Archive for the 'Bots' Category


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!

12 O’Clocker & MassDestruction 6: Where I Rebuild a Bot After the Event is Done

Feb 09, 2017 in Bots, Events, Twelve O'Clocker


I feel like this website has become the Life of Charles, what with real editorials and non-stop round-the-clock van coverage and my tenuous professional aspirations… This is not the man I know. Where has he gone? *looks at own hands*

But now I’m back, with some new developments for Überclocker in preparation for Motorama coming up next week, as well as 12 O’Clocker stories to tell first. This bouncy little thing has been going to events and demos since 2013 with hardly any changes – just switching motors, basically. It’s gotten sufficiently worn down to a stub in the past few months that I decided to do a full teardown rebuild with some new parts!

To tell this story, we go back to the dark days of MassDestruction #5, like 3 months ago… Wait, CAN YOU BELIEVE THERE’S BEEN 5 OF THESE THINGS ALREADY? THAT’S MORE SEASON THAN BATTLEBOTS please take me back greg ;~;

This MassD, I took a more organizational role, helping judge and run matches. However, this didn’t prevent me from putting 12 O’Clocker (at the time, my only working bot -_-) into the arena in the somewhat informal 12lb Sportsman’s Class, where pretty neat matches like this occurred. MassDestruction has become a popular regional attraction; word has gotten out, and we pretty much filled out the Artisans’ Asylum event room to capacity. Like, look at this photo.

This is “filming a music video using the flashmob mosh pit at your post-phlegmpunk band’s free unannounced concert” level stuff. What’s better is that the builder population is getting more and more towards being newbie-dominated. This is a great problem to have.

12 O’Clocker came in 2nd place (out of like….3?) at this event, which was great, but it did take some damage. For the deterioriating ABS motor mounts that retained the lift motor finally gave out completely, wrenching the drill casing apart under its own torque:

Oooooh, that’s not good. I finished the tournament using a found drill motor given to me by an Artisans’ member, unceremoniously hot glue MIG-welded into the remaining mounting block pieces. At some point in the final against Snek Plissken, I also lost the lift motors which turned out to be one of the logic capacitors on the old RageBridge 1 units in 12 O’Clocker just breaking off the board. I also ended up demolishing another motor pinion just like at Momocon; the most recent set of motors for 12 O’Clocker came from some 12V Ryobi drill motors, and it seems like they were not up to the task of being run at ~20 volts.

Fast forward another 2 months, and MassDestruction the SIXTH! was on the horizon.  With the promise of more rematches with Alex Horne’s not-Sewer-Snake, I decided on a quick tuneup by replacing the broken ABS lift motor mounts with MarkForged Onyx prints because of course I did. New drive motors were also on the docket.

The Rage Panel slides out from the bottom, so I took the bottom plate off, which also let me do a hardware inspection on parts of the bot I rarely touch after finishing. This level of surgery was also needed to finally detach those ABS blocks.

So new drive motors were a bit of a conundrum. When 12 O’Clocker was built, it was still common to find generic cordless drill motors with 9-tooth pinion gears and 36:1 reduction (two 6:1 stages, 9 tooth sun, 18 tooth planets, and 45 tooth ring) gearboxes. Nowadays, it’s almost impossible to find these kinds of gearboxes, with 24:1 being the most common such as being found in all of the Harbor Freight 18v drills and most other rebrands. The 24:1 boxes have a 4:1 first stage using a 15 tooth pinion.

Trouble is, 12 O’Clocker was already geared to go fast, and dropping the gear ratio another 50% would have made it impractically fast and probably burnt out the motors in short order. Those Ryobi drill motors that I kept slipping the pinion on were attempts to find more 9-tooth motor pinions to fit the existing gearboxes.


After some haunting online, I found that one of my usual Amazon suspects uxcell sold 18v rated 550-sized motors with steel pinions already installed. Well imagine that, a prepared artificially flavored drill motor!  So I got a bunch to play with. They certainly look like 550-size motors and quack like them. The cans are a little thin, pretty typical of a mature Chinese genericized product… I can pick them up with a screwdriver. Every possible area of cost cutting has been well optimized!  The bronze shaft bearings obviously have no oil in them, since they are a little rattly, but a drop of motor oil in each solved that.

