Boom Zoom MK 4 Build Diary
Boom Zoom MK3.5 had come and gone, and at this stage I was at a crossroads of whether to go for another total redesign, or create a more refined version of basically the same robot. Not satisfied I’d learned all I could from MK3.5 I chose the latter, and began work tweaking the existing design to address some of the small flaws I’d noticed. These were:
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With them being rigidly mounted, only 1 lifter fork would be on the ground at any one time.
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The rear wheels didn’t entirely clear the baseplate, meaning if an opponent wedged under they could take all of the robot’s wheels off the ground.
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During awkward lifts the robot would tip forward, taking the wheels off the ground.
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The wheelguards had very weak layer adhesion and impact resistance thanks to using an unsuitable filament.
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The M3 set screws in the wheel hubs were rounding out and getting stuck/falling off the shafts with use.
With this all in mind I jumped into CAD and began work! I won’t bother with pictures here as it’s visually nearly identical to MK3.5, instead I’ll jump right into how I tackled each problem:
The first issue was pretty simple to fix, the forks were secured to the lifter via 2 bolts. By removing the top bolt the fork would pivot on the bottom bolt, but was still limited in how far it could rotate by the fork’s geometry. On the CAD I just removed the top bolt hole entirely so it wasn’t reducing the overall strength of the lifter. Now both forks could rotate a little and keep in constant contact with the floor! If only all the fixes were that easy…
Fixing the second issue involved moving the wheels back a little. 3mm backwards was enough to fully clear the baseplate, but this then made the drive motors clip into the back panel. I got around this by designing some pockets into the back panel for the motor to sit in. That wasn’t so bad either!
The third issue was solved by limiting the upward travel of the non-lifter forks, tweaking the design of the front armour to stop them rotating upward past a certain point. This allowed them to act as outriggers, giving me much more leverage when lifting and stopping the robot falling onto its face. In some test lifts the front wheels stayed on the ground the entire time YIPPEE!
The fourth issue was solved by swapping yellow filaments from E-DA 97A to Polymaker 95A, which is a fair bit softer and much more impact-resistant. My hope was that this new material would flex much more, hold together better and NOT wrap itself around any more spinners!!!
The fifth issue was still straightforward to fix but involved my least favourite job in all of combat robots: tapping. Following Jack Franklin’s advice, I drilled out the Pololu hubs from M3 to M4, then tapped the new hole and added an M4 set screw. These are much less likely to round out, get stuck or fall off and were a nice if time-consuming quality of life upgrade. Here’s a before and after example of this process:
This was also my first opportunity to CNC my own frame for Boom Zoom after picking up a used 3018 desktop router from Andy Davies. After watching some tutorials and generating some gcode using Fusion 360’s CAM suite I set the machine going and was left with a lovely pile of vaguely beetle-shaped plastic. I was able to add a little pocketing on the back panel to save some weight and make room for the motors, which went swimmingly. I 3D printed some jigs for drilling the fastener holes to make sure even the manual parts of the manufacturing process were idiot-proof.
For the fasteners themselves I swapped all stainless steel fasteners to 10.9 ones for better tensile strength, and went with torx heads on fasteners wherever possible, as these are less likely to round out than hex heads and easier to remove when bent.
Robonerd Football 2023
With all this said and done, the robot was ready to go! Once again the first outing for a new chassis would be Robonerd, this time for the football! My printer quickly squirted out a custom setup for mine and Sion’s team, Crystal Meth Palace FC!
Our matches are at 6:00 and 1:59:08.
The robot put in a performance not unlike that of Prime Vinnie Jones, and together we finished 2nd overall, denied joint first by a dodgy VAR call. Game’s gone.
RoboDojo October 2023
With the testing complete, Boom Zoom was ready for a foray into full combat, just in time for October’s Robodojo meet.
My fights are at 2:40, 5:32, 14:48 and 24:38.
