Approximation Robotics at Robodojo 2023/2024

Thought I’d start a thread to cover all the Robodojo 2023/24 season events I go to, starting with round 1 that happened on the 10th June.

For those unfamiliar with Robodojo events, there are 6 beetle/ant events every 2 months during the season (starting in June and ending in April the following year). A robot’s performance is based on its best 3 events. One event usually consists of 4 rounds of 1-v-1 fights, and are scored 4 points for a KO, 3 for a judges win and 1 otherwise, with playoffs to resolve ties.

Ant fights: Robodojo 2023/2024 Season Round 1 Antweights - YouTube
Beetle fights: Robodojo 2023/24 Season Round 1 Beetles - YouTube

Usually, I’d enter Déjà Two alongside 3 ants, but with Medway in a few weeks, and being busy for most of the time from now till then, I chose not to enter the beetle as I didn’t fancy potentially doing a full rebuild (and making more spare wheels!) in that time. I did still bring it along to do some testing, primarily if I could get a magnet setup working. In the end, I think I am going to ditch the magnets again - while this time the setup allowed me to move around, I felt it compromised the manoeuvrability too much. One day I’ll get the hang of magnets!

For the ants, I entered the regulars PLA-ST Is a Perfectly Legitimate Choice of Material and Percussive Maintenance 4, along with the newly rebuilt Runtime Exception. Overall performance was quite good, with PLA getting 3/1 and ending up 4th overall, falling just short of 3rd place in the playoff. Lumberthwack managed to land a lot of hits in the first fight, damaging some of the wheels, but the armour packages saved the important bits. Against the scary one wheeled Weaponised Incompetance, the Ti plough protected me enough to eventually pin and grab it and bring it to the pit.

Runtime went 2/2, but managed to win its playoff ending at 6th. The armour configs worked quite well, the ad-hoc 1.5mm polycarb wedge surviving the first fight against a horizontal called Stolen Concept, though by the end of it a crack had developed down the bend line. I need to find a Ti sheet larger than 100mm x 100mm. Against Lumberthwack, the HDPE hat proved critical, as observing the damage afterwards, there was a pronounced mark just above the switch, so if the HDPE hadn’t been there, he would have sniped the switch! Aside from sourcing Ti for proper armour configs, I need to adjust the turning curves, as it felt very twitchy.

PM4 went 1/3, but I’m not displeased with that, as PM4 is not particularly competitive, and it proved to be the toughest in my team again, managing to tank enough blows from a horizontal for the screws holding the bar to back out in the one fight it won.


The next Robodojo ant/beetle event has come and gone so it’s time for another writeup. Footage can be found here.

This time, I decided to try running two beetleweights at the same time, plus a new ant I built in the week after Sub Showdown, as the main ant fleet is in need of a bit of TLC after SCAR 5. PMXL is fresh from Sub Showdown with no repairs to make (having not fought any spinners there!), with the only change being some tweaked turning settings in the form of a more aggressive expo curve for better low speed control. DJ2 got repaired from Rapture damage, and gained some TPU cheeks to better protect the seam between the front and side panels. The new ant is Percussive Maintenance 5, a literal 1/2 scale version of PMXL! For now, I’ll talk about the beetles until I can watch back footage of the antweight fights.

Round 1
The first round was a tough one for the beetles, with DJ2 drawn up against Baby Dead Bod and PXML against End Boss. DJ2 has previously had a whole frame written off by BDB, but I’ve made improvements to the anti-horizontal config since then, so I was hoping to hold out better than back then. The anti-horizontal wedge which doubles as extra cross-bracing did its job in keeping the front of the robot together, and the TPU cheeks protected the front seams. Unfortunately BDB managed to catch the back corner, peeling the side panel away, before hitting the front so hard the battery unplugged itself!

PMXL didn’t last very long against End Boss, though that was because of poor driving as I was getting used to the new turning settings and drove into the pit. The shape of the bot helps quite a bit in avoiding vertical spinners it turns out, as when End Boss got to my side, it couldn’t hit me because its front was pushing against the skirt with the cut out exactly where its disk was.

Round 2
DJ2 had another tough draw, this time against Baby Shrektforce, Sam Price’s 4WD vert which went on to come 1st at this event. I had a bit of trouble with one side dragging on the arena (I think one of the TPU cheeks was a bit low), but I managed to keep the front to him in almost every engagement, but his fork setup was better suited to the fight and each engagement resulted in him catching my leading edge until I got hit into the pit. Not much damage here fortunately, though one fork did get pretty bent up.

PMXL drew Crazy Horse, a 1WD(!) pusher with feather-grade drive. This was a great fight to give PMXL a proper run out due to the lack of damaging weapons. Having adjusted to the new control settings, I managed to keep the front pointed to him at every engagement, swiging away with the hammer. In the last 30 seconds, one of my drive motors appeared to have died, but I managed to win the judges decision.

Round 3
PMXL got another non-damaging bot in Sad Boi. Sad Boi is the ideal target for PMXL, with no weapon and a flat top. This played out similarly to the fight against Crazy Horse, though he did get some good pins in the later half of the fight. It was a close judges decision in my favour.

DJ2 drew another spinner in End Boss, a rematch from Rapture. It at least went a bit better than that fight, as the link didn’t get sniped this time. Again, I managed to keep the front mostly towards him, but lost the ground game. A few shots to my front and my lifter mechanism were followed by him pushing me out.

I lost a couple of wheels, and the threaded rods for the weapon got bent. I didn’t have enough time/spares to fix the weapon mechanism properly, so it went into the next fight with just the lower arms freely hinged.

Round 4
PMXL’s final fight was against Icebreaker. This was my highlight fight despite losing, as I managed to keep the front pointed to him, and winning the ground game, in pretty much every engagement for the first minute or so. Unfortunately, as I got more confident, I started throwing the axe out… until one attack went directly into his disk and cutting the head off (it’s still somewhere in the Dojo arena, we couldn’t find it afterwards). This resulted in me losing brief control, which Icebreaker capitalised on, hitting me in the side which flipped me over, and the follow up sniped the link and a wheel.

I need to resist firing the weapon into verts in the future! I’m also annoyed at myself that that was the only fight I forgot to hit record on :(. However, I was really pleased with my driving in this fight.

With DJ2’s weapon out of commission, it was lucky to draw Crazy Horse. With mecanums hwoever, it makes a pushing match difficult, but I managed to get enough control over him to slowly push him into the pit.

Overall, one of the most enjoyable Dojo events to date. I think I’ll be able to manage two beetles at other events, so I can start bringing one as a main competitor and the other as a reserve. I definitely feel like I’m improving with driving holonomic robots, and PMXL in particular drives really nicely. For now, a bit of a break until War in the Wirral at the end of September, I might rebuild Déjà Two using the CNC for that.

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