Percussive Maintenance XL - Beetleweight Build Diary

[T_Y (Thomas Yau)]

I popped over to Norwich this weekend to compete at the inaugural MITE with PMXL

Fight 1 was against Flick!, an amazing first build that won Best Design, and rightly so, as it is a choo choo spring flipper! My works were very effective in this fight in getting under their wedgelets, which let me largely dictate the pace of the fight. The new weapon module is hitting hard, with inital misses impacting the floor with even louder bangs than previously. I managed to push them against the wall a couple of times, firing my axe while they were pinned. At one point, I managed to overturn them, but they managed to self-right. Around half-way into the fight, I opened the pit as KOs were worth more than a judges win in this format. I lost a couple of rollers at this point - these wheels had already seen a handful of events, so they were wearing down. I managed to get them in between me and the pit, and a combination of me pushing and them reversing to try to escape had them in to the pit.

It turns out that I had forgotten to add the backstop before the first fight - the top armour is used for the tech check as you have to weigh in with the heaviest config, and that integrates the backstop in. This meant that during the first fight, I sometimes had some control issues as the retracted axe was rubbing against the rear wheel.

With the backstop attached, I was up against AOB, a pneumatic flipper. We started by circling around the centre, then we went head on. They missed with his flipper, and I swung my axe in return. It turns out their top armour is 1mm polycarb, and the axe had no trouble punching through, actually getting stuck! AOB pushed me back into a wall before using its flipper to free me. I managed to get round to their back and push them against the wall, but my axe wasn’t working properly for some reason. We locked horns again and they managed to partially lift me. I managed to get around to the side again but missed my attacks, or they were weaker than usual. Another head-on engagement had AOB under me and managing to flip me over next to the OOTA zone. For some reason, the axe was struggling to self-right, until eventually it righted me. The pit got dropped in the meantime, and AOB managed to get a good pin and lift against me. We spent some time jockeying for position, until I managed to get to the side and land a full power axe hit, getting embedded again. I tried to drag them into the pit, but not quite managing it. Retracting and firing again, the axe got stuck, and this time AOB pushed me over to the pit button. The fight closed with a few more swings from me, ending the fight embedded in their top once again.

That was a very nervous fight for me, due to the self-righting issues and the control AOB exerted over me in the second half of the fight/ However, I did get the judges win.

In between rounds, I tweaked the axe settings, so retract and throttle control were upped to 50% from 30%. I suspect the slightly smaller motor and reduction were the cause of my self-righting issues, so I was hoping that just giving it more power would resolve it.

Everyone’s third fight was a 3-way melee, with my opponents being BAM!, a 2WD vert using a big brushed motor, and Gremlin Bait, a low 2WD wedge. I started the fight by going for BAM!, getting two hits in which appeared to cut all power to it. I think I managed to ever the fuse in his removable link, as it was still in the bot but there was not motion. I then went after gremlin Bait, my forks consistently getting under their wedge. I pushed them against the wall and fired a few times, severing the power light, though I initially thought I had hit their link. I managed to pin them several times, each pin accompanied with several axe hits, then the pit got dropped. Gremlin Bait got caught on the edge of the pit and I pushed them in, earning me a win.

Now into the top 8, my opponent was Boom Zoom. He was all over me in this fight, I couldn’t manage to get any hits in, and he kpt on getting round to my sides and pushing me across the arena and slamming me against the wall. He eventually got a great push and lift that sent me cleanly over the OOTA wall and out! Great job by Rob.

Overall, a great day out, well done to the MITE team for putting on a great event. I’m happy with the new weapon module, and I’m generally happy with how PMXL is running. I’v egot some AM32 ESCs on order though, I’m hoping that will help with the low speed power that would be required for self-righting. These should arrive in time for Roboshowdown at the start of May.

[McMullet (Sam Roberts)]

Nice write-up, thanks for sharing!
I’m impressed by the polycarb impaling!

[T_Y (Thomas Yau)]

I’m planning on testing some upgrades at RoboShowdown, hopefully working out well enough to be retained for June NHRL (oh yeah, I haven’t mentioned this here! PMXL will be going to June NHRL!).

I had a productive weekend - first up was upgrading the weapon ESC to AM32. Having some self-righting issues at MITE made me finally pull the trigger on some AM32 ESCs, so I picked up some Ranglebox AM32s. I also set up an Arduino Nano to tweak the settings, to remove braking and change the kv tuning to match my weapon. Initial tests are promising!

