Schnake (BW) - Build Diary

The new (mostly finished) Schnake.

Schnake was an experimental BW slapped together in record time for us to compete with for Robot Rebellion 2022, using mostly the same components as Babróg for convenience. The robot was novel and durable, but there were several issues that prevented it from meeting its full potential. Fortunately, Schnake was already severely underweight, so changes could be made with little concern. To address all of these issues, we decided to do a near-total redesign of the design, to arrive at what could basically be called a Schnake 2: similar in concept but different in many ways.

By far Schnake’s worst issue was in how it handled. The robot was very twitchy, couldn’t drive properly upside down, the hubs kept coming loose, and seemed to constantly drift in one direction, with no seeming way to fix it. As it turns out, the drifting seemed to be a result of a twisted front piece that twisted the chassis in such a way as to keep one front wheel off the ground, but the other issues would need a good quality rethink.

The new 3D printed hubs for the wheels.

A productive tire creation session, complete with a new hubbed design for Babróg.

My first call with the new robot was to change the drive from the 1806/22mm gearbox setup used in Babróg to a more conventional BBB 22mm brushed motor setup. I’d lose a bit of the speed and compactness that comes with the brushless drive, but the robot would become far easier to control at slower speeds, which would be critical when positioning the robot for a grab or trying to orbit an opponent. Schnake also no longer uses the 49mm wheels used in Babróg, but now custom wheels, 40mm at the front and 60mm at the back. The increased size at the back allows us to drive more reliably when upside down, and should grant a very slight boost in speed from that lost with the brushed drive. The new larger diameter rear wheels can now fit a proper Pololu hub, which should be far less likely to come loose in a fight.

“Your three choices of tire compound for the weekend are the 60mm C1’s, the 49mm C1’s, and the 40mm C1’s.”

Finding the right sized belt was tricky to ensure a decent wraparound, especially on the front wheels. Unfortunately, my previous belt supplier now charges £30 minimum in shipping for any orders, including two tiny HTD3 belts in a jiffy bag (thanks Brexiteers). After about an hour of searching, I finally found a supplier providing the belts in the right length, only to discover once I got them that I had ordered 9mm width belts, when I can only fit 6mm. Fortunately, within 10 minutes of letting Jack Tweedy know about this, he had sent over a custom .stl file for a belt cutting design, which I had printed in an hour and had the perfect belt for the job.

That’s why he’s the GOAT!

One big concern from last year was how Schnake managed to get stuck under the arena wall so often with its forks. As a result we have designed and ordered new forks with a less shallow angle at the front, which should allow us to drive head on to an arena wall with little chance of getting stuck. The new forks will likely not be as effective at getting under opponents as the old ones, but they will be able to make it harder for an opponent to drive off once grabbed.

As of writing this, I do not have the forks, I will pick them up at Robot Rebellion, but you can get the impression here.

The old servo never necessarily failed, but that was mainly because it was never actually used, and I still have major doubts as to its effectiveness. With this in mind, Schnake now uses a 37mm 80rpm 18kg-cm Pololu motor, similar to those used in other grabbers and lifters in the European scene. This allows me to do a few things. First: a motor setup that’s far less likely to self-destruct and far more likely to grab and hold something. Second: I can now use a simple brushed ESC for control, allowing me to move away from the bulky and complicated dual UBEC setup used before. A new much smaller voltage limiter provides power to the receivers. Third: I will now have the motor connected to a separate receiver, which I will control while my dad drives. This alone will allow the weapon to work much more easily in tandem with the rest of the bot, while my dad can fully focus on driving.

The new electionics smushed in. The battery and electronics will swap places, but everything fits in snugly.

One major issue I struggled with in this design was that my CNC machine started to wear and flex quite dramatically, to the point where I could’t really reliably pocket parts anymore. Most of the pieces were finished before the problem got really bad, but I still had to rely on some good old fashioned chiselling from time to time.

The back pieces on my robot always seem to end up curved. A fiddly one to do, but happy with the results!

All of these changes have resulted in a nearly total rebuild, with very few parts perfectly carried over (most notably are the grabbing panels, simply because they took a ton of time to make and I’m not doing that again in a hurry). All of this is being written before Schnake V2’s debut at Robot Rebellion 2023, and while a lot of stuff could still go wrong, we are confident that this iteration of the design should perform much much better than before!

Schnake from the back, now with a much cleaner action on the grabber.

Schnake from the side with its new, more aggressive side profile.

Schnake and Babróg, ready to take on the best of the UK!


Lovely work there. The hub design is really well done! Has some great signature style to it while being a very unique design. It’s what Lycan from Battlebots should/could have been!

I’m interested in the wear going on with your CNC though- I’m assuming it is one of the desktop ones. What is breaking down on it and what sort of working lifespan has it had?

It’s a 3018-PRO Genmitsu from Sainsmart, which I’ve had for roughly a year and a half. It’s done some really fantastic work with HDPE, and it’s only just in the last few jobs that I’ve noticed the deflection has been really awful. I’ve tried tightening and lubricating every moving component I can think of in the machine, and made sure that the bed is still level, I reckon I may have weakened something with the few times the software glitched on me and kept pushing the Z axis spindle down in one direction (there are no limit switches on the machine). It really seems bad on the Y axis in particular, likely due to the spindle holder flexing forward and back. I’ve seen some DIY fixes in some FB groups, by adding some extra bracing in the form of linear rails, so I may see if that could do anything.

The machine. The zipties are my own recent addition in the hopes of adding some rigidity to the mechanism.

The machine during a 2D contour action. both the piece and the bed are totally flat and level, you can see where it’s trying to dig in, but it doesn’t seem to have the force to cut properly into the plastic until another mm or two.

