR400 steel that makes up Overhaul’s clamp and fork profiles. Basically, the material seems to come and go at McMaster, who also seems to source it from the depths of a tropical rainforest as all of the AR grade steel I’ve ever gotten from them has been covered in rust and not a single one has really been straight.

Through a lot of calling around local steel companies, I was given an inside sales contact at SSAB – the international manufacturer of the UK/Europe robot fighting circle’s preferred armor steel, Hardox. The gist of the conversation was essentially “Hold on, what did you say you guys were building? Let me talk to the sales manager and we will see what we can do”.

Only afterwards did I do some research and found that SSAB was essentially the U.S. Steel of Sweden. To be fair, I’m not sure what I was expecting, since it’s not like some small mom-and-pop operation produces 8 million tons of high strength steel alloys a year.

So there we go – I’d like to formally welcome SSAB Americas as a sponsor of Overhaul this season! This explains the big Hardox logo on the Equals Zero Robotics Facebook page now.

They not only straight up sent me a diced up 4′ x 8′ plate of 4mm Hardox 450, but also helped find a local steel distributor who had a fast-turnaround plasma cutting service for even more Hardox. This will come into play just a little later.

Alright, presented with several hundred pounds of steel, I will obviously go waterjet. I paid some hush money to the MIT Edgerton Center and popped out a few parts on the Omax 5555 in an evening. I started with 2 full “heads” for Overhaul and basically all of the kibbles which go into the new lift hub design, as well as one set of titanium brace plates.

Here’s the finished parts in the middle of some post-machining.

Back at my shop, I cleaned up the actuator-mounting bore on the clamp side plates. The actuator trunions will ride directly in these holes, so I wanted a not-sandpaper finish here. I didn’t have a carbide boring bar that fit my old boring head, so I reground the old HSS lathe rool I used in there and just ran it very slowly and gently to scrape the little bit of Hardox off.

Harder steels might be horrifying to machine, but they do leave wonderful finishes if you know their weaknesses.

I made a design change to the lift clutch which entailed cutting out some new parts. I wanted to increase the clamping pressure significantly because Overhaul had a lot of trouble actually hauling stuff over during Season 2. To do this, I made new thicker pressure plates such that the tightening nut could exert a lot more force without causing bowing and decreasing of the contact area. I also switched to a higher-friction clutch material (what McMaster calls their high-coefficient of friction), from a medium one.

Additionally, I made over a half pound back here by machining down the Epic Lift Pinion and clutch gear! Technically, that shaft also never ever had to be made of steel – 7075 aluminum would have been highly reasonabel… but I already had slugs of steel sitting around in the right size back then…

Just a couple of days later, the new actuator bodies arrived from my Chinese CM.

Oh. My. Baby robot Jesus.

Probably the most gorgeous assemblies I myself have ever designed and carried to fruition (if I do say so myself). The story of the gear-nut is a tragedy upon itself. I originally threw it at my Chinese shop along with the billet halves, expecting them to basically tell me to quit it with my English Acme thread in the middle of a gear nonsense.  I was fully expecting to just buy two bronze nuts and shove machined stock catalog gears around them.

The problem is then they asked me for a sample of the 1″-4 leadscrew, which is obviously not easy to get in China, as an assembly fitment. They already made one. What?

Absent the ability to mail a chunk of leadscrew (which I didn’t even order yet) in a timely fashion, we settled on the next best thing: I would send them a 3D model of the leadscrew, and they will SLA resin print it and use it as a fitment test. These gearnuts have less slop in the Acme thread than my Bridgeport does.

In the end, it was worth it! The gearnuts are probably the highlight of this whole operation – on almost every project and bot, I have something I call the “penising piece”, referencing the unfortunate tendency for us guys to put a lot of effort into something very showy and impractical for the sake of one-upping each other.

You know what I’m talking about. Don’t deny it. Think about what sport this is.

Too many parts and assemblies like that and your whole project becomes very out-of-scope quickly. Trust me on this, I used to do entire projects that way.

That is not industry terminology. Do not dare try to make it standardized.

There was only one “quality control” problem, and it wasn’t the Chinese’s fault. You see, the thrust bearings I specified on McMaster had a nominal outer diameter, which I designed the pocket for. It in fact was a full 0.02″ larger in real life.

I’m technically not even mad – it’s a thrust bearing. What kind of dumbass tries to make a radially tight-tolerenced fit on something like that?!

The outer shell of those bearings is just a stamped piece of steel – it doesn’t acually Bearing anything, it just vaguely holds the upper and lower races together so you don’t sprinkle the rollers everywhere.

Sadly, I had to bore out my beautiful Chinesium to accommodate the ingrates.

Here is how things fit together. The big thrust bearings sit directly on the face of the gear. The pinion shaft is retained via snap ring and has another bearing that carries it, located in the half not shown here.

And this is how it fits together. I’m quite thrilled with this unit! It ended up weighing about 1lb less than the fiasco I designed last time around, is much smaller and also capable of much heavier loads due to the large trunnion diameter and thicker leadscrew.  The rod end is threaded into the leadscrew and retained with two cross-drilled 1/8″ roll pins each.

