Quote:
Originally Posted by ctt956
This doesn't need to go fast; probably not faster than 5 MPH(7.33 FPS). I checked wheelchair motors, and they seem to be on the expensive side. I considered CIMs, but I'm not sure if they could handle this much weight. Could they run at 24 volts? The runtime would vary, but the battery would limit it. It would mostly be fairly short though.
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I wasn’t necessarily suggesting just getting the motor/gearbox assembly.
The entire wheelchair base, seems to fit your requirements well. You should be able to get the base of an old wheelchair much cheaper than the cost of the motors, gearboxes, wheels and frame. I have a base of an old wheelchair around the side of my house, that had been thrown out simply because the SLA batteries had died.
Old ones are pretty common going for free( in Australia anyway), otherwise an operational wheelchair( but with dead batteries) can be got for less than $100 online.
One CIM( at 12volts) on each side should easily be able to drive the robot at 7.33fps.
I would not recommend running CIM's at 24volts. First of all doubling the voltage, means double the motor RPM. This will mean you need a massive gear reduction if you want to go 7.33fps( especially if you use big wheels say 8 or 10inch). Secondly increasing the voltage from 12volts to 24volts is going to give to increase your power by 4 times. So your 24volt CIM's will be outputting almost 1350watts.
Running one CIM at 24volts, is going to cause a current draw higher than normal FRC motor controllers can handle, forcing you to move to expensive high current motor controllers more typically used in Battlebots, such as Victor 883/885's and the new VEX Victor BB controller. Running the CIM at 24volts, will also massively decrease the operational life as they are case sealed it will be unable to dissipate the heat. The brushes will also wear out quickly( although these are pretty simple to replace in CIM's).