Archive for the 'Bots' Category


Franklin Institute 2017 with Überclocker!

Dec 04, 2017 in Bots, Events

At the end of October, I took Clocker to its now annual fall robot party, the Franklin Institute “Battle on the Parkway” event. Last year, it was horrifically oversubscribed due to the surge in popularity after BattleBots Season 2 aired. This time, more restricted registration was enacted such that we had a chance of finishing in the allotted time, so I actually had to fight a little to get in.

This event would basically be the final test of Brushless Rage pre-production units. I had begin sending out PCB assembly orders the week before, so any last-minute messups were going to have to be revealed now. They did spectacularly at Dragon Con, so I wasn’t expecting any bugs, just the ability to abuse them in an arena environment where careful driving kind of goes out the window.


Clocker didn’t need any kind of prep for FI except to change the conventional lithium brick pack for a lithium iron phosphate (LiFe) pack at the behest of the museum which only wanted us to run not very flammable battery chemistries. I whipped out the same 7S dynamite bundle I used last year, topped it off, and off we went! Other changes were minor and were more or less maintenance from Dragon Con, such as putting in newly reprinted chain tensioners.

And here we are at the event! The FI arena is getting pretty long in the tooth. This year, a change was made where there were no longer any full-contact 30lbers due to the condition of the arena Lexan and its generally mid-2000s construction. So there were only 30lb Sportsman class bots besides 12s, 3s, and 1s. It also coincided with the conclusion of changes to the 30lb Sportsman class rules.

In short, wedges in limited form are now allowed, and all spinning objects are subject to a chart-based weight and RPM restriction. The restriction heavily favors light and high-speed saw blades, as there was some controversy last year about some robots using coarse-toothed sawblades in an impact (usual spinner weapon) fashion.

The neat thing? Clocker 4.0 is now Sportsmans-legal! Being arena-optimized and Overhaul-shaped meant it began being Sportsmans-illegal last year and this past Motorama.

While I ran it in 30SC this time, I think for Motorama I will still go for the 30lb Featherweight class to ensure I stay practice for KE weapon tactics, as there’s a few modifications I want to make now after this event as well as leftover plans from Motorama 2017.

Roll Cake came along for the ride! Not to compete, but just as a display item for builders curious about the whacky  clockwork that powers the flipper. Zac (of flywheel whipper Magneato) and I had some mutual neckbearding moments over flywheel flipper design, and Clocker would eventually face Magneato.

Clocker’s first match was against Congo… a robot made with a folding chair as a hammer/lifter. The face of 30lb Sportsman’s Class, everyone.

This match was extra hilarious in many ways. First, Clocker got stuck on the wrong side of the chair near the beginning – it was fully hooked over the fork and clamp so neither of us could get anything done. At some point during the wrestling to remedy this, the drive chain on the …. chair shaft? fell apart and proceeded to drop right into Clocker’s left drive side, high-centering it as I tried to push it around.

The match was stopped to detangle Congo, but at that point I hadn’t yet noticed the #40 chain slurping under the bot. As a result, I spent most of the match hobbling around. By the way, Congo at full chair spin packs a nontrivial amount of energy. With neither of us being able to do all that much, we just spend the last part of the match dancing, upon which I promptly overdrove the clamp actuator and the leadscrew rod fell out.

Abject failure. I lost a narrow judge’s descision to a robot with a folding chair as its only weapon!


Clocker’s second match (first in the loser’s bracket) was against BEEESS?!, a round tube bot with lifting tines. It was where we discovered that BEEESS?! fits perfectly inside the curved claw of Clocker, and so this match was mostly spent driving for dominance and me getting a couple of good grabs on it. I have yet to discover video of this match

Next up was the ultimate challenge of ultimate destiny against the feared new underdog….


Be Kind, Rewind.

we’re so postmodern This thing was built from a VCR – one hell of a VCR. In fact, after fighting it, I wanted to go out and try to find and purchase a model, because it survived an absolute pounding in the arena and actually won two matches unexpectedly prior to facing me.  Realistically, though, it wasn’t that much of a threat, so I threw it around a few times, did some wall runs, and the match went the distance.

This then put me up against Magneato.


Clocker and Magneato (along with its previous version, Jack Reacher) have a history. Now, Magneato  has 4 wheel drive and Zac has tuned out the mechanism to have variable firing power for self-righting versus various strength flips.

This was really the first match I was scared for, and I mounted the Clocker Unicorn in at attempt to either try and jam it into the flipper linkage or bluff a flip from afar. I did manage to bluff a few flips, but Clocker did go end over end several times. Magneato had a few issues self-righting, so I was able to dominate just enough to win the decision, including one or two cross-box runs with it in the air.

Next match was against Heracross, a pretty classic lifter bot.

I don’t have video from this one either, and from my memory only, it was an equally classic driving match where I had him in the air and ran across the box a few times, but Clocker also was rolled over and his driving kept me from righting immediately.

Clocker did land on its head at least once, causing the ears to shear out of their alignment lands and give it an adorable droopy effect. The problem was actually not the Onyx-Kevlar print breaking, but the 1/8″ aluminum section in the region bending inwards! The print was cracked, but the fibers held it together.

At this point I was in the loser’s bracket final, where I met…

CLOMP!!! (the exclamation marks are to be included) is a conceptual takeoff of Tentomushi/Mega Tento built by a group of high schoolers.  It’s deceptive effective – those little tines which stick out the front can easily high center you, which is generally how it won its matches. I was in general able to get a good hold of it and put in a few body slams and wall rushes, but Clocker also happened to fit precisely into the laundry basket, leading to some moments of dubious traction.

And finally, with that match done, Clocker had climbed back into the finals, where it had to face the smol-Yeti that was True Grit. Alex had also taken advantage of the new Sportsmans’ rule changes and upgraded the bot significantly.

This was an intense driving match. I like to think that Overhaul vs. Yeti would have gone down about the same way! Around 45 seconds left, I lost the lifter and so could only harrass True Grit around using the clamping arm and keeping it on the forks.

The problem!? After a year of slamming bots up and down, the two #10-32 bolts holding the lift gear to its hub finally sheared off. This joint, I realized, really could be a pin joint as the gear is sandwiched and can’t move. Putting screws in shear is always bad news – even if the joint was originally tight, enough smashing around and material is going to deform and cause the joint to loosen anyway.  Well, luckily I had already made a pinned hub since I was doing some Markforged lift gear experiments a few months ago. So this gear is likely going to get recut or machined out to accept that bore.

Other than that, I didn’t open the bot up once. The Brushless Rages took all of the event abuse without any issues, even with Clocker’s fairly OP drivetrain (42-50 brushless and only 6:1 on each side). It’s a good thing Brushless Rage preorders are shipping day by day now! If you missed the bus, their general availability will be in mid January.

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

Oct 02, 2017 in Bots, Events

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

*trips over Chibikart on the ground and dies*

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

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

roll cake

It all begins with a wheel.

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

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

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

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

Finished and ready for printing!

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

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

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

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

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

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


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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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


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

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


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

Well, everything is technically ready for reassembly!

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


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

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

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

the charles and the dragon con

Welcome to Dragon Con! Have a van.

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

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

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

The cotton candy committee has arrived.

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

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

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



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

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

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

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

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

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

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

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

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

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

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

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

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

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

And now it’s Monday!


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

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

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

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

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

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

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

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

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

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


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

This is a 12lb shell spinner.

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

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

NERC Sportsman’s Class Reform Notes

May 08, 2017 in Bots

[Note: This post was originally directed towards a specific audience and contains a lot of jargon and insider knowledge of the robot combat scene. Don't ask me what anything means.]

The NERC 30lb Sportsman’s class currently faces a few challenges with regard to defining its direction. In my opinion, the root cause comes from the builder base having mixed priorities and interpretations of the intent of the class. Here are two interpretations I think are the most common; particular concerns with the competitiveness of the class recently will be addressed with the subjects.

