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 exampleBlacksmith 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. ａｍｅｒｉｃａｗｉｌｌｎｅｖｅｒｂｅｇｒｅａｔａｇａｉｎ
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!
So now that we’ve gone over the build of Clocker 4, it’s time to talk about how the bot did! The Franklin event was one that I went to the first time last year, and it was quite the experience – if not extremely busy since the whole tournament has to be finished in 1 day.
Everything I needed for this event fit on one handtruck. See? Why can’t we just build 30lbers for BattleBots? Film the whole damn tournament in macro so they look huge!
I was prepared to take a few last-minute MITERS people, so I showed up ready to go. However, plans suddenly changed…
Mr. “I’m not sure if I’m going to go and it’s 9PM the night before the event” decided to take 30lb-SawBlaze. Given its reliance on conventional lithium batteries, we had to really quickly make a replacement battery using 18650-sized A123 cells pulled from my stock, using the last minute MITERS robots’ prep time to do this. This battery furthermore had to fit in the former space occupied by two flat LiPoly packs, so it ended up looking like a weird laptop battery. The vertical cells leaked into spaces the flat packs did not, in order to get some more battery energy.
MegatRON/30-Sawblaze also uses the Axiii motors attached to P60s, incidentally. That means we’re well matched for speed and power. This should get exciting!
Five hours later, we emerge out of hyperspace into the orbit of Philadelphia, only losing $26 of toll money in the process. On the way, I stopped in Manhattan to pick up two spontaneous teammates, Cassandra and Allen-chan (for whom this is public notice towards to put a real damn website together). Cassandra took most of the photos to follow, since I was too busy running around headlessly.
All set up and ready at the event, with a pipefessionalism to the left. The pits at Franklin are always tight due to the space available, so I actually shared a table with Jamison. Getting pointy 30lbers in and out of the aisles was always a dance routine.
What’s that on the back of Clocker? Why it’s chibi-Haru-chan! Join Cynthia in a month of drawing cute chibi-style BattleBots entries!
IT’S ROBOT FIGHTING TIME! In the Red Sharpie Blob, it’s… god dammit Charles, get out of here, you’re not Faruq!
Clocker’s first opponent was Melvin, a modular pushybot with different pushy type attachments. It was a fairly easy target to grab, and I didn’t feel particularly threatened by it so I took the time to get to know the drivetrain better. I got a few good grabs on it, and then….
…whoops. After those good slams, the upper jaw just comes off. Well, this is disappointing, but I can’t say that the dislocated look isn’t neat in its own way. The weak link was the linear actuator’s leadscrew anchor.
I had two 1/4″-20 set screws – the same kind that took out Overhaul – holding onto the leadscrew in a notch, but I guess the force of the lift and clamp crashing down was enough to tear the end of the notch, and off the leadscrew came.
This was resolved by using two oversize drill bits to drill deep dimples into the location where the set screws landed, turning them more into pins. I didn’t have issues with this the rest of the event.
My next match was none other than Mr. “I’m glad there was still a registration spot open when I got there”, 30lb Sawblaze a.k.a Megatron. This was a spoiler for #season3 excellent driving and maneuvering match that I just barely lost. Having weight on the front of your robot still trumps (We need to find a new word for this activity eventually) any amount of fine compliant wedge tuning, I think. I was hard pressed to attack Megatron head-on, so I concentrated on keeping it rolling over and self-righting, but there were more moments when he had control. Once Clocker was propped on the prongs of Megatron’s plow, it was more difficult to un-prop.
Near the end, Clocker was stuck upside-down momentarily. I thought it was the DeWuts clutching out, but looking at one of the match video angles showed that Megatron had spun off one of the nuts that holds the cross-fork tie rod together, and the tie rod was fallen out and jammed between the forks and pontoon. It took several seconds of forcing it back and forth before it finally bent enough to let me flip back over. However, in that few seconds, I lost significant mojo with the judges.
Some nice sparks coming off Clocker’s pontoons from the sawblade!
After this match, the rear wheels were basically worn flat. This is fairly consistent behavior – a few Motoramas ago, Clocker ran out of wheels. After that, I was replacing the duallie BaneBots 50A durometer wheels once per tournament. This version of Clocker combines smaller wheel contact area with a lot more drive power, so I was expecting to burn them down faster. There’s still a lot of “eraser flakes” going on, so I might want to look into a harder compound or just more durable material. I also openly admit that my casting technique might need some work.
The front wheels suffered less, since they were unloaded somewhat by the pontoons. I’ll add that having the pontoons firmly on the ground was not that helpful – I felt like I had traction issues, but it was really the pontoons and forks making the bot act like it’s front-heavy. It drove much better if I had the forks up a little. This is actually good to know for #season3, and I’ll talk about that later.
Some nice gouge marks in the pontoons from being held under the saw for a few seconds!
This is the cause of the jamming. The threaded rod tying the forks together backed out – most likely due to the saw, given there’s a significant cut mark on the standoff like someone took a poorly sharpened lathe parting tool to it!
Alright, I had maybe 10 minutes until my next match (Franklin runs FAST – you aren’t guaranteed the usual 20 minutes of repair time). Can we change the wheels in time? I brought my pack of spares that were cast days before. This batch had air bubble problems, clearly visible in the wheel, since I could not locate the makerspace’s vacuum mold degassing chamber. Someone probably ran off with it for New York Comic Con. I was curious now about how the airy wheels will wear down, so I swapped them on anyway.
The next match was against Duck Yeah, a vertical spinning “STD” bot (where STD has now become popular robot slang for Single Tooth Disc). This is architecturally similar to BattleBots like Witch Doctor, Brutus, or Hypershock, so I was excited for this match. I don’t have a good tactic against STDs or other vertical wedged weapons besides “Don’t Fuck Up”.
Well, I did. My penchant for backsliding into head-on assaults did not end well. In fact I fucked up almost immediately, and the pontoons and arms bent up enough for it to be almost impossible to get back under Duck Yeah.
I got tangled in a hit shortly after that which let Duck Yeah go Full Mike Tyson and nip off one of the ears. These ears were definitely more risky than Overhaul’s – I got stuck sideways on them once while the clamp was open and I forgot how to self-right. Overhaul 1 and 2′s self-righting do depend on the clamp being closed past a certain position, which is easy to forget without practice. PRACTICE DRIVING YOUR DAMN ROBOTS!
The bright red glow coming from the middle of Clocker is the clamp motor’s endcap which got blown off in an impact – the brushes are touching and heated to incandescence by the current flowing through them!
Match video here. About midway through, I gave up on lifting since the pontoon edges were mangled and the forks bent, and just drove it around slamming it into walls more. I won the match on this basis.
So far: 2/1
The ear that got nibbled split pretty cleanly along layers. You can also see that the weapon made contact with my clamp motor at least once!
Alright, not much more time until I have to get back in the box, so I quickly swapped a spare clamp motor in. This actuator, thank goodness, is far easier to service than the previous ones!
One thing I did not have was spare forks. This was a pretty severe oversight, as I had the ability to cut them out the week before and dd not do so. I also didn’t have a big enough press, or enough time, to straighten them out again to a degree that would be useful. As such, out comes the angle grinder. I’d rather fight with 1 fork than two are are kind of at different levels.
After this bold move, I try testing the repaired clamp arm and……. nothing. The motor wiggles a whole lot, but doesn’t really move the leadscrew. Uh oh…. I pull the thing apart and discover that it had a totally different pinion. I grabbed a motor for an incompatible drill out of my bin, went “LOOKS OK FROM HERE”, and threw it in the parts box! The gear was similar in diameter, so it “kind of worked”, but really didn’t. Cue 10 minutes of trying to find either a replacement motor or a pinion puller – someone came through with the latter, and I was able to transfer the pinion off the destroyed motor.
The next match was another cripple fight against a decidedly less mobile Melvin. This time, Melvin busted out a thwackbot assembly since they could only spin in place with 1 functioning motor. This was a match where I drove a little harder and went for broke. I had so little time after discovering the motor mishap that I left the ears off. Nontheless, it was a match full of a few full power, cross-arena drives which I had not attempted up to that point. One of these dislodged the bumper inside the arena!
Here’s that match. Near the end, I stranded Melvin sideways on the bumper. I generally have a policy of freeing opponents if they get stuck once, but if I get them twice, I’m done. 3/1 now, and Clocker moves onto the Loser’s Bracket finals (aka the most winning of the losers!)
And who was my next match? A rather crippled Megatron, who just got recently bounced off the ceiling by Big Ripto, in an event which called into question the integrity of the arena. This match wasn’t long – Jamison didn’t have enough time, nor the means, to reattach the plow in a way beyond large quantities of what he calles “Harambe Tape”. Nor was the saw functional. So the plow fell off early on and he decided to call it. Here’s the match from Fred – this put Clocker in the finals at 4/1….. against Big Ripto.
The finals didn’t happen. You can tell because here’s a photo of Clocker still in one piece. The event organizers decided to ban Ripto from the arena again citing the danger of ejecting parts from the roof. This was made known to us when the organizers pulled Kyle and I aside and had a chat about the arena falling apart. While there was some rock-paper-scissors involved, I handed the victory to Kyle unconditionally. There was no way I would have stood a chance in the shape Clocker was in at this point, and Ripto had taken literally no damage. It’s a rock solid design that’s hard to counter, especially when nothing on the front of your bot lines up any more.
I just made the organizers promise to match Ripto and Clocker up first thing at Motorama 2017 next year. By then, hopefully my strategy against vertical weapons will be more evoled. That ought to be funny.