Next time on Overhaulin‘ – lots of welding. so much welding.

The Overhaul 2018 Design and Build Series, Part 2: Where Everything Gets Easier

Apr 23, 2018 in BattleBots 2018, Bots, Events, Overhaul 2

Hey! There’s a robot-related TV show premiering on May 11th you might be interested in. There are robots on it, and they do stuff. They might even tell you about how the robots were made or about who made them! I might even be on it occasionally (But for sure not the first episode: The new format of the show was filmed in fairly cleanly episode-divided chunks, and I’m not quite at liberty to say which episode(s) Overhaul stars in)

Guess what? It’s finally after BattleBots. This means my life has finally returned to roughly normal (whatever that…. is), and most importantly, I can actually finish these damn build reports. Remember back in the day when this site was more hardcore, where I posted basically daily about what I made that day? It turns out “real life” is a class you can’t skip too many times a week. Build everything in college and ditch your classes, kids! I mean, uhh, be a responsible young adult and remain engaged in your education. Yeah. That’s the right message to send! Something something public facing role model…

We return to the design stage of Overhaul by picking up after the most imperative task – redoing the steel frontal parts of the bot – was finished. In fact, I left this post half-finished before I dove into making sure everything was done and had spares, etc.

Everything else honestly seemed easy by comparison, because I already determined what was going on with the other aspects of the bot beforehand, and it really only needed to be pounded through. The next two priorities after the new forks and clamp actuator were to finish designing the drive wheels so I could immediately start 3D printing cores and molds for production, and retrofitting the bot with Brushless Rages.

 

The wheel technology I wanted to use on the bot was pretty well developed by prototyping it with Überclocker last year for the Franklin and Motorama events. I essentially just scaled it up and kept the “scooter wheel” style molding features.

 

Something cool you can do with 3D printing easily is make fully interior voids that have no opening to the outside world. I didn’t want to waste material and time by printing a huge wheel which is mostly hollow anyway, and wanted more material perimeters near the highly-stressed hub area. But a fully spoked design would have been extra fragile in my mind.

Solution? I enclosed the spokes with endcaps that have 45-degree chamfered lead-ins so it can print without support. This way, I get the concentrated materal perimeter in the center and the outer regions, as well as two relatively solid endcaps. You can’t see these from the outside at all – they look like blank wheels.

The molds are constructed the exact same as Überclocker’s, too. I’m hurrying on the wheels first because I wanted to test the viability of the “twist to unlock” demolding strategy that I piloted with the smaller wheels. As you can see, I designed in giant wrench flats (or perhaps vising flats) so I can hold the mold in something. Up until this point, I was completely unsure if twist-to-unlock was even going to begin to work!

Parametric generation made designing the 3″ front wheels super easy! To really do parametric modeling well, you have to pay a lot of attention to the order that your features were made in. I’ve practiced using parametric-CAD for its actual parametric properties more in the past few years with consulting jobs, and Überclocker’s wheels were the first multi-variant parametric part of this complexity I’ve done and had gotten it to generate correctly on the first try. I haven’t even dared touch fully parametric assemblies.

The parameters were essentially related to wheel diameter/feature thicknesses, number of thru-slots, and suppression of the interior spokes of the larger one.

(Useful side note – the continuation of that article series about horizontal modeling is something that experienced CAD users all do subconsciously. I learned it the hard way through many of my models exploding, and watching friends with bad CAD habits having entire assemblies made of parts that are exploding. If you look back through how I generate Overhaul’s relatively complex wedge facets, that’s probably the best example I have visible of horizontal modeling concepts)

I imported the wheel assemblies and also added new 12-tooth drive sprockets. I’ve described many times how Overhaul was very under-geared with a design top speed of 18-19mph and could not use nearly all of its velocity space in the arena, coupled with limited traction (hopefully less an issue this time). My experiences with Clocker at Motorama with its new 10mph top speed showed that it felt a lot less squirrely and linear to drive despite not having the best traction.

Going to 12-tooth motor sprockets from the 15 tooth ones would bring that down to 14mph, which was historically a “sweet spot” speed for the 48ft BattleBox.

The liftgear remains pretty much the exact same as last time, but the gearboxes are now the BaneBots BB220 series. I got to test drive these in some of my recent consulting projects after talking with BaneBots post-Season 2. The problem with the P80s was the Double-D coupling inside starting to round off under high-torque loads. The BB220 shares a gear pitch with the P80s, so all my spare purchased gearsets are still useable, but have output stage carriers that are twice as thick and connected using a 12mm hex bore and not a 10mm DD.

I only had to design a different mounting plate to adapt these – the ratios are otherwise the same. BaneBots only sells 4:1 stages for this gearbox right now, but with the ring gear being the same gear pitch and tooth counts as the P80, you COULD fiddle a 3:1 stage anywhere but the output.