What I did notice was that the pinions’ press fits weren’t that tight. It was actually easy to undo them with a flat-blade screwdriver alone. To pre-emptively avoid embarrassing public gear slips, I took the pinions off and repressed them with a healthy dose of lime-flavored Loctite.

You know what – I’m just all giddy at the fact that they’re motor-shaped at all.

At some point in one of its tournaments, 12 O’Clocker either fell off a Dragon Con stage and landed on its main sprocket, or I got beaned by some flying robot, because the sprocket developed a flat spot which caused the chain tension to vary cyclically, leading to some lost chain moments.

In a moment of either desperation or brilliance, I decided to use my Harbor Freight slide hammer kit with a hook end to pull the sprocket rim back out like you would pound a very reticient dent. I bought this originally for van repair, but it looks like it works for robot dent pulling too!

Putting things back together, sans battery. The Ragebridge 1 with the missing capacitor had that repaired; the capacitor ripped out a logic power trace when it fell off, so it just turned the controller off. All the caps were securely Goop’d in place after the replacement surgery. If you’re using a Rage or a Rage 2, you should do this just in case also.

The biggest problem plaguing 12 O’Clocker was its battery, which I balanced once in 2013 and never again since. The cells had drifted far enough apart since then such that two of them flatlined at MassD #5, and I could no longer revive them. This meant I had to cut the battery open and undo the cell joints to the point where I could pull the two dead cells out and replace them with fresh cells. I closed the battery up again after this replacement (the green tape is new and covers the modded solder joints) with some thicker heat shrink, and making my charger do 5 overnight balance-charge-to-discharge cycles evened the cells out.

One last mod before MassD #6 was the permanent resolution of the clamp motor coming loose. The threads in the face of these Pololu 25D HP motors had completely stripped, so the motor was really just holding on by the electroweak interaction at the end. To remedy this quickly, I just took the faceplate off, slammed a #6-32 tap through them both, and then countersunk the original mounting holes in my actuator body. #zerosigmas is best Sigmas!

If you use these motors, or any of the similar motors from Servocity or Kitbots (or the straight shit from eBay), make sure to also take the motor off, clean the area, and use blue Loctite or similar threadlocker on the reassembly path. The motor does like to also wiggle loose – this is what the “battle hardening” mod offered by Kitbots helps prevent.

So anyways, it’s the morning of 1/28. Time to….

literally all the robots

This is what I trained for.

That’s Overhaul, Sawblaze, and two lift carts in the back. With space for another smaller heavyweight, or a dozen 30lbers and tools & equipment. And probably like 27 people. Some times it’s nice to just bring the U.S.S. BROWN C. STENNIS to an event.

This time, the event was held at the Charles River Museum of Industry, in one of their large event rooms. I once again helped with event logistics including box setup and judging. Overhaul and Sawblaze were brought along for visual stimulation, which was unfortunately because the event room has neither loading dock nor wheelchair ramp, and was, of course, a New England First Floor – 6 feet up the stairs.

Running 12 O’Clocker – especially when things started breaking – and half a robot show at the same time was a unique and singular experience. I will never do it again.

Have some 12 O’Clocker matches!

The match against Don’t Step on Snek, a.k.a Snek Plissken, a.k.a Sewer Snek… god dammit Alex, pick a name already!

By this point, 12 O’Clocker had lost basically all of its forks. They finally reached their fatigue limit at this event, one by one breaking off, until I had basically a big spatula. In the match prior, the right side motor pinion slipped its press fit as I had feared, so I went into the final match (also against Alex) one-motored. Which is fine, since Alex at this point had also started to run out of motors. The finals match was such a headdesking, facepalming occasion that I’m not even going to bother finding a video.

Poor 12 O’Clocker before the finals with the forks arranged the best I can, so SOMETHING AT ALL is still sticking out ):

Well, that’s it for the event. I broke the damn thing so much that I felt like I might as well use the momentum of the event to make spare parts. As I needed to also waterjet-cut spares for Überclocker, I threw on replacement forks for 12 O’Clocker in the same run.

Tearing down the bot completely up front to replace the fork components! This is where I discovered that despite my best attempts at anti-seize grease usage, the lift sprocket’s hub had galled onto the aluminum tube shaft, so the slide hammer was needed again just to break those two apart. I reamed all the shaft collars out again and cleaned up the aluminum shaft surface. This time, I tightened all the collars as much as I could – no longer relying on clutching the lift sprocket for torque limitng, but just setting the RageBridge current limit low enough that running into itself will not cause problems.

