Archive for the 'Überclocker 5.0 – 30Haul' Category

 

Robot Ruckus at Orlando Maker Faire: How to Somewhat Scale-Model Test Your BattleBots

Dec 21, 2019 in Events, Overhaul 3, Überclocker 5.0 - 30Haul

Hello everyone. Here’s a photo of Überclocker 5 experiencing Waffle House for the first time, alongside Earl of Bale Spear team, who makes a better “BIG CHUCK” figure than I ever will.

Let that image never fade from the collective knowledge of mankind.

Anyways, as Robot Ruckus approached, I had to figure out how to get my bots all the way to Florida. Taking a week or so to drive there and back was kind of out of my realm of possibility at the time, so I decided to run a little bit of a relay race with the HUGE team.  They’re in Connecticut , which is either a suburb of New York or Boston depending on who you talk to.

I delivered Sadbot, Clocker, a tote of spare parts, and a toolbox to them one fine Sunday afternoon. They were then going to drive everything – Huge included to Earl in New Jersey (if you recall, Earl also brought Overhaul to Battlebots in 2018!) upon which he will travel to Florida. So after the delivery, I had plenty of time to do Other Stuff before flying down to Orlando.

Upon my arrival, I obviously had to grab a rental car. I figured that I’d get the shittiest econobox possible since I wasn’t going many places, just to the event and a hotel room. Well, when I got the reservation and headed over to the rental car garage, it turns out the company was out of shitty econoboxes.

So what now, do I get a free bicycle instead? Nope. Free upgrade time! The garage handlers throw me a key fob which I assume was to the small dorky crossover nearby.

Nope, behind that:

Thanks, I hate it.

Let me be very clear: I’ve forgotten how to drive. No, not in general, but remember what I’m mentally calibrated and trained to for years: Being high up and on top of the front axle, and having a very short or nonexistent hood.  THIS WAS NEITHER. You cannot see out of these. Not out the sides, not out the back, and barely out the front.  I guess that’s the trade for prioritizing looking cool and edgy. For yours truly, stepping into any modern car requires some zen and meditation, and a constant reminder that I now have a front.

I am always terrified of automatically failing over into “van mode” while driving anything rental, and going full Unintended Acceleration into a store or dumpster or fire hydrant as I try to park 1 foot away from something.

How fast does it go? Greater than Van. I dunno man, I don’t have a good sense for How To Fast. My friends who work at GM (who had to listen to me complain about it in real-time) said it likely has the rental-car spec turbocharged 4-cylinder Ecotec engine, which may explain why I was experience what I swore was turbo lag, but more likely might be several inter-related drive feel variables like any economy modes it was stuck in.

2019 Chevrolet Camaro: Faster than a 1986 Ford Econoline.

 

Also, this interior panel fell off while I was heading back from the event at one point. It snapped back in, of course, but seriously?

The trip from the airport to my hotel was made in complete darkness, in the rain. Great. So I’m sitting 2 inches off the floor behind 8 feet of snout, unable to see anything, trying to figure out why every new car is a forsaken spaceship simulator inside, and mingling with other equally lost tourists trying to figure out their own rental cars on the fly. Through several construction zones, to boot. I guess I’m glad I went ahead and got the full-plausible-deniability add-on.

When I arrived at the event the next morning, I found Uberclocker like this.

 

Aaaaaaaaaaaaaawwwwwwwwwwwww. Earl took it in a South of the Border restaurant apparently, and they had these convenient accessories available.

 

I unloaded totes and began setting the bots and infrastructure up for safety inspections.

Sadbot

Sadbot was up first against the multibot Crash and Burn, built by Fingertech Robotics (incidentally, a Ragebridge dealer!) and which has done very well at Robogames events. They were running in kind of a reduced functionality state for this event, so it was more or less a pushing match. Sadbot is obviously a great shape to get pushed around, so it went about as expected with the exception of me getting a few good shoves in. At one point, I took a huge gouge out of the railroad tie side bumpers with the log splitter tip. It definitely did its job.

In the first 30 seconds of the match, the lifter controller popped. Uh oh!

 

It was a pre-production 12-FET brushless Rage board that I pulled out of a bucket labeled “SAD RAGEBRIDGES” and wired up. I probably deserved this.

It would appear I neglected to solder some of the pins on the MOSFET packge. Quality control! That probably popped as soon as it saw any heavy load. I replaced it with a “production model” I brought along in the pile of Equals Zero wares.

What’s more important, though, was the powertrain holding up great for that entire match of me running around and into things. The C80/100 drive motors were lukewarm, and so was the aluminum heat spreader plate in the electronics deck. And even better? I loved driving the damn thing. I mean, saying it handled like Overhaul 1 would be cheeky. Obviously from the video, I took a while to get re-engaged with bot dynamics. But afterwards, it felt like driving a big 30lber, which is my desired effect. Big wheels and conservative gearing seems to be holding up so far.

Sadbot’s next match wasn’t going to be until Sunday at this point, so I decided to take the opportunity to go to Home Depot and grab some….

…masking tape, a big wire brush, and some spraypaint.

This thing has always needed a paint job, and I wanted to paint the frame pastel purple to match the Miku blue and pink attachment aesthetics. Well what better time than now? It was a bright and only somewhat windy day outside and around 70-something degrees. I brushed off the accumulated rust and grunge on the outside and had at it. Paint+Primer, you say? I dare you.

So there you have it. Sadbot will be purple from now on.

My next match was against the other multibot, Macaroni and Cheese. The matchups are “DETERMINED RANDOMLY”, or so I am told. Maybe the random quantum computer just really likes seeing multibots get thrown around.

I went a little more hard-headed in this match with the added confidence of the previous fight, more actively chasing as well as trying to back off from engagements. I stayed to a “I weigh more than thee” strategy instead of trying to capture with the pokey dingle, and managed to drive both halves in the wall a good few times, including propping them both up by the end.

One of these power charges had the unfortunate side effect of making Sadbot somewhat droopy.

Ah well. This match was a much more aggressive one from the stick perspective. I purposefully drove like the maniac I should be driving like, to see if I could get anything to upset itself. The motors got warmer, but not concerningly warm, and I unfortunately neglected to take a controller temperature.

I asked Earl to use Farmer Force™ to straighten out the pokey dingle a little – the upside of it being slightly bent was it at least touched the floor.

 

Sadbot’s final matchup was against Kraken, the actual BattleBots entry. This was finally a chance to drive a match against an opponent of equal weight, and what an intense driving match it was – I went full hard as if it the Giant Nut depended on it. This thing also perfectly fit in Kraken’s trap, as I found out. I kept the pokey dingle at a height to engage Kraken “in the jaws”, and did it once and drove it into the corner. However, once we recovered, Kraken got a better bite on the lid, which led to…

Oops. That’s the outrunner’s wires getting squashed into the rotor. One of the downsides of using external rotor’d motors is you have to pay a lot of attention to where your wires are going. It would have been better to make this a side-exit mounting instead of top-exit. Overhaul, if I keep this drive setup, will definitely have an external shield over the rotor to prevent this.

The wires took a little while to get chewed through, during which it was shooting sparks out the side of the bot which I thought was the controller exploding. I lost this side of drive around 75% of the way through the match, so had to play defense and pivot to keep facing Kraken. Anyhow, I couldn’t find any explosion signs on that Brushless Rage, but I also didn’t feel like repairing this at the event after the Heavyweight bracket ran out of time – originally, each bot was supposed to get 4 matchups, but only we had three in the end. This will be a forensic investigation for later!

Überclocker

Clocker got off to a …. great? Memeful? start by fighting “Marty”.

I’m going to let the video explain itself. Well, I found out it’s definitely front heavy, but it’s also compounded by the fact that Marty is enormous. I also found out this match that Clocker gets stuck on the floors very easily here – they’re plate steel laid on wood foundation, and definitely were shifting around as the event wore on. That’s one of the foils to having a super low wedge in BattleBots – the arena floor will only get shittier, and you’ll definitely regret missing your charges. It’s a tradeoff – possibly get stuck or bounce off a seam, but have weight on the ground.

After I parked the bot at the end of the match, I noticed when picking it up that the lifter was actually seized. What on earth?