The Sportsman’s Class is to encourage nontraditional, creative designs in contrast to the polarized wedge-vs-spinner nature of the open classes

Nominally the reason why the 30lb Sportsman’s class was created in the first place. We can generally agree that the rise of extremely competitive spinner weapons came with the decreasing cost of Chinese brushless systems and lithium batteries during the middle and latter 2000s decade. This meant that in the open arena of most builder-run events (no hazards, no pits, pushouts, or other match-affecting devices), it became extremely easy to store large amounts of KE, and the only way to defend against KE was to armor up and build more compact robots with less exposed features.

Consequentually, robots with weapons which required less dense designs became extremely disadvantageous to build. The current balance of the sport is extremely noticeable in all weight classes running in the US. In particular the insectweight classes, the 12lb class and edu-league dominated 15lb class, and the 220lb Heavyweight class suffer the most from the “meta” (highly competitive strategy favored by a large percentage of participants) of a compact design with a spinning element.

It’s interesting to note in particular the 30lber scenes in other countries. In the UK, the Featherweights circuit is dominated by flippers and to a lesser degree, wedge-hammers. The UK featherweight arenas are generally elevated inside of a larger protective Lexan enclosure which only has 6mm polycarbonate (Robots Live), as well as having a pit hazard. This outright prevents high-KE weapons from becoming established, and the elevated stage allows more out-of-arena wins.

The UK meta is the fast flipper as a result. Video of FRA Championships 2016 rumble – notice the presence of US-style compact drum and vertical disc weapons, but they did not dominate the rumble for the vast majority of the time. The winner was a beater-drum design, but arguable it won on durability as it was one of the only robots left working at the end. Note as well as the presense of numerous flippers and inactive wedges (7 each, out of a field of 22).

Australia also has a growing Featherweights class as well as a 30lb-Sportsman’s class with similar rules. In their standard 30lb class which features an open arena, they have similar levels of design polarization. These videos from their National 2016 competition shows a greater prevalence of compact VD/drum weapons (as well as one midcutter style bot), comprising 6 of the 8 first round matches.

Robowars Austrailia also operates a 30lb Sportsman’s Class. For their upcoming event in 2017, this is the field of entries:

We compare the design trends with the most recent entries from Motorama 2017:

And actually from the featherweights at Motorama 2017:

Compare this with the Featherweights of Motorama 2005:


We note the following design trends:

  • That on the whole, the Austrailian (as well as the UK feathers, which don’t have a centralized registration system I’m aware of) tend to be less slab-sided and square with enclosed wheels.
  • Conversely, no matter if Featherweight or Sportsman, the US builds have been generally more square/flat sided with much less pronounced protrusions and a tendency to have doubly enclosed wheels
  • This tendency of US Featherweights really goes back – over 10 years. Many of the current crop of builders who started the 30lb Sportsman’s class and participate in it had entries in Featherweights in the mid 2000s.

(Note that a lot of Motorama entries are missing descriptive photos – we are relying a lot on the fact that we know what the entries ended up looking like here. Videos of Motorama 2017 are available here.)

Generally, designs with non-right angles are harder to make robust, as right-angle joints are stronger and simpler. Designs with protruding elements are also harder to armor and in a field of KE weapons, tend to have those features removed quickly.  As a result, those builders used to fighting against KE weapons will tend to keep using tried-and-true methods even in other weight classes and Sportsman’s Class – build what you know.  In my opinion, you can continue to go back through the history of robot combat (e.g. Jim Smentowski’s event photos from old-Battlebots) and see the variation of shapes and topologies become more streamlined and simplified as early as old Seasons 4 and 5.

I therefore conjecture the following:

  • It’s really the rise of high KE weapons which has forced designs to polarize between those weapons and the armor that can fend them off, not because competitors generally enjoy making wedges.
  • The open arena nature of most builder-run events has favorited KE weapons over other designs historically, since it’s easy to run away and spin up, and there’s nothing to hide behind.

How this relates to the issues facing the 30lb Sportsman’s Class is also heavily influenced by the attitude of the builders competing in the class. The next commonly-cited upside of the 30lb Sportsman’s Class which gets brought up is:

The Sportsman’s Class exists as a reprieve from the extreme competitiveness of the open class where people can run their robots for longer or build and operate less ‘serious’ designs repeatedly


One important side effect of completely eliminating high-KE impact weapons from the field was that Sportsman’s Class bots tended to have longer careers in the US. For example, Upheaval competed in Motoramas 2006-2014 with only one major rework; similarly, Gigarange has competed in almost a decade of Motoramas consistently. Überclocker 2.0 ran from Moto 2009 to 2012, and 3.0 from 2013 to 2015 (as well as several non-Motorama events in that time).

Looking through registrations of Motoramas past, it seems far more common for 30lb Sportsman bots to retire because of builder retirement or outright design retirement (e.g. Upheaval, Clocker 2.0, Nyx 1) versus being dismantled beyond repair in a single fight or tournament. I think a large part of builder retirement in the “in-between years” of ~2004 to 2014, prior to the revival of new BattleBots and Robot Wars, was due to builders simply quitting after their last tournament where they lost to a high-KE weapon and had nothing easy to salvage or repair; this was especially true of the higher weight classes (60-340lb) which were more expensive to rebuild.

The class has grown the most in recent years from builders who already have a Featherweight entry, and either decided to build a Sportsman’s Class entry to try other ideas or had their Featherweight damaged beyond repair in a match and wanted to try something different. Some new bots have been build specifically for the class with the understanding that they’ll get to run longer with less intensive damage. On the whole, it shows that a lot of builders are becoming weary of the repetitive neature of the current open-arena meta of spinners vs. armor.

New builders are also generally more attracted to building designs which are known to be competitive, or the most people have advice and tactics for. Conversely, existing builders will often build to survive tournaments, which means in the Featherweights they either tend to build successful KE-based designs or heavily armored bots with extensive spare parts or replaceable modules (at least one of which, for instance, might be a large slab of steel). In comparison to the UK featherweight and Austrailian 30SC classes, the US has less new builders who start out under its limited ruleset. More often these days builders begin in the 1-3lb classes, where the competition is extremely spinner-vs-wedge skewed, and build upwards from there, whereas the Australian 30SC has a higher percentage of new builders. We associate this with an increase in the amount of “unconventionally shaped” designs.

In a short conversation with Steven Martin, the organizer of Robowars Austrailia, he said this about their current state:

The attitude and outlook about the Sportsman’s class, in my opinion, are extremely similar between us and Steven. The consequence of the builder demographic in the US is that the builders who participate in the open class take their competitiveness with them into the Sportsman’s Class. If there is a “design meta” in the compact KE weapon vs. armored plow, then the “competition meta” is build-to-win versus build-to-entertain, one of the stated goals of the Sportsman’s Class. This is also an important point to relate back to the issue of high-KE weapons dominating in the arena.

The reason this “competition meta” still exists is because the tournament is run exactly the same as Featherweights and the rest of the event: A double elimination bracket with a single first and second place winner, etc.  coupled with the same kind of prizes. In other words, there’s no explicit incentive to build something that doesn’t win, even in the 30lb Sportsman’s Class, as you’re not otherwise going to get more than 2 matches (possibly both of which you lose). The judging guidelines are still the same as the main tournament. This is one element which I think causes the Sportsman’s Class to be as competitive as the open Featherweights class.  What happens in this case is the argument for Sportsman’s Class is at least in part defeated by the perverse incentive that is still building-to-win.

(It’s actually interesting to point out that the 30lb Sportsman’s Class has a different design-meta also: The fast lifter/flipper. Nyx, Überclocker, and Upheaval are among the most consistently winning entries.)

