Motorama 2018: How Not to Scale Model Test Your BattleBots, The Remix

I had originally intended to go to Motorama 2018 solely for #vantruckjustice and to serve as an event volunteer and purveyor of Ragebridges and Brushless Rages. But with the announcement of Season 3, it became clear to me that I really should take the opportunity to get some practice driving in with 30-haul a.k.a. Überclocker v4.

Not only was my list of “things I didn’t like about Overhaul” extensively long, but based on my experiences after Franklin Institute and Moto 2017, I had several mental strategies against KE weapons I wanted to try out. Better do it on the small scale where it’s less expensive, right!?

So onto modifying Clocker!

One of my recurring themes in the past few event reports where I ran Überclocker has been the idea of reducing my wedge cross section against vertical drum and disc style spinners. I’ve had a theory for a long time now that broad armored wedges/plows are actually a liability against those kinds of weapons, despite being more effective against horizontals. There’s nothing better to confirm my theory besides Blacksmith vs Minotaur – in which Blacksmith actually does quite well against Minotaur until the latter manages to land a square hit upon the front of Blacksmith.

Essentially, a vertical weapon will tend to bend up your defenses by hitting it at a single point along its bottom edge, effectively making the length of the plow/wedge useless especially if the vertical weaponed bot has a feeder leg of some sort.

One countering strategy is going fully vertical with your defenses, like a crossing vertical bar of steel or something, making sure you hit the weapon before any feeders are able to touch you. Whoops! used this reasonable effectively against totally-not-Minotaur for quite a few hits.

That doesn’t quite work for me, though, because Clocker/Overhaul both have lifting forks.

 

Another strategy is minimizing your cross section ot exposure to those weapons by being extra pointy, giving them less of a chance to hit something important. This is also a strategy that I began moving towards with other ‘wedge fights’ – a broad surface is, again, vulnerable to any imperfections in not only itself but also the floor. I wanted to explore this strategy with what I call the “Wedges of Limited Liability” seen above – basically turning the armor pods into little shanky forks. I designed them to follow the profile of the existing wedges, out of the same 4mm-ish AR500 material.

These are a few ounces lighter apiece than the regular ones, which is going to mean a couple of pounds at the Overhaul scale. So it was interesting to begin thinking of the configurations I could get – freeing up a few pounds on Overhaul could let me add other attachments or additional armor (e.g. if I had to face Beta again, I’d spend the extra pounds on top armor).

While I was at it, I also redesigned the normal heavy wedges in the style of Overhaul. I had thought about ways to retain the double-angle feature but significantly reduce the number of pieces needed to construct it. Overhaul’s wedges were rather complex and made of 9 individual pieces each. I came up with an idea of making the second angled facet into a ‘backstop’ of sorts, attaching directly to the outside surfaces through extended tabs that also acted as gussets.

In essence, the above is what Overhaul’s new wedges will look like, but with some geometry placement changes. Clocker’s front is a lot more tapered than Overhaul’s, meaning the ‘backstop’ begins too far back to be really useful here to protect the gear from another Glasgow Kissing. I was more interested in the construction and their potential behavior towards deflecting  hits in general, rather than specifically trying to address last year’s weakness.

One change that has been on the docket since Franklin late last year was changing Clocker’s gearing. Using the lowest RPM/v rated NTM 42mm motors was still too much – I rarely exceeded 50% stick travel while driving, and the constant burnout mode the motors ran in during each match made fine control actually rather difficult. To give the bot more control over its own inertia, I was going to go to 11:1 P60s (from 4:1) but with a bump in motor Kv from 650 to 750. While this reduces Clocker’s nominal top speed drastically to only 10mph from like 20, it was going to mean more speed in a useful range. A lot of my strategy relies on being able to carefully control my approach and orientation to opponents, after all.

The same changes will be carrying through to Overhaul, but less drastically – I’m changing only the external motor sprockets, from 15 tooth to 12 tooth, moving the system reduction from 8:1 to more like 10:1, which is what Sadbot has been running in testing and whose maneuverability characteristics I like more. It will reduce Overhaul’s nominal top speed from 19mph to 15mph.

By the way, the NTM Propdrive 42mm series have a Mabuchi RS-700 size bolt pattern and a 5mm shaft, which mates with the Banebots P60 700-series motor blocks, not the 500 size.

Since I finally blew up the clamp collar joint at Franklin, I drilled the sheared bolts out and replaced them with a pin drive. The holes in the gear were bored out, and the “pins” in the shaft collar are actually shoulder screws with their heads milled off! I literally tightened shoulder screws into these holes and then clamped against the screws on the mill and blazed the heads off.

