# motors in robotics

• posted

Hello,

I am not sure if its the right place for this but here goes. I am constructing a line following robot. it is going to ba a wooden platform 2x3 feet. I will be putting around 60lbs on it. Is there an equation that will guide me to the right specification of a motor, (in watt). I bought these geared motors:

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but the motor turn bery slowly and I afraid they will heat up in time. Plus the gearhead of one of the motors just stripped. Is there a weight to motor power conversion ? I guess the motors I have, ran at 24 v max, with a calculated 0.2 amp max, so 4.8 watt? Also those geared motors are hard to find, i did not want to go into the trouble building my own gears, it probably would not be as precise and strong.

thanks

ken O

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• posted

I go to skycraft every Saturday. Cool place. Get a spring scale and see how many pounds it takes to pull the thing. Lets say 10 lbs. Now decide how fast you want it to go. Lets say 10 ft/sec. So thats 100 ftlbs/sec. A HP is 550ftlbs/sec, so you need one fifth of that...A HP is 746 watts... 746/5 is about 125 watts... 12V 10A or 24V 5A about. You can compute rpm needed at the wheel if you know wheel diam. And torque needed at the wheel.

• posted

I used to go there once in a while, but I miss the real surplus stores in Dayton, ohio.

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• posted

That's interesting, you make it sound simple. I wonder if it is (simple)

You mention torque and wheel diameter ... do those affect the selection of motor size as well, or are they independent?

And I have a second question, about braking. Our robotics team uses Victor speed controllers with a jumper that provides motor braking by shorting the motor terminals. But given the momentum of the robot, it still doesn't stop right away.

I know if we put the motors into reverse, it stops very suddenly but puts great stress (and I imagine, current load) on the motors. If instead we were to arrange to 'pulse' the speed controllers between neutral(braking) and slightly reverse, would we be able to stop sooner without tearing the motor out of the robot, overheating the Victors and blowing breakers, or both?

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