From the other side of this proposition is the influence of the less serious nature of the competition. Because the matches are less likely to result in your robot being damaged beyond repair in one or two hits (as is common in the open class), it’s a chance for robot that nominally fit the rules, but may not be geared towards excitement, to flourish. This has been demonstrated recently by the increasing number of simple lifter designs which would be quickly defeated in the open class, but also are technically Sportsman-legal. See the Motorama 2017 roster: Gigarange, Lil’ Bale Kicker, Ralph, and Coup de Gracey are all considered part of this. These are all bots which should do better in the open  bracket if KE weapons were not extremely overpowered; it could be argued even further that designs like Nyx and Upheaval can be considered the same.

I contend that the greatest signifier of build-to-win’s importance in the 30lb Sportsman’s Class in the US is that absent the high-KE designs in the Featherweights, most of the Sportsman’s Class entries will perform just fine in the Featherweights tournament. This is troublesome; if you want Mechadons fighting Obwalden Overlords, you have to go a step farther than just prohibiting certain designs, because other designs will take their place in a time-honored race to the top format.

Herein lies the conundrum: At the same time we would like to make 30lb Sportsman’s the “exciting” class, we also want to make it the “easy” class. The bottom line is it’s basically impossible and also unfair to compare Sportsman’s Class to the Featherweights open bracket on the basis of competitive excitement, as it runs counter to both aforementioned goals of the class. (Note: These might not be explicitly stated desires, just sentiments I’ve heard or seen reflected in 30SC-style contests nationwide)

It is therefore my stance that…

To reform the 30lb Sportsman’s Class, you need to break the “Meta”, the element which forces people to cluster around a competitive edge. The hard part lies in deciding which meta to counter.


Historically, I’ve been opposed to changing the design meta by legislation. The current Sportsman’s Class rules prohibit wedges (sloped surfaces within 1 inch of the floor) as well as impose RPM limits on kinetic energy weapons (“All devices rotating more than 360 degrees must not exceed 400 rpm”). However, both of those rules then have somewhat ill-defined caveats for lifter forks and plates and the like; spinning sawblades are also generally exempt from the RPM limit. Several recent attempts at reforming the rules have centered on defining better what these grey zones are, with maximum/minimum sizes of the lifter, or requiring the robot to pass a functional inspection at the event (cut-not-fling a test weight for saw blades, do not wedge under a certain test block with a fixed ground clearance, and so on).

I am not a supporter of this approach. First, while you do change the robot shape to eliminate “undesirables”, it then becomes which shape under the rules will still be the most optimal one. By (for example) limiting the width and length of lifting forks, those who would want to build lifters have an exact guideline to follow, knowing their future opponents will have to adhere to the same guidelines. By limiting the size and speed of sawblades, it’s now advantageous to always pack the largest one. It’s my opinion that design limitations actually erode the creative foundation (conjecture #1) of the class in favor of increasing the outright competitiveness.

Rules legislation has in fact resulted in “optimal” designs for different environments; in the realm of auto racing, the most legislated competitions are Formula 1 and NASCAR. Teams spend immense amounts of money in R&D attempting to optimize their car under very limited and regulated circumstances. One of the most important aspects of both auto racing series is in fact trying to ‘skirt the rules’ without visibly violating them, or being caught. In the realm of robotics, task-based competitions with a limited budget and limited BOM variety like the FIRST Robotics Competition are good examples.

While we would prefer our sport to help inculcate some engineering knowledge into its participants, we also have many good examples of what a purely engineering-driven competition looks like, and it is my belief that it counters the spirit of the 30lb Sportsman’s Class. Essentially, if you remove one design from the pool, others will simply take its place, or the designs will evolve to the new local maximum of effectiveness. The more design rules are laid, the more points of contention and Well Technically exist.

One positive example of design meta changing is the Plastic Ants class. In this relatively new class, the only materials permitted to be used in the construction of the robot beyond fasteners and some mechanical parts like axles and hubs must be made of common consumer & engineering plastics. The destruction level is greatly reduced, and it has become both a newbie-friendly class at events it is run at as well as a breeding ground for unusual designs such as bristlebot drive, omnidirectionality, etc.

This is not to say design limits are completely ineffective – some times they can be practical. For instance, kinetic energy limits are fairly easy to enforce by creating a weight-to-RPM table. Obviously the result won’t be 100% accurate due to varying MOI of different weapon shapes, but as robot weapons can really come in only a few shapes anyway, it’s an “in the range of” type decision.

For 30lb Sportsman’s Class, I support modifying the competitive meta as much as we can in lieu of making the design requirements more strict. Because the creation of the 30lb Sportsman’s Class was driven in part by intent, I strongly think intent also has to be an element of the competition. This can be done in a few ways:

We can change the tournament structure such that outright winning isn’t necessarily rewarded

Recently, local small-class events have begun experimenting with alternative tournament structures. The goals are mixed, but generally the idea has been to give people the most fights they can, against different opponents, and have fun versus win every match decisively. Two examples of these kinds of events are PCT SWORD Fights and MassDestruction, where 3-way battles, rumbles, and round-robin & Swiss tournaments. At MassDestruction, for instance, entrants are guaranteed 4 rounds of fighting through the Swiss tournament, with a smaller elimination tournament following for the top-ranked bots. At PCT SWORD, 3-bot fights are used.

An alternative tournament structure for 30lb Sportsmans would mitigate some of the 2-loss concerns (i.e. in a sea of lifters, a bristlebot would still quickly be defeated). A Swiss tournament would gaurantee a certain number of fights (the elimination thereafter is optional), while 3+ robot fights would cause the instantaneous competitive meta to change as the strategies of more bots come into play. By guaranteeing more matches, some designs which are most definitely considered ineffective (such as true-walkers, tethered projectiles, jumping robots, etc.) would become more appealing for people to try; this has the compound appeal of potentially encouraging people who take the event less seriously, or who just want to build for fun i.e. adding a small element of assbots to the competition.

I consider this the easiest-to-implement change which minimizes the impact on existing designs, rules, and arenas alike, which is why it’s listed first here. The only potential downside is at large general-public events, it may be harder for the public to follow the bracket. Mixing 3+ robot matches with a regular one-on-one elimination tournament might also disrupt the perception of the event. However, it’s my and other builders’ experiences that at an event like Motorama, people are not following the bracket anyway and are only there for good matches. Events like PCT and MassD simply assume this is the case, and that the builders are furthermore just there to get some good matches in.

Otherwise, absent of dedicating an entire event towards the 30lb Sportsman’s Class, and switching between two-bot fights and 3+ bot fights, we could also consider an different judging system for the class only.

The judging for the 30lb Sportsman’s Class should be weighed differently from the open class, with an explicit discouragement of passive behavior.

This kind of approach is the purest from an “intent-of-class” perspective, but is also the most controversial (and for good reason). It wanders closely to the BattleBots 2016 “active weapon rule” controversy, where several bots in the tournament lost due to a clause in the rules which said they must use their primary weapon in the match, and is unpopular with builders for that reason. While it did have the effect of eliminating bots which were primarily wedging and pushing, the announcement of the rule was sudden (at the tournament) and the enforcement was considered by some competitiors to be unfair. Furthermore, the BattleBots rule was criticized because in an open competition with a proliferation of KE weapons, they had effectively eliminated the ability to defend against them. The design meta was forcefully tilted in favor of KE weapons, as not even using armor to slow them was considered aggression or damage.

I believe such an intent-based judging approach CAN be effective if it is disclosed in full beforehand, and my favored interpretation is actually not that much different than what ended up happening at BattleBots Season 2. The key lies in the already limited nature of the 30lb Sportsman’s Class. There are no Tombstones to defend against, so it is more fair to encourage builders to attack  strategically versus trying to stop a kinetic weapon with brute force.

For our purposes, “passive activity” could be defined as pushing/wedging/pinning in lieu of use of the robot’s weaponry. This does bring up an important collateral to consider, which is what happens if the robot weapon(s) break(s) and it has nothing left to do except push.

The implementation difficulty of this approach is twofold, as you have to create criteria to decide when a robot is engaging in ‘passive’ activity, as well as ensure those criteria will be hard to interpret differently between judges. Rarely do builder-run events have consistent judges throughout the match, and people swap in and out almost at will. It would help to have judges which have been 30SC competitiors themselves, but the robustness of the guidelines will help mitigate the subjectivity.