The shorter 4238 size motors, in combination with the 2-stage gearboxes, actually end up at the same length as before! This package is fairly potent and is a brushless 30lb drivetran of choice currently. The same two beta-version Brushless Rages still run the bot, dating now all the way back to Dragon Con 2017 and carrying the bot to victory at Franklin, then several demos at MassDestructions.

Fast forward a few days and an uneventful (!) vantrucking trip later, and here we are at the event:

So I didn’t get a chance to actually weld up the new heavy wedges – they’re shown sitting in a pile next to the bot, ready to become accessories. Since the only welder on site was a 115 v MIG welder powered by a 50 foot extension cord, my plan was basically to add some little barriers to the existing wedges in the form of strips cut from the new design.

Clocker’s first match was actually a “wedge fight” against the twin over-powered wedgebots of Boom Boom. This match was conceptually easy, but a little frustrating because Clocker kept digging into the wood floor. It was in fact too pokey and I could barely maneuver forwards. So it really wasn’t that good of a test of the Wedges of Limited Liability at all.

My next match was against Botceps, a pretty classic vertical eggbeater style spinner. Built pretty much like a BattleBotsIQ/NRL archetype, it had a very potent 50mm TPPower inrunner on the weapon. This was one of those “if I make a driving mistake, I’m kind of done” matches, so I had to be on my toes. I don’t have a video link of my match here at the moment, but should I discover one, I’ll add it in.

As you can see, I did end up making at least 1 driving error – at the beginning, a few seconds in where I missed a charge and Clocker went halfway across the arena. Luckily, the weapon motor fizzled out barely a minute in, but I did lose the tip off one of the forks and the left pointy-wedge.

The punt that send Clocker up and over also squished one of the outer rail mounting screws clean out of its hole.

At one point, I managed to execute my anti-vertical spinner strategy well, plunging the pointy-wedge straight under the weapon of Botceps – which managed to machine the entire row of rake teeth off it! The match ended with a serendipitous flip which put Botceps on its face (“doing the thing” in robotland) and without weapon torque, it was stuck in that position.

My next match was against Crippling Depression, a pretty innocuous-looking bot (by design) that actually puts a massive amount of power into the undercutter disc – two NTM 50-series motors, which is more motor than Glasgow Kiss. By the way, its builder Robert Cowan has a very detailed video series on a lot of engineering subjects, including full video reports of the build of CD. Basically if I were more keen about doing video versus text, I’d be like that! So go Like and Subscribe™

Clocker didn’t make it out of this match all that well, and I ended up tapping out.

The disc of CD hits very hard, and very low – lower than most of my side rails, so it polished off a lot of the bottom screw heads. It was also positioned just at the right height for Clocker to barely ride up on it, meaning I would actually lose a head to head pushing match. With brushless drive and weapons, we’re now squarely in the era of 30lbers with absolutely no compromises – CD and Clocker have identical drive motors and identical gearing!

The super low level of impact meant a lot of extra stress was put on the wedges here, and it never actually got to ride up to the point of hitting my welded barrier strips. In fact, the first few hits managed to bend down the corners of the left side wedge enough that I had some trouble driving afterwards due to it being hung up on the arena floor on occasion. It also caused the rubber shock mounts to shear off early, leaving me with fewer defensive options as the match wore on, until both the wedges came off and my only real strategy was to try and stay on him. You can see some of the resultant impacts causing a little bit of “Cobalting” on the right side (upper of image), but the middle tie plate kept this very limited and I didn’t even notice while servicing.

Eventually, the disc ended up shearing out a few sprocket teeth and jamming the drive on one side, so I just wiggled my way around until I decided I got the idea and should probably keep it repairable for the loser’s bracket.

This was about the moment I realized that disc weapons (and by extension, shell spinners and other lower-prominence weapons) were going to be a much different story than the archetypal big bar spinner in terms of how to fend them off and deflect their energy, and I decided Overhaul needed a full-span front plow style defense no matter what. Watching Jamison fight CD later on with megatRon confirmed this belief even more. I’m pretty sure if Clocker had a full span wedge, even a connector plate between the two halves, it would have gone differently.

I was losing wubbies at an alarming rate and did not have any more spares, so I had to source them from other builders. Clocker was short spare parts in general – I never got to waterjet additional frame parts or cast new wheels either, since the decision to go compete was made in very short order. This event was actually a great study in how far the design would go on attrition alone.

That was all for Saturday – on Sunday, my first match was against BEAM, a tiny Tombstone. A rookie bot that was still BRUSH-POWERED and with an EV Warrior motor at that! Basically running a classic car in battle, but it had done tremendously well up to this point.