The new forks are slightly modified from the current design by adding more meat to the areas where the tie rods pass through. This was previously where they broke, so I made sure to add at least a majority of the cross-sectional area found in the rest of the fork.

By the way, this tube-removing service is also a problem with Clocker, especially after everything got twanged far up its own ass at the Franklin Institute event. I’m going to reconsider using a live shaft with shaft collar hubs to the forks for this reason, possibly considering a more Overhaul-like tie rod and central hub approach. Otherwise, I’m going to make an attachment for the slide hammer specifically for this purpose!

And here’s the refreshed 12 O’Clocker! Hopefully a staple of many demos to come.

Shut Up about “Modern Technologies in Robot Fighting” Already: A Charles Editorial

Jan 20, 2017 in Bots

So I very rarely go off on polemics on this website. In fact, I can’t recall the last time I straight up roasted something, besides laying on Sparkfun periodically for getting their breakout boards amateurishly wrong, or complaining about literally everyone else’s motor controllers. I try to stay focused on relaying the technical and weaving tales of implementation while discussing mistakes and could-have-beens, because I enjoy clearing up the fog of knowledge when it comes to building. Not only do I like making my work accessible, but I hope every motor controller I blow up also creates a record of what kind of REALLY? IT WAS THAT? mistake the problem ended up being. It’s always that.

A little to this end is my tendency to never claim I know something that I actually don’t. I hope I’ve been pretty good at keeping to this philosophy, and you’ll notice in many posts that I tend to express uncertainty when explaining a problem because I don’t know everything about it at the time, and the reasoning will probably change later. Furthermore, as you doubtlessly know already if you’ve been on the Internet more than an hour, the quickest way to get correct information on the Internet – whether you like it or not – is to be publicly wrong about it.

This is a double-edged sword; I’ve wielded it cloak and dagger to get correct information from enthusiast groups & forums of technical discussion before, and it works great! Try it some time… just say something nitpickingly wrong, such as “You can totally use frequency-injection rotor saliency detection on surface permanent magnet motors with an Arduino!” and someone will be bound to reply “Well technically, it depends on your stator saturation model“.

Well Technically is the zip ties and duct tape of unsound technical reasoning – collect enough Well Technicallies and any poorly-founded conjecture will stand up on its own, suspended by the tensegrity of vague wording and handwaved speculation.

If you didn’t understand what the hell that example meant, don’t worry – I didn’t either. That’s why it’s nitpickingly wrong.

On the other side, relaying incorrect or incomplete information opens yourself to being called the fuck out, which is what I intend to do. So let me begin with

Stop. Talking. About how every problem in the robot fighting world will be solved by the Inter-fucking-net of Things. Or how builders should just try smartphone control already. Why don’t we all use DEEP LEARNING to strategize matches in realtime? Just shut up and build your first kit antweight.

It seems like every few months, someone on a public robot fighting related forum will make a contentious point about how NOBODY USES WIFI TO CONTROL THEIR ROBOTS? WHY? or champions the favorable characteristics of switched-reluctance motors which they learned about on Youtube approximately one millennial attention-span ago (Oh shit, I made a millennial joke! Is this self-deprecating humor or am I just a lawn security officer now?!). I regularly have people ask me why nobody uses Swerve Drives when all the high schooler robots do it already. With near certainty the poster is pretentiously tech-savvy about the Connected World or is an Internet of Things developer who probably has an Amazon Echo bickering with a Google Home about control of the sex lighting in the basement, ON YOUTUBE.


Robin Mitchell of Allaboutcircuits, I am now talking directly to you. In your recent article “The Resurgence of BattleBots and Robot Wars“, you put forth such affronts as “…the new Battlebot and Robot Wars series showed little technological advancement with regards to sensors, microcontrollers, and electronic warfare.” and propositions such as “…use multiple relays that isolate separate batteries from the robot which can be switched on and off using the main controller.”

Hang on a second – let me go find a “relay” that is rated for the combined current draw of all of Overhaul’s drive motors. Want to see what it looks like? This is it:

When they get that big, they’re called “contactors”, but that is besides the point; I’ll get to reasons why automatic power failover is a nice thing but (to my knowledge) completely unseen in robot combat.