Lastly, what I think will bring about the greatest sea change in designs but also be difficult to implement with existing infrastructure is:

Changing the nature of the arena will effect evolutionary pressure on existing and new designs.

All of life as we know it responds to environmental pressures, and so do robots. As discussed previously, the current open-arena with no hazards, pushouts, etc. is the idea place for storing up lots of kinetic energy over several seconds (run away to spin up) before you become effectively unapproachable. The advent of high-powered electronics has only made the window of opportunity for countering a spinner smaller. Arguable, the open arena itself was originally a response to the extremely cluttered arenas of BattleBots and Robot Wars i.e. ‘No house bots, no hazards, no bullshit’, and the continuing motivation is ease of setup and low cost of maintenance, since all of the arenas are maintained by their own builder base without significant investment from outside sources.

There is plenty of precedent for insectweight arenas that have arena hazards which mix up the fight, but do not cause outright destruction of the bots (something the BB and RW arenas did regularly, leading to the psychological aversion). I’ve even built one for one of the Atlanta arenas. It’s a 12″ diameter spinning flat disc which has sandpaper bonded to the spinning portion; it will grab and spin bots, and maybe sand their wheels down a little, before rising up and causing them to escape in some hard-to-predict direction.

Understandably, in-floor mechanisms like pits, flippers, or spinning turntables will add significant cost & maintenance and furthermore requires an elevated arena structure to support it. While arenas have been purpose-built for this (e.g. the UK arenas), existing US builder-run events will be hard-pressed to use this approach.

I technically don’t even like pits, as they also contribute regularly to accidental match ends when one bot ends up in it (or bounces into one) and can’t escape the pit.

Another approach with precedent is purposefully leaving arena floors beat up to add a semblance of terrain. This approach is used explicitly at Robot Battles events where the edges of the stage risers are purposefully left unmaintained, and arguably at most events implicitly as the floor material gets more and more gouged and damaged. While at Robot Battles this has successfully deterred low wedges multiple times, it does so inconsistently, also foiling many types of active weapons and forcing attacks to stop and bots to reposition away from a problematic floor seam.

One untried way to add some variation to arena terrain is replacing floor panels (typically 4 x 4 foot or 4 x 8 foot panels of wood and/or steel) with “something else”. This is the approach I favor for a future event of my own. The “something” in my case would be some low flat-topped pyramidal structures, probably welded out of AR400/500 plate. The edges won’t be so steep as to cause everybody to get high-centered, perhaps 10-15 degrees at most, but it would offer some strategic changes and open up the possibility of new match modes (e.g. capture-the-hill, domination) with multiple bots, which I think is super interesting to explore.

Such an approach won’t work well if it’s interspersed with other weight classes in the same arena, unless it’s announced well in advance that all weight classes will be sharing the same features. Otherwise there’s an additional logistics problem of transporting the terrain in and out and replacing the stock floor panel just for a few matches.

I’ve also thought about the idea of adding an “arena toy” to the mix. It could be a small weldment of steel tubes weighing approx. 30 pounds, something easy to grab onto by any bot with a moving lifting arm or grabbing claws. Or it could be as simple as a stock iron anvil or a truck tire. These wouldn’t be difficult to remove for open class matches, and would add some unique strategic enhancements.

Ultimately, most of these terrain and hazard ideas are supposed to shake up the strategic game in order to affect designs. It actually is another way of targeting the competitive meta more than the game itself. I don’t emphasize terrain when talking about rule changes because of the difficulty involved in changing aspects of arenas – it’s something I will gladly “put up or shut up” on when I run my own event. That said, prepare for #RAGEBOTICA to have some weird floor tiles.

Example Rule Implementation

A phrase I learned from one of my professors back in grad school was “If you bring the whine, so must you bring the cheese”. That means offer suggestions for change or improvement along with your complaining. For how much I complain about things, I actually try to open with suggestions for alternatives before really busting out the complaint cannon. So here we go! A lot of this is plagiarized from the current NERC Sportsman’s Class ruleset, Battlebots rules, and Robot Battles rules.

0.0 Spirit Rule: The spirit of the Sportsman’s Class is to encourage creative, unique designs and strategies. The rules are not exhaustively written to account for every possible circumstance. You should not design your bot to push the limits of the rules. The Event Organizer reserves the right to disqualify a robot under this clause should it appear to exploit the intent of the rules. If you have any question about the legality of your robot, you should probably make it more interesting.

First things first. I love spirit rules. WE’RE HERE TO HAVE FUN! They’ve actually done a good job of keeping Robot Battles franchise events running smoothly. This spirit rule does have a few teeth in that it allows EO discretion for admitting bots. I think 95% of current active 30lb Sportsman’s Class bots won’t have any issue here.

x.0 Active Weapon Requirement: Your robot must feature at least 1 active weapon. An active weapon is defined as an independently powered device that can seriously affect the operation of another BattleBot. If your bot does not enter the arena with a functional, effective weapon, you will forfeit your match.

Now, what I think is also important is a way for event organizer discretion for cool drivetrain-based bots, like melty-brain (translate while spinning in place) technologies and unique gyroscopic-based drives, which have long been locked out of the Sportsman’s Class for not really being an active weapon. This, in my opinion, is actually quite easy to address. For example,

x.0.1 Active Weapon Exemptions: Under certain circumstances, the event organizer may permit a robot without an active weapon to enter in the Sportsman’s Class. These exemptions will typically be reserved for unconventional locomotion methods. All robots who wish to use this exemption must be approved by the Event Organizer prior to registration.

This would let your bristlebots, gyro-waddlers, and melty-brains (what a sentence) into the class. However, some of these bots also use that main gyroscope/vibration source as a weapon. We’d still not allow that so they’d have to come up with some independent weapon if they want to play:

x.1 Kinetic Energy Restriction: All weapons of a robot capable of rotating continuously are defined as spinning in nature and will be subject to a kinetic energy restriction enforced via rotational speed (RPM) limit. The RPM limit shall be [Jim’s big premade table here. I think it’s completely reasonable]

Alternatively, we could keep the existing “400RPM” wording (or any other speed; while I do not like magic numbers in rules, you have to start somewhere) with an exemption for commercially-available saw blades:

x.1 Kinetic Energy Restriction: All weapons of a robot capable of rotating continuously are defined as spinning in nature and will be subject to a maximum rotational speed (RPM) of 400 RPM, with the exception of commercially-purchased unmodified cutting blades (e.g. saw blades, abrasive cutting wheels, sanding discs and drums) which may not be lower than 1.0 TPI (teeth per inch) in tooth count. Variable TPI blades shall be considered at their lowest effective TPI.

I proposed this TPI lower limit after observing and getting opinions on what sawbots were too ‘flingy’ – meaning the teeth were so large they dug in and transferred energy like a KE weapon instead of cutting. This TPI basically covers every saw blade that would be reasonable to use in a bot like megatRON, Gloomy, Pitter-Patter, and other saw-on-a-stick style bots. It only really eliminates very coarse wood-ripping blades, dado blades, and things like edger/trimmer blades for cheeky interpretation of “commercially purchased, umodified”.

In this case, only the Forrest and Freud saws would be against the rules. A 7″ blade would be permitted to have 24 teeth, for instance. A 12″ saw would need to be a 40-toother or up. And for anyone who wants to make some kind of bandsaw bot? That’s quite a lower bound to hit…

Moving towards the judging aspects now. This is ideally where we’ll take care of the “wedge and not-quite-wedge problem”. By design, this proposed rule implementation permits wedges and sloped surfaces as well as traction-breaking corrals, forks, spatulas, and the like.

x.1 Judging Guidelines

x.1.1 Definition of Passive Attacks A passive attack by a robot shall constitute using horizontal and inclined surfaces on the robot to impede the motion of an opponent robot. Passive attacks include, in the absence of Active Weapon use: pinning, ramming, wedging, or using your robot to high-center the opponent robot.

x.1.1.1 Scoring of Passive Attacks Passive attacks alone will not count towards Aggression, Damage, or Control points. Only passive attacks used in conjunction with the robot’s Active Weapon(s) will be considered in Aggression, Damage, and Control points.

