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Total Recoil - Chunkulator - NSW
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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Once I was pretty sure everything was going to fit, I sent it out for laser cutting in 3mm Hardox 450 (8mm for the snail cam) at Action Laser Cutting in Perth. It cost about $230 for the cutting and took about a week. I booked TNT to pick it up from Action and bring it to me in Sydney for about $80 overnight (Action don't do interstate shipping, but are heaps cheaper than anyone on the eastern seaboard):

The next job was to countersink a bunch of the holes in the frame and file off any burrs left from the laser cutting:

Then I set up to TIG weld it. It was a pain to weld because all the joints are internal. I ended up tacking the sidewalls together and then taking the walls off the base to get to the underside of the flange, then fitting it back onto the base and welding the bottom corners:

Here is the frame after welding. You can see I also put in M5 rivnuts for the lid before welding:

I welded up the outside and ground down the corners too:



Here is the arm being welded:

Later I discovered it had a tendancy to flip itself over backwards so I took the arm off and welded on some bits of SHS the day before the event:


I gave it a quick spray with Rust-o-leum flat black:

And the frame was good to go:

Post Sat May 26, 2018 12:41 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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I 3D printed some holders for the ESCs (3 VESCs), batteries etc:

and started assembling everything:

Here it is with everything assembled. You can just see the Teensy 3.2 micro which is the brains of the operation. It connects to the receiver using FrSky iBus serial protocol which allows it to report the position of the snail cam back to the transmitter using telemetry:

With the rubber bands mounted I went about developing the firmware to automatically tension and release the snail cam:
https://youtu.be/0nml9lKUK5k
https://youtu.be/yr24oZCFjyY

And here's a successful test-fire:
https://youtu.be/OK5L9l7URng


Last edited by chunkulator on Sat May 26, 2018 1:10 pm; edited 1 time in total

Post Sat May 26, 2018 12:53 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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And here is the finished bot. In this shot you can see the polycarb covers which I CNC cut and the 3d printed spring loaded link hatch and 3d printed encoder mount.


Once I got it together and tested it a few times I worked out the force from the springs was seriously bending the arm out of shape so it no longer contacted the floor. Just before I got on the plane for the event I tried a last ditch effort to bend the arm back into shape:


It didn't do much good. The arm ended up being so bent that it was 2cm off the ground in its first fight and couldn't hold together. Shafts kept falling out. A redesign of the arm is required to make this bot work with that much spring force in there. This might require weight savings in the frame. The only way I can think of making the frame lighter is to cut big holes in the sides and cover them with HDPE, polycarb or carbon fibre armour. More work needed!

Post Sat May 26, 2018 12:59 pm 
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