So that’s the story of how Überclocker 4 / 30-haul took 2nd place at Franklin 2016!
On the way out, we stopped for dinner at a place I was explicitly recommended to go for the best Philly Cheesesteak. While I agree that it was very good, we all fucked up on a very important aspect: Not realizing the place offered toppings. Now, up until this point, I had never ordered a geuine Philadelphia-sourced cheesesteak sandwich, so I thought it was SUPPOSED to be just an amalgamation of meat and cheese. Again, this was a very good amalgamation of meat and chese, but it could have had onions, peppers, bacon, more cheese, more bacon, and all sorts of sauces on it for no additional charge. So I lost this round, and will need to correct this next FI.
In the end, how does this event affect my outlook for #season3? The “lessons learned” fall primarily into the strategic, but there were also physical results.
First off, the molded wheels worked excellently. They did wear quickly, but not unusually so. I would have actually accepted consuming a set of wheels per match. That’s actually why Overhaul ended up having so many spare wheels made. So the task at hand is to investigate more compounds and see if one or the other yields better wear life while not giving up traction. In terms of raw traction, I was satisfied. I’ll probably commission a few pull tests on a steel panel covered in the same “traction paint” as used in the box, on a small scale first with promising candidates moving to Overhaul-sized 5″ wheels. While there were times I thought I had poor traction, it was largely interweaved with the ground force exerted by the forks and pontoons.
Speaking of which, I’m thinking some system of continuously adjustable ground force is needed. Clocker begin the tournament with pontoons slightly too low, and this obviously impeded maneuverability since it preferentially loaded the rear wheels and left the fronts almost unworn – hence wasted. After some big hits, the pontoon edges became worn back and I actually began driving better as evidenced in my second MegatRON and Melvin matches. In fact, this is something Beta has the ability to do. I can pre-load the shock mounts using different height spacers, but it would be nice to have a set that’s adjustable in height somehow. This is to make sure I can perform fine tuning of the contact while Overhaul is loaded up in the test arena for functional verification before the match. I’ll have to think about if this system is worth pursuing and in what form it will manifest, but I want to MACHINE THE PAINT OFF THE FLOOR (so, you know, I can get better traction).
Likewise, I should think harder about an adjustable hard stop for the arm travel. Clocker 3 had one, but Clocker 4 just relies on the frame rail. This is not adjustable and obviously the zero point will change with damage. Same goes for Overhaul.
I’ve got a lot to learn about driving strategy now that I’m back in the high energy class. It’s completely acceptable to attack Sportsman’s class bots head-on since the chances of you exploding doing so are minimal, and this has clearly influenced my attack style with Clocker, since the ‘smash and grab’ visual is also an audience pleaser. This is obviously dangerous if you are liable to being fed into a vertical drumlet. I still consider the vertical wedged weapon the most dangerous adversary, given that Overhaul has taken on a high powered horizontal weapon well (okay…. you know what I mean) and Clocker fared so poorly against Duck Yeah. Ripto would have been a disaster for sure.
It’s very obvious that I cannot count on every part of the bot lining up to make the front impregnable. I used to drive pushybots with hinged wedges which were lightly pressed against the ground. This, besides not interfering with traction unlike hard-mounted wedges, also affords a chance to escape if you go up on the opponent. In the first battle of MegatRON, Clocker was constantly getting stuck on the attack phase since I would charge into an equivalent charge by Jamison. It was also well evidenced against Beta that Overhaul was hard pressed to escape getting wedged. How to prevent this without compromising the function of the pontoons I am less sure – it could very likely just come down to more strategic driving.
I furthermore have some thoughts about minimizing my defensive cross section against vertical wedged weapons that I will keep offline for the time being. The upcoming MassDestruction event in 3 weeks might be a good chance for me to test some of the ideas on the beetleweight scale, where drums reign supreme. I’m tempted to build a simple beetleweight pushy-wedge (sigh) to exercise my skills and countermeasures against vertical weapons. (It’s important to note, however, that nothing scales directly; concepts can be expanded, but I can’t magnify everything I did on Clocker by 2x and expect it to behave the same way)
We interrupt this irregularly scheduled build report for VAAAAAAAAAAAAAAAAANNNNN TIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIME!
Contrary to most years that I’ve returned from Dragon Con by road, I did not have a job pressing need to return to Boston, so could take a few days to roam around Atlanta. This time, I revisited a couple of old haunting spots from the high school days – namely, junkyards, flea markets, electronics shops (what remained, anyway), aaaaand McMaster-Carr. When it was time to return, I decided to do something which I’d been thinking about for a while, and had been recommended by “car people” friends – hit up the mountain roads of the Blue Ridge Mountains and Great Smoky Mountains National Park. Many moons ago, my parents took me on a road trip to Harrah’s Cherokee Casino in North Carolina via some scenic routes such as U.S. 441, and I’d been reading up on the area as of late. Back then, I certainly didn’t appreciate the scenery or natural surroundings as much as I d…. nah, I still don’t, but those mountain curves I remembered as being awesome.
I solidified the plan as diffusing through North Georgia using U.S. 19/129 through Blairsville into North Carolina, then ascending via U.S. 74 eastwards until the intersection with N.C. 28. From there, I would follow the Tail of the Dragon (returning to U.S. 129) and eventually end up in Knoxville, from which it is easy to return to the Interstates. It was an incredibly scenic adventure – I definitely want to return here next year and perhaps try a different tourist trap on the way down – I’m hankering a little for the Diamondback 226.
The careful reader would notice that yes, this means I took a heavily-loaded Mikuvan filled with an entire Dragon Con of robot gear with Overhaul in the back and everything up and down twisty two-land forested mountain roads.
I must point out – loaded heavy in the back with about 500 pounds (Overhaul, all the robot gear and tools, all of Jamison’s robot gear and tools, and whatnot) made the handling and ride better than empty, I’m pretty sure. I tend to throw MV around like a go-kart, and the back end does get light due to the front mid-engine and front driving position. In winters, I regularly keep tools and heavy objects in the hatch to get more purchase during slushy or snowy weather. So I think riding empty might not have been any better, and it’s not like you can actually go that fast on the road while maintaining your lane. It took a few turns to “get it” (and probably warm the tires up a little) before I began really tossing it into the curves. “Continuous tire squeal” must have been concerning to bystanders…
Here’s the whole run from my high-mounted dashcam. Note that this is a very different and weird position compared to most dashcam videos – it’s mounted high up on the very tall cabin, pointed more down than forward, and Mikuvan has no front. Some people actually have said it made them dizzy due to the different motion experienced.
I think around the 3-minute mark is when I started getting more adventurous. Cynthia can be seen trying to constrain herself, her phone (recording a different perspective), and random objects in the cabin.
Anyways, fun times. But you guys came here to see Über-haul work! Here’s what went on in the few weeks before Franklin 2016. In this timeframe, I also went to New York Maker Faire to marshal the Power Racing Series race there again – Chibi Mikuvan came along as an exhibition item, but I didn’t race. I’ll need to post an update about the Detroit and New York Maker Faires at some point.
I did a fair amount of work in the remaining few days in Atlanta. One of the first things I did when I returned was drop by MITERS and use the large drill press to finish drilling some of the frame holes all the way. I then assembled the bot more completely to test the fit of everything.
Verdict: Yeah, sure, whatever. #zerosigmas
One element that has been missing up to this point which you people keep pointing out is that Clocker 4 is missing the classic Overhaul ears. Yes, yes I know, I just haven’t gotten to them yet.
The purpose of the ears on Overhaul 1 were to permit self-righting – the bot had a stable 45-degree-roll upside-down orientation that in testing, we could not get out of. Overhaul 2 addressed that problem a little with geometry, but it was still there – so the ears appear in a slightly different shape. The shape of the ears is a compromise between eliminating this 45-degree stable spot and extending far enough up to tip the bot over once it was fully on its back, using the action of the forks. OH2 traded some of this latter ‘stickup’ distance for more sideways extension, which is why its ears appear proportionally smaller and flatter than OH1. The tradeoff is it takes a full power swing of the forks to get back over, something I was not too happy about and which contributed to a fair amount of pre-event paranoia in the team.
For Clocker, I wanted to explore the ‘high stickup’ option. This meant the ears have to be shifted forward some to not interfere with making the upside-down stable spot worse. It also makes the bot look very much like some kind of micro-fox or Gundam headpiece.
The ears are designed to be printed using Onyx with additional carbon fiber perimeter reinforcement, so they ought to be immensely beefy. They have to stand being landed on if this thing gets flipped.
I printed these while in Atlanta, but the installation came afterwards. They push into one of the circular cutouts in the clamp arm, have a flange to maintain the tilt angle, and is sandwiched together with 4 bolts. This configuration means they don’t wrench on the side plates of the clamp arm, which are aluminum and would likely bend, instead bracing each other using the bolted connection… It also hopefully also makes them replaceable. I may pursue a similar strategy for Overhaul this coming BattleBots season, even if the ears are individual weldments.
The chain path for Clocker 4 was never quite decided, but I figured there would be a third tensioner or chain guide involved to force the chain to contact the motor drive sprocket more. This manifested itself in this slip-on tensioner that I designed after seeing the most perfect location for it also coincided with one of the frame rail trusses, so it was easy to make something that mounted directly on it. Unlike Überclocker 3, it doesn’t have roller tensioners on eggy cams, so is not adjustable in this manifestation, maybe the next one.
Problem: I got paranoid and piled everything onto my scale, and it came out two pounds overweight. Wait, what? The CAD model says 29.5 pounds!
