Attitude Adjuster (Beetleweight)

[scott]

Inspired by going to the filming of S1 and S3 of the Robot Wars reboot, my friend and I have decided to each build a beetleweight robot and are aiming to complete them in time for the Euro championships.

I want something that's more interesting than a box on wheels and I've always liked hammer/axe bots like Terrorhurtz, Beta and Mega Melvin so I've decided to design and build one of those. I know they're not super effective at the lower weight classes, but that suits me as I want something that isn't a scary spinner for my first build.

After reading all of the build threads in here (and being particularly inspired by the detailed build diary for This Is Not A Drill, amongst others), over the last few weeks and months I've been gathering bits and learning to CAD on Fusion 360. I used to "build" vapour bots in CAD back in the days of Series 5-7, so it is all coming back. I have also joined a local hackerspace, so I have access to a workspace with suitable tools for making a beetleweight.

This is the design I have so far. It's still WIP as I think there is some wasted space, and it is pretty close to the weight limit so I'll need to lighten it somehow.

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The bulkheads are 10mm HDPE, the wheelguards and rear are 5mm HDPE, the top and bottom are 2mm polycarb and the wedge is 1.2mm Grade 5 titanium.

It's driven by 2 of the standard 1000rpm motors, with a 3S 1000mAh Hobbyking lipo and a Sabertooth 2x12A ESC.

The axe is 10mm square aluminium 6061 bar, with a 2mm Grade 5 titanium axe head. It's currently powered by another 1000rpm motor geared down by a toothed belt at ~2.5:1. I think that probably needs to be changed though, it's too fast for an axe and I don't think it will have enough torque to self right. I was thinking about either a 37mm 500rpm gearmotor I have lying around, or possibly even going brushless for the weight/size reduction. The only doubts I have about brushless are that I'm not sure what motor to use or whether that's too ambitious for a first build?

Ebay has been my friend for this, I picked up a second hand DX6i, all the random bits of metal, a Chinese car ESC for messing around with and all the screws.

I've made a test bot made of some eBay motor mounts and a bit of polycarb that I can go chasing the cat with to prove that I can actually build a robot and wire it.

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I've also built a test axe platform using an old chopping board I had lying around. The cat REALLY doesn't like that.

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And finally a bit of CAD (cardboard aided design) to check that everything is a sensible scale.

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The most important part is thinking of a good name, which I am rubbish at. I decided to take inspiration from the ships of Iain Banks' Culture series of books, and the one that jumped out at me was "Attitude Adjuster", so I went for that.

As soon as I finish the CAD design to a "good enough" standard then I'll be able to start building! Any comments/feedback on my design so far? In particular I'm interested in feedback on the weapon, on electronics/brushless motors, and whether I'm doing anything stupid.