The most important application of motors in FRC is the drivetrain. Since driving moves motors from Stall Torque to Free Speed repeatedly it is important to consider the Sprint Distance that you want to optimize. Here is a list of the other requirements your drivetrain should meet.
- Sprint Speed should be optimized
- Pushing Force should be optimized if you have a second gear
- Current per Motor Channel should not be exceeded under sprint, wall-slip and turning conditions
- Current per Main Breaker should not be exceeded under sprint, wall-slip and turning conditions
- Bus Voltage Drop should not be excessive
- Battery should support sustained current draw for duration of match.
Focusing on the sprint speed requirement you should consider what the most important traversal your robot will perform for this year's particular game. Last year, FRC687 optimized for a 12 ft sprint distance since that was 2/3 of the distance to the far tote goal.
Then you should consider the motors you will allocate to your drive. In this case, you might choose between a six-CIM drive and four-CIM drive. The drivetrain calculators below are very powerful in that they simulate the acceleration of the robot during a sprint and can give you an accurate picture of the performance of your drivetrain at different gear ratios.
My drivetrain calculator, which borrows heavily from JVN and JesseK, allows you to input your desired drivetrain and identify the best gear ratio for that scenario directly by reading the graph of time-to-distance vs. gear ratio. You can access it below.
JVN
http://www.chiefdelphi.com/media/papers/2755
JesseK
http://www.chiefdelphi.com/media/papers/2274
FRC687
http://www.chiefdelphi.com/media/papers/3086