After significant investigation, it turned out that my beautiful PAXi motors were never assigned a finished weight. They each contributed 2.2 pounds to the bot in real life, but were modeled as only 12 ounces apiece…. basically, the P80 parts that I did assign weights for during the design of Overhaul 2….
However, I might actually swap these out before FI 2016 for modified P60s, since having the armor weight back would be nice.
Well then. Turns out I needed more than armor weight! Even eliminating 1lb each would still put the bot overweight. The remainder, I figured, came from wiring (all the 12 gauge adds up) and additional hardware.
Alright, time to borrow a P60 model and smash the AXi onto it. At this point, I do not own a P60, so I didn’t know how easy this was to do, but it was still 2 weeks out from FI so there was plenty of time to find out.
Since the frame was designed around and cut out for a P80, I actually had to make a P60 to P80 adapter plate. This attaches to the front of the motor using its existing tie rods in counterbored holes, so the front face is flush. The tapped holes are at the P80 bolt circle locations.
A week later, a pile of BaneBots equipment appears. I took the opportunity to also investigate their new BB series gearboxes – Building Block, so named because they feature stackable designs similar to the Vexboxen. I got a BB150 thinking it was similar to a P60.
I was wrong. It’s like a P70 or something, literally almost the middle in dimensions between the P60 and P80. Their BB220 gearbox is the same square size as the P80, however. Internally, it’s quite massive and a huge improvement over the P60 architecturally, with widely spaced bearings and a double-thick output carrier plate. I will keep the BB150 around for other applications – it’s too big for this one. Banebots have come a long way from their early brass gear days, but I feel like people never quite let them live that down. The six P80s in Overhaul 2 speak to that well.
THIS IS WHAT ROBOTIC FRUSTRATION LOOKS LIKE.
Mabuchi 700 series motor bolt circle: 2x M4 on 29mm
AXi 4120 bolt circle: 4x M4 on….
Look at us, we’re so brushless we need to be just different enough to piss everyone off.
Luckily, “drill out the mounting holes 0.5mm larger each” was enough and the M4 cap screws just barely slipped into the existing counterbores.
To mount the pinion, I borrowed a 0.2357″ (6mm minus 0.0005″, because what are units?) reamer from Jamison and expanded the 5mm bore with it, then pressed the pinion on. This fit is backed up with green Loctite 609 retaining compound. It mildly makes me worry, bu Jamison swears it works… alright, we’ll find out. I’d personally have gone -0.001″.
Here are the two completed P60 & Axi sandwiches ready to mount in the bot. This setup weighed 19oz each, down from 34oz of the P80 combos, putting the bot at still a half pound overweight.
With the motors now secure, I returned to the parts of the bot I stopped caring about before Dragon Con – namely, the electronics mounting. I first cooked up this DLUX 160 bracket in Atlanta and tried 3D printing a version. It worked fine, except there was not really a way to retain the top one since the gap now crossed by the N shape was open. I closed the gap using the diagonal brace that acts a little bit like a flexure spring.
Now the DLUX controllers take some effort to push in, which is great, since they won’t easily slide around.
The bracket attaches to the bottom of the bot with four #4-40 screws.
Next up? Battery tray. Clocker 3 just cinched the battery to the baseplate but I wanted something more constraining for the full contact 30lb class. Now the battery will sit in a 4-sided tray so it can’t move, and secured using nylon Velcro straps to that. The 4.4ah 7S lithium pack I had been using in Clocker was downsized to a 3.3Ah 6S pack to save more weight.
Clocker is known to work for exactly 1 match on a 2.3Ah battery thanks to FI 2015, and I originally used the 4.4Ah lipo packs because I had them and because Dragon Con matches tended to run back-to-back with minimal repair time.
The reason the tray looks oversized for that 3.3Ah battery is because it’s actually designed to house a row of A123 cells. The Franklin museum does not permit conventional Lithium batteries in anything above the 3lb class, since it’s entirely indoors in a museum and magic lithium smoke & fire cannot be tolerated. So, A123s it is. This means most bots run on reduced power for FI since you can’t fit as much battery into the same location using round cells as prismatic ones.
Pictured is 8 A123 cells. I plan on fitting as many cells in series as I have weight for at the end.
The final 3d printed bracket of convenience is the receiver and other electronics housing. This is taken care of by using the RageBridge lift & clamp controller as a cap! It’s a hollow case secured to the baseplate with more #4-40 screws, then the Rage comes in upside-down and is retained the same way.
After the New York Makre Faire, it’s time to perform the final fitting-out of the bot. Here’s everything being installed in place…
Another experiment I wanted to try in the interest of #season3 Overhaul was tilting the rubber shock mount wubbies to dig the front of the wedge into the ground. Since these wubbies were in a regular pattern, it was easy to put an equally regularly increasing spacer height under them progressively. For weight and lack of steel fender washer purposes, I made quick 3D-printed (this word….. I swear) spacers to test a few orientations. I think they’ll make it into the final assembly because nylon is still far more rigid than rubber – there’s actually no need for steel washers.
It’s coming down to the last three days before Franklin now, and I’ve started mass producing wheels and…………… set screws. I promised to bring a bag of them to the event to sprinkle into the arena. They’re 1.5″ diameter and 2″ tall, made of genuine organic Miku Blue PLA (get yours today!).
Wiring completion was fast, as more than half of was done in Atlanta. I just had to make a few more extensions and replace the 3mm bullet connectors on the AXi motors with 4mm ones. I decided to not make a switch panel for now, opting to just do it like most of my other smaller bots and just plug & unplug the battery cable.
Checking out the weight I had left over, I decided to run a 7S A123 pack instead. I weighed the bot with the FI-illegal lithium polymer battery to establish an upper limit, and then just added as many A123 cells as I could under that limit.
Now, look at that battery and tell me that you’d rather have that bullshit than a professionally made lithium cobalt battery!
And here it is! The finished Clocker 4, alongside a toy Overhaul for even more scaling fun.
But the story doesn’t stop there. At this point, the bot was still around 6 ounces overweight (with the FI-illegal battery, which is 2 ounces heavier than the 7S A123 pack). So I at minimum still had to cut off 4 ounces, preferably more.
I decided the best way to do this was to trim off the inside corners of the pontoons. They’re actually now shaped more like Overhaul’s. The flange on the interior only reaches back about 3/4″, which should be enough to still hide the edges from intruding weaponry. This actually removed about 3 ounces per side, putting me a healthy amount underweight.
Another funny robot exercise: Trimming the pontoon bottoms to be level and also riding flush with the ground. Just throw the whole thing on a belt grinder and have at it!
Just barely under now, with the 3.3Ah LiPo pack and all remaining hardware I could think of added, so I actually have a healthy margin for FI with the 7S A123 battery.
Here’s a test video of Clocker 4 playing with the (still working, just sans actuator) carcass of Clocker 3.
As I point out in the video, it’s way more stable when lifting than I anticipated. Clocker 3 is huge for a 30lber, and it just gets picked up and whammed around almost effortlessly. I was super happy with the speed of the lifter. While the clamp could be faster, the priority was on holding force for this edition with speed only coming from severely overvolting the clamp motor. Recall that the clamp motor is the same as what 12 O’Clocker used for drive this year – I just made sure to order a bunch of spare motors.
Oh hello everybody! It’s a few days after Dragon Con and I’ve finally woken back up. Where the hell am I?! What is this metallic coating all over my face? Why have I gained 20 delicious pounds?
Here it is, the Post Dragon Con 2016 recap. I didn’t get a change to put out another update before leaving for Atlanta, and then it was a mad pre-convention dash. So this update will cover all of the construction of Roll Cake, as well as get started on the Bot that Charles Forgot – Überclocker 4.0, a.k.a “I Can’t Believe It’s Not Overhaul!”.
Amazingly enough, there were no van shenanigans on the way down. I’m staying in Atlanta a few days later again, so the return trip is still clouded in the ether, but at this time (Boston to Atlanta and now a few hundred miles locally) there are no issues to report.
Alright, I lied a little – at some point a few weeks (months???) ago, the rearmost portion of the exhaust pipe decided to fall off. It had a hanger at the very back of the frame, so did not fall completely off, but just rattled haplessly.
I think it was due to the bend passing over the rear axle being repeatedly struck by said axle when Mikuvan is loaded heavy – such as the trip to Detroit Maker Faire. So anyway, all it manifested in was things being a little louder, but at times due to the exhaust being trapped under the body and in my 3-mile-long wake vorticies, exhaust smell would creep into the cabin. This is not something I wanted to deal with for the long trip down, so I repaired in the best WEEABOO REDNECK way possible:
None of this BEER CAN bullshit… only the best Ramune bottles will be used for MY hoodrat repairs!
This held all the way until South Carolina. When I rolled into town, one of my pre-convention stops was the local Advance Auto Parts to pick up a patch pipe. The whole system is definitely in need of replacement, though. Who wants to hook me up with D U A L F L O W M A S T E R S?
Anyways, without further ado, here are the sections of this roman noir de robots:
So this is where we build up to that ‘preview picture’ I posted last time. One of the first things I did as soon as I put the frame pieces printing on the Mark Two was go and do basically the only machining thing, which was make the drum.
For this, I brought back an old friend. One of my first major tool purchases was this little indexing head, which made its first appearance here in a LOLioKart build report. It became my most prized possession for some time thereafter, but I left it in the shop when I mostly scuttled off to main campus and upstairs into the IDC for graduate school nonsense. With my departure, it began becoming decrepit under usage by random newbies. One of the dividing plates was lost, and one of the tilting locks was also lost after someone cranked the locking bolt too tight and sheared it off.
