I am acting as an advisor for my High School Science Olympiad team (I am a graduate), in their endeavors in building a competition robot. It's kind of a low budget thing so they are using an aircraft controller and receiver to control a tank style tracked building platform. I'd post a link but I haven't met the requirements to post links as a new member... It's a LynxMotion tri-track kit if you're curious.
If you can help me select an ESC that will correctly drive the motors it would help me a lot. I've only ever run nitro myself so I'm not very familiar with electric drivetrains, manufactures, part sources, etc. I am on the other hand a Computer Engineering major so I understand the material.
Here is a segment from the the spec sheet on the motor they are running...
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12vdc 235rpm, Gear Head Motor / Part no.
GHM-12
Torque = 138.9 oz. in.
Weight = 7.15 oz.
Reduction = 30 :1
Length = 59.2mm (motor and gear)
Length = 22.6mm (shaft only)
Diameter = 36.8mm (motor and gear)
Diameter = 6mm (shaft) (0.157")
Current = 145mA (at 12v no load)
Current = 3.8A (at 12v locked shaft)
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Specs are 3.8A stalled @ 12 volts. 12 volts is ideal but they can run at 10.8 or 9.6 although I would certainly prefer 12 volts since this is a "sumo" competition. Stalled motors defeats the point of treads
. The part that I am having trouble with is finding one that has reverse. If they have "micro" ESCs that will work that would be great because weight class is looking pretty close for the whole thing. The real catch is that it's $0 budget so the cheaper the better.
Found this cheap model from r2hobbies: rcps61604 that fits all of the requirements (100A draw is supposed to be grossly overestimated) but at 83g it's a bit chunky considering that the receiver weighs just 8g.
A BEC ESC would be nice too. Competition rules are stupid, all cells on the bot can't total more than 14.4v, even if they are on different circuits. Otherwise I was just going to use a LM7085 voltage regulator to drop the voltage off of the 12v pack anyway.
Thinking about using Kan 2/3 AA 700maH NiMH cells to build the 12v battery packs. I would prefer to use some ELITE 2/3A cells (I run them in airsoft guns) but the weight is really cramping my style. Matches only last 2 minutes and with mixed loads I estimated 10+ minutes of runtime for a pack. Full load from 2 motors is 7.6A while these are capable of 10A draw so they seem like the best option. Are there any better batteries that are roughly the same weight (without going to lithium)?
Thanks for the help guys, I really appreciate it and I'm sure the team will too.
-Nick