Passive attacks will be discounted in considering attacks. Basically, you can spend the entire match wedging someone around the arena and still lose. I don’t think the typical guidelines for match scoring (1 point each for aggression, damage, and control) need to be repeated here. I some times explain the three to people who are confused about them, such as what’s the difference between aggression and control, as the following:

  • You can be constantly beating at your opponent but never have influence direction of the match. Likewise, you can keep your opponent at arm’s length for the whole match but not do much with them beyond that.

One is aggressive but lacks control – someone who keeps running into Clocker’s waiting grabber only for me to toss them around and then they come back again is being aggressive but it’s arguable I have control of the match. Similarly, a spinner weapon who keeps beaching upon an effectively designed wedge to make a few sparks and run away is facing much the same issue; provided the wedge isn’t just sitting around waiting to be hit (lack of aggression)

I think this is pretty clear for what constitutes a passive attack. Obviously, there will be a gray zone still, and it could be argued either way for wording and stated intent.


The 30lb Sportsman’s Class has a noble goal and a lot of ambition and potential, but we should all take a step back to appreciate what has led to its current mixed role in promoting the sport. I think overall changes to the structure of the weight class, whether in design rules or in competition rules, is important to keeping designs fresh and the class entertaining and welcoming. We should heavily consider adding new tournament formats and arena elements to make maximum use of existing designs, and encourage new designs to follow a more open and intent-based ruleset versus specifying mandated design elements.





Motorama 2017: The Event Report; Or, How Not to Scale-Model Test Your BattleBots

Feb 26, 2017 in Bots, Events, Überclocker 4

And we’re back! I must say, in a way, I miss the abject chaos (read: spinners) of the full-contact weight classes, but it is glaringly clear that I need to get my strategy back in shape. In all, this event was a good wake-up call for me if I want to play the BattleBots #season3 game seriously, but that’s for a later analysis. Here’s how things went down, starting with the finishing of Clocker a few days before.

One of my last to-dos was making spare armor wedges. I’d already waterjet-cut the plates, so they just needed to be cleaned and welded. These wedges represent a simplification of the design used on Overhaul that I would like to transfer. They’re simpler, reducing the number of facets and panels by half*,while also retaining the same lower-edge durability with a (higher mounted) gusset. However, they are missing the “Jersey barrier” double-angle front that Overhaul has, and this will be important later.

So there are four wedges – two are made from regular cold-roll mild steel, and the other two from 4mm AR500 plate. I’m really expecting to run the AR500 plate as primaries, and only ditch out to the mild if they get (somehow) demolished. I suspect there wouldn’t be much left of the bot if that were the case, but it’s good to have options! The 4mm plate one weighs several ounces more than the mild steel, owing to higher plate thickness (.125″ vs .140″) so I’ll definitely have to free up weight for it.

I jigged the whole thing up since it tabs together into itself and tack-welded the panels together using a TIG welder, before switching to the good ol’ spray-and-pray MIG welder to blend the outside seams together and drop a huge interior fillet into whatever edges I could on the inside. I am still the only person I know who tacks assemblies together using a TIG welder, and then switches to using a MIG welder. I write this off as me having zero patience for welding, but needing the initial assembly to be straight, so I do it with the precise near-zero-force application of a TIG welder.

*Note that Clocker doesn’t have forward- or side-facing wubbies like Overhaul, so if those features are being added back, it would increase the plate count, but still not to the point  where I had them for #season2

Free up weight? Where the hell else can I do that from!? It seems like Clocker’s been pretty well dieted, but a few weeks prior I had started thinking of do I really need semi-infinite drive power? in the form of possibly replacing the AXi motors. They work great, yes, but are definitely overpowered and therefore heavier than I need. I decided to swap to a set of 42mm SK3 outrunners, which would reduce me by around 4 ounces per motor, allowing me to use the AR500 wedges as the heaviest configuration. Power-wise, the SK3 outrunners would have been just fine. They also pair up with the pinions of the 4:1 P60 gearboxes from BaneBots I ordered (due to the higher Kv) and bolt to the motor plate with no modifications.  This is a great combo – I highly recommend it as a plug-and-play 30lber-scale brushless drive rig now.

The motors were basically the last thing to arrive before I had to leave, so I decided to hold off swapping the parts in until we got to the event.


The following image shows the totality of the glory of America:



On Thursday night, we packed Literally All the robots into vantruck, along with a sizeable amount of tools, support equipment, and other miscellanea. I planned to get there early-ish Friday to help set up and also to aid in Antweight & Fairyweight tournament logistics. Along with me were SawBlaze and Overhaul for display at the front of the audience section.

Sadly, this trip as-photographed did not happen, but that is an entire other story that has to be told separately. Long story short, the haulage minus SawBlaze and Overhaul were reshuffled into Mikuvan. This is a great story, I guarantee you (if you stalk me on the Internet, you already know it, so no spoilers!)

Alright, so it’s like 2PM on Friday now when I get there and everything is horrible and nothing matters. Let’s swap the motors onto Clocker:

Boy, those ESCs – spares left over from Overhaul and Sadbot, Dlux 160A HV units – are now officially overkill too. That’s what happens when you make a parts-bin robot. With the motor reduction, I was able to make weight using the AR500 wedges. Also in the same disassembly service were the floor scrubber tires:


Here’s a better look at them. I liked how they handled in the test box – still just a little light on traction, but very predictable. I brought along the Forsch (black) 60A wheels also, but decided to run these first since the Forsch ones felt a little more stiff.

Fast forward to Saturday and….

I feel like I’m at some kind of  career fair or anime convention. The people-ocean density was staggering; this is the largest Motorama Robot Conflict historically, and the largest year-by-year growth (over 50%). A lot of new faces, probably 25% of builders, and also quite a few returning legends. It’s a good problem to have.

In the interest of not dying, the 3lbers (beetlewights) were basically running in a parallel event with an 8 foot arena just off screen to the left, with only large bots – 12lbers, 30lbers, and 30lb Sportsman’s – running in the big arena.  Given the sheer number of beetles, it was the only way!

What’s great is MassDestruction helped spawn several ‘newb-vets’ who cut (….blunted?) their teeth in the MassD arena over the course of the last year.  These are two of Alex Hattori‘s robots. At this time last year, he had a 30lber made of two steel bars welded to a cast iron pot, and since then he’s cleaned house at like, every MassD ever, I swear.



Some other remarkable bots forged at MassDestruction from guys who work at, uh, MarkForged. Crap, my sponsor is beating me at my own game! What do I do!?

Another one of my favorites return – this is Pitter Patter, a 30lb shuffler (actually 45lb in the weight class) which way back in the olden days of Motorama 2015 was the original design model for Overhaul 1′s shuffle drives, which were basically a direct knock of this thing! For this version, the saw got smaller, but the shufflers got way faster… like 3000 RPM fast. This thing was cookin’ it in the arena.

Basically, you’re not getting anywhere NEAR the whole story just from these few photos. I remember when robot tournaments were this big, from the momentum of the first run of BattleBots, and I hope I see the 2nd Great Awakening of robots progress further still.

Anyways, onto my matches! This is Glasgow Kiss.

Topologically, it’s a good mockup of the Cobalt match. This is okay too! I’d actually hoped for a vertical spinner opponent so I can practice my anticipated strategy of using the ünicorn. However, I’ll gladly try to practice my horizontal-fending tactics too. The high level plan is to come into his weapon tangentially using the AR500 wedges and bounce him around, ideally towards walls, and try to corral into corners. More or less the same plan as for when I fought Cobalt.