Every once in a while, someone does find it again and use it, so I knew it was still operational. I gave it a once-over cleanup and adjustment before starting here.
The drum blank was carved out on New MITERlathe before being transferred to the indexing head for feature drilling. I originally specified 6 bolt holes. But as it turns out, 8 holes is easier to use the indexer for, since it didn’t involve going in partial circles using the dividing plates. Just 5 cranks of the handle… So, 8 holes it is.
Next up, putting the big 1/2″-13 threads in for the cap screw “teeth”.
One tricky operation was broaching the 8mm bore for a 2mm keyway. Since Roll Cake is being built from Banebots P80 parts, so it must be compatible with an 8mm keyed shaft. I could not get a 8mm bushing & 2mm broach in time – nor did i want to spent dozens of dollars for the honor. So I did what, I guess, I would do, and carefully hacked at it with a 1/16″ endmill until I got a 2mm slot with a bit of radius at the end.
Precision! Craftsmanship! Finesse! We strive to be the opposite of this at Big Chuck’s Robot Warehouse. Zero sigmas, guaranteed, or I’m keeping your damn money anyway.
The frame parts have finished printing from the new Onyx material!
Well, hold up a little… These are extremely hollow prints that were solely to test for dimensional correctness. Things like “Does the motor fit in this hole?” and similar.
Here is a mock fit with some of the parts. I used a paint marker to pinpoint locations which needed rework – generally increasing slop or tolerances in the CAD model to get a better fit in real life.
Another arrangement of “DO NOT USE THESE FOR REAL” parts, which all had X marked on them so I was not tempted.
The two main frame halves are actually made from regular nylon for the most part, with carbon fiber loops in the center of the bot to strengthen the area. Otherwise, the regular nylon is tough and a bit flexible, which will hopefully help against some impacts.
A little pile of wheels with grommet-tires installed…
I next synthesized these planet gears from spare P80 4:1 and 3:1 planet gears. The 4:1 gears were bored out and cut to half a normal pinion length. Then the 3:1 gears were machined down for half their length, and then promptly shoved into the 4:1 hollow half-gears. The shoving first involved lining one tooth with one valley between teeth on each gear. As mentioned in the design post, these compound gears require the correct phasing of teeth to be assembled succesfully. I was probably off by some fractions of a degree on each gear.
THAT’S WHY WE HAVE A PLASTIC RING GEAR
The ring gear itself has also been reprinted in carbon fiber back Onyx (a material we came to call RMCC – Reinforced MarkForged Carbon-Carbon). I made the number of engagement dogs lower to guarantee the servo being able to reach between them.
Assembly for realsies begins with the bolting together of the sides. On each side, three #4-40 cap screws with washers and nuts retain the sides to the center U, and at the very rear, a #4-40 threaded rod with 4 nuts provides last-ditch backup if those front fasteners fail.
The ‘flaps’ are waterjet-cut 6061 aluminum 1/16″ thick sheet, which are bent up at the edges like so:
Well, that’s how it’s supposed to work. I really need to watch some tutorials on how to use a box-and-pan metal brake correctly, because I clearly can’t do so, ever – and it probably doesn’t help that I make sheet metal parts infrequently enough that the shared machinery is never in the same condition twice (or some times working at all), so I have no clue how it’s supposed to behave. Anyways, no two bends on this thing are alike in location and alignment. One side is workable, the other side is very twisted… Oh well, we’ll fix it in post.
Time to solve the never-quite-solved wiring problem. I made access tunnel paths for the hypothetical wiring through the back end of the U-bracket that makes the center of the bot, but physically doing it was another whole issue. “Haphazard” and “ad-hoc” are two words that each don’t quite describe Roll Cake’s wiring on their own.
I basically had to make three long cables, fish them through the two wire tunnels, and then wire everything in-place at the ends and cut them to length. These cables were the main battery, left side drive motor, and firing servo cables. The right side drive motor also passed through the right tunnel, so really it was 4 cables.
For this purpose, I used the thinnest wire I could find for the drive motors, which was some 30 gauge blue wirewrapping wire.
Everything in the bot could run directly off 11.1v – the drive ESCs (VEX controllers), even the Hobbyking TR6Av2 receiver believe it or not – you can run basically every new receiver from battery voltages since they have onboard regulators for the microcontrollers. However, the firing servo still needs 5 volts to not go crazy and burn out.
Therefore, I made a super small in-line 5V regulator from two Chinese’d LM1117 parts.
Don’t give me no “that’s racist” bullshit – you and I know this happens on a regular basis.
This 5V line then feeds the receiver, and the servo cable is a 3-pin custom cable which comes from that. Essentially as if I were to plug it in without hacking anything.
After the electronics are installed, I made the orange roundbelts and started closing everything up. The round belts are measured using the hypothetical pitch line in the belt circle drawing in the CAD model, then shortened about 10% to accommodate stretching.
The final act is to install the linkages. This is done using long M3 bolts cut down such that their unthreaded shoulder acted as the joint pin, but I could still put a locknut on the end.
Here is the finished bot from the flappy end.
And a photo from the ‘business end’.
So how does this thing work? Well, it doesn’t really. The serpentine roundbelt drive has too much friction for the Fingertech motors to overcome. While Stance Stance Revolution used two 22:1 Fingertech motors, they were direct driving small wheels. Each pulley adds some friction, since the belts need to be tight to transmit torque and the pulleys do not have rolling bearings, just nylon on shoulder screws. Roll Cake therefore could not move at all. I’ve built some pretty damn immobile bots, but this is literally the most immobile thing I’ve ever made!
You can hear the motors strain to move, slipping on the belt, and occasionally it scoots forward a fraction of an inch. That’s about it. In doing this, I actually burned out one of my 22:1 motors.
I began making arrangements to get some 33:1 motors from fellow competitors down in Atlanta, which should help the torque problem, and also began the search for small timing belts. MXL and 2mm timing belts come in 1/8″ wide / 3mm wide, so I could redesign the pulleys to that tooth profile. Then, the matter becomes if the Mark Two can hold the kind of tolerances needed for the tooth geometry to work out. I decided to leave that to Atlanta.
While the driving test was a bust, I did get a few flipper tests in with the drum going full speed. I’m glad to say that this part seems to work great. The servo engagement is clean and predictable. Here’s a test against a roughly 3.5 pound empty toolbox. Note that I don’t have anything springy or elastic that’s preferentially loading the linkage closed, so it depends on good firing servo timing to bring it back down.
That was actually the second test. The first test was against a heavier (4.5 pound) aluminum rail – coincidentally, the unmachined blank frame rail for Uberclocker 4. On this test, the deceleration of the drum was severe enough that the bot rotated forward against the linkage… causing the drum to strike the ground and hilarity to ensue.
Well, truth be told, that was the part of the bot I cared about. I packed all of the parts up for Roll Cake anticipating needing to do some re-engineering once I was on site. Just prior to leaving, I ordered two sizes of timing belts from SDP-SI based on the existing pitch length and what was closest to it – two 155 tooth 1/8″ wide MXL belts, and two 160 tooth ones. At least one of these will be close enough after I redesign the pulleys to be timing belt profiles with roughly the same pitch circle.
No fake-outs with wheels this time! This is the real deal now.
I’d been MEANING to retire Clocker version 3 (Überclocker Advance) since after Motorama 2015. Then came Dragon Con 2015…and then Franklin Institute 2015. After it won handily at FI, I decided to force myself to retire it, leaving the broken actuator unrepaired. Clocker 4.0, which has no witty Engrish name, was meant to be designed much earlier in the summer, post #season2.
Well that clearly didn’t happen… I actually started working on the design on and off in mid-July, but some contract work was keeping me entertained at the time – so designing didn’t start in earnest until August. That’s one side of being “funemployed” is that the work you do pick up is often stuff you like to do, meaning you adopt it as your own, meaning certain death if you have zero time management ability like me.
The first thing I designed up was actually the custom cast wheels that I talked about last time. I decided to use Clocker 4 as a smaller-scale experiment to try out the technique and different materials without wasting a bunch of money. The wheels were made with a 3/4 hex hub, which Clocker 3 uses and which I intend to carry over to the new bot. They were made in two sizes – 3 inch and 2 inch – to reflect the needs of the new bot.
So let’s go through the design of the bot now! Keep in mind through all of this that the principal design constraint was “Is this dimension about 50% of what it would be on Overhaul 2?” and is definitely a departure from my usual tactic of letting the part placement drive the robot. In fact, you could argue that both Roll Cake and Clocker 4 represent me trying to “design to look like something first” – Roll Cake being an old robot vision from years ago, and Clocker 4 being a scale model of Overhaul.
Just like with Overhaul 2, I began with a sanity check sketch to make sure the dimensions aren’t impossible. In this picture, the only things fixed are the wheel sizes and chassis height. Much like OH2′s design phase, I was going to let the length of the frame be malleable in order to fit components. But it should end up somewhere around 30″ in the ideal case.
I focused a little more on the pontoons first. The rectangles shown are a size of wubbie that is the closest to 50% scaled down from the type used in OH2. While their final shape and dimensions is not settled by this sketch, I just wanted to factor them in to get an idea of the size boundaries.
Bringing in more geometry into the mix now by playing with lifting fork lengths and the height of the arm towers.
Probably the terminal stage of The One Sketch has the 2.5″ square DeWut motor profiles imported, the length of the frame adjusted, and the first pass at the upper clamp arm also drawn. Most dimensions line up with OH2 within 10% or so, which is fine. Nothing truly scales directly in robotworld, and I figure so long as the visual is complete, nobody else but me will notice!
