Transmission Design Help

[JoelP]

Hi, I'm Joel from team 1155, the Sciborgs, and we are interested in designing a custom transmission in the off season. I've looked around the forums and read the other threads regarding transmissions and learned alot but I still have a few questions.

1. How do you calculate the minimum amount of torque needed to spin out the wheels to prevent the breakers from tripping? And how do you calculate the coefficient of friction of your wheels?

2. I've noticed in some other threads that a drivetrain efficiency of 81% was used. How was this efficiency calculated?

3. Which maximum RPM value of the motor is used to calculate the maximum output speed of the transmission, the free load, average load, max efficiency, or max power?

4. I know the efficiency of the transmission applies to the maximum RPM, but does it also apply to the maximum torque?

5. What are the pros and cons of using direct drive and using chain reductions?

6. I know that by using smaller wheels, I don't need as much reduction, but what are the other pro's and cons of larger and smaller wheels? Specifically 4" and 6" wheels?

7. I've made my own spreadsheet over the past few days to calculate things such as max rpm, max torque, and total reduction at various stages of reduction through the transmission, as well as Pitch diameter, center to center distances, total weight, and final speed and torque. Can you direct me to another spreadsheet made by someone more experienced to check mine against?

I hope that isn't too much to ask, but I've only been looking into this subject area for a few days. I'm also a software guy venturing into the hardware world, but I learn quickly .

Thanks for any help!!!.