It would seem that I #HardParked it maybe a little too much, and the P61 bent in half.

Uh oh. This is maybe an engineering oversight, but the failure mode is also a little infuriating. See, the P6x series shafts neck down to 10mm no matter what diameter you order them as, to pass through the bearings which are of limited size to support the mounting hole pattern. They’re also made of stainless steel.

 

This last part I don’t really get, but basically the shafts are rather soft. So once the preload on the screws is overcome, the whole thing will buckle. Maybe I should have secured them with a 2nd plane or backup plate of some sort. Or maybe I should have used a face-mount technique instead so there’s no “gear climbing” force. Or maybe…

Okay, whatever. I didn’t need the full torque that the 45:1 ratio was going to give – I more did it for a limited lifter speed, but I suppose that’s why I took the care of engineering clutches into Overhaul, and Clockers Past, so it didn’t consume itself.

That’s why you might have noticed the bot split in two for service during Sadbot’s segment. I managed to get a P60 from another team that was the 16:1, two stage ratio, so I had to fiddle it into the bot. This involved cutting the height spacer down in length because the mounting pattern changed. Luckily, I anticipated something dumb like this happening, and the bottom rail has both the 2:1 and 3:1 pattern.

The only downside of going 16:1 is the lifter will be almost hammer-speed. But this could be entertaining in its own right!

Clocker’s next fight was against Ascend, a very powerful 30lb pneumatic flipper. This was going to be a durability test!

It was hard to get under using conventional means, so I mostly had to drive around it and hope to catch it vulnerable post-flip. I also spent an infuriating amount of time trying to get out of a floor seam.  Clocker went flying several times in the fight, which was the shakedown test I wanted.

Near the end, it got stuck upside down because the retaining bolt for the lift axle on the left (gear) side actually backed out and fell out somewhere!  So the gear just skipped as I tried to put it back upright. I managed to get one good grab-and-lift and a couple of other pushes, but didn’t prevail in the decision.

What was cool was I actually got a wheel nibbled off from a direct flipper shot in the first 30 seconds, then drove the entire rest of the match on 3 wheels. Just fine.

This was very exciting. To me, this means if I can keep the chain and inner hubs on, I can treat the wheels very disposably. Not that I’d do it as an explicit tactic, but as get out of jail cards if the situation forced it.

In Overhaul, I’d likely keep the inner wheel tightly retained while the outers are left to float on plastic/shear-rated hardware. I have a few ideas of how to do this for Clocker itself come Motorama.

Another downside of just coupling your actuator to the bot lazily: When your actuator suddenly has 3 times the power, it’s gonna start consuming itself! Remember I put a 42mm brushless on the leadscrew drive instead of the usual 500-class drill motor.  Overhaul has a dedicated trunnion on the lift hub, this is just me not wanting to bother redesigning everything after the lift gear to use a 30lb-scaled one.

The lift motor didn’t blow itself up this time, and in a way I found the lessened torque to be more tolerable. I still clearly had grab and lift ability, but now with the weight of the bot having more leverage against the motor, I noticed I could “trim” the bot better in that match. I’d stick-down just a bit, and gradually the thing finds its self-levelling point. I could then periodically stick-down to refresh it, in a way.

All patched up after wheel service.

Clocker’s 3rd and last fight was against BEEESS???!! (You must only say its name with the upward questioning inflection). I found it hard to get a grab on with his defensive tines sticking out everywhere, so this match was just a lot of driving practice.

And that’s it. Sadbot came away 1/2, and Clocker ended up 2/1! After the event was packed up, I sent the bots back up north with Earl and picked them up from Connecticut again the week after.

Well, not before getting up to some shenanigans in the dark behind the building.

Sadbot, being “Extremely robot shaped” as we termed it, was used as a test dummy by a few teams with lifters/grabbers. Here is a future possible BattleBots entry, Claw Viper, tuning lift motor settings using Sadbot as a dead weight.

The Real Giant Nut was the Lessons We Learned Along The Way

So I’ll do a  more in-depth discussion of the implications for Overhaul separately as its own design series. But here were my two biggest takeaways from this event:

  • If I can make the equation “Overhaul 3 drives like Sadbot drives like Overhaul 1″ work, then I feel far more confident bringing sexy back in the arena. I’m satisfied with this powertrain setup, consisting of the single 80mm brushless motor on a Brushless Rage, geared conservatively for about 13mph, and back riding on big blobby wheels.  What I’d probably do is use this as an initial design path, but have a failover ESC solution (VESC controllers have grown up a lot in the past 2 years) as well as a failover brush DC solution. I have some candidates in mind for the latter which I tested over these few months and think are a good idea. More on that later!
  • Clocker was a great architectural test beyond what I intended to accomplish. I definitely wasn’t counting on losing a wheel here! The bot was vastly easier to maintain, even replacing the lift gearbox with a different ratio. I now know that the frame should get longer to better grab and lift – part of the issues stemmed from having to move the front wheels so far back. The small poker wedge legs worked out reasonably, but I’d probably want to make several kinds because of the arena floor. There’s only minor changes and mods I want to make before Motorama. For one, it needs to test the DETHPLOW architecture for Overhaul, and maybe implement my 2-stage breakaway wheels.

One thing to note about Clocker is that I should have dropped the Angerbox clamp drive system to a single stage. I’ve basically done away with the requirement that either Clocker or Overhaul can crush stuff. The clamp should therefore be fast to close, something it wasn’t really at this event. Clocker and Overhaul will likely run single-stage gearing into their clamps for future events.

Between these two major differential tests, I think I have a good handle on what Overhaul 3 has to be.

Namely, it should be Sadbot, but with a grabber and lif….. wait a minute. #holup I swear I’ve built this bot before.

 

Überclocker 5: Finishing Up The Everything Else

Dec 16, 2019 in Überclocker 5.0 - 30Haul

Last episode, I had just finished machining and assembling the frame. As I said then, it felt a little wrong. Almost too simple compared to my usual. Well given that’s one of the major directives of this build, and for Overhaul 3, I’d better get used to the feeling. So with the aluminum machining taken care of, it was time to do some welding and final assembly.

The new leg design is almost 1 for 1 what I want to build for Overhaul. Its armored pontoons were a good idea for some forms of kinetic energy weapon dispersal, but weren’t very good at wedging otherwise. Last season I made the “stiletto” versions for matches where having broad surfaces against the ground would be a liability, but the way it mounted to the bot was still predicated by the angled wubbies. I could adjust their ‘preload’ into the floor with washers, but this was permanent (for the match duration) and they actually would impede the bot’s motion by slightly lifting the front small wheels off the ground. There’s really no substitute for a good set of hinged wedges that will always conform to the floor under gravity. I’d eventually want to redo these plates from an alloy steel like Hardox or good ol’ AR400, but for now, a surplus piece of on-hand 1/8″ cold roll steel works too.

Initial tack welds were laid down the parts as-fixtured, then I’d remove the leg itself and add a dab more weld bead. The design was specified for approximately 4mm gauge AR steel, but using 1/8″ cold roll meant there was a lot of placement slop, so I’d rather fixture as the parts were going to be used.

Top side in progress, mostly done.

And then backfilled from the underside. I then ground all four undersides smooth, and painted over the legs and mounts in black.

While the various painted parts are all drying, onto assembly work.  There’s a series of little spacers that have to be installed for the wheels to attach at the right distance to clear the drive chains. Not the most elegant approach, perhaps, but one that was workable given the commercial nature of the parts. For Overhaul I’d have custom hubs with the correct spacing already designed in.

On the inside, a series of washers to hold the hub face on. Another slight point of tack is to put the wheels on, you really need to remove the outer “hubcap” plastic Versahub because otherwise there’s no easy way to line everything up looking through the 1/2″ hex bore. A minor complaint, and really I could just put a plastic circle piece here instead of the Versahub.

Well, it has wheels now!

The lifter motor is suspended off the lower plate by a large gearbox-shaped spacer. It’s a bit of an overconstraint with a fixed bearing in the frame rail; same with the external bearings on the drive motors. Overhaul will have these be isolated systems with flexible couplings like I have on the existing lifter design.

 

The lifter fork and clamp parts all slide onto the main shaft one by one. The dead shaft does allow this thing to be far more serviceable than Clockers Past.