I also made a new standard armour config, taking the weight savings from the hammersaw armour config - 4mm sides and rear (down from 8mm) and aggressively removing excess material from the front. With this config and 4 forks, PMXL is still under 3lb, so if it goes well enough at RoboShowdown, it’ll stick around.

[T_Y (Thomas Yau)]

Back from Roboshowdown in Birmingham with another Top 8 performance from PMXL!

Roboshowdown ran a 3 fight Fight Night format with a top 8 (it was going to be top 16 but was reduced due to time constraints). The first fight was against Mow Problem, Rob Weston’s Bloodshot/Billy inspired big wheel undercutter. Because I was concerned about his blade height when inverted, I went with a split wedge design - one half anti-horizontal and one half anti-hammer saw (sans forks), the idea that if he was inverted I could use the higher wall to protect the bulkheads better. I slightly whiffed the initial box-rush, and Mow Problems was able to get up to speed for several big impacts early on, which cut the anti-hammersaw flap off and detached the anti-horizontal side from the front of the bot. His weapon started screaming (literally - check out the footage!) - his weapon gears had partially melted and weren’t meshing as well. This gave me the opportunity to assert a bit more control over the engagements rather than just impacting and flying apart. I eventually got the pit dropped and managed to get the fight close enough to the pit that he went in.

Both front wedges were badly damaged and essentially written off due to the mounting points being torn - these were given to Rob as a trophy. I also swapped out the weapon module as one of the bulkheads was cracked, and replaced a wheel that had been clipped.

Fight 2 was another horizontal in New York Slice. Slice is an interesting design in that it has an undercutter on the front but forks on the back. Because of this, I went for another split wedge, anti-horizontal and twin forks. The motor on Slice stuck out the top, and the link door was thin, so I was hoping to hit either one of those. The box-rush went a lot better this time, and the wedge held out a lot better against his undercutter. For the most part, I managed to keep engagements to the wedge, but there were a few times where he managed to clip the forks, eventually partly pulling out one of the mounting bolts causing the forks to splay out. I took several shots with the hammer where I could, but I was mostly focused on keeping the wedge pointed at the blade. Halfway through the fight, he got inverted after a big impact, which put his blade at a much more dangerous height. I eventually managed to get him turned over for a couple more hits, before the fight went to the judges, which I won.

I managed to get some fairly good shots at his top plate. There’s an impact right next to the motor, I wonder what would have happened if I had hit the shot!

The final fight night fight was against Blahaj, a great first build that was a 4WD 4-bar lifter. This time, I put on the 4 fork front and the cleaver, hoping to cut his link wire. My forks consistently got under him, but I couldn’t quite reach his link from the front. He also did a good job of either blocking me from flanking him to get to the link, or using his lifter to block blows. The fight went to the judges which I won.

Winning my 3 fights meant I was in the top 8 again! My opponent for this was Inversion, a very well-driven lifter. His forks were just a tad longer and more effective than mine, resulting in many pushes and pins from him. Unfortunately, my axe arm was too short for me to hit his link over his front wedge, and I couldn’t quite get the hit I needed on his weapon belt. There was a scare early on where he pushed me over to the OOTA zone and nearly got ne out, but I think PMXL’s awkward shape prevented it from happening. Eventually, he dropped the pit and I got pushed in. Very well done to Inversion, who ended up placing 2nd overall!

Overall, a great day out, big thanks to Tom and Sarah for putting it on, I look forward to more! And to each of my opponents, who all gave great fights. This marks the 4th event in the past 5 running tournament structures that PMXL has finished in the top 8, a fact which I’m very happy about. Its performance in all of Sunday’s fights was great as well, and I think I’m in a good place in the lead up to NHRL in June.

I’ve got a couple of changes in mind, primarily aimed at control bots. The first is slightly longer forks, with hooks (akin to Shatter’s ‘social distancing forks’) to catch robots riding up the fork and preventing them from getting too close. This should hopefully keep the main body from being engaged by a control bot’s weapon, and coupled with a longer axe arm, should let me hit them safely. The armour will also be lifted around the wheels, exposing them more, so if a lifter does get under me, I’m more likely to have at least one wheel touching the floor with thich I can try to wriggle free.

[T_Y (Thomas Yau)]

Prepwork for NHRL is basically done! With NHRL’s rapid schedule, I decided to build a second PMXL to aid with turnaround time.

I’ve added two new configurations to my arsenal. First up is the control bot config.

This is just the standard config, with some modified armour panels, where I’ve cut away some of the armour skirt to expose the wheels more. This means that when a bot gets under me, I can keep my wheels in contact with the ground for longer and hopefully wiggle free.

The second config is a NHRL exclusive, due to the fact that they allow flamethrowers.