The beginnings of the 3D design went much the same way as with most of my bots, Overhaul included, with the generation of frame rails. You have to start somewhere, so I usually start with the back or left side, and everything sort of grows off that.
I imported the One Sketch and aligned it with the bot as a reference.
Moving on ahead a little bit, here is a more complete drive side. The front wheel is inset significantly into the plane of the front endcaps which hold the rubber shock mounts. I wanted to do this to maximize the wheelbase. Previous Clockers have had the “reactive outriggers” up front to maintain front traction when an opponent gets picked up. This version is relying solely on the rubber shock mounts deflecting, and it will be riding on the front edge of the pontoons thereafter. To maximize the chances of retaining traction in that scenario, I wanted to push the front wheels as far forward as I could.
This does open up a gap in the otherwise fully constrained tab of the frame rail, so here’s hoping that spamming the region with cap screws will make up for it.
Frame rail service for Clocker will also be a little harder harder than Overhaul. In this design, to pull the left frame rail, the pontoons and three of the six shock mounts have to be removed, and there is now more than 1 bit driver size needed. However, you could argue that OH2 also needed two bit sizes – 7/32 for the pontoon screws and 5/16 for the frame bolts.
Cloning stuff to the other side…
A very difficult step came afterwards. I now had to fit the DeWuts from Clocker 3 into this frame (I SOLEMNLY PROMISE DEWUTS WILL BE BACK IN STOCK SOON) . This presented a very serious problem, which is well summarized by NO.
You see, the average Featherweight, full-contact 30lber is generally much smaller than the Sportsman class bots, since they’re built denser with thicker materials to take KE weapon impacts. Clocker 3 is very large for a 30lb bot to begin with, at 20″ wide and 27″ long end to end, it’s almost the footprint of some of the denser 250lbers like Poison Arrow.
In order to make weight, as well as stay roughly true to Overhaul’s dimensions, Clocker 4 needs to be around 16″ wide. However, this utterly precludes the use of the DeWuts. I would need to make the bot at least 18″ wide to use them. That means proportionally more weight to cover the additional width of the bot, as well as a lot of inside space that’s kind of wasted lengthwise since more components would be able to fit next to the motors. This isn’t a bad thing by itself, but two DeWuts back to back kind of forces a different shape robot than what I was pursuing.
So I began working on the inevitable: going brushless with the drivetrain to save volume. I studied a few options which all revolved around a handful of AXi motors I picked up a few months ago (get yours today!). I borrowed a BaneBots P60 model since Jamison had already played with mounting P60s to the AXi motors. I also investigated stuffing the AXi motors into my spare P80s from Overhaul.
In the name of expediency – namely, that I had the spare P80 drive motors on hand, the AXi + P80 combination won. The 4:1 Overhaul P80s combined with the AXi motors at 7S (26v) ought to give a top speed of about 17mph, which is plenty.
The downside is extra weight. While the P80 and AXi combo weighs less than the DeWut, it weighs more than the P60 equivalent which would handle the motor power just fine. For Robot Battles where I won’t need extensive armor, I figured that letting the drive motors have 2 more pounds is fine.
However, I might actually swap these out before FI 2016 for modified P60s, since having the armor weight back would be nice.
Now importing more components – the space inside the bot is filling up fast!
I devised this quickly-3D-printable-from-Onyx mounting bracket for the AXi motor. A new pinion with a 6mm bore will be crafted out of spare 4:1 planet gears, which have 4mm bores I can hollow out.
So the AXi drive will solve the issue of width in the bot. I’m now toying with placement of the internal components. To start with, I’ll be using two of the spare DLUX 160A controllers I took out of Overhaul before the Season 2 tournament began, with a possible upgrade to Brushless Rage later using a 6-FET board (think Brushless HalfRage)
I settled for the two DLUX controllers up front mounted to a (not yet modeled) non-structural interior bulkhead, and the RageBridge in the rear corner to handle lift and clamp, also with a yet-unmodeled bracket.
Let’s begin on the fork tines now. I traced out the basic shape of Overhaul’s fork, but unlike Overhaul which uses a dead (fixed) lift shaft, I’m keeping the live life shaft of Clocker 3 since it’s fairly easy to attach to. The force transmission will be using clamp shaft collars made into hubs. There won’t be a central tube structure in the fork – both will just be held together with standoffs. The forks should, like in Overhaul, never be taking direct impacts unless I messed up horribly.
After I imported the quick fork model, which is still missing specific details like standoff mounting, I also began playing with the clamp actuator. I imported a few older Clocker actuators to check size and placement.
For this edition, I really wanted to move back to a full 550 motor actuator. This should actually give the bot a clamping force of several hundred pounds, which I wanted to have since most Featherweight class bots have negligible top armor.
The issue wasn’t so much weight (it would weigh around 1 cheap drill motor) as space. It had to fit in between the side plates of the clamp arm, first of all, and then anchor itself in a useful location that won’t impede the fork travel much. Overhaul has some issues with this which I would like to remedy for #season3 – so in a way, this is once again using the small bot to pilot something for the big one.
More details have been modeled into the fork plates now. The cross holes will have standoffs like good ol’ Clocker, not just to hold the fork sides together, but keep them level between arms. Overhaul has no such crossing feature near the tip of the arms, only the base. This was the cause of the forks becoming cockeyed during the Beta match when it got a good boop in on one of them, and I’d definitely like to solve this problem.
I decided to pursue the full 550 motor actuator at all costs, so I made one similar in construction to Clocker 3′s final actuator. The motor and gearbox? Just a 12 O’Clocker spare motor! The gears will be purchased from Vex, then modified – one to a 12mm bore, the other bored out to shove an Acme nut into.
Not shown in the above image is an “anti-buckle” MarkTwo printed piece that bridges the two thin plates and cradles the leadscrew for more of its travel. The actuator sides are in tension when clamping, but will be subject to sudden compression shock if the bot lands upside-down or I try reversing out of a grab, so I didn’t want to count on JUST 1/8″ aluminum plates.
Here it is loaded in place and showing placement. The upper anchor point was open to negotiation because the clamp arm sides hadn’t been designed yet. The lower anchor point for the leadscrew will just be a pin that is shoved through the first hole in the fork side plates, closest to the pivot point. The neat thing is this is somewhat adjustable for leverage ratios if I choose to use another hole instead.
I generated the fork side plates based on the dimensions of the One Sketch. It, too, will be held together by a bunch of standoffs – no welding here. This drawing shows some possible standoff positions. I was going to alternate inside and outside circles as I moved from left to right, like so:
The standoffs used are just some big McMaster-Carr 5/8″ hex aluminum standoffs, which for some reason are almost half the price of the neighboring sizes.
Actuator placement was a compromise between “How far does the motor stick out the top?” vs. “How far does the motor stick into the grabbing region?” since I could make the leadscrew as long or short as I pleased.
About this time, I threw Clocker 3 into the CAD model. The size different is almost comical, and at this point I wondered if Clocker 4 could pick up anything at all without falling on its face. Definitely will have trouble with the average 30SC sized bot, but again, 30lb Featherweights are smaller in general.
Anyways, moving on.
One of the next mods I want to make to Overhaul is what I call the “Anti-Cobalt System” – in other words, putting something between the frame rails so this doesn’t happen again. For Overhaul, I’ve been mentally designing it as a top and bottom plate fastened together in the middle, to close off the box and transfer sideway forces more rearward in the bot.
Since Clocker will now be competing in a high-energy class, I decided to implement the ACS for the most part on the bottom of the bot. This also acts to keep the drive chains above the plate, so they’ll be less vulnerable. I could still see this having a failure mode where in a very energetic sideways hit, the frame rails will deform in a parallelogram between the ACS plate on the bottom and the angled endcap on the top.
I’m now in the stage of generating top and bottom plates as well as random spacers. MarkForged spacers for everybody!
The single tooth will be made from some left over 1/2″ AR500 steel – good enough for the task.
I began the process of making the armor pontoons using the same method as on Overhaul. I made a master 2D sketch that represents the front face, and then a series of 3D Sketches thereafter, then defined surfaces using the sketch lines as their bounds.
The geometry for Clocker 4 is a lot simpler. There are no vertical forward-facing or side-facing wubbies, just the six widely spaced ones on the angled face. In a future revision I may consider adding forward-facing ones like Overhaul, if this decision comes back to bite me.
One major difference with these? They ride a lot closer to the ground than Overhaul’s. In fact, I will most definitely have to finish-grind the bottom edge to get enough clearance to not get hung up on them.
This is a good thing, because it resolves the other weakness of Overhaul that was clear during the beta match – the pontoons were simply up too high to be helpful, being designed to take a whomping instead of be good foot-in-the-door implements.
An overhead view of the bot basically done – you can see the standoffs between each pair of fork plates, the tie bar between the forks, and the tube which acts as the anchor for the leadscrew.
I added tabs and slots the same way as on Overhaul to prepare the pontoons for cutting and welding.
Here’s the finished bot minus cat ears!
The ears don’t seem to be necessary on Clocker 4, but it just doesn’t look right, man. I will probably design a pair up to be printed in RMCC which will bolt to the topmost hole in the clamp arm.
I left design of the internal brackets as an exercise to be done in Atlanta, since by this point I was running up on the last week available for fabrication. Hot off the CAD presses and into real life we go!
Man, it’s been a LONG TIME since I’ve done a one-shot epic waterjetting session to pop out a robot. Pictured above is the “Clocker kit”… or some 10 gauge mild steel, 1/4″ 1/2″ and 3/4″ aluminum, and some 1/16″ FR-4 laminate.