Once the three crossing tie rods and spacers are tightened, the assembly is rock solid. Unlike Clockers Past, the only method of force transmission  from the lift gear side to the “drive” side (right hand) is through those three interspersed tie rods. With the live drive shaft, both forks directly received motor torque. Now, My Calculations Show™ that the rigidity is adequate even picking up a 30lb opponent entirely on the right fork.

Overhaul already has a method of through-transmitting lift motor torque in the form of the big hollow hub the arms sit on, so the considerations there are much different.

Support legs all installed and tightened. A shoulder screw whose shoulder is the length between the hinge sides gets tightened down, and that’s all.

As I expected, this thing is really front heavy. The CAD model doesn’t quiet show it all, even, because it’s a static representation. With nothing in the back, the bot tips forward on its two front wheels immediately.

There will be things in the back, of course, and the final design showed I could possibly have a 3 pound counterweight spanning the back frame rail.  We’ll see how it ends up. I also suspected that the bot will drive very differently depending on how squished the front wheels are (i.e. how much downforce is placed on the arms).

One minor “oh yeah, I modeled that” as I mounted the drive chains: I specified flat-head screws for most of these frame connections, but to do waterjet layout when I wasn’t the one using the machine, I had to make a configuration of each part with the countersink diameters suppressed.

Then I promptly forgot I was supposed to use flathead screws, so installed button heads. This works fine for every place that doesn’t have a chain run next to it, of course, so I didn’t even notice until now.

Ah, that’s much better.

Electronics installation goes quickly, but first, I needed to throw things inside to get wire run distances.

Another “PM Charles” habit I learned and now don’t feel right without: I even created a wiring diagram for this thing with gauges, connections, and lengths before I cut a single piece of sumptuous silicone-insulated ultra-flexible noodle wire. And labeled every cable as I made them.

(As wires get into the multiple-0 gauge, they and their connectors begin getting more and more sumptuous as well as expensive if you fuck it up)

I avoided making something intelligent like Super DEANSBUS and instead just went for the good ol’ Hong Kong Soldered-Shrunken Squid. I only needed four ESCs and an auxiliary connection (for receiver power).

Prepped and ready after a couple more hours of soldering. I’m very much now used to crimp tooling and contact systems used in commercial/industrial connectors. The R/C world really needs a “crimpable bullet connector” of some sort (And I don’t mean these trash-tier things), because solder cup filling for dozens of wires just takes so much manpower.

And here it is!

I was very much right when I said it would drive differently depending on if I had the arms down or up. If the arms are raised, the back two wheels basically aren’t there – it drives like a 2WD bot and is almost too squirrely. Overhaul 1 had similar issues, but the long triangular pontoons damped it a lot.

However, if I drop the arms down and preload them into the ground even a little, it will transfer some weight to the back wheels, unsquishing the front wheels just a little. It gains 4WD-like traction, but still puts substantial weight down on the forks. I actually managed to accidentally sand a good mount of the forks off on the bottom driving around in the rough concrete area of the shop.

This is a desired result. If I make sure Overhaul can sink down a good half inch or so in the front when the arms are raised, it means I have a fairly large band where the arms can be down and the bot still retain full traction. OH2.x wasn’t capable of this – the small wheels deformed so little that it propped the front 4 off the ground, making it act like a front-dragging 2WD bot.

On my mind now is a good way to make an easily adjustable travel limiter so I can, if need be, just slam the arms down without having to modulate them carefully. On this bot, if I drive them down too far, I can get it to start behaving like OH2.X – turns become more difficult and less predictable as the rear of the bot is trying to pivot around a drag point in the front.

The final weigh-in is pretty much on the money minus the weight of the wires, which I didn’t put in a simulated blob of copper for. The CAD weight was 26.7lb. Looks like either way I’ll have around that 3 pounds to play with to install a counterweight on the back plate!

Stay tuned for some exciting Orlando Maker Faire coverage, where I’ll get to find out if everything is wrong.

Überclocker 5.0: In Which I Actually Have to Build the Bot, Not Just Talk About It

Dec 11, 2019 in Überclocker 5.0 - 30Haul

Here, have an Überclocker kit. That’s it. My job is done and I’m going home.

Hah – funny story though. The past 3 generations of Uberclocker were actually ALL sold in the end to other builders. That’s right – before this build, I didn’t possess a single one of them. They were sold in various states of disrepair, of course. But sadly, I have yet to see any of them back in the arena, or face my own follies.

By the last week of September, this was the pile that I’d collected. The last head assembly is just for show – it was a spare made for the previous bot (Uberclocker 4.0) and is damaged in a couple of places. I’d gotten orders in for motors and pulled a couple of other Clocker 4.0 parts out of the organizer. A lot of this will see reuse intentionally.

Putting together a wheel assembly revealed that the Vex aluminum Versahub downloadable model is WRONG! It shows up as a flat face on the oberse, but in reality, has a shoulder that is larger than the 1.125″ on the other side. Vex uses 1-1/8″ as the standard because it also happens to be the outer diameter of a Type R8 or FR8 bearing, a very common bearing size.

So I had to turn the short shoulder down to 1.125″ in order for it to actually fit the plate sprocket. No biggie, but hey, update your damn CAD model.

Notice how the wheels are mated together – they have the previously mentioned #8-32 standoffs crammed into them. If I trusted friction enough, there isn’t even a need to have something on the other side. These were rather tough to press through!

One of the plastic Versahubs caps off the outside here. The whole assembly slips on to the P80 keyed shaft and is retained by the shaft’s end-tap screw hole and spacers.

That’s it. What? I made a drive system that’s one gearbox bolted to one wheel? On purpose? Boy, haven’t done that in a while.

The P61 gearboxes assemble almost directly onto the Sk3-4240 motors using the Mabuchi 775 motor mount kit. The shaft is too long by about 6mm however, so I had to trim all of them with a Dremel disc and cleaned up on the belt sander.

I printed off a couple more of these “Angerboxen” as I call them, which have been a staple of my bots for a few years. They’re based on a design I made all the way back in high school (with less tools) and carried through to bots like 12 O’Clocker, and then a spare motor from that made it into Uberclocker v4.

They’re just repackages of generic single speed drill gearboxes into a 1.5″ square profile, compared with their usual 2″ funny shapes. This will be the first time I cram a brushless motor into them, though. For the sake of convenience and expedience, it’s easier to keep this bot all brushless instead of make room for a brushed Ragebridge. Previously, Uberclocker 4.0 had a DeWut for the lift and a 550 size drill motor for the clamp, so it made sense.

I picked up a 4.95mm reamer to bore out some spare drill pinions (I have a 10 pound bag of loose random cordless drill guts) to turn them into pinions for the SK3 motors.

And here it is ready to close up!

…and a day later, after a quick redesign.

 

You see,  the SK3-42mm motors are bigger in diameter than a 550-size drill motor. Not by much, but by annoyingly enough that I could not feed one of the threaded tie screws in from the motor side.

I ended up changing the design up to have the tie rods enter from the front, basically making this an ersatz P60/61 gearbox. I mean, at this point there’s no real need to have a custom design and I might as well do an “embedded P61″ like Overhaul had the P80 integrated into the clamp motor. But this setup is lighter and already designed in, and it was easy to replicate.

I added a set of 2 smaller holes in the center for a Mabuchi 400 size motor. This faceplate mount is often found in the smaller 28-30mm brushless motors – if weight got out of control, I could quickly drop the motor weight in half by going to one of them. I don’t need the full power of a 42mm brushless on the clamp arm anyway, but it was there and easy.

All of the subassemblies and components are starting to come together now. If there’s one thing that 1. Building Overhauls and 2. Doing Massive Drone Startups have taught me, it’s always just pipeline spares if you have the materials on hand. You will need them sooner or later, whether gust of wind or gust of Tombstone.

The lift arm shaft, unlike Clocker 4.0, is now a dead axle like Overhaul. I wanted to ensure the less complex box frame had more members to tie it together side to side. Pretty much every Clocker Past has had a live axle to let me easily turn a shaft collar into a torque clutch., but for this one I’m doing it dirty! Shown here are a bunch of spacers to keep the arm elements at the right distance apart. The shaft material is McMaster’s “ceramic coated aluminum” shaft material. Easy to machine, but you have to break the ceramic coating which is actually fairly tough. It will eat regular steel tools, but carbide will defeat it.