It’s common for bots to wrap aluminium or heat tape around them to protect against flames, but it seems to only delay the melting, and the flames can still get through gaps in the armour package. I opted to make a 0.5mm Grade 2 titanium shield and attach it to the front of the bot. The plan is to rely on the manoeuvrability of my drive to keep the front pointed to the flames as best as I can. Titanium is a poor conductor of heat, and with the shield pushed forward of the main body, it should hopefully keep the heat away from critical components. The forward rake of the upper part of the wedge is intended to redirect the flames away from PMXL and possibly towards the opponent. The axe arm is also slightly modified to angle forward 15 degrres or so to get around the fact that the arm can’t swing all the way through now (not pictured above).

Looking forward to fighting in a completely different scene!

[T_Y (Thomas Yau)]

Last week, I went international for the first time for an event, bringing PMXL to NHRL’s June 22nd event! While PMXL did not do very well in competition, the whole experience was great, if tiring!

I got to the venue on Friday to set up the bots after flying them across the Atlantic and pass safety early. They have some seriously impressive premises there.

Fight 1 was to be against Mr. Scrubbles, a 2WD eggbeater. However, despite testing on the Friday and on the morning of the event, when I loaded into the arena, the bot refused to connect to the transmitter, leading to a TKO.

On return to the pit table, the other bot also had the same issue. It took us a good while to sort it out, and we’re still not sure of the root cause, but after getting a new receiver which did the same thing, trying all receivers on a new BEC, I got one of the existing receivers to work by plugging it into one of Baby Dead Bod’s minibots to use its integrated BEC, and was able to bind to it, at which point it started working again in the original PMXL. Gonna be doing some testing this weekend hopefully to see if I can replicate the failure mode.

Fight 2 was against Codename Pinto, a 2WD drisk (or trisk, according to their wiki photos). My forks were consistently getting under him, but because his wheels were at the back, he could still push. This was made worse when my front wedges popped out of their mounts early on in the fight - it turns out I had forgotten to replace the retaining bolts when I was faffing about with the electronics!

The upside to this fight was the ability of the axe to cause damage. Pinto had their weapon motor exposed, behind the weapobn, and I managed to land several blows on it, in 3 instances - the first when I got behind them and fired the axe a few times, the other two head on, where I went into full send it mode and went directly into the weapon! In the second head on engagement, my axe arm was twisted and the hardox axe head was misaligned, limiting its effectiveness, but I had managed to hit the weapon motor enough times and hard enough to shut down their weapon! Unfortunately, I had some grub screws shake a bit loose, and some good driving by them got me inverted and unable to self-right, even with the one unstick from Brett.

We exchanged parts after the fight - my wheel and their weapon motor - and the motor is VERY crunchy! You can clearly see several gouges where I hit the motor, as well as the dents from those hits. Really happy about that.

Overall, while disappointed by PMXL’s tournament run, I was very happy with doing some proper damage with an axe, and the event experience itself was amazing! The UK builders there (Thistle, Turbulent Juice nad Baby/12lber Dead Bod) essentially became one big team helping each other get bots repaired, which was a cool experience.

Next up is Sceetles on the 6th July, for which I have some upgrades already in the works.

[T_Y (Thomas Yau)]

Upgrade time for PMXL ahead of Sceetles next week!

On the flight back from NHRL, I started thinking about clutch mechanisms for the axe. I came up with a compliant ratchet made of TPU sitting inside the gear, inspired by some conversations I have had with Jack Franklin about the topic.

Not sure if it comes across well on the footage, but I do need to put a fair amount of force into backdriving the axe by hand.

It does not seem to have compromised the axe power or self-righting in any way, so I’ll be testing this out at Sceetles. It also has the side effect of no longer requiring set screws and a live shaft, which was one of my goals after the Codename Pinto fight, as well as saving the weight of 3 alu mounting hubs.

[McMullet (Sam Roberts)]

Amazing to see some really proper damage done by a beetle hammer! And the clutch is chef’s kiss

[T_Y (Thomas Yau)]

MITE 2 was a blast, and tandem improvements to PMXL and Overclocked have really borne fruit in this event!

To repeat myself from the Overclocked build thread, I changed up the clutch mechanism to make it easier to replace, and I got some sharper axe heads made.

Fight 1 was against Toucan. I’ve always maintained that control bots are PMXL’s least favourite opponents to fight, because they usually do not have exposed elements on the top for me to hit. However, the new axe heads really made a difference, as I managed to get lodged several times in the TPU top plates of Toucan! Toucan managed to get some good control, with some flips and nearly getting me into the pit, but I managed to get the win via a very narrow split judges decision!