Let me be clear here – I have no personal grudge against you, Robin, nor do I have a problem with Allaboutcircuits, a site that I used to reference daily years ago and should continue making a habit of. If you’ve never built and fought robots, it’s a perfectly excusable pass on the misinformation front. Everything you presented can technically be achieved and could possibly be used productively in robot combat. However, recall the 2nd part of my thesis regarding being wrong on the internet: this article is also epitomic of all of my presented complaints about outsiders observing the “technology” in combat robots and snidely commenting on it, so I feel implored to reply.

1. On the structure of precision language

One of the hallmarks of technical misinformation is nebulous & vague wording that sounds good to the casual onlooker, but sooner or later you’ll run into someone who actually know what the hell they’re talking about. The article is absolutely infested with these missteps, starting from the very beginning about rapid prototyping.

No, rapid prototyping is not JUST 3D-printing. Rapid Prototyping is a set of techniques – of which 3D printing is just one – which ideally help you reduce the time and effort needed to produce working products or concepts thereof. Though everything I do can technically (there’s that word again) be construed as rapid prototyping, nothing about Rapid Prototyping must involve a computer or a poorly-built kit noodle-pooper.

In modern parlance it is often assumed to mean the same as digital fabrication, which 3D Printing is most definitely a part of: computer-controlled machines which generally perform one task whether it be machining or extruding or lasering the ever-loving shit out of something, which can be quickly set up (rapid) for the creation of objects (prototyping!) more or less directly from a digital design file.

Now, what does this have to do with robots? Rapid prototyping techniques (plug!) and equipment have contributed to a vast paradigm shift  in how small and large class entries alike are built, and despite not being very visible on the BattleBots TV show, a significant number of entries had 3D-printed parts inside. Hell, I’m one of the two teams sponsored by MarkForged, a 3D printer company which is on the intermolecular-bond-splitting edge of 3D printed material properties.  You can also barely find a 150 gram to 3lb (“insects” class) bot these days which doesn’t have some kind of 3D printed artifact on it, possibly even entire frames and even including weaponry in the new “Plastic Ants” class.

The newest “easy way” for builders to start is no longer piecing together R/C cars with Home Depot sheet metal, but grabbing a 3D printer. That is huge. The first moment I ever felt old was the first time I was casually talking to a freshman in the fab shop that I ran at MIT and the subject of building a 3D printer just casually came up as “Oh yeah I built one of those in high school”. Bam, just like that, I officially entered intellectual cruftdom, the derpy 80s prismatic van state of epistemological being.

Beyond the limited definition of 3D printing, you have robots utilizing laser-cut steel unibodies that are ordered direct from a steel vendor by sending them CAD files and pieced together in just hours with a welder, bypassing dozens if not hundreds of man-hours of shaping metal, fitting it together, jigging it all up for welding, and then doing the welding. Every curvy or fancy looking robot exterior on the most recent show was likely not trimmed by hand, but waterjet- or laser-cut in minutes. That is the real magic of RP techniques in robot building, and I do think a lot of the current “innovators” in this realm are recent college grads & young professionals who have seen the techniques used elsewhere and brought it to the forefront in the sport.

Besides painting ideas in broad strokes, there is also a tendency by Modern Technology people to speak generally of executions, never having to have executed them or thought about what their ideas really entail. Going back to the relay problem, the solution (to a problem I contend does not actually exist) is:

One possible method is to use multiple relays that isolate separate batteries from the robot which can be switched on and off using the main controller.

Soooo…. does that mean making a battery isolation system out of relays? They sell devices for that, often for RVs and boats with multiple batteries. Either solution (neglecting the practicality of a 3rd or nth power source exclusively for the logic) means you need “relays” that can each take the full operating current of the bot, and I showed you how big that part is. Wait – no, back up. Before we even reach that, this implies you already have multiple batteries each capable of running the bot separately for the duration of the match, unless you size them to require mid-fight changeover.

Imagine if Tombstone had 3x the number of batteries it actually needed to run a match. That would be a riot! Good luck designing this system within the weight limit while still maximizing your robot’s operational ability! Lithium polymer batteries be magic, but they’re not that magic just yet.

On top of that, you have things like

The communication system could also be improved in many other ways including the use of a microcontroller instead of using an RC module with outputs that connect to actuators and subsystems.