After the first week of October (Well, there goes Franklin Institute), my waterjet parts arrived from a local vendor. I dropped off material the week prior, so an average turnaround time, plus picked up a handful of company parts while I was at it.

This was enough parts for two bots except the frame, which I figured wasn’t going to get trashed at a Sportsman’s Class competition like Robot Ruckus, so I decided to not incur the extra cost and the having to order additional material.  I’ll do this for Motorama instead, where I plan to enter Clocker into the full combat 30s.

Checking off your own fabrication prints is always satisfying. Maybe just left-over project managment energy in me, but this is definitely my most documented and organized bot in years. Having other people needing to read your thoughts and intentions clearly in mission-critical systems is something I’ve had to get used to in the past 2-3 years, and I most definitely learned a ton from other folks at the company with more extensive industry experience.

(Not to say these are remotely version-trackable and custody-chain verified prints…)

I even back-added the “live edits” into the drawing files and annotated the CAD model. Oh, the horror.

 

Both Uberclocker and Overhaul make extensive use of these 12 pitch, 12 tooth, 20 degrees P/A stock spur gears. I made a point of just ordering a half dozen and broaching them all, because again, I’ll need these again for OH3.

Anyone ever find it funny when company logos and motivational posters show odd numbers of gears in mutual mesh?

It’s really just a Freudian slip into the culture of the organization.

Machined rear axle spindles and a test fit in a hub. The rear hubs are the same Vex aluminum Versahubs, but bored out on both sides and a type R1212 miniature bearing stuffed into the pockets. They’re retained by a big washer at the end of the spindle so will take more effort to peel off than just ripping out a set of tiny bearings. I could have gone for simplicity and done a Delrin bushing too, but a large overhung load onto the relatively short (5/8″ wide) spindles made me leery about added friction under the bending load of the bot.

Next up, frame rails that need channelling and pocketing. I knew this was going to end badly for me if I didn’t mark them very clearly.

 

They also needed the top and bottom plate holes drilled and threaded – I set all of them up at once in the mill with the same reference edge and played a bit of paint-by-numbers on which hole has to go where, making something like the world’s most impractically slow subtractive dot-matrix printer.

Invitably, I had to bum it up somewhere, and that’s being off by one edge-finder radius on an arm tower. Everyone does this eventually, no matter how veteran! So I had to slot one of the arm towers to let it actually sit where it needed to be.

The top and bottom plates are being test fit here. Overall the tolerances were alright, but they do add up, so some of the holes just barely did not align and needed to be step-drilled up a 1/32 in size. I went 1/16″ over as extra future slop insurance.

Next, the frame was set up and clamped to the table to perform the drilling / tapping operation of the front bulkhead which was just going to get line-drilled in place. I didn’t feel like tilting the Bridgeport head 15 degrees and doing those coordinate transforms to get to the hole placements this time! Stabbing straight inwards with a drill was going to be all the grace this frame sees.

And that’s it.

The frame’s now fully assembled. 5 parts for the base and 2 for the arm towers. In some ways, this kind of bulky rail construction is elegant in its own right. Clockers Past have had elaborately puzzled together plate frames with part counts that ranged from 15 to 20 or so, and Overhaul carried that over for version 2. It’s now something I aim to move away from for V3.

Next up: Filling in the other parts of it that make it more robot-shaped.

Überclocker 5.0: The Big Post of Designy-Stuff

Dec 07, 2019 in Überclocker 5.0 - 30Haul

Alright! So previously I established some of the bot’s principal geometry. Now I had to actually import more components and try to flesh it out, and make little edits here and there. Recall this was where I ended before:

I’d already tabled the idea of moving the clamp motor to the arm tower region, and the lift motor has been moved slightly forward and under the lift gear. This had the side effect of pushing the drive motor (and hence the front wheels) rearward a good half inch or so, and I was a little dubious on if the bot would have weight far enough towards the rear to lift anything.

The clamp arm (the “head” as everyone calls it) was going to stay identical to the previous 30Haul version; I already had parts to fit it, and so it didn’t make too much sense to change. This was, after all, an exercise to see if I could keep a lot of Overhaul 2.x parts the same when it comes to the liftgear. So far, I think I can keep the entire top half of the bot using the same parts, so it will save a ton of redesign effort.

I’m now continuing to flesh out geometry and adding more critical (but blank) parts. The lift gear was going to grow some compared to last 30Haul, to give it more of a ratio with the lift gear. I had a plan this time of running a 3-stage P61 gearbox and using a single larger output stage, in order to be a little more commensurate with the old DeWalt-based lifter which was a 52:1 ratio with a roughly 4:1 output stage. The plan here was for a 45:1 P61 with 5:1 on the main lift gears. The motor shaft would stick through the left frame rail some, so the plan was to put an outboard bearing in to greatly reduce the bending burden that the narrow, necked P6x shaft would have to take otherwise; that’s what the large clearance hole where the lifter gear should go is for.

The intermediate vertical bulkhead from before has been turned into a kind of quasi-bottom-plate made of the same thickness material. All 3 motors bolt to this plate with spacers between them and the plate.

I’ve fully fleshed out the drive system here (all…6 parts of it) and given more detail to the lift assembly, including generation of the arm towers which are hidden in this view.

The Wall of Wub positioning was going to be two large groupings on either side to accommodate the legs Uberclocker is known for (which turned into the wedge pontoons on Overhaul). I also made volume claims for the center shock mounts when 30Haul gets its very own DETHPLOW.

I just imported a 30haul old arm in for geometry and visualization purposes. At this point, the bot’s CG was already very close to exceeding the front wheel line (a.k.a it’ll always tip forward). The height change of the main lift axle meant the forks themselves had to be shorter with a more severe curve. I decided to start over instead of trying to change the geometry of the existing arms, because there was something else I wanted to try.

One of my perceived flaws of the Overhaul lifter fork design is they’re still rather wide at the tips. I wanted the lateral rigidity there, but it did mean if the arm tip got bent up it was hard to get under someone with it ever again.

My bright idea for 30Haul, which would be equally reproducible for Overhaul, is to have a main plate member that is extra thick and rigid, but only have its thickness sticking out as the attack interface. Something set a little more inboard can provide the overall side to side rigidity.

For 30haul, this meant I was actually going to make each fork from a solid backbone of 1/2″ aluminum. We start with the basic dropdown shape which will clear the frame. I made some push and pull adjustments as I went, since I wanted the arms to descend down quickly, but shouldn’t cut away too much of the front frame rail.

The upper curve is generated with some tangent arcs.

And the bottom curve just follows the same arc center with some more edgy features. This is actually how Overhaul 2.x forks were all generated too!

I smoothed things out and added some thru-spacer holes as well as bolt circles.

Check out that arc of 5 holes that runs roughly down the length of the arc shape.  This is what they’re for:

Instead of discrete standoffs like last 30Haul, I’m going to be using a single solid plastic spacer between the inner and outer fork. The discrete spacers were fine for 30lb Sportsman’s Class duty. But they just entered Full Dab mode under any significant side impact since the standoff thru-bolts provided bending axes!

The idea of this fork is the thinner reinforcement plate and the thicker main plate are supported full-contact with the rigid plastic insert. Hopefully, this means it will act substantially like a sandwich composite in that side bending regime, and maybe a hard smack from a weapon will introduce a bend or a bow, but it won’t just completely fold up.

I was planning on using the Markforged machines to print the center spacers in Onyx, but they could also be cut from solid plastic.

 

After specifying and adding the inter-arm spacers, the majority of the bot’s mechanical needs are done now. Seriously, there’s so little going on compared to one of my average designs.  It’s kind of a refreshing change, honestly.

I next moved onto making the basic support legs that enable the bot to grab and lift. These front legs had to be Sportsman’s Class rules compliant first, which is why I’m going for a simple fork tine-like projection instead of the crazy angled wedges.

I started with the sketch plane that’s defined off the thickness of the rubber shock mounts, and made a big plate which covers all of them.