One of the suggestions I saw online.

Robot Rebellion 2023:

Robot Rebellion 2023 would see both of us returning in a very similar manner to 2022, with minor upgrades to Babróg and the entirely new Schnake to test. This year the format of the competition was slightly different: each of the 12 heats would contain four robots in a round robin format, with the only rule to the order being that the winners in the first round would fight each other in the second. Points were no longer being used to score a heat by the method of winning or losing, merely if the fight was one or lost. The robot with the best record would go through in each heat, with the second place robot going to a three way playoff to determine the final entrants to the top 16. There was also the potential for “lockdown” melees to determine heat order should three robots have the same W:L record by the end. Finally, each heat would have a seeded robot competing, where Schnake had Bby Shrekt as its seeded opponent.

Here is the heat Schnake took part in, which has every fight it took part in except for the whiteboard rumble.

Schnake: Fight 1 Vs. Aggro Wobba: Smidders Edition

Schnake’s first match was actually against Babróg’s first opponent from last year, Aggro Wobba: Smidders Edition. This fight was definitely a match for teething issues: one of the teeth on the grabbing arm was getting caught on the plastic front, and prevented me from being able to use the grabber at all, meanwhile the new mixing I had done on Schnake made the robot less likely to be uncontrollable, but had the opposite issue for my dad in being too sluggish to handle, especially with turning. This left a fight where Schnake was never able to really get around Aggro Wobba, and when it could, it just didn’t seem to have the pushing power. Schnake was slowly making its way to the first loss of the competition, before a driving error from Aggro Wobba left it stuck in the arena wall, with Schnake literally too slow to free it, resulting in a rather undeserved KO to start things off. Nice to have a win, but definitely a lot to improve.

Schnake: Fight 2 Vs. Bby Shrekt

Schnake’s second fight was against Bby Shrekt, one of the favourites to win the competition, and a real test for the robots durability. Unfortunately there wasn’t too much to talk about with this match. Schnake drove straight into Bby Shrekt, before then reversing into it again. This combo of hits caused the robot to limp on one side, before another hit at the back knocked the link loose, leading to a nasty KO.

This match was a nasty loss. In the few seconds it lasted, Bby Shrekt managed to mangle a gearbox, the threaded support of the armour, killed a drive motor, and snapped the rear bulkhead of the robot, twisting the entire chassis in the process. A lot would be needed to fix the robot going forward, but this fight also revealed just how weak the structure of Schnake actually was without enough bracing at the rear of the robot.

Schnake: Fight 3 Vs. MOTHenator MKII: CODENAME LITHIUM

Schnake’s final fight was one that would, thanks to how the group had gone so far, determine if it would finish its heat 2nd, and secure a spot in a playoff rumble for the top 16. In its way was MOTHenator MKII: CODENAME LITHIUM, an undercutter that had lost its weapon, and was now reduced to a 2WD pushbot. This should have been the type of fight where Schnake could have gotten one good bite and won it, but unfortunately things didn’t go our way thanks to a few factors. The wedgelets at either side of MOTHenator were perfectly positioned to prevent the grabber from getting a hold, and MOTHenator was driven very well to make the most of this. The real kicker however was how this was Schnake’s first real demonstration of pushing power, and boy howdy was it a stinker. I had expected some drop in performance from switching back to brushed motors, but I had massively overestimated how strong a pusher with only two 22mm motors was. Without a useful weapon, pushing power, and a seeming drop in power near the end, Schnake was finally pitted, ending with a 1-2 record.

Heat G 2nd Place Playoff: Schnake Vs. MOTHenator MKII: CODENAME LITHIUM Vs. Aggro Wobba: Smidders Edition

Due to the format of the competition, each of our robots ended up in different rumbles to remain in contention. While Bby Shrekt strolled away with a comfortable 3-0 record, Schnake managed to score a second chance due to both of the other robots in the heat also having a 1-2 record. Unfortunately Aggro Wobba had to pull out of the fight due to transmitter issues, and so the fight basically ended up being a repeat of the last match. For whatever reason, using the grabber seemed to be playing havoc with the electronics, so after a near scare early in the fight I decided not to use it any more. The fight was a near copy of the previous fight: MOTHenator had better control, a design that negated Schnake’s weapon, and crucially electronics that didn’t seem to be iffy, resulting in a win late into the match, leaving Schnake 3rd in its heat, knocking out of the competition.

I really must apologise, but I took very few photos from this event, and if you can believe it, this is the only photo I have of Schnake while there.


Robot Rebellion 2023 was certainly an event with a lot to teach us. Schnake’s redesign was a pretty big disappointment, and a lot of the errors with the design should have been spotted by myself way earlier. The most major issue was the drive power: I had expected some reduction in drive power by going from a brushless to a brushed drive system, but I did not expect the downturn in pushing power to be so dramatic. On top of that, the robot was just not as durable as I would have hoped it would be: I never really came to appreciate how well supported Babróg was until I noticed how little support Schnake had for the baseplate to flex outwards from the robot, and the machine payed the price as a result. I don’t believe that all the changes were bad, the weapon motor in particular seems to be a massive improvement. I can see this design being worth at least one more crack, though I’d like to take a break for a while before committing to anything major.

So that was Robot Rebellion 2023! Apologies for the delay in posting this, it’s just been a challenge to find the time to sit down and properly write all of this down. I am unsure how much time I will have in July 2024 for what I’m assuming will be Robot Rebellion 2024, but I definitely intend to have both me and my dad competing at a BW event together at some point in the following year. Stay tuned in the coming days for some more event reports!