I mounted the ünicorn anyway in case it could be used – I wasn’t counting on trying to swipe the belt pulley, as it’s too far inwards.

So how did this match go? Uhhh…

Well that’s not very typical at all.

Let’s watch the match video to find out what happend!

Alright, so my strategy starts out working fairly well. I’d say about 0:30 is when things start going awry. While I get a few more good tangential shots in, Glasgow Kiss is able to get one or two shots in which climb up the wedges and take out the clamp actuator and main lift gear.

At 0:49 I make a pretty bad driving error and end up plowing directly into the blade, so the forks and clamp are pretty much done by then – you’ll see me raise them to try and keep them up and out of the way.

The last big connection throws both of us apart across the arena, and I’ve lost all drive power by now so I tap out.

What Andrew (driver of Glasgow Kiss) does well is pivot the bot on the blade axis – in part a consequence of it being so heavy – such that it’s hard to just ‘get around the back of’ or execute similar strategies. He does this several times to leak away from Clocker’s grasp succesfully, leaving me to chase while he spins back up.

If you watch closely, you can see Clocker has some maneuverability issues right away. One of them is the bot’s right side having a tendency to stop and not reverse, which means I missed a few in-place turns. This occurred to me as strange – I mentally wrote it off to the smaller brushless motors in the drive cogging on start, but it definitely didn’t occur in test box driving. The heat of the match kept me moving, though, and I elected to try and drive around the problem, exercising the tactics I outlined in how2brushless at the bottom.

So Clocker seemed to be in one piece still at the end. Time to appraise the damage:

Check out the gear carnage. This gear is made from 7075 aluminum. It’s a nice and rigid alloy, one of the strongest by tensile strength aluminums, but it’s really best used in bulk such as gearboxes or bearing blocks and the like, not in thin sections. The gear is fairly heavily webbed out for weight, so it cracked through readily instead of bending. A 6061 gear would have bent and I would have had a chance to sledgehammer it back to something resembling flat.


Glasgow Kiss machined off most of this corner here when I was turned around. I’ve thought about making plastic corner hoopy-jiggles before, but haven’t been compelled to yet. As a part of a comprehensive horizontal weapon defense strategy, it might be worthwhile to do for Clocker using some 1/4″ UHMW or a thinner spring steel.

D’oh. I think the cross-arena impact stripped all the #6-32 threads from the end of the gearbox, so I lost drive on this side. On the other side, the chain jumped between the drive sprocket and the rear wheel sprocket.

You know what was awesome though? The AR500 wedges, on both sides, are practically untouched. Lightly divoted, but they were still flat to the ground. I did write off two of the lower wubbles on each side which had some tearing damage beginning.

But you know what – this setup went head to head with one of the biggest 30lb weapons a dozen times and isn’t much worse for the wear. What it really showed me is that Clocker’s frame and armor is perhaps overly built for the weight class now that geometry is compensating up front for frame thickness.

By near complete accident I’d say, the ünicorn came THIS CLOSE to piking the pulley and belt.

Alright, it’s time to fix everything up. Both sides of the bot had to be disassembled to replace the drive motor studs with longer ones. Since the P60 motor plate screws don’t go all the way through, there was some thread left which I could use with longer #6-32 bolts.

It looks like the frame was tweaked about 1/16″ in a parallelogram shape, from a similar corner hit on the rear right side (opposite the well-machined one), so the left side drive sprockets became offset enough to cause problems.

Getting the damaged lifter parts off was an adventure that took a long time. I’m now heavily rethinking the clamp collars on live shaft approach. It was fine in the Sportsman’s class where Clocker never took any real damage there, but with everything twanged up, there was hearty use of deadblow mallets, aluminum pusher tubes (to avoid marring the shaft), screwdrivers, etc.

What I couldn’t save were the clamp actuator and lift gear. I had thought about machining another lift gear the week before, but it remained just a thought. While I had a newly assembled and painted clamp arm ready, I didn’t bring spares for the clamp actuator. Without a backup clamp actuator – since Glasgow Kiss had basically wiped all the internals out also – I had to push everything back together in “spatula mode”, just with the lower forks and around 120 useful degrees of gear. Once again showing the difference between Sportsman’s and the full contact weight classes – just like in BattleBots, you should really be prepared to build 2.5 robots, one full set of spares and another for the things which break the most often.

So I delay my next match (and run down that delay as far as I can) to get spatula mode together. When I finally hustled into the arena, though, I discovered that Clocker could only spin in place or turn right. I clearly had wired one of the drive motors backwards, but what? Moving only channel 1 in my elevon-mixed (single-stick driving, basically) radio only caused the left side of the bot to move, with no response from the right side. However, it could obviously spin in place; without a motor being backwards, it means it could drive straight forward or backwards, but only turn right with 1 channel.

Without more time, I had to forfeit my match against Shaka, who, I will point out, somehow went 2/2 at this tournament using only forfeits. It won its matches by forfeit, but had endemic electronics problems which caused it also to lose by forfeit… I am told that in testing shortly after our non-match, it blew up.

Back in the pits, it took me a little more investigation to discover that my Hobbyking radio had somehow lost a mix. When you configure a radio for single-stick driving (or Delta Wing, Elevon, V-tail, etc. for aircraft), you assign mixes to tell channel outputs to listen to certain combinations of stick inputs. Here’s what a typical simple elevon mix looks like for my Hobbyking T6A-v2 transmitter:

There’s two mixes involved – one to tell Channel 1 to move with Channel 2, which on a typical radio is the vertical throw of the right-hand joystick. This means pushing forward on the stick sends the same signal to both outputs on the receiver, so the robot drives forward.

The other mix is to tell Channel 2 to move the opposite of Channel 1, which on a typical radio is the horizontal throw of the joystick. This means if you push stick right, one side of the bot moves forward and the other moves backwards, and is accomplished by setting the mix percentage to be -100 in both directions (do the opposite no matter which direction the stick is moved)

For me, the latter mix – the one outlined in Miku Pink – was NOT responding, despite showing correctly! This meant moving Channel 1 resulted in no opposite motion, just the bot pulling right. This was exactly the behavior seen in the arena, and I would never have discovered it if I had not accidentally put a motor in backwards.

I said the maneuverability tics Clocker showed in its first match will come into play later. I’m now 99% sure that this issue affected the match, and I tried to dynamically drive through it since I try to avoid stationary directional changes (turning in place) due to the brushless drive. A non-working Elevon mix will still kind of work if you move Channel 2 first – it will simply add and subtract Channel 1′s value from one side. In this case, it left the bot prone to pulling right, which is exactly what I saw.

How did I discover this was the problem? Well, I simply had it resend all the settings to the radio without touching a single one and it resolved itself. My radio literally lost a mix from its memory between Friday and Saturday for reasons unknown, even to the point where it convinced its software that the mix was still present.

I must say, I am not even mad. This is an impressive failure mode that I’ve literally never seen before, ever. Before anyone dishes on Hobbyking radios, though, I personally have owned a half-dozen (I keep accidentally giving them to newbies or random students and then getting another one) and also worked with hundreds back in my 2.007 days when they were the radio of choice for the class, and this is the first one I’ve ever seen DROP A SICK MIX like that.

With Clocker out of the tournament and the radio issue solved (!?), I waited for the 30lb rumble to join in on, where I basically overdrove the arm past the end of the gear immediately….. so I simply ran around as a wedge corralling bots in corners until the Vex sprockets’ teeth all came off!

My chain gliders probably wore  enough in that 5 minutes of crazy driving to make the chain skip on the sprocket (since it doesn’t have that great wrap angle), and the power of the brushless drive proceedd to machine the teeth off in short order. Ah well – it was a great rumble anyway. At one point I had every bot except Translationally Inconsistent, who kept slithering away sideways, piled in one corner.

Once I find a good video of it, I shall update the post to include it.