I had a change of heart at this stage, and instead of making solid projections that altogether ride on the wubbie mounts, I decided to pursue a hinged design.

I always thought I could preload Overhaul’s wedges into the ground with carefully adjusting spacers/washers on the wubbies. Yes, I technically could, but they then weren’t far from a permanent setting anyway. I found that the previous 30Haul only exhibited a narrow range of satisfactory wedging versus propping its own front wheels off the ground.

Hinged wedges have been on the retreat in the sport for a while (albeit slowly) because of their vulnerability to getting damaged. But a lot of bots still sport them, because having something load itself into the ground with its own gravity beats you carefully applying a pre-determined force trying to do the same in an environment that can throw anything at you, at any time.

The legs themselves will be made from thick aluminum also, for this time. They’ll be allowed to hinge upwards about 10 degrees – something can get under them without consequence as long as I back off in time. Even a fixed-but-compliant  wedge would, in that circumstance, still cause the bot to lose traction in the front if lifted.

I just drew some lines that looked cool first and foremost before making the geometry compatible.

Here’s what that assembly looks like up front. Now, it IS true that having hinged elements that are also on wubbie mounts is superfluous, and I agree. If the wubbies proved to add just too much extra compliance, I was satisfied with running plastic spacers underneath for Franklin and Robot Ruckus.

A size comparison between Clockers 4 and 5 (a.k.a first 30haul and new 30haul). The new bot is shorter by a bit – maaaaaaaaaaaaaaybe even too short on the wheelbase. But it’s not outlandishly compact like I worried about going in.

Before I started on the electronics layout, I decided to put the finishing fastening detail touches on the mechanical end – Every hole got at least one sample fastener as a sanity check, and I also laid out top and bottom plate bolt patterns.

 

Up until this point, I’d actually never designed the rear idler hub. I modeled it as kind of a top-hat shaped spacer with two shoulders, one for the wheel hub bearings and the other to space it out from the frame. It would just get anchored in with an extra-long frame rail screw after the wheel is mounted.  Relatively simple and durable!

I also decided to knock off a few BB entry trends and add “breadboard holes” to the frame. Some on the sides,  as can be seen, but mostly on the back.

The idea of these breadboard holes is to be able to add attachments and defenses in a quick, reasonably strong way. You standardize on your own bolt pattern when designing these accessories. I didn’t have any in mind at the time, but it’s one of those “Boy, it’ll be annoying to drill them later” features.

 

The clamp actuator was imported from Uberclocker v4 and is almost completely unmodified except for a total height trim right next to the three small mounting holes. There was just a lot of unnecessary material here before, and this allows the actuator to be about as compact as I can get  it.

So that’s about it, mechanically, for the bot. I’m definitely not used to something having this few parts, and I really hope the design approach works for Overhaul proper.

With this allowed to rest for a while, I turned my attention to “things which hold electronics”.

I’m reusing the design of the battery tray from Uberclocker 4 with a few small geometry shifts to accommodate the frame shape of this bot. It has slots underneath where hook-and-loop cinching straps get fed through, which hold the battery down.

The “Rage-hutches” as I call them each hold two 6-FET Brushless Rages face to face stacked vertically. I found this was a convenient height – just barely under the thickness of the frame!  They’re made of 2 pieces each. One is a baseplate with mounting ears, and the other is the perimeter “U” shape with holes and reliefs for the heat sinks.

In another deviation from my usual form that I want to point out is the utter lack of small hardware on the bot now. The top and bottom plates are retained by 1/4″-20 thread size, and even the electronics mounts get 1/4″ compatible clearance holes for a nut-and-bolt interface with the bottom plate.

I’ve tended to use #4 screws – or at least very small screws – to hold ancillary parts and electronics in. One of the critical exercises we did for the company products was really trying to standardize on hardware, and after being part of that, I am keeping in mind the number and types of fasteners in use in the bot. A long time ago, most everything I made robot-wise was just using whatever hardware conveniently fit the geometry…which meant I might have needed 4 different hex wrenches to change a motor, for instance.

Working  on deployable products, plus the much higher regimentation requirements of the BattleBots pits if you actually wanted to get things done fast, have made me think of all this from the start. This bot should be serviceable for the most part with a 5/32″ hex wrench. I actually spec’d button head 1/4-20 (frame and top/bottom plate) but regular socket head #10 screws (motor mounts) because they share the 5/32″ drive. I made more use of #8-32 than I ever have before as my “small screw”, because Vex parts are made for 8-32.

And here’s the size comparison again from the top view. I was fully expecting Uberclocker 5 to not be able to drive without the opponent raised very high. Overhaul 2.x and Uberclocker v4 both have substantial front traction in the form of small wheels located nearer the center of lift. Other things of note – the inner frame rails of Uberclocker 4 are about the same width as the “Outer” ones of v5. The attacking cross-section of the bot remains much the same in terms of width and height. Really it’s those big Vex wheels that sort of make the thing look small, in my mind – the body looks visually smaller in comparison to the large wheels that poke out.

From the side, the bot has gained some height, but pretty much solely due to the added chassis height. I was able to keep the curvature of the fork tips not too severe – the taller they are, the harder it will be to grab opponents.

Overhaul 3 itself should still have a somewhat longer wheelbase and better proportions of the wheelbase x track rectangle. Remember, I had to move the front wheels backwards. By the original design, they should be very close to the front transverse frame rail.

I personally felt, too, the bot could have stood to be a bit longer even here. But, it really couldn’t get longer. Why?

If the bot went further back, the thing wouldn’t really be able to self right. I’m sure it can throw itself back over with the momentum of the lifting assembly, but I like being deterministic from the start. This was a length restriction for Overhaul 2.x also – in one swing of the forks, I had to be able to tip the bot onto its wheels again. So this means Overhaul 3 is going to have to gain wheelbase, If I so desired, by moving the front wheels forward again to where I intended them.

Next up, the initial rounds of fabrication begin!

The Overhaul of the Future Begins Now: Überclocker 5.0 (Also, Welcome Back to Robots)

Dec 04, 2019 in Overhaul 3, Überclocker 5.0 - 30Haul

After season 2, I had a whole list of changes I wanted to make and “design regrets” …that I wanted to address.

Really, I… see #season3 as a chance to do Season 2 “correctly”, addressing things that didn’t go the way we want or designs that could have been done better.

And frankly, anybody trying to build from scratch for the season now is either a dumbass or more of a man than I…

-me, some time in 2018

 

AAAAAAAAAAAAAAHHHHHHHHHHHHH

Those words have come back to haunt me.  Great! That’s totally never happened before, right? 

Okay, okay. No more vans, I promise – not for a while, as the Cold Brutal Winter of I Hate New England Weather has fully settled in. Here we are, on the cusp of another potential (#NextWeek) BattleBots season. I still owe the world a “event report” and summary for BattleBots Season 4/2019, which I went to anyway and set up in the pits as a Ragebridge dealer.  While I obviously didn’t bring Overhaul nor was involved in any of the matches, I did get up to a lot of Learnin’ and Talkin’ to with everybody there, as well as some incidental brushless motor troubleshooting. I tell you what, kids: brushless motors are a mistake.

My takeaway from the whole two weeks of hanging out with everyone, watching all the matches, and being in the pits acting sporadically helpful or like a nuisance? The metagame has moved on, and Overhaul has to move on with it. Consider this post really a recap of all of the off-season work since then, up until a few weeks ago which I’ll cover more in detail as this post series grows. Sit down, because it’s gonna be long and filled with Philosoraptor Charles Mangst!

