Torque Calculations

[Dan Petrovic]

Disclaimer Not all of this may be correct. So please don't hold it against me if it is

Okay. Now's a good time to ask this question:

Does having two motors supply more torque? or does it seem that way because there is less load on each motor?

One of our engineers said that our stall torque should be around 25% higher than our required torque. This is to make up for friction. However, that only works if you know exactly where the center of gravity will be and exactly how much it will weigh.

We assumed what the weight will be and where the center of gravity will be so the required torque calculations were definately off.

We aimed to have half of 25% above the required torque (required: 100 lb-ft, stall: 187.5lb-ft)

Also, the center of gravity is roughly the middle of the arm. So if your arm is 60 inches, you should plan on the center of gravity being between 20 and 40 inches from the axel of the arm. (obviously...)

Make sure you are putting enough current into those globes. We made a big mistake this year and calculated what gear ratios we needed based off of the stall current of the FP motors. When we hooked it all up, we were only powering those motors at about 1/3rd the current we had expected and the arm didn't run. That only set us back about a week

Also, with that ratio. That arm is going to move very slowly. If you are planning on using it for a FIRST application, you might want to lower that ratio, cause as it is right now, you've got almost 17 times as much torque as you need. (34 if you lower that length down to 30 inches).

Also. I like working with lb-ft better than oz-in simply because the numbers are smaller and easier to work with