Poor guy was probably being gunned after by every BattleBots competitor there, who saw him as “tombstone practice”. Honestly, so did I, because it could portend the results of #season3.

For this match, I was only able to get 4 wubbies per wedge, and changed out to another used wheel which didn’t have huge chunks gouged out of it. I also cut off the bent tips of the forks so they were a bit shorter, but now much less structural than they already weren’t to begin with. It is what it is, given the lack of preparation.

So how did Overhaul do against Tombstone?

That’s, uhh, not very typical, I’d like to make that point clear. Well, it seems like the front fell off again – much more epicly this time!

With as much handicap as the bot was facing, I sort of ‘drove for broke’ in this match and was determined to see how pure attrition would play out. I think I was actually quite happy with how I was able to deflect Beam repeatedly, even getting it to do The Tombstone Dance a few times.

I felt like I had Beam reasonably until roughly the 2 minute mark when one motor was knocked off internally causing it to lose drive one side. I then just kept pivoting to try and meet it with the wedges.  Also, I again kept the arms up to try and keep them out of the way of the bar, but ultimately they still ended up in Full Dab; these arms for Clocker were built quickly to Sportsmans’ class specs, so any sideways ping is going to bend them.

Near the end, though, one of my welded barriers came off due to lack of penetration from the event welder. At the last possible second, we got in a good head to head charge, and….

Clocker’s frame rails are made from 7075 aluminum, which is really a mistake. I already had the plate when it was being designed, so went for Easy first. 7075 is more brittle than 6061, and will crack instead of bending. You can see that clearly in the arm tower that took the brunt of the last hit. This is why Overhaul’s entire frame including the arm towers are 6061, and only the liftgear and clamp & actuator aluminum housing parts are 7075.

From watching videos in slow motion, Beam was able to climb up the de-barriered wedge much like Glasgow Kiss and firmly planted the bar into the side of the head, which of course shoved everything out the other side. The lift gear was also made of 7075, and I lost a chunk of it near the end – check out how clean the shatter line is. It’s barely bent at all along the rim and still sits quite flat on a table.

The ears were also obviously very suboptimal – they were re-printed, but weren’t bridged or braced and so had the same kind of failure when the bot landed upside-down with an opponent – they simply bent the aluminum clamp sides and rotated, making Clocker adorable and droopy for most of the match.

With the base still working fine after the drive motor was reattached, I entered the Sportsman’s rumble to run around like a dumbass. The P60 motor plates only have two screws, not four, so it was asking a lot to hang the entire drive motor off them. This is actually why Overhaul’s motor assemblies have bracing plates behind the motor endcap. Dumbassery was achieved until Pitter Patter sniped the power link with its sawblade.

So that’s Motorama 2018 for Überclocker. Going 2/2 against three heavy KE weapons with almost no spare parts was certainly more than I expected, which was more along the lines of instant vaporization. I think I confirmed about every fear I had for Overhaul, whose upgrades were almost done at this point otherwise, but now needed revisiting.

but what about the Implication?

I spent the joyride back from Motorama consolidating everything I learned while running Clocker and as well as watching other matches including the final few fights with megatRon, Beam, Cripping Depression, and others. As a fair percentage of the builders at Motorama were also building for #season3, we did some bonding at the event and over pizza dinner Saturday night to consider strategies for the “full size” bots.

In terms of the knowledge gained from testing, it’s a fairly established rule of thumb in the community (if you ask) that “designs don’t scale”. The sentiment is you can’t expect to scale up or down a design 1-for-1 in terms of material sizing and dimensions of weapons and motors and expect the same kind of behavior. It’s a consequence of a whole lot of square-cube laws: motor power scales by volume, kinetic energy stored in a spinning weapon by square of velocity but also implicitly square of weapon dimensions due to moment of inertia changes, material strength both by dimension cubed and linearly by yield strength, etc. It’s why historically speaking, a scaled up or down version of a successful design might perform horribly.

Essentially, the idea is that at the small-bot scale, the energy transferred and dissipated in a hit tends to be much less than the energy needed to permanently deform a material of a given strength and size. This is how 3D printed 1lb and 3lb bots fly around arenas and bounce off walls on a whim and keep going. It’s related to the concept of why you can drop an ant off a building and have it survive the fall, but not an elephant. As robot dimensions increase, the kinetic energies stored in weapons – whether spinners, or transferred in a powerful flipper connect, or in the form of a hammer tip – begin overtaking the ability of the material to elastically deform and dissipate energy, so you end up with a lot more things bent out of shape rather than two heavyweights suddenly reappearing at the other side of the arena.