The Exposition

Coming out of Season 3 in 2018, I was actually very satisfied with the bot mechanically. Here’s what that entails:

  • The Fantastic Combination Gearnut and packaging of the clamp actuator was greatly improved over the Season 2 ball screw design, and it worked swell the entire time. This part – and really the entire updated clamp arm for S3 – is probably going to make a straight unedited return.
  • The frame brace that was added to the intersection between the outer rails and the front crossing bulkhead greatly increased the rigidity of that area, to the point where there’s no visible deflection even after getting thrown around by Witch Doctor and Warhawk.  To be fair, OH got some reasonably softball matches that season, and I’d love to see just how it would have done in another old-Cobalt style hit. But it truly was a hack to try and patch a deficiency in the original design.
  • I was super into the redesign of the main lift hub, which was really my first on-purpose designed hollow weldment with attachment features. It  had a larger radius of engagement (bolt circle) with the lower forks, and enabled the forks themselves to be a single design instead of having 2 mirrored configurations.
  • The cast wheels and drivetrain proved also reasonable in service. The front wheels ended up being a little too fragile and had to be replaced almost every match, but I didn’t have any SET SCREW PROBLEMS this time at least. In all, even during Season 2, the drivetrain of the bot hasn’t been a source of mechanical headache – remember in S2 I drove the entire 3 minutes, even if underwhelmingly, against Beta, and this time around barring fire issues Overhaul was in pretty constant motion the entire time.

So in summary? I did get to do “Season 2 correctly” in that limited sense. But obviously, the whole bot catching on fire issue was…. suboptimal, among other emerging and now very salient problems.

The Conflict

So did I REALLY “do Season 3 correctly” either?

Brushless Rage was tested on the bench under some simulated use cases including throwing big hub motors around. But what I wasn’t able to make time for was actually putting the system in the bots, including Sadbot, and then driving it around enough to discover the transients that would ultimately cost it matches. The development of Brushless Rage took some of 2016 and 2017 while first I was kept busy at the (then) new shop space doing consulting work, and then the startup itself ramped up significantly closer to the back half of 2017 and going into 2018. 6-FET Brushless Rage has, by now, proven itself to be rock solid in the lighter weight classes, but I could not test 12-FET to discover its limits effectively.

Not that I’m blaming it exclusively, mind you: a few other bots including Brutus and Predator actually ran it fine for multiple matches during the season. Instead, in light of some new testing performed recently with Sadbot and Overhaul itself, which I’ll discuss here in the near future, I’m rather convinced that the interaction between Overhaul’s split drive motors (i.e. two ganged motors per side) was what led to my FIERY DEATH! problems.

Here’s what is going on in the Overhaul 2.x drivetrain. I have two 63mm brushless SK3 motors per side, each going into a Banebots P80 gearbox that’s a single stage 4:1, and the outputs joined by a short chain.

Seems legit, right? The problem is, if you hold one motor still, you can just about rotate the other motor a half or even 3/4 of a turn before the slop (made of two 4:1 derp-tier gearboxes and a kind of loose chain) is taken up and you actually “feel” the other motor.

The problem comes when direction changes and stops occur. No ESC is ever perfectly timed, and no R/C pulsewidth is noise-free. Nor can you guarantee the motor stops in a useful position to quickly push the other way.  Therefore, the chances are high that in stopping and direction changes, one motor acts first – and promptly runs into the other, possibly desynchronizing with the ESC momentarily too. When this happens with a brushless setup, you usually get high surge currents for that instant. Add up enough of them and I can pretty easily see the Brushless Rages simply overcooking themselves in under 3 minutes.

It took driving Overhaul hard around the expanses of the new shop which the company moved to only this past March, with the lid off, before I was able to witness this in action: some times, one motor will just start before the other on the same side. Before then, I’d never been up close to the bot as it was rapidly changing direction, turning, or stopping (…for good reason, I maintain). All because the old shop was too small and confined to safely do it, and the lack of ground level access and dismal state of the parking lot anyway meant the psychological need wasn’t there. It “drove fine” in the limited context of the shop floor, so I hoped for the best.

The original premise of this design was to load-share the 6374 motors, which definitely have adequate power output ability to drive a heavyweight around on only two, but which do not have nearly the thermal mass needed. Work done is still work, and the same amount of energy heating up a smaller mass makes it much hotter.

But in retrospect – and only can I really say in retrospect now because others have done it as an offshoot or variation on this design – the way to do it would have been to gang the motors together themselves, instead of through gearboxes. The Robot Wars entry Magnetar (and Pulsar) built by contemporary Brushless Hipster Ellis in the UK illustrates this: two 63mm brushless motors are ganged onto a single bull gear directly. There’s minimal slop between the two, virtually eliminating the chance of the motors contesting each other.

I’m not gonna write the OH2.x design off as “too complicated” – really, the mechanicals of the thing never gave us any problems in the pits. It was designed to allow quick disassembly of the frame rails and replacement of wheels, and it fulfilled that role well. We never had spontaneous chain-falling-off or wheel-jams-up issues like so many bots did (…minus #SetscrewGhazi). What I chalk it up to be is a 2nd-order phenomenon (slop between motors) that interacted very poorly with the control architecture (dumb R/C-style sensorless commutation) and whose cumulative effects (overheating and failure of one or both controllers) were not discovered due to lack of stress testing.

And I stuck with it for 2 BattleBots seasons – one because I didn’t know better at the time, and the next because I didn’t really have the time to deep-dive into these assumptions. As for why Overhaul didn’t catch fire during the regular Season 2 matches? Well, remember the 3-way “MIT Rumble” at the end. It did consume one of the dLux ESCs, and it was a match where I was much more involved in pushing and shoving and trying to flip Road Rash back over. In the Cobalt match, #SetScrewGhazi ended the match early. And I spent most of the Beta match running away from it!

I don’t know how much it all mattered in the end anyway, because the fact of the matter is: I never liked how Overhaul 2.x drove. Not with Colsons, and not with the urethane cast wheels.

Here’s the plight I face. Everyone plays me up to be a “good driver” because of my historical wins and my usually more showy driving style. I’ve never been able to bring it to bear on the TV show. It hurts to watch OH2.x matches, and believe it, it was even worse physically being up there. Unlike Overhaul 1, and by derivation Sadbot, OH2.x seemed sluggish to respond to inputs despite being – or maybe BECAUSE OF being – overpowered drive horsepower wise. I never felt one able to put the power into the box floor. Missed charges, lost or parried pushing matches, and just plain to-the-audience questionable maneuvering were all symptoms. Like just go back and watch Overhaul 1 and Bite Force 1 again. I live for driving matches like that, and OH2.x has not been able to follow through.

Remember the Sadbot driving video I linked above? The difference between doing that with Sadbot and trying to do it with Overhaul 2.x is, at all moments in that video I felt like I was in full control of Sadbot. With Overhaul, similar attempts this year felt stiffer, and the bot was less able to effect turns predictably – even after all of my arena time with it, on a bare polished concrete warehouse floor, I found myself going “Wow, this thing drives like garbage”.


If I actually ran this match, I’m fairly positive in Sadbot being able to win 100% of the time.

 

Part of it is geometry. Overhaul 2.x has a square drivetrain layout, where Overhaul 1 rested mostly on its front 2 wheels with a wheel arrangement that is much wider (track) than long (wheelbase).  Sadbot, using the same drive system but with a very central weight bias, handles even better. A slightly oversquare (wider than long) drive will be more favorable to quick turns and controllable slides, whereas a longer-than-wide setup is going to favor a more point-and-shoot driving approach where you tend to separate turning and forward-backward driving into more discrete events.

The other part of it, as we mused over in the pits at Season 4, is just sheer contact area. Academically speaking, no robot should ever have a traction advantage over the other except as a function of wheel compound softness. Because hey, Fₜ = μFₙ right? That’s how it’s presented math-wise in robot land, and is how must physics students learn about friction. And if both bots weigh 250 pounds, the vernacular rule of thumb always goes “softer tires win because the same weight will press downwards no matter how much contact patch there is”. Go ahead – ask a question on any robot builder group if treaded wheels are “better” than slick wheels.

What I think the basic theoretical treatment misses on is how dynamic forces from robot motion, wheel compliance, and weight shifting affect both contact patch and resultant available friction force. Think of it this way: A small and relatively stiff wheel like a Colson will never really change its contact properties with the arena floor no matter what angle you mash it into the floor at. It’s going to be tiny relative to the total wheel circumferential area, and vaguely parabolic or elliptical-looking.

However, a big go-kart tire, despite being made from a “harder” rubber compound, is designed to deflect and comply with the ground. A solid foam tire might be somewhere in the middle, offering more stiffness except when you really are putting power into it, deforming the foam carcass. What it means on a high level is that the contact properties with the floor exhibit a very wide variation with the potential for simply more favorable solutions to transmitting the total available drive power of a bot to the ground. I can’t really substantiate this without writing an entire thesis on it, but a gaggle of robot nerds petting each others’ confirmation bias is at least 80% as reliable!