Okay… yo, what does this even mean? You know all R/C receivers have microcontrollers in them, right? And every motor controller? If you don’t have an R/C module (which I guarantee the author doesn’t know is a real, commonly used, and nice thing that goes into your handheld transmitter  – Overhaul uses a 400mhz Long Range module system that can conceivably let me control the bot from over 10 miles away)  what does your microcontroller use to talk to your smart watch and smart dildo that you’re using as a robot control input?

If a player switched to 2.4GHz and used a module like the ESP8266 then…”

INTERNET OF THINGS BRO DETECTED! You’d swear with the number of people singing the gospel of the ESP82x system that it will singlehandedly stop Russia from starting Cold War 2: Thermonuclear Boogaloo on the 20th here or something.

(Nevermind the fact that the preceding sentence to this misplaced quote “The radio frequency that these robots use will most likely be around the 27MHz channel” is absolutely, indisputably incorrect, as 27mhz has been banned in most larger weight classes since the late 1990s and prior to the rise of 2.4G spread-spectrum hobby radios in the mid 2000s, most robots were mandated to run on 75mhz using compterized PCM transmitters. This is just being factually wrong instead of spiritually wrong.)

Anyways, in this case, I assume what’s going on is another case of hipster engineering colloquialism – when certain people say microcontroller what they mean is an Arduino. Yes, a separate microcontroller can be used to collect all of the information proposed – voltages, currents, temperatures, etc. Again, there’s that Well Technically factor: Yes, you could collect all of this data, and yes, you could transmit it over WiFi to an iPad set up with a custom dashboard app you wrote, but all of the data in the world about your CO2 tank upstream pressure doesn’t help you when the tank has been eviscerated and unceremoniously thrown across the arena by Minotaur.

Having these onboard sensors does not inherently make the robot better at robotting. It’s like having the same telemetry in a car – it will help you potentially tune the car for performance, but does not alone make it faster. This information could very well help you discover a design issue with the robot – motors drawing too much current and heating up too quickly? One weak battery out of four? Better take care of those before you run out of postponements! Telemetry and “sensors” comes up a lot – likely because people who keep ragging on this are IoT bros – and the praise of Team Storm in the opening for adding sensors to their old and tired design to instantly make it modern , parallel to the phrasing of robots being “improved” by sensors, is a good example of my second thematic struggle with futurists in the robot world, which is:

2. On optimality of cross-discipline solutions

I don’t blame people for talking about automatic battery-switching failure detectors or first-person view cameras with dynamic robot-to-field orientation control or any of that. The fact of the matter is, they could be speaking from experience (or out their ass) in a field where such things are common and expected – automatic failover is virtually required in server power supplies (and the servers themselves in modern datacenters). FPV is increasing in popularity within the vaping rig drone community because flying a drone while “sitting in it” can be very intuitive, more so than trying to stare at it from 1000 feet away.

It is the insistence that their favorite golden engineering goose will equally lay golden eggs across all fields, without any relevant experience to back up the fact, which I am considering here – the insidiousness of Well Technically is at play once more. Again, I don’t care so much about being straight-up factually incorrect, because that’s easy to fix.

Remember the Reddit thread I linked to at the beginning. If you haven’t Reddit, the gist of it went something like:

Well, robot builders don’t like new things like WiFi – look how long it took them to use 2.4Ghz radios!

That’s because most R/C 2.4ghz systems for sale did not meet robot-specific needs, but now they do.

…But robot builders definitely don’t like new things, look at how few people use brushless motors, everything uses brushless motors!

That’s because most brushless systems for sale did not meet robot-specific needs, and still kind of don’t.


Let’s talk more about swerve drives. Swerve drive, bro! Holonomic motion, bro! Got 8 degrees of freedom on my drivetrain, bro! Any direction, any time, bro! My conversations with what must be the closest thing to the Jehovah’s Witnesses of robotics because they will never, ever shut up about DO YOU HAVE A MOMENT TO TALK ABOUT OUR LORD AND SAVIOUR TEAM 221swerve drives once they find out I build combat robots consistently goes something like:

Do any battlebots [with a lower-case B, this is important] use swerve drives?

Not any current ones, only a few have tried in the past, but none have been successful.

Oh, that’s weird. They’re the best drivetrain for this kind of stuff.

Why do you say that?

You can move and attack from any direction!

You certainly could, but durability due to the increased mechanical complexity is a concern, as well as added weight.