Fight 2 was against Chucky, another matchup against a control bot and a familiar opponent from Dojo. Again, the sharper axe heads really did some damage to Chucky’s top plates, getting lodged again, which resulted in probably the coolest acrobatics I’ve ever seen a robot do, when I retracted the axe while being embedded in Chucky’s flipper! After some early control issues for Chucky, he eventually managed to get around to my side, pushed me to the OOTA zone and flipped me out!

Fight 3 was a melee against Mow Problems and Bulbaroar. Because of the mix of horizontal and eggbeater opponents, I opted for the split wedge setup. However, I had to use the left anti-horizontal side instead of the right, as I had forgotten that the print had failed on the right piece.

This meant that when Mow Problems hit me, it clipped both the link door and the right bulkhead. Combined with Bulbaroar clipping the axe head early on and breaking one of the mounting bolts, it meant I could not effectively use the axe. In addition, the opening of the link door let the link wriggle loose.

While I did not get past the fight night stage, I am still really happy about PMXL’s performance. I might reduce the turning rates, but am very pleased that the axe is doing proper damage now. It’s flattering that people are now telling me that they’re putting additional top armour on for an axe!

Repairs are underway for Beetle Champs in a few weeks. Hopefully I don’t crash out after 2 losses immediately!

[Shooty (Eoin Ó Cionna)]

So cool to see all the work you’re putting into this axe bot. Looks to deliver some really lovely hits, and that clutch mechanism is just chefs kiss. Excited to take a closer look at this bot in person at champs, really excellent work!

[T_Y (Thomas Yau)]

I found the time to do a teardown of the weapon modules. specifically the spare one that I swapped into the bot after the 3rd fight night fight.

I didn’t mention it in the previous post, but I also entered a whiteboard fight, but I ended up not doing much in that fight as I got flipped upside down and couldn’t self-right for some reason.

Upon disassembly, the problem was clear - the grub screw on the output shaft had managed wear away the keying, and so was no longer engaging properly.

I got my metal file and reground the flat on there so I could reuse the motor. I also put another flat on the opposite side so I could use the other set screw on the Repeat gold hubs.

I then repeated for the other weapon modules, so now I have 3 ready to go which should be more resistant to that failure mode.

Next step for Champs prep is to make more omni wheels!

[T_Y (Thomas Yau)]

Found the time to sit down and do the event writeup for Champs 2024. Many thanks to the BBB crew and everyone else involved for yet another enjoyable event!

The first fight would be a challenge, being a melee against Propane, a 4WD drum and a past event winner, and Impulse, an excellently driven font-hinge lifter. The axe worked well initially, managing to get some good swings into Propane’s top plate while the other two were engaged with each other, but Propane managed to juggle me and remove a wheel, which made getting involved in the fight difficult. Eventually I ended up in the pit as I was unable to properly manoeuvre.

The removed wheel was actually untouched, and the screws were still inside it, so I think the threads on the mounting hub had worn down. The screws I am using don;t thread all the way through the hub, so I got some slightly longer ones fitted for the next fight against Schism, a 2WD hammer saw. I was thoroughly outdriven in this fight, unable to get around Schism’s longer and better forks. Neither of us landed any properly damaging blows, though my link was nearly sniped on more than one occasion, but I was able to wriggle away by swinging my axe to dislodge myself. In return, I managed some hits very close to the weapon belts, as well as nearly hitting the opening where the arm was, under which Schism’s electronics were! Unfortunately, I drifted into the pit button at some point, and the greater control exerted by Shcism pushed me in.

I also entered a whiteboard, against Freak, a 2WD undercutter, Dolos and Got any Grapes?, a large shuffling vert. Similarly to the first fight, I lost wheels early on making enagement very difficult. Grapes smacked the back of one of the wheel pods, completely shearing the motor shaft but somehow not damaging the wheel at all, and the other front wheel was removed in the same fashion as the first fight. Lacking any reasonable control, I ended up in the pit.

An ejoyable day despite not winning any fight, as to top it all off, PMXL was awarded the Spirit of BBB. Rest assured I will keep building weird stuff!

Going forward, I’m going to replace all the wheel mounting screws with longer ones, to engage more thread, as I think the threads that I was using have been worn down with age. For the sheared motor shaft, I can just use one of the many spare gearboxes that come from making Rotalink conversions. I could consider changing to a different motor setup with 6mm motor shafts, but I have so many of these rotalink conversions (having built 3 different chassis with them, plus spares) I feel it would not be economical until I actually lose more of them.