Hey All! The build log for these next versions will be considerably longer as each version competed in several events, with numerous smaller changes taking place between these.
Boom Zoom MK3
Once again a new version of Boom Zoom had basically been written off after its first event, which was getting pretty tiring. I really wanted to take whatever came next to a level where it could survive multiple events without needing a rebuild. I’d been chatting with loads of builders at Robot Rebellion 2022, and decided to steal a load of the best ideas they’d had (and add a few of my own) for Boom Zoom MK3. The biggest changes were:
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A much smaller, CNC machined chassis.
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3D printed TPU front armour and wheelguards.
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Ditch the foamies for cast polyurethane wheels.
I went with a CNC’d chassis to ensure it would go together first time, with none of the errors that come with a hand cut chassis. It also makes fabricating spares much easier, and makes the whole build process much less labor-intensive. This was also the reason I wanted to try 3D printed armour, as well as being able to iterate on these much more easily than any other manufacturing method.
Only one problem: I didn’t know how to actually make any of this! Still, first things first, time to design the thing. I jumped back into Fusion 360 and before long had something I was pretty happy with.
As you can see, this new version was absolutely tidgey compared to the old one, making it pretty normal sized by average beetle standards. The Ti front panels are gone and the new TPU fronts are secured via a single M5 nut and bolt through 2x10mm bulkheads, which makes swapping out front armour packages incredibly easy. TPU has also been used for the top panel in the lifter, with a 4mm RAEX 400 steel panel on the front to eat the hits from those mean spinners. This version is also much more forky, featuring a grand total of 6 (count em, 6!) forks also made from 4mm RAEX 400. I decided against painting this version (except the RAEX bits) and instead of HDPE went with RG1000 for the green plastic and PE500 for the yellow plastic.
Not having a CNC router of my own at this point, the chassis was cut by the lovely Mr. Strang and even came with sweeties!
A few last bits were hand-cut by myself such as an 8mm back panel and a couple of spacers between the front bulkheads, but even with these it went together like a dream! I was really happy with how this came together, it looked so much cleaner than my hand builds but still had some of that element of high-functioning jank they’d so proudly displayed.
For the TPU I did decide to take the plunge and buy a 3D printer of my own. I went with a Sovol SV01 Pro, which is effectively an Ender 3 with some upgrades like a bigger bed, auto leveling system direct drive extruder. After some dialing in and messing with the slicer settings, it was pooping out pieces without a care in the world!. Alongside the other bits you can see on the robot I also got some wedge designs printed, though these never saw combat.
For the wheels I basically followed Just Cuz Robotics’ excellent guide on cast wheels:
I designed a 3D printed core with lots of keying features for the cast polyurethane to wrap around and grip, along with a mould for the wheel core to sit in during casting. I then printed a set of prototypes out of PLA-ST, greased up the moulds with vaseline and cast the wheels using Vytaflex 40 Polyurethane and a small amount (1% of the total mixture) of black dye. I mounted these wheels on Pololu universal mounting hubs.
I found demoulding the wheels to be a total pain and ended up having to cut the wheels out of their moulds with a hacksaw, so I decided on swapping to TPU moulds and wheel cores for future attempts.
For the lifter retraction I wanted something a little more stable than a length of elastic, so I popped into Claire’s and picked up a pack of hairbands. I secured these with zip ties, reasoning that a closed loop of material would be less likely to pull through its mounting hole or snap like the old elastic was prone to.
Very little in the electronics was changed from MK2, the only change of note being swapping from an XT60 to an XT30 for the link. I also added magnets to the base of the robot to improve traction, along with the new grippy wheels I was hoping this would absolutely bully other robots around on a steel floor.
I finished off by adding the customary John Deere decal and printing some optional top armour, and just like that, the robot was done! I took it for a spin at Robonerd Pinball 2022 with some 3D printed standins while I waited for the metal order to arrive and was very happy with how it did, even if I did drive it into the pit!
After Robonerd I replaced the wheelguards with some bulkier ones with bumpers to prevent getting stuck on its side, and fitted the metal parts once they arrived. With that it was time for Boom Zoom MK3 to see combat, which it would first do at BBB Champs 2022!
BBB CHAMPS 2022
My fights are at 0:00 and 36:50 in the first video, and 6:55 in the second video.
For my first fight I was drawn against Toxin and Keith the Teeth. Not knowing what Keith was but scared it was some kind of crusher, I slapped my top armour on as a precaution. The fight itself went about as well as it possibly could have, with Boom Zoom knocking out both opponents within a minute.The TPU armour stood up well to the hit it took from Toxin, and the robot was good to go again with basically no repairs! Next up was End Boss, which was pretty much the worst draw possible for me. End Boss spent most of the match outreaching Boom Zoom’s forks and bouncing it off the roof, with a particularly nasty shot bending the baseplate and knocking the servo free from its mounting brackets. The weapon still partially worked even with the servo dislodged, well enough to act as a self-righter anyway. I did at points take the fight to End Boss and managed a pin and lift onto my own lid, but thanks to the dislodged servo I couldn’t convert this lift to a grab, End Boss wiggled free and I ended up pitting myself. Crud.