Sadly, in my cruftiness, waterjetting is no longer free – this is probably around $400 of machine time.
To prevent the FR-4 from delaminating, I brought back one of my tricks of cutting the outer profile only, and using another material as a template. So here’s how this part went – I routed the parts manually to ensure it does all the interior holes first, then the outer profile.
I laid a piece of plywood in the machine first and had it cut only the holes. Then I clamped the FR-4 on top of the plywood and continued the toolpath to cut only the profile. The 1/2″ plywood pieces then become drilling templates for conventional drilling of the holes later, which otherwise might (WILL) delaminate since they’re piercing close to the edges.
While the design was slow-cooking to completion, I continued casting wheels, making 4 of each total. I’ve basically gotten this process down, so the next step is to try out different materials.
Here, I’m readying the frame rails for countersinking and counterboring. It’s built in the same style as Overhaul, and also many 30lbers and 12lbers. The frame rails will need machining to key into each other slightly too.
One of the last operations I was able to pull off before having to depart for Atlanta was the coring of the large lift gear. This was done using MITERlathe and like 5 different tools. MITERS didn’t have a spoon-type boring bar to make a plunging face cut easy, so I had to make do using a few different types of insert cutters, switching left-hand and right-hand tools to clean out the blind pocket.
Sadly, Monday the 28th of August was upon me. I actually spent more time in the week preceding finishing Roll Cake, since I cared a lot more about perfecting that mechanism, so Clocker 4 fell by the wayside. Clocker traveled to Atlanta in kit form, shown above. I needed to do some (lol) work on it in Atlanta, such as milling the frame slots, before it could be assembled.
And that’s the bot half of the story. Next, what about the convention!? I came this far for something, I think. Whatever is causing all that noise next to the robot events, dammit!
Robot Battles & Dragon Con 2016
So before we get to the convention proper, let me interject with a proud announcement that…
…I finally got pulled over for speeding.
You didn’t think it was physically possible, right?
I’d like to thank my parents, uhh… Boston area highways…. and, of course and Smooth Automotive for the Accidental Engine Rebuild of 2015 which has restored Mikuvan’s former power so much that I legitimately now can speed. I mean, it takes a little while to get there, and no hills please, but otherwise, I can cruise at 75mph all day – just enough to get in trouble in Virginia when the speed limit drops to 60mph for an upcoming work zone and I ABSOLUTELY, POSITIVELY MUST PASS THIS ONE LAST MOTHERFUCKER ON THE RIGHT HERE and… Dammit.
He got me fair and square. In fact, he didn’t even mention how I Boston’d someone immediately before the orange construction barrel forest began. So thank you in that way, Virginia State Trooper. I’m not even going to look at this ticket until I’m back in town now, because Virginia sucks.
Alright, enough of that. As I mentioned at the beginning, there were no van shenanigans to be had. I got into town around 4:30PM Wednesday, and immediately began plotting robot finishing tactics. The first order of business was getting Roll Cake its timing belt setup, which I designed quickly once I settled in and put on print. What?
Yes, I dragged the Mark Two provided by my lovely sponsor MarkForged along. Hey guys, how’s about some hot and humid weather testing?!
The SDP-SI timing belt order arrived on Thursday afternoon, so I could test the fit immediately. More importantly, though, on Thursday…
I busted into Dale‘s shop like the good ol’ days and basically took over his entire workbench. On deck were finishing some milling and turning parts for Clocker 4. I machined the axles, finished off the wheel hubs, and made the motor pinions, among other unfinished business.
The big rear chamfer for the frame rails was also cut by tilting the head of his CNC mill 30 degrees.
Friday bot work was mostly done at the GT Invention Studio. I primarily worked on Roll Cake, doing the final installation and tuning of the timing belt drive:
The pulleys were sized by how close they were to the pitch line defined in my belt loop sketch. The difference was then made up by changing the motor pulley tooth count until the tension was reasonable (just going from 21 tooth to 18 tooth in one try was enough).
This worked….. a little. Roll Cake’s movement was still extremely strained. There was no binding of the drivetrain anywhere I could see, just that there’s too many moving things for the 22:1 Fingertech motors. It moved slowly and quite arduously, and still could not turn.
Well, there wasn’t much else I could do to alleviate this problem except swap to the 33:1 gearmotors which I was able to pick up day-of MicroBattles from Mike Jeffries. Before the event started, I went ahead and did the motor transplant.
Operating sheets and all! This was so I didn’t get any abrasive/metallic grunge into the bot while cutting down the motor shafts.
The end result? I got Roll Cake to move somewhat reliably on the floor, so I went ahead and decided to put it in its first match anyway…. against Kurtis’ Black Adder.
Unfortunately, in the arena, it moved all of 18 inches or so before farting out again. It at least managed to flip Black Adder over with a chance collision. At this point, I stopped caring, since watching the mechanism test fire was more important to me than the rest of the bot, so I just kept flapping until the end.
Poor Roll Cake. It had such a bright future.
Okay, not really.
So the flipper mechanism kept working up until the end, even though I technically never got a direct shot at Black Adder.
That’s okay – I’m already out to rebuild this thing correctly such that it’s mobile. Roll Cake 2 will just have two brushless gimbal motors for drive, as hub motors, with the same Afro30 SimonK-enabled controllers driving them. It will have 2 larger wheels up front like a classic drumbot, not this 6WD business. Since Stance Stance Revolution could basically drive upside-down on its two discs, I’m much more confident in this setup working.
So that’s it for Roll Cake. Now back to your regularly scheduled Überclocker:
In the same work session as finishing out Roll Cake, I assembled all of the modules within Überclocker – the actuator, both drive motors, wheels, and the DeWut for the liftgear.
On Sunday afternoon, I returned to Dale’s shop to make a mess one more time. This time, to carve out the giant pocket that is in the back frame rail, formerly solid 6061 aluminum. Final weight estimates showed that I did need around 1.2 pounds out of the frame rail, so I calculated the pocket size needed, gave it some more oversize for weight tolerances, and went to town.
The next operation in Dale’s shop was putting some pilot holes into the end-tapped frame rails. I figured I could run with 1 bolt in each frame rail for now, and then drill them later once I had access again to a large drill press back at Artisan’s Asylum or MIT. This let me put most of the frame together on Sunday evening.
After I went back home, I did what I could using the remains of my high school workbench, which contained a small 10″ drill press, hand drill, and jigsaw, plus the hand tools and cordless tools I brought down, and a few kibbles of tooling that I didn’t take up to Boston with me originally.
The above was…. basically all that I could do. Mount the shaft collar to the big lift gear using a counterbore I brought. I didn’t even have any clamps left, and by the time I got back home, all of the hardware stores and home improvement stores were closed for Sunday night. I tried drilling and tapping a few of the frame screws by hand, which was an arduous procedure. I basically called it quits around 6AM Monday after trying to work on putting it together all night, and not getting much further than 10 or so drilled holes.
Basically the most important part of having tools is having consistent tools. Maybe these tools were enough for me during high school, but I also built bots in completely different ways to accommodate them (e.g. making things from UHMW plastic). Designing for tools that are not consistently available, or totally unavailable, will just end in disappointment. I realized no matter what, I could only hack Clocker so far in the remnants of my parents’ garage if it depended on a full service shop to be put together.
So here is the assembled husk of Clocker 4 next Overhaul at Robot Battles on Monday, showing what could have been if I didn’t kick my own ass… or as Will Bales puts it, Will Balesing.
By the way, shoutouts to Matt and Dan of Chaos Corps for taking the pieces of the pontoons from me on Friday and returning them completely welded on Saturday. Not just welded, but all ground and wire brushed. I owe you guys a small water balloon filled with argon!
But wait! The story doesn’t end there!
I also brought 12 O’Clocker along, figuring that I’d be able to run something in the Monday event at least. 12 O’Clocker was working fine after Momocon, so I basically packed it right back up with some spare motors. The clamp motor on it was a little baked, so I reached out to the group for spare Kitbots/1000rpm-style motors.
It actually got a few matches in and entertained the audience immensely.
In the rumble, the lift sprocket got bent hard enough to pop the lift chain off. Otherwise, 12 O’Clocker takes no damage once again! Gosh, maybe I should just scale this thing UP instead of Overhaul DOWN, right?
So no prizes this year, and not a very good Dragon Con for robots. I’m going to continue finishing Clocker 4 in the interest of Franklin Institute Robot Conflict 2016, where I hopefully will get to play with some of the big energy bots. I never had a strategy for Overhaul against vertical weapons like drums and discs (e.g. Hypershock, Witch Doctor) – besides Don’t Get Owned, I mean. I hope the Featherweight class, which is full of vertical spinners, will let me fine tune how to approach bots like that better for #season3.
By the way, there was a trip to the new Atlanta McMaster-Carr warehouse to pick up last-minute hardware. This place is
Okay, REALLY REALLY BIG. Douglasville and the surrounding west Atlanta area is kind of a new target for development, and besides industrial plazas and The McMastergon, there were plenty of housing developments. What could be better than stumbling out of bed and over to Will-Call to pick up your last night’s blurrily-assembled orders? Or hell, just wheel the robot over and work on it in the Will Call parking lot. It’s like working on your shitty car in an Advance Auto Parts parking lot! Who the hell’s ever done that… not me! Nope, never.
So wait… wasn’t there an ENTIRE CONVENTION going on besides just me working on robots? Absolutely… so let’s see how that went.