In other words, what a few of us pretty much concluded from the mutual chin-cupping and nodding of this season was that if you wanted a quick yet maneuverable bot, you pretty much had no choice but to use acres and acres of tires. Compliant, bouncy tires, of almost any compound and material. The most stupendously driving bots in the game – designs like Stinger/Sewer Snake, Hypershock, Free Shipping, Sawblaze, etc. all just have obnoxious amount of wheel – go look at their official bot photos.

Too much wheel for me, historically speaking. I grew up on the romance of graceful, low profile bots like the original Biohazard, and this has carried over in some way for almost all of my robot bloodlines. Even Overhaul 2.0 was, in a way, a romantic testament to the low-slung billet-machined box.  Take the top half of Overhaul off, and it’s just as nice looking as a flat lifter-box style of bot from the Classic Days. In fact, at one point, I was going to run “just the bottom” as a Middleweight at RoboGames.

That preference, I realized, also comes back to bite me when it comes to driveability. Small, rigid wheels are better suited for the point-and-shoot bots because their inflexibility also means their regime of best tractive performance is more limited.  My general feeling is that the custom cast urethane wheels with tread lines made OH2.x traction more linear and predictable, due to being able to clear box floor debris, but not necessarily any greater in magnitude. It was, at least, consistently bad to drive and I felt like I was able to somewhat work against it – but put me in a match where the opponent had Acres of Tire such as Sawblaze and even Witch Doctor at the end of Season 3, and the difference became stark.

In short, the 6 rigid and small wheels of Overhaul 2.x were not conducive to it handling predictably due to so many points of contact on a varying floor, and just not having the deformable contact patch to really transmit the power of the drivetrain into the ground, at least without overcoming the material’s own shear strength.

There was one final trend that bugged me to see in Overhaul 2.x that stemmed from its last 2 matches with Witch Doctor and Warhawk.

Even if I can self-right, the ability to get away quickly to do that somewhere else is absolutely critical.

Yes, Overhaul can self-right. It can even do so pretty quickly, but some times the bot needs a second or two to settle into the position, especially if the clamp is all the way extended. The ears actually help with this explicitly; on Overhaul 1 they were 100% critical to self-righting at all.

But, that second  will kill you because Bite Force can get the good ol’ one-two hit in. That’s the nice thing about little vertical spinners – you can just keep pointing yourself at the opponent and expect results. Again, look at the most legendary driving bots of today: they can drive in almost any position, even if not on all wheels, at least enough to get themselves out of a sticky situation. Overhaul 2.x can’t do that, and not even Overhaul 1 or Sadbot can.

In the end, if I wanted Overhaul to drive like Hypershock, so like Hypershock it must appear. I was going to have to dispsense with the romance of Biohazards Past and focus the bot’s geometry on being able to drive. I know, now, that it can grab and lift just fine. But no amount of high-performance grabby-lifty will win matches if you can’t feed the opponent in.

Personally, I wouldn’t be convinced at this point that I “do a season correctly” until Overhaul just gets out-robotted consistently. Losing repeatedly due to random mechanical and electrical bugs is just sloppy.

The Dénouement

As OPERATION RESTORING BROWN was ongoing, a lot of these newly updated design requirements were stirring in my mind. It’s what I was actually doing while brainlessly covering myself in “van powder”.  I wanted to get a new Überclocker (/30haul) together for Dragon Con, but let’s be real, van is already too much of a project anyway. The next best thing to aim for was NERC Franklin Institute in October, or the Orlando Maker Faire “Robot Ruckus” in early November after I get back from Dragon Con.

Basically, while I was destroying my brain cells painting the van cab, I was using the remaining few I had left to formulate what I wanted out of Überclocker v5 as a Robot Reynolds Number test model for Overhaul 3.

  • As I mentioned, the lift and clamp arrangement was going to remain unchanged. This goes for Clocker too – even V4 (with Overhaul 2.0′s general appearance) managed to get off some great throws, and I was familiar with the design needs of the leadscrew drive clamp and gear-drive forks.
  • It needed comically large wheels for its size. Mentally, I figured Overhaul was going to use a go-kart tire or foam-filled utility tire in the 8 to 10 inch range, so it implied a 4 inch and up wheel.
  • However, and this is the important part – I needed the wheels to at least behave, on the 30lb scale, like what a foam filled or solid foam tire would behave at the 250lb scale: fairly bouncy and compliant. This actually ruled out a lot of wheel and tire choices. I could get the 4 inch BaneBots wheels again which Clocker v3 used to amazing effect, but they are fairly rigid. Same with Colsons. Custom-cast silicone or urethane wheels with a durometer of 30A or so might have given me that compliance, but from my experience casting soft urethane wheels for Clocker v4 at Franklin Institute, they were also going to shred and burn out very fast.
  • The design had to accommodate what I called “butt traction”. Overhaul, and by extension Clocker v4, can’t get tilted backwards more than about 25 to 30 degrees before all the wheels are off the ground. Even Clocker v3 has “butt traction” ability – see how the rear wheels extend past the rear frame members? This is suboptimal from an armoring perspective, since a spinner can pretty easily pinch your wheels off from the back. But a part of me wondered if that was okay as long as you saw it coming.
  • With all this changeup going to bigger wheels, the frame would need to be taller and denser than I’m used to – I tend to lay a lot of components out flat since the bot bases were always very wide.  I’d need to pay attention to the center of gravity of the bot and make sure it can even still grab and lift things.

While these thought for Clocker were ruminating, I was also doing a bit of lookahead – we in fact bought a good handful of bouncy 8-12″ wheels for PRODUCT DEVELOPMENT REASONS (no, like actually for the products) which were a convenient time to sample tire candidates for Overhaul itself.

In summary, by Dragon Con’s end, I had the following anchors dropped for Overhaul 3:

  • It must reduce the drivetrain complexity and ideally run with 1 motor per side instead of 2, such as the C80/100 motors we extensively used before, or their equivalent today.
  • It needed to have the choice (at the time) of either a brushless powertrain or a brushed one. Tests during the fall, and with Sadbot, were to help with this design fork in terms of priority.
  • It will return to 4 wheel drive instead of 6 (with two awkward small front wheels). The wheelbase should be made as long as possible to accommodate for center of gravity needs, but….
  • It will be a lot taller and more squat looking, more Overhaul 1 in appearance, to accommodate large compliant tires
  • It needs to have tractive ability from as many angles as possible – dead upside-down, angled up-side down, butt-traction, etc.

Well, that seems like an all-new bot to me, doesn’t it? I’d said before that I’ll run Overhaul 2.x into the ground first before building a new one. But I think to be realistic, I have no other choice – modifying everything to try and satisfy these needs didn’t seem remotely practical.  Ideally, I figured, I can keep costs down by greatly simplifying the chassis design, to move to a “somewhat modified barstock” method like Season  3 Brutus or a aluminum tube-and-shapes construction like Stinger or Whiplash.

Let the Design Games Begin!

 

The “insect” classes – 1lb and 3lb bots, have foamy model airplane wheels, generically called “Lite Flites”, for the bouncy one-piece wheel solution.  Heavy bots have solid/flat-free utility wheels, which in fact a few builders cheekily call “heavyweight Lite Flites”.

In the middle, though, I haven’t really seen any compliant wheel solutions, at least not uniform material ones. What I do know exist are “shooter wheels” for robot competitions like FRC and Vex.

So I went back to good ol’ Andymark and VEXPro and checked in on what their latest lineup for these products are, and what do you know – the mass commercialization of robot competitions (BACK IN MY DAY… -me) has really diversified the product lines. Now these squishy flexure tweel things are available in multiple durometers and materials and hub configurations!

I figured my solution would be somewhere in this realm, so I got a small sampling.

I rather liked the Vex straight-flex wheels. The Andymark design is overmolded rubber on a solid core, which I felt like was more of a potential failure point, so I went for these Vex Versahub compatible 4″ diameter ones. I got a few VersaHub components along with them to see how I could make integrated drive hub solutions.

