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OK...a lot of hassle later, including a burglary 
- here goes the build thread! 
Sadly the brushless drumbot project got wrecked by having a toolbox holding most of the metal parts for the damn thing - including the very nicely machined drum done by Kenny (ALK Engineering) - stolen by some burglars. Thankfully insurance paid out - that and I feel better off at the moment - so it's time to go ahead! Here's the start of the build thread (requested by Dave):
Basically - T shaped spinning bar undercutter powered by two brushless motors, swinging a bar up to 800mm long (the bar in the above CAD renders is 700mm). The weapon drive is by a 90 degree twisted timing belt - by rule of thumb the belt should be long enough not to jump, especially with wider pulleys and flanges.
The rest of the bot is pretty straightforward - a couple of rock crawler motors run through 16:1 planetary gearboxes to the wheels, which should move it about nicely, RC helicopter gyro to stabilise it against the spinup torque of the weapon, and a whole bunch of batteries; I'm leaning in the direction of a small lipo pack to run the drives with A123s on the weapon for the insane 70c burst current they can deliver (that, and they're a lot cheaper than the huge lipo packs I'd need to run the weapon).
Most of the chassis will be heat bent grade 5 Ti of various thicknesses; work on that will start after the New Year
- here goes the build thread! Sadly the brushless drumbot project got wrecked by having a toolbox holding most of the metal parts for the damn thing - including the very nicely machined drum done by Kenny (ALK Engineering) - stolen by some burglars. Thankfully insurance paid out - that and I feel better off at the moment - so it's time to go ahead! Here's the start of the build thread (requested by Dave):Basically - T shaped spinning bar undercutter powered by two brushless motors, swinging a bar up to 800mm long (the bar in the above CAD renders is 700mm). The weapon drive is by a 90 degree twisted timing belt - by rule of thumb the belt should be long enough not to jump, especially with wider pulleys and flanges.
The rest of the bot is pretty straightforward - a couple of rock crawler motors run through 16:1 planetary gearboxes to the wheels, which should move it about nicely, RC helicopter gyro to stabilise it against the spinup torque of the weapon, and a whole bunch of batteries; I'm leaning in the direction of a small lipo pack to run the drives with A123s on the weapon for the insane 70c burst current they can deliver (that, and they're a lot cheaper than the huge lipo packs I'd need to run the weapon).
Most of the chassis will be heat bent grade 5 Ti of various thicknesses; work on that will start after the New Year
: S7 just has such a high impact strength compared to a lot of steels that it's a lot easier to get away with.
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