As usual, I’m too lazy to put together a worthwhile costume, so I went lazily all days as “me”. Just the Overhaul team shirt, and also wearing the Axent Wear headphones around.
I got stopped way more times than I expected.
Shown above is the crew of Jamison, Cynthia, Hannalin, and Lucy, formerly all of JACD last season. This year’s group is Overwatch. Overwatch is a video game. I haven’t played a video game with any degree of seriousness since Descent II Vertigo. I assume this is all legit. Wait until you see the construction Cynthia put into the giant bow…
There was a massive Overwatch photo gathering which took us an hour or more to get out of. Pictured above in the group are Pizoobie and Bonnie.
I generally haunt costumes which have had a lot of work put into them, especially very large and unwieldy ones. I swear at some point I will make an overly complex and elaborate costume. You could argue that Overhaul is in fact such a prop.
This was cool, too. These guys were cruisingly slowly around the convention. P I P E S
Okay, I don’t even know what’s going on any more. Overwatch players, I assume this is something you’d understand.
Alright, I usually don’t give a spare minute for Kantai Collection because it’s utterly destroyed my favorite genre. But I will make exceptions for well done ones. Behold, the U.S.S. Iowa. I watched her being “assembled” on the spot, and before that, I followed the ant trail of battleship parts being carried high overhead down the packed street by her pit crew. Her drydock workers?
I’m telling you all, #season3 will be one big weeb convention. Everything is falling into place, exactly according to keikaku. Cynthia is the designer of Haru-Chan, so it was only natural that she also sketched up plans for Sawblaze and Road Rash.
Now for the event recap!
MicroBattles this year was bigger than ever. With the insect classes (1s and 3s) being the easiest and cheapest to start in, the newbie and first timer proportion this year was immense. We ended up getting over 40 robots!
Sadly I actually missed a lot of the action getting Roll Cake prepared, but here are some of my favorites.
Here we have the wild Killer Colsonbot, which is believed to have evolved from escaped Domestic Colsonbots.
That’s Pvt. Slicer, or what happens when Mike gets ahold of the Colsonbot CAD. The cage is made of layers of waterjet-cut 4130 steel carefully welded together. It had friction drive reliability issues, but it somehow won 2 matches as round pushybot. When the cage met a vertical spinner, it died.
Representing the “meh” department of Dale’s Homemade Robots, this is Noodles, a 4wd pushybot. Besides all brushless drive, steering gyro, and a crafty urethane-sheet-mounted steel plow, it has pool noodle wheels which caused a bit of controversy because in the final a piece of them came off and jammed Black Adder’s drum.
Now, unintentional entanglement is allowed in the rules for the precise reason of a part inadvertantly coming off and getting stuck in something (as opposed to intentionally throwing things into a weapon to jam it), but there was still a fair bit of “Who do you think won this match?” talk. I actually think repeatedly hitting the ceiling against Black Adder and coming back each time is a mark against the effectiveness of Black Adder’s weapon in this match.
It’s big bot time! After being forced to run 12 O’Clocker only, I had more time to go around and appreciate the 12s and 30s. The newbie count was great at this event also – I think probably 25% first or second events.
Pictured above, The Magical Lipo-Fire or…. something or other. The build looked great! Sadly only one match however, and fortunately did not live up to its name.
First time 30lb entry “STICK A FORK IN IT!” which was having some DeWut clutch issues this event. Hey, people, read the manual! Tighten down your DeWut clutches before using!
Team JACD Season 1 principal cheerleader Andrew brings Pusheen-Bot, a pushy-bot. It’s laser-cut out of wood, so naturally it faced a chainsaw first match. This thing actually has two 50mm outrunners in it. It’s basically BurnoutChibi in a 30lb bot, so-illustrated by Andrew riding the bot around the room before (and during…) the event.
Another new 30lber with some heavy inspiration from Clocker and megaRon (under whichever moniker Jamison decides to run it at Robot Battles…)
There were obviously a lot of bots that I skipped, and you kind of get the idea. With the return of BattleBots to a mass audience, so the hobby grows! Robot Battles, fortunately, is one of the lowest barriers-to-entry competitions there is.
12 O’Clocker all set up and with spare clamp motor installed, ready for its first match. I had immense fun in its match with Dingleframus – it was the hardest physical driving match I’ve had in a little while, and in the end, a missed charge basically caused it to hover off the stage.
Here’s “Metric Brushless Hipster 12 O’Clocker” LiftLord, a Xo creation but shown with optional interchangeable Aaron module.
12 O’Clocker ready for its first match against Abrasive Personality, a design I really want to see more of – it has a belt sander running the length of the bot, with a backstop and all. I think this kind of design needs exploring. Putting more horsepower behind it and using a super gritty belt might actually result in some serious unconventional damage.
So what the hell are those blue things on the stage that have been appearing in every video so far?
They’re my secret weapon: 3D printed model set screws. I printed about a dozen, then another dozen or so followed me to Atlanta courtesy of RocketProps. Some local folks contributed a few more…. and suddenly, a stage full of giant set screws. Robot Battles: serious business since 1967 or whatever.
Not sure what I was doing here – probably double checking the chain drive after the rumble where it was derailed due to the main sprocket being physically bent. 12 o’clocker went 1/1 plus hanging around during the rumble, which was hugely entertaining.
Well look who’s on display! I’m told that Witch Doctor & Hypershock were also going to be present. Lies! I didn’t see any of y’all this whole weekend, so Overhaul had to have all the fans to itself. Such a sad day.
That’s a wrap for Dragon Con 2016. Once again, I’m staying a few days extra in Atlanta, and will diffuse back up north some time this week. On deck for robot work is finishing Clocker and a quick revamp of Roll Cake before FI in about 1 month. Otherwise, I’ll be hopefully creating more problems for myself with van work soon, since I want to re-winterize a few spots before things get cold (e.g. in 2 months or so). Some of my earliest rust repair is starting to come apart finally, and I have better weaponry against it now. Further down the line is word about # s e a s o n 3 and starting Overhaul….overhaul…. work in earnest. This will ideally occur over the coming winter.
On this episode of “Charles is still CADing everything distressingly close to Dragon Con“, we continue with the development of Roll Cake to the point of completion, as well as begin with I CAN’T BELIEVE IT’S NOT OVERHAUL! Überclocker 4! I depart for DC 2016 in a few days, so there will hopefully be some updates on the physical construction of these bots on the road and in Atlanta.
So I spent quite a few days on and off puzzling over how to place components in Roll Cake. As I said last time, putting square things into a triangular robot often requires a lot of compromises and “dimensional exhuberance”.
This was one of the choice placements, using a 850mAh 3-cell lithium battery, the same kind used in Colsonbot. I also had a few 1000mAh ones used in Stance Stance Revolution, but they proved to be too long in every configuration here.
One of the other “mid experimentation” screenshots. I tried locating the battery on the same side as the drum motor. This involved pushing the drum motor to the interior of the bot, an option I was not favoring since it means the drive pulley was going to be pulling on the motor can farthest away from its bearings. This would end in certain tragedy.
Plus, it’s not like this side of the bot somehow had MORE length to put a battery in!
I decided on the configuration seen here after more component juggling. This places the battery in the flatter configuration (meaning it sticks out of the side more), necessitating making the whole bot wider by about 1/4″ to accept it. However, this meant the servo could be on the same side as the battery, which was highly advantageous.
Here, I’ve also generated the motor pulleys. The wheels were a design I already had; it is a little hard to tell, but the pulley sections have a V profile instead of the square bottom usually seen in small round-belt drive pulleys. I’ve found that this tends to give better grip for small pulley diameters, working a little like a V-belt. It also tends to be more tolerant of misalignments, since there is no square side for the belt to suddenly grab and be pulled off, and is also auto-centering.
The tires are a takeaway from Colsonbot and SSR, and are actually 1″ diameter rubber grommets (for sheet metal panel holes where, for instance, wiring or tubing pass through). They’re made of soft rubber and can be easily stretched over a hub. In this application, I’ve stretched them to being 1.25″ diameter.
Due to the tightness of the space around the battery, I did something I rarely do – simulate the chain or belt path. The 3/32″ roundbelt drive unfortunately has to make a Cleveland Left past the battery, in an area with minimal clearance. I specified and ordere some tiny little type MR63 bearings for this job – 3mm ID, 6mm OD.
Here’s the belt path simulated . It will need some grooves designed in into the frame to clear. I didn’t want to make the wheel pulleys any smaller due to the limitations of the round belt – too small a pulley and they don’t grip nearly as well.
The belt kink also allows the motor drive pulleys to achieve nearly 180 degrees of wrap. So at least I know that part isn’t going to be slipping! It also directs the belt up and away from the drum motor. I changed the drum motor to a slightly larger 2836 type motor which has a larger 4mm shaft. This desketchifies the pulley mounting significantly. The motor has been moved back to the interior of the drive pods, with the region around it beefed up in thickness and ribbed for its pleasure and rigidity.
All of the control electronics have now been moved to a pocket on the right side of the bot.
With the sides of the bot figured out as much as I care to, it was time to move to the clutch triggering mechanism. You know your unibody design has gone horrifyingly wrong when you have to start slicing the view to work on stuff.
The channel cut into the body here holds a sliding bolt-like structure which will be toggled by the servo.
Like so. This is shown in the retracted position, where the linkage holds the planetary gearbox’s output ring stationary and therefore the dog clutch ring spins freely.
And in the “This kills the servo.” position, where the sliding bolt impedes the motion of the dog clutch gear, forcing the output ring to begin spinning. This throws the cam linkage.