Not a huge amount to say about this one, 4 knockouts all by getting my opponents stuck in various compromising positions was pretty sweet! The changes worked perfectly, and helped by some favorable draws and no other robot scoring 4 knockouts, Boom Zoom fought its way to its first event win! I asked around and to my knowledge this was the first time a non-spinner had won a beetle event since the pandemic! I was really chuffed, even more so at the robot taking no damage.
That being said, this event really wasn’t a good test of the changes made since MK3.5. Most of the robots I fought were either very favorable matchups, having issues of their own that made it an easier fight, or some mix of the two. I was anxious to get the robot back into the arena and see if this was just a fluke, or if this robot really was a contender now. Cut to 6 weeks later…
Battle In The ‘Burgh 3
It was once again time to make the trip up to Edinburgh, this time with basically no changes made between events which was a nice change of pace.
Apologies for the choppy video, the later fights are better. Vortex was an awkward opponent, the wide gap between its forks fit my front end perfectly, and I found it was able to win frontal exchanges every time. To make matters worse, Boom Zoom was catching the floor seams much worse than usual, particularly around the pit panel. This made driving around to the sides and capitalizing on Vortex’s gyro when turning pretty difficult, but I eventually managed the push down the pit I’d been looking for. The robot had been knocked around a fair bit but it was all cosmetic damage, and before long I was ready for fight 2!
This was a rematch from earlier in the year, and since then Mark had fitted a link door to Kriegsmesser, meaning I probably wouldn’t be winning this one the same way as last time. Frontal engagements were kind of a stalemate in this fight, but I took advantage of the vert’s gyro, got to the side, flipped it onto its weapon and got it to roof itself. The shock from this knocked the weapon motor and caused it to burn itself out against its own guard. I mistook this for a more serious fire and put down my transmitter, but quickly picked it back up when it became clear the fight was continuing! With Kriegmesser’s weapon down there wasn’t a huge amount he could do except push me, so I took my foot off the gas a bit and settled for a pushing match for the rest of the fight, which despite some near misses with the pit ended in a JD Boom Zoom win!
My third qualifying fight sadly didn’t happen, as Downward Spiral was left irreparable after an earlier fight, which meant with a 3:0 record I automatically qualified for the top 16!
My top 16 fights are at 8:50, 15:11, 20:00 and 23:50.
Another rematch, this time from ‘Burgh the previous year in 7th Circle. I felt a lot better about my chances this time around having fought lots of very similar robots in the year since our last fight. This started well, with Boom Zoom getting under 7th Circle most of the time, but a good counter from 7th got Boom Zoom upside down. By following up with another hit to the lifter while self-righting, 7th backdrove the lifter and stripped the servo horn, killing Boom Zoom’s weapon for the first time since its first event and leaving it upside down. Finally, insisting on making it invertible actually pays off! Driving into 7th’s spinner provided a nice self-right, then I was able to control the rest of the fight with some good pushes, and despite 7th throwing its entire weapon stack at me I was able to eke out a narrow win via the judges! The stripped servo horn meant the servo itself was mercifully spared, and a new horn had the lifter working again in no time. This marked another milestone for Boom Zoom, it was the first time it had ever won a fight in a tournament bracket!