The damage from this fight was pretty gnarly, aside from the baseplate and servo damage the front armour was looking majorly worse for wear, and half a wheelguard had been completely ripped off. The forks were also varying degrees of bent and chipped, but honestly this was all fixable! I replaced the front armour and forks with spares, bent the servo bracket and baseplate back into shape with some pliers and reseated the servo, and just like that I was ready for a whiteboard!
Some very scary spinners in this one, but once again Boom Zoom held up well against them, getting some more good lifts and what was probably my proudest moment of the day, pushing 3.5 kilos of robot from one side of the arena to the other! Winning this one was a nice way to end the day. I felt had the draw been a little kinder I could’ve gone further in the main competition, but was still happy with the robot’s overall performance, and happier still it had actually survived without too much damage! The cherry on the cake was the “Most Improved” award that Boom Zoom walked away with, I’d really gone for it with this version of the robot and it meant the world to see that recognised.
Overall the changes held up great! The printed armour and mounting was a big success, both in terms of maintainability and durability. The new forks did their job, the lifting arm and elastic took several shots from verts without failing, and the tyres and magnets gave it a heck of a lot of push. For once I wasn’t staring down the barrel of a total rebuild after the event, which was a huge relief, but I still had some changes I wanted to make.
First up, I wanted a setup to fight drums and egg beaters with. In that last whiteboard, Bakugo had bent up a couple of forks pretty badly, so I wanted something a little more suited to fighting that kind of wide weapon. I went with this wide “claw” design, the idea being that the radius of the fork’s curve was bigger than that of a standard Fingertech Beater Bar, so all a weapon that size could do is grind against this surface without biting properly. Sadly I didn’t have time to get these cut out of metal, so some hastily printed TPU substitutes would have to suffice. I also thickened up the wheelguards so they wouldn’t be torn off as easily.
Battle In The ‘Burgh 2
Before I knew it, it was time to fight again! This time I made the long trek up to Scotland to compete in Battle in the ‘Burgh 2. This was my first time taking largely the same robot to its second event, and boy was it nice not having to rebuild this thing in the month between BBB and Burgh. It was also a good opportunity to learn a bit more about this design, 3 fights, none of which went 2 minutes isn’t a good sample size and this being a 2-day event had the promise of a lot of arena time.
My first 4 fights are timestamped, skip to 27:50 of the third video for my play-in rumble.
My Bounty Hunter fights are at 0:00, 1:53 and 4:20.
In my first fight against Uplift, a couple of fatal flaws in the robot were revealed. First off, the new anti-drum attachments were ripped apart. I’d put these on as the claw shape would allow me to control the high front end of Uplift’s chassis easier, but instead they were just shredded by the spinner. To make matters worse, I found that if Boom Zoom was knocked upside down with the lifter open it would become stuck in that position. The hairband didn’t have enough strength to retract the lifter from this position, and I was quickly counted out. Nuts.
I swapped out the mangled front for the default forks when I fought Panthor, and was very happy with how I performed. The magnets seemed to really like the floor in Shane’s arena, and the robot moved like it was on rails. I was able to bully Panthor around for the most part, but it did land a couple of solid shots before its weapon gave up the ghost. Despite this I was able to stack the robot awkwardly and narrowly get it counted out.
For 7th Circle it was much of the same, however I found myself losing the ground game more often than not once again, and getting popped into the air for my troubles. Once again that retraction problem reared its head, and I was left stuck upside down and counted out. The damage from this one was pretty tasty, another drive motor had come away from the gearbox, 7th Circle exploded a couple of my magnets which created some pretty sparks, and completely “fishhooked” a fork, bending it beyond the point of recognition. The repair job was majorly rushed for this, as Boom Zoom still had a shot at the top 16 by entering a rumble!
After scraping through the rumble without too many issues I once again was drawn against Uplift in the round of 16. I was a lot more cautious in this fight, attempting to go around Uplift’s side and bait it into making a mistake. This backfired when I left Boom Zoom’s backside exposed for a second too long. Uplift managed to catch my exposed link, breaking the wire and removing it from the robot.
All was not lost though! I could still enter the Bounty Hunter tournament for a shot at fighting Saw Loser. With basically no repairs to do except dig the spare link out of my toolbox I jumped right in, and after frauding my way through 2 fights made it to the final against Speeny. Ironically all of my anti-drum forks had already been mangled at this point, and my longer forks were also all trashed. I had no choice but to use my short forks, which Speeny got under every time. Eventually Speeny got me upside down, grinded against my lid for a while, then once again pulled out my exposed link.
4 cheap losses from 2 very obvious problems there, that was painful. There was a lot I wanted to do to the robot before I was happy competing with it again, which I’ll be diving into when I write up the next iteration of this robot: Boom Zoom MK3.5! See you then 