Next item on my agenda was the “Anti-Cobalting System” for the outer frame rails. I stewed pretty hard on how to implement these. The ideal solution would have been to box off the top and bottom of the rails with an intermediate tying member, or try to do it Clocker style with a thicker single spanning piece.

Problem is, there is a lot going on in that area – on one side, all the liftgear intermediate bearings are built into the frame rail, and the front drive chain also snakes around there. There’s also not much space to attach an upper brace plate on the inside frame rails without making it fully service-dependent on removing the arm towers (and hence the top half of the bot) for any kind of access to the drivetrain from the top.

I didn’t want to sacrifice that serviceability, and I was also much LESS concerned about “Cobalting” the rails save for a direct side hit because of DETHPLOW now tying both sides together with wubbie isolation. So the ACS became a single bridge plate which spanned the entire unsupported length between the center and front axles. I decided to make it from left over 4mm titanium stitched in through its entire length by 1/4-20 Grade 8 screws.

In a realistic direct hit to the frame side, that plate is still going to buckle and likely pop a few screws. Generally though, it takes transferring a relatively minusule amount of energy to the inner frame rail to prevent buckling. If I had more material and time, I would actually have made an entire width-of-bot bridging piece to act as a huge gusset for this whole area.

But I don’t! So here we are.

That’s actually….. it. There’s not much else going on in this bot which is substantially different this year. Electrically, though, it’s a different story. I decided to drastically refactor and simplify the electrical deck. Last season’s mantra was designing the E-deck and battery as two modules which are replaced wholesale in event of failure, then we figure out what’s wrong with the broken one later.

I really consider that system over-engineered now, and especially with DETHPLOW mode, I needed a lot of that weight back first. With the ESC choice being standardized, there wasn’t a need to make a whole rack of them removable at a time.

I also thought about the number of times I swapped a battery out to charge it and replaced it with a freshly charged one: 0

Every lithium battery worth using in a robot nowadays can charge at 2-5C rates. That means a full charge in 30 minutes or less, and matches at BattleBots will not occur that quickly. Overhaul is also not a bot which is so strenous on batteries that it will roll through an entire charge in one match – Overhaul 1 took up about half of is battery nominal capacity, and OH2 was even worse at like 1/3rd per match.

Therefore, I settled for keeping the Brushless Rages on a single plate accessible from the top for individual removal if needed, and batteries considered now non-removable and better armored within the bot.

So here’s what’s going on! My HobbyKing sponsorship was renewed around now, and they finally had the high C-rating Graphene packs in stock and ready to fire (heh) over to me. I was interested in these last season, but they had been very recently introduced then and the larger sizes were not yet in production.

I am not going to harp on the potential upsides and/or downsides of graphene battery marketing (bad sponsoree…. bad!), but 65C lipos are 65C lipos. Technically Overhaul would be just fine running 2 of them, but I had space for all 4.

The batteries form a single layer in the bot instead of being double-stacked near the back now.

A little hole-patterning later, and the new e-deck unit is basically done. The whole assembly is now wubbie-suspended within the bot, with the batteries (in real life) double-sided taped together into a brick and then sandwiched between the aluminum plate and a lower either-metal-or-Garolite plate, depending on available weight.

This is the assembly by itself. I found some space to squeeze in the 7th Brushless Rage to handle the clamp drive. This whole stack is around 3.5″ tall, so it leaves about 1/2 of air gap between the top plate and my ESCs. That miiiiiiiiiiiiiight be enough?

Seen in faint outline in the e-deck installation photo is a new top plate. I decided to do away with all the fancy cutouts and vents since the ESCs have a giant heat sink for a home. It will exist in two versions – a titanium 4mm one for DETHPLOW mode which trades about 3 pounds I can use, and one made of 4mm AR400/500 steel that weighs more for wedge fight mode (which is looking more and more like it’ll need ballasting)

Finally, the completing modification….. is moving the master switches to somewhere else that isn’t directly accessible on the top of the bot by wayward hammers. Hey, if someone reaches all the way back there (last season), we’re fucked anyway, right? Well guess what – someone did reach all the way there, and we were fucked.

The new location is accessible with the same tool, and with the activator still standing off to the side. The switches face 45-degrees upward directly under the arm tubes and sunk into the frame rail cubby – formerly occupied by Overhaul’s well-meaning but ineffective server fan exhaust port.

So here we go! The two master configurations for Overhaul this time:

General purpose match mode -wedge fights and vertical type weapons alike get the long arms and Limited Liability wedges, with exact positioning depending on who. The heavy top plate is in play. The configuration weight here is 230 pounds only, so I have a lot of wiggle room for silly accessories, minibots, and customized countermeasures.

The anti-KE DETHPLOW mode is specifically for horizontal bar and disc spinners. This mode is actually questionable against higher-hitting bar weapons like Icewave, but I’ve also not had to face such a thing yet, so hell if I know what happens!

And that’s it! The fabrication of everything obviously had to move quickly, so the build reports for Overhaul this year will be a little short. Stay tuned!