Well you just have to { CNC machine all of the parts from titanium, use this design I found on ChiefDelphi, place them closer to the center of the robot and armor around them };

Additionally, not many weapons and strategies can take full advantage of omnidirectional motion. It all comes down to design compromise and what you want from your robot.

Well you can just…

Those choices in brackets? I’ve personally had to absorb and nod my head to each of them. My most memerable instance involved someone literally following me for 10 minutes describing how if the robot just had 4 flipping arms, one on each side, then it would be a good use of swerve drive because it would be universally defended.


That word is like the dual of Well Technically, like the superhero and supervillain comic story of Half-Baked Idea City. For every Well Technically rebuttal, there is a Just conjecture.

Now hang on a minute here… If your robot already has weapons on every side, does it really need omnidirectional motion at that point!?

All of this might sound like I am the sheriff of the GET OFF MY LAWN police force. And you know what – maybe I am a rookie officer in training, having been in the game for too long and the ‘stock solutions’ for common strategic problems having calcified in my design process. But let me be clear here: What really Brinells my bearing races is not that people want to try to build Cloud-powered Robots-as-a-Service, but that they immediately pose it as the best possible solution to a problem they otherwise profess ignorance to. It’s not that you can’t use ESP8266 modules in your custom radio, but the coming right out guns-ablaze and saying that it is better than R/C radios. Better in what way, being easily customizable beyond user comprehension in an application where communication errors can result (and have resulted) in the runaway of a machine literally designed to kill the fuck out of other machines? It’s not that swerve drives have never been used in BattleBots (we don’t talk about Radioactive), but it is always presented as inherently better than tank-style steering, despite the added moving parts that must remain in close alignment to work properly, because in combat robotics all of your parts always stay aligned!

What these examples have in common is that people will take their knowledge of something which has an apex predator status in their field of work (or interest) and assume that it would work just as well in another context, change be damned. Robot fighting, truth be told, is a pretty damn redneck sport in the grand scheme of technological competitions. Nothing that relies on banging two objects into eachother really hard for entertaniment can be that refined, right? We are, in some sense, a bloodsport of technology. That has historically made robot fighting easy to talk down to by people working in technological industries, especially software and AI. Add to this most bot builders being in the mechancal engineering or machining/fabrication industries, or simply being mechanically inclined, and you have a perfect fuck-shit-stack of lost-in-translation: The finery of the often extensive mechanical design work and manufacturing effort being unappreciated by someone who’s never picked up a tool, and the perception of sophistication they associate with their choice of career, or their preference of controls and intelligence complexity.

The person who followed me around the building trying to convince me that swerve drives were the Alpha and Omega of robotic drive solutions? I challenged him to build a scale model of his concept robot in any weight class, and that I would permit full normal usage of my shop for the purpose and make myself available for consultation. Never heard a peep from him since.

Don’t be that guy. If you want to explore “smartening up” the sport, do so and deliver. Probably the most under-stated thing at BattleBots Season 2 was the auto-targeting hammer of Chomp, and it’s a shame they devoted only like 3 sentences on the show to it. Very few people have ever attempted auto-firing or target-seeking weapons. They knew it was a huge risk and that it might not work, but GOD DAMN IT WAS DELIVERED. I like to think that I pushed the front of using hobby-class brushless gear in robot drives with my 6-month-long development cycle and immense risktaking getting Overhaul 2 into the arena with all HobbyKing motors and controllers. The evolution of technology in robot fighting is truly, and some times literally, trial-by-fire.

Go to a competition and learn what kind of details you might have missed while perfecting your off-the-wall design concept; enter a kit antweight and get your ass handed to you in a match to see how hard it is to maintain an entry. Then build your gesture-controlled SLAM-navigated swerve-drive Hoverboard-motored* Internet-of-Things-connected self-Tweeting BattleBot. The whole sport would appreciate your contribution, even if it gets turned off at 0:11 by an errant power-handling relay.

*I challenged myself after talking to the High Priest of Swerve Drives to design a swerve-module which could conceivably drive a 250lb Battlebot and not weigh much more than a typical drivetrain does, while being heavy duty. This actually is possible, as illustrated by DeathRoll during Season2; it had four seg-thing motors running at 36V each and was pretty maneuverable. The module ended up weighing around 25 pounds, and used a A23-150 Ampflow motor for steering. Four of these would weigh about 100 pounds, so it could happen, but would need tight integration into the frame design to have weight for anything else like weaponry.