Léim - Beetleweight Spring Flipper Build Diary

[Shooty]

Well, this post may be a smidgen late (ahem), but I’m finally at a point where Season 2 has aired, I have enough time to do a large write-up, and most importantly, I can be arsed to do this. So before going into the event, let’s take a quick look at how Léim Thart came together.


The Léim Thart chassis nearing completion.

For the drive setup, I built a mock platform which was meant to replicate the drive of the final machine on a one to one scale. Getting the DYS1906 motors to work with the 22mm planetaries wasn’t easy, but a handy guide done by Cosmin Gorgovan on the Beetleweight Robot Combat page got me through, and the end result was very compact. Flashing the ESC’s proved a bit trickier, requiring an Arduino to program as well as some custom firmware to get everything working correctly, but after a bit of tweaking I had a working drive system going!


The new wheels and brushless drive. Note the mould for cutting tires in the background.

This project also marked the first time I could use a 3D printer (in my case a Wanhao i3 Duplicator Plus), and this would prove very useful in the creation of my new wheels. The wheels on one end press-fitted onto the gearbox shaft, and the other wheel ran on a bearing at the front of the machine. I could even use 3D printing to make a guide that allowed me to get perfect cuts out of a silicone hose I was using for tires (thanks for the inspiration RobertK!). I used rubber bands to transmit drive in the short term in place of the proper PU belts, and when run on 4S the speed and control of this bot was a substantial improvement compared to the original Léim!


The drive platform I used for testing.



Having good drive was just one piece of the puzzle however, as if I wanted to have a good bot, I needed a weapon that would actually function this time. This involved 3D printed shock absorbers that required multiple revisions to take the forces demanded of the springs, and though frustrating to redesign and reprint over and over again, the fifth revision would ultimately prove successful.


The testing platform for the spring flipper.




Some more views of the mechanism.

Cutting plastics comprised a lot of the challenge of this mechanism, most notably the snail cam that drove the mechanism (thanks to Mark Joerger for the advice for improvements, and Shakey for the milled cam later on). After a few revisions though I finally had everything assembled and could test it on the old Léim chassis. While not a massive flip, it *technically* went airborne, and as those were the less powerful springs I had in the mechanism, I was confident I could improve it more in the future.


Mid-way through cutting the weapon cam. This was all painstakingly done by hand, and while the finish was excellent, I outsourced the final product just to be even more safe.


The machined finished cam next to my first attempt (I gave it two tries before outsourcing).



So at this point I had improved both my drive setup, and my weapon, and all that would be required now would be to combine the two setups. Seems like smooth sailing doesn’t it? Well, while everything looked good from this angle, we are merely in the eye of a storm that brought up many problems that nearly sunk the whole project.