I mentally call this idea the “robot Reynolds Number” when comparing designs of different sizes: to get the same physical behavior, a bigger robot has to be simultaneously more powerful yet built more rigidly. Consider it characterized conceptually as the ratio of average kinetic energy transferred per hit in a weight class to the material yield stress * volume used in your robot ( KE [J] / σᵧ [Pa] * volume [m³ ). The best example I can think of is probably how Big Ripto and Triggo (30lbers) can both bounce around arenas like beetleweights – but both robots are made of hardened steel when it comes to the bodies in contact, whereas plastics or even aluminum is likely to just deform in the same application; as well, they both cram about 4 to 5 kW of weapon motor power behind them, which is actually more than an order of magnitude from the typical beetleweight (3lbs).

What this means for me is that I have to be careful with interpreting the results of my matches. For instance, it’s highly unlikely that Overhaul will get sent flying end over end from a single spinner hit such as that from Botceps, but rather depending on what gets hit, I’d lose one of the wedges or have a pretty big chunk bitten out of the frame. The best-in-class KE weapons in BattleBots right now run right around 15-20 kW and around 50-100kJ. Going back to Blacksmith vs. Minotaur, you’d expect with strength-invariant scaling that Blacksmith would easily hit the box lights, but rather what happens is the frame/wedge deform and fasteners begin failing.  Also, in my match against Cobalt, my one good deflect was the end result not of being ultra-rigid, but backing the hit with the arena floor by virtue of the rubber-suspended wedges, which is obviously something I want to keep.

While the exact physics won’t carry over through scaling, concepts will. For example, I am fairly confident that

  • Weapons of low prominence, such as discs/drums/shells, are best kept away from you and interacted with lightly since they are less likely to grab entire portions of your bot at once, rather chipping away at it. This is best illustrated by how megatRon was able to keep Crippling Depression at bay with a single low front armor piece, whereas CD had more inroads to damaging Clocker’s separate armor pieces.
  • Weapons of high prominence, like the archetypical spinning bar or single-tooth style weapons, should be more readily deflected if possible, since they have more potential reach (i.e. far more “bite per tooth”) and less predictable reactions. You want them to go away from you as much as possible. I rather enjoyed a lot of the driving against Beam and making it do “the Tombstone dance”, and even the small welded barrier strip made a lot of difference until it failed.

Ultimately, I had to rethink Overhaul’s armor approach and how it interacts with the lifting forks.

  • I came away 1000% convinced it needs a Full frontalplow-like surface up front. It’ll be heavier – I will make weight for it somehow. One downside of separate wedges is only one set of rubber mounts takes all the load of an impact, and while my Cobalt flip was perfect, 99% of hits I take won’t be that perfect. A spanning plow will allow the mounts on both sides to take the load. Besides that, it will obviously decrease the amount of open corners Overhaul (and Clocker!) has. In fact, the plan was for the original Overhaul 1 to have such a thing, but we ran out of weight.
  • I had to retain the ability to lift independently of being able to deflect hits. Did you see me pin CD and Beam against the wall several times, but having to back off to try and get the forks underneath them – which in both cases had bent up beyond the point of usefulness? That’s how they escaped and the match continued. I need the ability to corral spinners against a wall but keep the arms tucked behind the plow, maybe exiting via a small cutout. Overhaul has a set of short arms which remain behind the wedge profile – imagine a cross piece in front of them connecting the two wedges.
  • Beyond just dealing with horizontal KE weapons, Overhaul needs a “Wedge of Limited Liability” of its own, which still supports the bot during a lift but otherwise takes the form of a skinny fork or tine so vertical weapons and things like flipper spatulas have less edges to find. I didn’t get to exercise the WLLs of Clocker this time against a vertical drumlet weapon like Other Disko, Mega Overload, etc. but I did like piking it under Botceps. Depending on the length of the tines, it could be effective on its own by being jammed under vertical spinners, for instance.
  • I need to learn to drive “dirtier”. What this means is foregoing my desire for continous showy and aggressive action – something I am used to in the 30lb Sportsman’s class – and instead maximizing my usage of pin times and arena-outs. Jamison is a more strategic and methodical driver me in this regard – he drives to win, whereas I tend to drive to shitpost. Compare his style when fighting CD (and other heavy weapons) versus mine. In the BB arena, survival is going to be key since we are more in the realm of throwing elephants off skyscrapers than insects. The NERC arena doesn’t really have facilities for arena-outs, but the BattleBots arena does, and I think it will be a key portion of my strategy. Bounce bots up and away, keep them corralled, and try to manipulate them behind the low walls and screw embankments.

Once I got back to the shop, it was time to refactor Overhaul’s design a little. Stay tuned for those updates!

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

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.

motomumu

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!