My quarter final fight was against Baby Dead Bod, my first horizontal spinner opponent since MK2 and the defending ‘Burgh champion. I slapped the Jungle Man setup on, and got my box rush in well. After knocking BDB around the arena a while, one of its drive motors dislodged and was caught in its own spinner, forcing a tap out. The wedge held up great in this fight, better than I could have expected, and came out with a few chunks missing but largely intact. A hit to the wheelguard bent the mounting through-bolts, not quite enough to lock up a wheel but still a cause for concern. After swapping these out I was ready for my semi-final against Bby Shrekt…
With Shrekt the strategy was largely the same as last time: attack the parts of his front not covered by forks. This fight started badly, with Boomy getting caught on the same floor seam it had trouble with against Vortex and being forced into a head to head engagement with Shrekt. This snapped off one of the lifter fork mounts just like at Rapture, and broke the zip tie securing the lifter elastic meaning I had no means of retracting it. I backed into the wall to try and manually retract the lifter, but Shrekt was on me and roofed Boomy with a shot that killed a drive motor. Shrekt kept the shots coming, damaging a wheelguard and killing another drive motor. Eventually Shrekt landed another shot to the damaged wheelguard and completely ripped it off, ingesting it into the weapon and completely killing itself. I managed to keep my robot moving while Shrekt was counted out, getting me into my first major beetle tournament final. I didn’t feel good about this win, and was on the verge of tapping out while Shrekt was being counted out. It was only blind luck and a bad bit of print geometry that saved me, and I resolved to make sure that could not happen with the next version of the robot. The print had torn away around the mounting bolt holes where I’d really skimped on support material. This was a totally different filament and failure mode to what happened at Rapture, where the layer lines had separated instead. With all that said and done, I had one of the bigger repair jobs I’d ever done at an event on my hands and set to work replacing the dead drive motors and ruined lifting arm, along with fixing a number of other bent bits and backed out screws.
For the final against Grab Crab I swapped out to my control bot setup, ditching the wheelguards and going with the low profile front, intent on giving him as little on me to catch and throw as possible. I also put on fresh wheels for this, as I didn’t know when I’d next be in a final and could use every advantage I could get! Things got off to a rocky start, with Grab Crab getting under me and getting me most of the way to the roof with an incredible yeet. It kept up the pressure and kept me off balance with a series of smaller flips before I was able to turn the tide with a pin and grab, pushing him towards the pit before the Crab reversed by lifting me, and after quite a struggle dumping me down the pit. I wasn’t unhappy with this result, Grab Crab was clearly the better robot and deserved the win, I was just buzzing we’d made it an all non-spinner final, and that I’d managed my first podium place at a big tournament!
Satisfied that the changes from MK3 had made a difference and that the robot was on the right path, I still had a few changes I was considering. For now though I had a robot very much still in fighting condition, and one last event to round out the year: December Dojo!
RoboDojo December 2023
My fights are at 0:00, 8:00, 17:26, 22:43 and 23:54
My fight against Screaming Banshee was a nice one to start the day, no damage, a good pushing match, a gentle pitting, voila. Next up was Icebreaker, and the warmup was well and truly over. Front to front Icebreaker was winning every engagement, and getting around to the sides proved impossible with how well driven a machine it is. Our forks were locking together and protecting me from harm for the most part, but my lifter was getting slowly eaten every time I tried a lift or to wiggle free. Eventually, he took out yet another 22mm drive motor, making getting to the side much more difficult. A couple of flips were a nice consolation, and I was able to hang in there for a Judge’s Decision but deservedly it went to Icebreaker. After this I had a good scrap with Hooligan, where the drum forks were once again put to the test and held up fairly well, allowing me to push it out of the arena, and my control bot setup allowed me to do the same with Toucan in my next fight. This put me in a playoff for third place, with Chucky and Baby Dead Bod. For this fight I opted for a “sword and shield” approach, with forks on one half of the bot to handle Chucky, and a Jungle Man wedge on the other for Baby Dead Bod. Despite what you can hear me say in the video, I didn’t forget to put the mounting bolt in, Baby Dead Bod managed to pull the bolt through its mount with the force of its first hit, ruining the frame rail on that side. With my wedge gone, I got a little trigger happy on the sticks and when an opportunity to pit BDB came along I went full send, pitting both myself and the spinner, snagging 4th overall.
With the frame rail ruined, I once again had a choice: cut and fit a new one, or take the opportunity to redesign the robot like I’d been tempted to after Rapture. I decided this would be a good place to leave MK4, join me next time for the most extensive redesign so far, Boom Zoom MK5! This next one might take a little longer as MK5 is still active, and I’d like to wait until the version retired before I write about it. Until then ![:slight_smile: :slight_smile:](https://forum.bristolbotbuilders.com/images/emoji/twitter/slight_smile.png?v=12)