In handling these wheels, I found out that they’re maybe just a little too compliant to run as single wheels, even in the 40A hardness. What happens is, they deform between the spokes fairly badly and begin rolling more like octagons. So at this point was when I had the idea of doubling them up – they’d better approximate the aspect ratio of a fat utility wheel or small go-kart wheel anyway, and would contribute even more to available contact area. #BotsGotDuallies is an idea that might also make it over to Overhaul itself.

One of my perennial FAQs when I taught mechanical design lectures/seminars was “Where do I even start?”. Good question – what’s the first CAD file made of an Airbus A380 anyway?

I usually told people my preference is just to make one of the small, well-defined subassemblies or parts first. You can always come back to any aspect of the design later, but “grounding” the design will help lock in variables and drive other placement and geometry needs. For me, it’s almost always the drivetrain of the bot and furthermore, almost always a wheel.

So there it is – I spent a few minutes staring at the Vex parts while thinking of easy ways to put them together. I ended up settling on using the Versahub sprocket on the “wrong side” of the hub itself so I can have a wheel on one side and a sprocket on the other. I think you’re supposed to use the Vex provided spacers with the sprocket on the projecting boss side.

This assembly is the kernel of the new 30haul drivetrain. The front hubs will be keyed to mate to a live driveshaft instead of being an idler, but the rear hubs will be bored out for bearing inserts for that role. Why this configuration instead of the multiple wheeled, indirect chain drive of Clockers past (or of Overhaul present)?  That’s influenced by another durability and “mobility in depth, at all costs” consideration to be explained.

I then started with dumping geometry haphazardly to think of some high level part placement needs. See the yellow square in the middle? That was an initial placement candidate for the main lift motor. It was a study in whether or not I could separate Overhaul fully into an upper and lower half. Right now, it’s basically there with the interface between the main lift gear and its pinion being where the bot can be “split” vertically when the arm towers are unbolted. Because I was anticipating the whole chassis becoming denser, I figured the lift motors might eventually make it upwards, especially with bigger drivetrain components possibly having to occupy where they roughly sit now.

As a sketching guide, I overlaid and mated the sketch into a dummy assembly and started organizing existing 30Haul parts into it.

One of the major improvements I wanted to make, as I mentioned, was greatly simplifying the frame design into something easier to construct on the inside, but keeping the bot’s visual identity on the outside. Unlike Overhaul 2.x or even the previous 30haul/Uberclocker which sought to imitate its topology, the frame of this new design is 5 major rails and a few plates/covers, ideally down from 14 parts.  All of these rails will simply be end-drilled and tapped – no fancy corner mating blocks (I’d favored the mating block/nutstrip approach back in the day when my fabrication means were much more limited).

Will the wheels be exposed? Absolutely. Is this a bad idea? Maybe a little. Here is where my “mobility in depth” plan is fully integrated.

I realized that the doubled up wheels could offer a defensive advantage. If they are mutually connected by “not much”, such as purposefully weak bolted connection or some shear pins and the like, then under normal driving they’d act as one wheel but the outer one will be very prone to shearing off once a big enough hit gets registered. For these Vex wheels, you’re supposed to bolt through them with spacers. I’m electing to use nylon standoffs to be threaded into from both ends – so the only connection between the inner and outer wheel is nylon. I got this idea from the HDPE side bumpers I installed on Overhaul in anticipation of the War Hawk and Witch Doctor matches – they’re designed to give me an extra life if it got broadsided, tearing off first and hopefully allowing a clean escape, which they did until I ran out of them of course.

The next element is why I have the front axle as a live, driven one. Overhaul 2.x has all “dead” axles – they add immense rigidity in the neighborhood of the axle connection. In Uberclockers of the past, I’ve then indirectly driven the wheel with another chain or serpentine chain setup (ooooh, instant single point of failure) or, as in the case of Überclocker Remix, through a gear. I’ve far more been a dead axle guy, is what I’m saying. The premise of this change is to have the dead, idler wheel in the back and the live driven wheel in the front. The rear wheel will be the most exposed and vulnerable, so it should not be the entry point of power into the system. The front wheel, in an ideal world, is going to be hiding behind the Overhaul-shaped wedge pods for one, and whatever else I put on the side of the bot.

I could make the front wheel technically also an idler and use an indirect chain or a gear drive. But the durability advantage I also want to confer is toleration of being bent. If the axle is bent and the wheel is wobbly, chances are another drive chain won’t stay on and a gear drive will no longer mesh correctly. But a live axle spinning in two self-aligning bearings may still stand a chance of both just transmitting wobbly wheel motion and hopefully, with the bearing constraints, prevent the bending motion from being propagated to the other side.

All of these combined inform the drive system placements for 30Haul. I decided to mount the wheels directly to the BaneBots P61 gearboxes here, for simplicity. For Overhaul, it’s likely going to be a double bearing system with an internal intermediate sprocket/gear stage if I can’t get a good direct motor placement.  I’d prefer to keep the motors as close to the rear of the bot as possible still anyway, for center of gravity and balance concerns.

In the most ideal worst case scenario (?????!) possible 30haul/Overhaul can take a direct broadside of some kind, get a wheel(s) pinched off and get flipped over, and I can skitter away with the remaining wheel on the other side (or be completely operable still with the “inner duallie” on the damaged side), self-right, and try to return the favor. That’s my story and I’m sticking to it.

 

First passes at generating frame rails are more or less complete – there would only be slight dimensional shifts from here.

Another major facet of Overhaul 1.0 inspiration that’s making it back into the design is the “wall of wubbies”. Overhaul 2.x was designed more like Überclocker since I obviously had that creative leverage, with the frame and drivetrain extending under the lift point where an opponent would be. Optimal, perhaps, for carrying, but it complicated the chassis and those front wheels were always a source of maintenance concern (since putting so much force through even smaller than usual wheels made them come apart or wear extremely fast).

If you recall from looking at Overhaul 1 in its early stages, it just has a big rail of rubber shock mounts on the front. This was definitely a compromise with the frame we already had put together, and they proved to be too bendy in operation once we really picked something up, like Bite Force.

Wubbies need to be spaced apart to approximate being used in tension and compression to be effective – they’re not very strong in either shear, or direct application of bending.  The idea was to give 30haul a “wall of wubs” of its own, but angled, numerous and in mutual contact, and with the outer ones arranged to mimic the ‘pontoons’ of Overhaul 1.

 

I’m testing the arrangement of the above-board lift motor placement here. While I like it, it had an unfortunate side effect of placing the motor directly in the path of the clamp arm. I’d have to sink the motor below the top plate level (making mounting more complicated again) to prevent this, or make some kind of U-turn drive to keep the motor package contact.

This is a manifestation of the robot part quantum principle that I’ve talked about some times. It’s harder to arrange parts in a smaller bot, because they are relatively so much bigger. A motor package not all that much bigger than this 42mm brushless setup plus a gearbox – my 63mm brushless motors into BB220 gearboxes – is used in a robot almost 10 times the mass and over twice as large in every dimension. Just the flexibility of having more volume to put things could be enough to mitigate design conflicts.

So I wasn’t really feeling this placement after a while. I’ll keep it in the back of my mind for Overhaul itself, though.

Therefore, the next stage of the design after a lot of rough geometries and placements were done is to push things around and see if I could get a more satisfactory solution. I moved the lift motor to a position rather close to under the lift gear. This allowed all 3 of the major motors to be in close proximity, which was nice, and it changed the forward bulkhead seen in the previous photo to a horizontal one that supports all the motors from below at once.

The downside? I had to shift the front wheels back to accommodate this position change, unless I wanted to implement the indirect-drive internal chain setup right away. Given that I was more interested in the bot as an exterior topology test, I didn’t want to add complications at this stage.

So I already knew 30Haul is going to have some center of gravity issues. I was fine with accepting this as an experiment to get a feel for how Overhaul 3 might drive (and Overhaul 1 DID drive – the placement of things is not all that different between it and this design!). It was clear the design would come in underweight anyhow, so worst case I’ll add a Shiny Metal Ass as a counterweight.

The next episode: Filling in more of the CAD details and executing my famous “Build it as I design it” strategy. I think the DoD calls it “Concurrency”. Say, how’s that aircraft carrier coming along?