What’s great to see is that the 60A wheels hardly wore. Obviously this is both good and bad, since it means I could have traded hardness for more traction. For the 30lbers, I might go back to the 50A compound – Clocker in previous incarnations has run 50A wheels and I’ve been satisfied. Now is when pouring a few full-size wheels for Overhaul to try and drive around would be a next step.

We part with some shots of gourmet damage from one of Jamison’s loser’s bracket matches against Triggo. megatRON was upgraded to have an AR500 impactor disc on the end instead of a saw, and having that house brought down on you is capable of some serious damage:

this kills the triggo :c

Check out the 1/8″ heat-treated chromoly-steel shell rim also, from the same weapon:

This thing is not trivial; megatRON was actually one of my more feared potential matches because I have relatively weak top side defenses. Expect potentially interesting changes to Sawblaze for #season3 perhaps?!

Speaking of which, what takeaways for Overhaul do we have here besides the obvious bring a spare of the thing you don’t think you need spares of. Or three.

  • DAMN, THAT WAS A GOOD MATCH THOUGH. Honestly, if I had the choice of losing like that to Cobalt, versus the way I did via #setscrewghazi, I’d have picked the former in a hurry. I would have had enough spares to bring Overhaul back online quickly anyway, and it would have made for a much better show and much better test of the bot.
  • I’m highly satisfied with the AR500 wedges. So happy. It deflected the hits from Glasgow Kiss with ease, and also seems to have done its job of transferring the energy into the floor. AR500 has become a bit of a crack epidemic in robot fighting recently as more of it is readily sourced along with laser/waterjet services to handle it. It’s a nice alloy, really – heat treated to the high 40s Rockwell C already, and easy to weld with conventional consumables.
  • Good deflection is also a curse, because you aren’t in control of where the big beating-stick goes afterwards. I’m more convinced than ever – besides by this hit – that the double angle on the front of Overhaul’s pontoons is an absolute necessity. I designed without them for Clocker for simplicity and to see if I’m just being alarmist, but what the single slope let Glasgow Kiss do is deflect its own way upwards and clean house in the clamp actuator. I will need to think about how to  how to retain or improve this design for Overhaul, and to add it to Clocker.
  • I think it might be time for a scoop, for both Clocker and Overhaul. You know how Overhaul has the short arms that I used against Cobalt? Imagine those becoming vestigial and ending behind a angled steel plow which could nest in between the wedges on their inside slopes, making the front of the bot more contiguous. The remnants of this design can be seen in the forward-angled plate that resides on OH1′s forks.
  • It’s more clear than ever that a self-reinforcing geometry trumps material thickness outright. If scaled down directly without changes, Clocker would have 0.75″ thick frame rails, which it clearly doesn’t. It has 0.5″ thick, heavily-machined out side rails with 1/4″ thick cross-bracing plates, and that left the match against Glasgow Kiss needing a single screw extraction and maybe a hit from a good ol’ Engineering Hammer. What this actually means is I spent much of the 6 hour drive back from Harrisburg trying to rationalize that maybe I do need to have Overhaul’s frame remachined again. I’d be able to optimize for the geometry of the side rails. It would shed a lot of weight which can go into other systems I was running out of weight for, and really, based on how deeply Overhaul’s frame rails are pocketed, it’s almost useless to be made from 1.5″ thick stock. But UUUUUUUUGGGGGGGGGGHHHHHHHHHHHH.
  • I’m really, really itching to leave the clamp collars behind when it comes to power transmission to the forks. I think when it comes to fork improvements, just adding cross-bracing to Overhaul is enough, and I way more favor the 8-bolts-to-remove-an-arm setup on it right now for serviceability. I can replace a full set of arms and the clamp actuator on Overhaul faster than I could get the damaged forks off Clocker.

I would love the opportunity to test these hypotheses on a 30lb scale again in less than 1 year, especially because I (think) #season3 is still going down this year. Even if I can’t prove my hypotheses in short order, this was all good stuff to know!

It’s Motorama 2017 Time! Überclocker Changes and Upgrades

Feb 15, 2017 in Bots, Events, Überclocker 4

Since Franklin Institute this past year, I’ve been spending quite some time thinking about what changes I need to make to Überclocker for the annual winter robot party, Motorama. It’s the largest event on the east coast for years running, and the ONLY one left with full-contact 30lbers; I’ve gone basically every year since 2013, and sporadically before that (2008, 2010). This year is slated to be some kind of BattleBots #season2 reunion (where Season 2 was called “Motorama, the TV Show” since so many builders who regularly participate ended up on teams!), and there are some of us who are taking the opportunity to do some… scale model testing. Quick! What is the Reynolds Number of a flying Tombstone!?

So here’s what has been going on during the past few weeks! In my summary of the Franklin event, I identified a couple of strategic issues with Clocker which would also concern Overhaul for #season3, given that they’re built so alike.

The first was having everything ‘line up’ in the front. While it also included making the pontoons more adjustable, higher priority on my mind was making sure the arms have enough constraint that they don’t just splay out. We saw this happen in the Overhaul vs. Beta match where I caught Beta with one arm over and one arm under, so the arms because angularly misaligned. Recall that Clocker 3 and before all have multiple spanning elements holding the forks together; alignment was never a problem with that, but Overhaul didn’t have those elements primarily for an aesthetic reason (to maximize the forkiness). While Clocker sort of did have those constraints at Franklin, it was just one spacer stack, and that was quickly lopped off by megatRON.


So I’m gonna add more, duh! These two additional spacer & tie rod stacks are located out-of-plane with the one at the end, which will yield much greater torsional stiffness.

One issue is that another 18″ of threaded rods and aluminum tubes will put the bot back overweight a few ounces. Nonetheless, I intend to just build everything out to my desires, and then try to weight-cut from there, rather than compromising early. To pre-compensate a little, I decided to order replacement smaller drive motors. The AXi motors are great, but they are dramatically overkill for power, and I can definitely afford to lose a few ounces. Going to the 42mm outrunners will save me about 3 ounces a side, which alone might be enough. In order to utilize the smaller, higher-Kv motors, I also decided to order a pair of Banebots P60s in the 4:1 ratio instead of my current 3:1s, which should allow me to keep about the same speed.

Now, the 2nd big strategic weakness I want to experiment with is where it gets a little interesting.

I mentioned in the FI post about minimizing my defensive cross-section when it comes to vertical weapons. Those things – including drums, drumlet-drumettes (smaller in diameter and width) and vertical discs/blades are actually what I fear the most designwise, because they do two things to you in a match. One is flip your bot over, from which you need to recover (and which would take precious seconds where you’re vulnerable to followup attack from a good driver), but the more insidious one is ruining any straight edges you might have had where the weapon hits. A small KE weapon will put all of its energy into your material like a singularity; it will deform wedges and protrusions, basically preventing you from having an advantage again. All it takes it one fuckup, as Clocker’s match with Duck Yeah and even better example Blacksmith vs. Minotaur show. Notice how Blacksmith more or less has control of the match before it gets dinged once.

So to counter these kinds of weapons, you would have to do two things. Number one is keep them away from you, and number two is present as small of an area for them to touch you in as possible. There’s a lot of precedent in the sport with “keep away sticks”, including one used to great effect on Icewave last time on the show. To reduce my “vulnerable edge length”, then, I basically had to distill the front wedges down to points.

I take that back: this got interesting very quickly.



So that’s revision 1 of the design. See those perforations? That’s for if I mess up and somehow manage to plant these into someone’s weapon instead of besides it. This design is intended to be cut out of AR500 grade steel, which is extremely rigid and springy but won’t stretch that much, so it will preferentially break at the postage stamp line. It’s like an active salamander tail system.

The saw teeth on top are the real bad idea here. Instead of a keepaway stick, I wondered what would happen if I made it a part of the offensive strategy. Most of these little vertical weapons have rubber belts attaching them to their motors. What if I just went straight for that with a very sharp stick? Stab into the gap between weapon and robot frame until you damage the belt or take it right off. That would take some serious driving and luck to pull off, which lured me to the idea further.

