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Ondray
Joined: 06 Jul 2015
Posts: 142
Location: Newcastle
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Warbros - Andre NSW
I'll start my build thread with my first 'finished' bot Corpus:
Finishing involved adding a master switch, power light and a flail. It's pretty fail, but I've learned a lot.
Today I started playing with stuff to build a sportsman for vivid, here's the very rough layout (yet to be named):
Two ozito drill motors - the wheels were added today and two electric window motors from an old volvo (so indestructible). The plan is to use the low speed and high torque of the window motors to run some short lifter arms (which won't be shifters in the build). I wasn't initially thinking of making a wide bot, but after playing with the parts on the floor I think I like it, makes it harder to get around and keeps the center of gravity over the wheels and at the axis of the lifter arms. Plus I can add some thwack weapons on the sides. A pretty simple build, going to go with the rectangular section again I like working with it, but I may invest in some brazing equipment so the Al can hold itself together without the top and bottom. Biggest thing I'm pondering on at the moment is whether if or not to make the wheels bigger so it's invertable, the bunnings red wheels are 95mm and the window motors are 100mm, so going to the 125mm wheels would allow for invertiblity.
I was playing with arduino/esp8266 with some 30A ebay h-bridges with a grand plan of an xbox controller/tablet controlled bot. I haven't got very far. So now I think I'll save the headache for now and go with the RC equipment I bought to get started on corpus. Which is a nice easy to program turnigy transmitter and receiver plus some 10A crappy ebay speed controllers. The 10A speed controllers will definitely need to be upgraded to some at least 30A, probably going to go with botbitz (looking for advice there).
Otherwise I just need to get some polycarb, which is $240 for a 2.4mx.1.2mx6mm piece from the plastic shop down the road and some thicker Al section - thinking 4mm wall 50x50mm tube. I'll be spending Easter break with my Dad who's also keen for some building and has more tools than me, so I'll get started on the building then and have some more updates.
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Sun Mar 20, 2016 9:59 pm |
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Ondray
Joined: 06 Jul 2015
Posts: 142
Location: Newcastle
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So far I haven't done a full 3 min worth of driving with Corpus, but the tests so far haven't seen them get too hot. I use a rough method for calculating the stall current - I measure the internal resistance of the motor with a multimeter while it's stationary, in this case the little 12V air compressor motors on Corpus are a bit over an Ohm, I'm running a 2S lipo which is about 8V charged (which means the motors are way undervolted), I = V/R which is nice and easy for this, 8/1 so about 8 amps max draw, which the 10A controller can handle.
For the sportsman (I'm thinking of calling it Hellamax) the 12V ozito drill motor are about 0.5ohm and the window motors are about 1.8ohm, running off a 15V 4S lipo, so I'd need at least 30A for the drills and could maybe get away with a 10A controller for the lifters, but those basic 10A speed controllers I have only do 2S lipos so I still need the Botbitz 30A.
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Mon Mar 21, 2016 9:33 pm |
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