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Unread 08-08-2002, 22:53
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Gui Cavalcanti Gui Cavalcanti is offline
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Team Role: College Student
 
Join Date: May 2001
Rookie Year: 2001
Location: Needham, MA
Posts: 224
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Alright, let me get this straight, once again.

Alright, tell me if the steps for this are off, or if I have it right, or what.

To determine the gear ratios for your drive train by solving for torque:

- Your maximum pushing power is going to be the friction coefficient of your materials on whatever surface FIRST decides on multiplied by the weight of your robot and whatever you are lifting. You want to increase this number a little bit in order to spin your wheels/treads without burning out motors and breakers.

- Shoot for a peak torque/power/efficiency to gear from on the motors charts, making sure it's within current limits and the like. Divide the torque of your robot overall by the radius of your wheels (drive pulleys for belts). Compare the torque from your motors to the torque from your robot with the wheel figured to get the ratio you're shooting for in the gearing. Remember that gears lose efficiency (10% I believe for every spur gear stage). Figure out the gears you need.

- Now that you have your maximum pushing power, you determine the torque needed to simply move the drive train around. To do this, you buy all the gears and assembly your drive train and pull it around with a spring scale (*NOTE* What happens if you have a worm gear in there...?) to determine the torque necessary to drive your robot. Once you find that out, you plug that torque into your equations and figure out what torque the motor is outputting, grab the speed at that torque, and plug the speed into the equation. Out pops your robot's ground speed with that type of drive train.

*gasp* Ok then. That seems easy enough. Now, my question is, how do you make a drive train based on speed? Don't you need to know the minimum torque to move your robot around, but you don't get that until you put gears on it? (Enter catch-22) How did other teams deal with this?
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Gui Cavalcanti

All-Purpose College Mentor with a Mechanical Specialty

Franklin W. Olin College of Engineering, Class of 2008