Based on the advisory speed of the clutch gears, which is 237.5 RPM (950 rpm/V * 11V battery / 2:1 gear ratio, then divided by another 22:1 in the gearbox) and the width of the valley between dog clutch teeth, the servo will have roughly 70 milliseconds to move the sliding bolt. These servos are rated at 0.11s per 60 degrees, and the bolt travel only needs about 15 degrees, so I HOPE there’s a healthy margin here.
The directionality of spin matter s alot. The frame is only bracing the sliding bolt in the configuration shown where the dog clutch gear is spinning clockwise. This means Roll Cake actually does have an “upside down” since the drum can only spin in one direction to use the flipping linkage. Hopefully, in a bigger version of the bot, this shortcoming will be addressed.
During this design work, I was thinking ahead a little as to how to 3D print the final product. The unibody turned out far too complicated to print in one piece, so I elected to split it into 3 pieces – left, right, and center.
One problem though. The bearing mounting supports for the drum, which are also the pivot points for the hinged flippers, make the left and right sides not completely flat if I sliced the part on the inner faces of the left and right sides.
I decided to make those rings a separate print each, allowing me to print the two halves concave-side up using no support structures, which results in a cleaner print.
Therefore, I added makeshift bolt holes on the inside of the drive sides, which eventually will have screws threaded through into the bearing mounting rings.
Each side had features added which allow me to fasten the side covers. Because the bot wasn’t symmetric, the attachment to the center U frame was different on the left and right.
One last detail was how to pass wires through. Besides the through-hole at the very back of the bot, which is supposed to fit a threaded rod (a last ditch everything-is-fucked way to keep the bot together), I put in two more semi-through-holes linking the left and right via the central frame. One will pass the battery cable, and another will be servo power and drive motor wiring.
I moved onto the final little details of the bot. Drums aren’t that effective without little feeder wedges to direct opponents into them, so I made small extensions that will mount metal — likely spring steel – wedgelets.
The side covers contain a few more injection-mold like elements to line up with the left and right sides. These will be made of heavily fiber-laden Onyx material as a desperate bid to fend off other weapons. Unfortunately the bot was already a bit overweight at this point, so no real armor here!
With the addition of the wedgelets and filleting every interior corner, the design is complete. To service either side of the bot, the five countersunk screws are unscrewed (the shoulder screw for each wheel axle is not bolted in, having clearance holes for the heads, so I can run the bot without sides easily and also not have to juggle wheels each service.
The hypothetical open position of the flipper.
And here is a “transparent frog” photo showing the incredible mess going on inside this bot. Like I keep saying, I’ll be damned if it does anything meaningful besides self-destruct.
And now I cut up the frame for 3D printing! Five parts total – two sides, the center U-frame (which will be heavily fiber-braced), and the two bearing support rings.
As a preview for what Roll Cake looks like IRL, here’s a pretend-o-bot from this past weekend. There will be build reports!
I CAN’T BELIEVE IT’S NOT OVERHAUL!
This post is now about wheels.
Hah, you thought you were getting a Überclocker design update. Well, in a way, it’s highly relevant, since I’m designing and casting custom wheels for this build from urethane resin and 3D printed molds.
One of the shortcomings of Overhaul this year at BattleBots Season 2 was the horrifyingly bad traction in the arena, compounded with my choice of wheel being poor for an overpowered drivetrain. I discussed a lot of this in the beta match recap. Basically, after the tournament, I was determined to investigate making my own wheels after seeing a few builders (including Beta) do the same. For me, the goal was less to get a specific wheel size or custom geometry than to find an alternative to the thermoplastic rubber Colson wheels, since nobody to my knowledge makes a real vulcanized-rubber 5 inch tire.
After doing some Internet Research, I decided the easiest way to start was to go with a polyurethane compound. There are many choices in that space designed to fit different applications.
Most of it, though, is optimized for some kind of mold making and so was hard to find relevant information for . That’s in fact one problem for me coming in as an outsider to the industry – I don’t know the industry words and niches where different terms mean different things. I tried finding natural rubbers and synthetic rubber base ingredients, as well as vulcanizing compounds (‘cure packages’) for natural rubber. But the only companies I was able to get ahold of were in the moldmaking & casting industry, and they’re so specialized that they didn’t know anything outside of the use of their product for moldmaking. Anyone with connection to the world of flubby substances is welcome to make recommendations – I really want to create a wheel with the same durability as a vulcanized rubber tire, like a car or go-kart tire, just with a softer compound. Now, slicing bits of tread off real tires and bonding/screwing into a custom hub is a possibility, but I really want to look at the next level up in elegance first.
As luck would have it, I was at the Detroit Maker Faire that weekend with the usual Power Racing Series crew. I had come only to help marshal the race and act as a tech/safety inspector – Chibi-Mikuvan sat out this race since I had not repaired the damage from last year’s New York Maker Faire. 10/10 would get sunburned again. I managed to get ahold of some Smooth-On company reps at a booth, so I got to hassle them with questions about the gooey substances they manufacture, including such cold-open gems like “So, what rubber would you use for a Battlebot wheel?” Based on the response, I’m apparently better at picking up middle-aged company sales reps than the ladies.
After 10 minutes of explaining what the hell it is I’m actually doing… since they’re mostly here again for the moldmaking and resin casting of tiny figurines and the like, two compounds came up very quickly – ReoFlex, a urethane rubber, and Simpact, a “rubberized plastic” as they put it. Both are, as far as I can tell, urethane-based. ReoFlex comes in softer Shore hardness ratings (20-50A) and Simpact in higher ones (60-80A). For reference, a skateboard wheel is usally 70 to 80A, a car tire around 60-70, and Colsons that are used in robots are usually their 65A Performa line. They were both recommended for higher tear strength relative to other similar products, which is important for wheel integrity.
Lovely. Now what? Do I just pour one into the other and run for it?!
I next designed a core to hold onto the rubber tire. I knew nothing about this, and couldn’t find any good resources about “How to design cores for urethane rubber wheels”, so I freelanced based on what makes sense in my head. Those features were:
Lack of hard square edges – gradual transition angles between rubber and plastic
High surface area for good bonding
No overhangs that can trap air bubbles
Through-hole features to enhance gripping the rubber in case bonding fails
That’s what I came up with. Just a basic tapered V shape that has a bunch of through-holes around the permieter. I referenced the outer dimension of a 3″ Colson wheel, so if everything fails miserably, I can bail out to Colson wheels.
I desigend it so it could be 3D printed without support structures, so I can pass it directly from print bed to mold. Speaking of mold,
I then designed up a two piece mold that the wheel core sits in. The tread around the outside was added as an additional element to help traction in a box environment. The argument of tread vs. slicks has been a perennial subject in robotland, and now with my experience in the BattleBox, I think it’s pretty critical to increasing your effective traction. While a smaller bot like Clocker won’t really need it, I wanted to experiment with the molding aspect more, so treads it is!
The reason I think a light tread pattern is beneficial is because while you’re not trying to displace water or mud like in a road car tire, or grab onto rocks and dirt off-road, there is still plenty of fine powder-scale debris in the average arena. This debris is made of little metal bits, worn tire rubber, and SET SCREWS some times loose hardware. A tread that helps evacuate this debris would help put more rubber on the floor.
Tread design is one of those things I could spend a lot more time reading about than I had patience for at the moment, so I went for a simple helical groove pattern. The idea of the helical groove is to keep the contact patch relatively consistent (think meshing with the ground like helical gears) while trying to spread box debris sideways.
The mold was designed as one piece and then split into two pieces. Registration pin holes (not shown here) will keep the two mold halves aligned when together. A hexagonal bushing fits in the wheel and also keeps it centered in the mold.
By the way, I FINALLY, after literally 10 years, learned and used what Autodesk Inventor has for “part configurations”. In Solidworks, configurations are variations on a part stored in the same part file, so you can make different length standoffs, or different sized wheels, that each have the same feature history – no Save Copy As bullshit. In Inventor, this has been JUST barely out of my workflow path to be annoying enough and JUST stupidly named enough (SERIOUSLY? iPART???) that I have, almost on principle, never learned it. As a result, when I need to do a project that will make use of Configurations, I actually use Solidworks. And when I do my own stuff where my CAD file structure can be a Nightmare beta, I just Save Copy As or liberally spam Derived Components.
But that’s no more, because I watched a 5 minute Youtube video showing the basics of iParts, iAssemblies, and iMates, and just freelanced the rest based on expectations and mapping from Solidworks. So there! Now I’m fully Solidworks-free :p
And that’s how I made a 2″ wheel and mold just by editing some numbers in a table!
The molds were printed using the Mark Two machine in basic nylon, almost hollow. These didn’t need to be structural, after all, just quick to make.
Mold halves with finish-sanding on the flat face (there was a small amount of warping) and installed registration pins.
The retainment method is by a single hose clamp.
This is what the wheel looks like seated into the mold. A 1/4″-20 bolt keeps the wheel core tight against the bottom of the mold to prevent overspill.
I mixed up a dose of Reoflex 50 and put it in a borrowed vacuum chamber to pull out air bubbles. The mixing process introduces air, which makes your material basically a shittily-blown foam once cured and robs it of structural integrity (and surface smoothess & dimentional accuracy for people making cast objects from the material).
Next came the gentle resin pour. Simply fill to the top of the rim!
This is what the wheels look like. Pretty bland B R O W N color, but this can be pigmented if I so desire (Miku Blue wheel time??)
They feel pretty durable, but only testing will tell. This involves actually having a bot together to use them. So on the next episode: How to Scale your 250lb BattleBot and not Hate Yourself, a Self-Help Book by Charles.