There was only one thing I didn’t like, and it was one of those “come back to what you CADed up last night in the morning and think again”. One of my complaints in the FI recap was getting stuck on MegatRON when we charged at each other. These extra-long death-shanks are attached just as the pontoons are, so if I run up on someone else’s wedge I can just as easily prevent Clocker from getting back off. Which is serious bad news when it comes to avoiding a vertical disc/drum spinner, since now they can just turn slightly for a broadside.

This led to revision 2:

Yeah. “It looks like a sawfish-unicorn”, or an Overwhal. That’s right, I decided to affix it to the clamp arm instead, exactly in the fashion shown.

This position I liked a whole lot better for two reasons. One is that it’s implicitly height-adjustable, and can actually be a manipulator weapon of its own. Clocker’s top clamp arm is not trivial – it is designed and built for about 500-600 pounds of closing force. It will lift a lot of things on its own, and is more finely positionable than the lower forks. It’s also more durable with its leadscrew attachment, but the leadscrew anchor is also a mechanical fuse for if things go very wrong and it gets the uppercut treatment – it will break away and probably fling the clamp arm backwards and out of the way, leaving the forks still usable. If I attached this to the forks, and they get bent, then my life becomes very difficult.

The second is a takeoff from the height adjustability. I realized that offensive unicorn strategy #2 was that now I can reach around weapons and bring the house down on their retreating sides, where the disc necessarily disappears back into the robot. With crafty positioning (or a lot of flailing) I could pretty easily literally throw a wrench in the works and shove a wad of AR500 directly between the robot and its own weapon. This would probably result in a very sad unicorn horn and ideally more sad opponent; for me, that’s why the postage stamp holes are kept, so not only will it break away on a successful landing, but will also do it and leave me a 2nd chance if I miss.

Strategically now, I can keep the clamp arm closed and all the way down and use the horn as a keep-away stick of minimum attackable cross section, and also manipulate bots from afar, or get it caught in something else like exposed drive wheels.

….and if you thought it looks silly in the CAD, it looks 10 times as silly in real life. I actually want to make another one of a different length now!

This is another ‘attachment of several ounces’ which would necessitate shedding weight elsewhere, which I will find. One thing I designed up previously but never implemented in real life was a set of light wedges, to be made of sheet 1/8″ aluminum bent into shape. I’m going to go ahead and make them, since they’ll cut around 1 pound off the bot each (Those steel wedges are HEAVY!)

I won’t need that much reduction in weight to use the horn of course, so maybe the configuration will add something else interesting to make up the weight, or just ballast. There is literally no point in weighing less than 30.00 pounds.

So that does it for major design changes. Moving onto more minor quibbles, I wanted to go back and have a look at the wheels again. The custom 50A cast urethane wheels worked beautifully at Franklin, and I now had a bucket of Simpact 60 and Forsch URS-2160 (McMaster part number 8644K24), both 60A urethanes with much higher tear strength ratings, to try.

Now that I was confident in the process, I revisited the hub design. I just designed the first hubs with circular thru-holes for rubber retainment so they could print without support, but the circular holes caused the diameter of the hub to start getting large. I didn’t have much more than the 1/8″ tread pattern’s worth of tread thickness per wheel. With a more rigid rubber, I might be able to increase the relative thickness of the tread portion.

I updated the hub to look pretty much like a scooter or skate wheel core – through-slots replace the circular holes, and the walls are thinner. This brought inwards the OD about 1/4″, which is great!

I also wanted to play with another tire geometry. A little earlier in the year, when Big Chuck’s Robot Warehouse was just being set up, we rented a floor grinder to strip the wooden floor of the decades of industrial grunge that had set up colonies within it:

Well gee, as soon as I saw that, how could I not clone the design in one of my own wheels? So if you’ve never used a floor grinder, a big sanding drum gets shoved over this flappy-wheel. To install it, you lock the rotation of the flappy-wheel and gently rotate the drum over it (in thise case, clockwise) while pushing it on. The flappy-wheel is effectively a huge sprag clutch with the drum as the outer race and the flaps as the ratchets/sprags. When the wheel is spun by the motor and the drum gets loaded against a floor, the flaps get forced open a little from the transmitted force of friction, causing them to push out against the drum harder, which causes more friction.

After I finished going “Well huh, that’s kinda smart’ I realized this design would get very good traction in one direction as each flap gets forcibly planted into the arena floor. The reverse direction might not be as spectacualr. Before I got ahead of myself with anisotropic traction designs, I decided to just imitate the flappiness  in my current tire design.

That’s the same helical tread sweep, just with many more slits of a greater depth and narrower width. I did this for “easy” (change the number and size of swept features) for the time being. I’d like to play with a straight-cut geometry like the floor scrubber in the future.

Printing this damn thing was an ordeal. Unlike the previous wheels, the molds could no longer be printed upright without support structures due to the way the helical threads are placed. Furthermore, the deeper tread features also prevent demolding in two halves, so I had to split the mold into quarters. Attempt #1 with supports was basically a no-go, since it was almost impossible to get them out cleanly and not leave little strands and hairs everywhere.

I next tried to print the mold wedges “pointy side up”, making a flat face on the outside of the circle for them to sit on. This was okay, but the nylon warped just enough on each print to make the edges not seal at all – this was attempts #2 and #3. I guess I could have made an Onyx mold too, since it has virtually no deflection, but by that time I’d mentally moved on.

The fourth and successful attempt was a single-piece mold which simply had the upper lip chopped off. I don’t even know why I thought the upper lip was needed now. Just fill to the top and be done!

That’s the model with the lip removed.

So how do you demold this damn thing? It was risky, but I decided the one-piece mold was okay because of the spiral nature of the tread allowed me to helically demold the cured wheel from the mold. And this ended up being completely true! I back out the hex bushing a half-inch, take a wrench, and untighten the wheel right out!

This worked quite well. Here are the two first wheels to emerge with the new material and tread! I stuffed the leftover mixed rubber into an old wheel/hub combination, because wheels are wheels. Notice the white core of the two new ones – they’re made from plain ABS, since I wasn’t about to waste the Onyx material on something I wasn’t sure could ever be removed from the mold. They’ll be on standby as low-priority spares nontheless.

Next up, the Forsch Polymers URS-5160. Forsch is one of those “Call Billy” companies that I always complain about – just go look at their 1997-chic website! Except this time, I was literally told that I had to call Billy (over in BILLING no less) and FAX him the order, then MAIL them a check. Credit card? Paypal? Pffff.       

Oh, Billy also leaves at 2pm each day, so I gave up after 3 days of failing to get in contact with him because I might have trouble waking up before 2pm on most days. Luckily, someone clued me in that McMaster’s general purpose pourable 60A urethane is manufactured by Forsch, otherwise I would have given up completely.

So why the hunt for a product which tries so desperately to not be purchased by anyone? Well, it advertises around 25% more tear strength and ultimate tensile strength than Smooth-on’s Simpact 60. Smooth-on is geared towards being easy to use – everything is made 1:1 or 1:2 mix ratios, so it doubtlessly sacrifies some strength and performance for convenience. I figured that polyurethanes worked like tacos – the shadier and harder to find that a Mexican restuarant is, the better the food. This has been almost bulletproof in my experience. I made it a point to obtain a Forsch product and use it like Robot Jesus Himself intended.

What I really want to try getting my hands on is the URS-2450, which has basically the same tear strength but in a 50A durometer. May Billy and I finally meet in the grand arena of procurement soon.

I cut new wedges out from AR500 plate. These were what they were meant to be, but I couldn’t get the material in 1/8″ (or 4mm-ish) thickness in time before Franklin. This was actually cut from one of Jamison’s spare plates left over from Sawblaze. I’m preparing them for welding here by grinding the incredibly thick scale they all seem to come with off.

Stay tuned for more, though with Motorama now 2 days away, I might just be updating after the fact! Still to come are the making of the pontoons, the spare lighter drive motors, and maybe a little bit of wheel testing!