[jimfortytwo]

For what its worth, I have compared free speed extrapolations to ground speed measurements for all the robots presently in our "garage." The trend is pretty obvious.

2001: two 3/8" drill motors
32% 6ft/s real, 18ft/sec projected

2003: two 1/2" drill motors in high
38% 10.5ft/s real, 27ft/sec projected
(resulted in intermittent breaker and controller resets!! )

2003: two 1/2" drill motors in low
68% 5.6ft/s real, 8.2ft/sec projected

2004: two 1/2" drill and two CIM
78% 7ft/sec real, 9ft/sec projected

You can see that our "speed efficiency" rose dramatically once my team started choosing reasonable gear ratios. If you were to take these speeds and work backwards to the assumed load on the motor to get that speed, and the resulting current draw... the currents are astronomical, obviously. I hate to think what was happening while we were turning. I've always wanted to use a clamp on meter to find out if all this empirical data is self-consistent.

Oh, and for all of these tests I also did a "wheels off the floor" rpm measurement, which without fail was very very close to the free speed expected. Take this measurement, and just see if robot weight on those axles doesn't somehow make a difference.

As far as our measurement methods, we timed the robots on the ground over a 50 foot window following a 30 foot accelleration zone. I imagine that was fairly accurate.

Given this history, my adjusted calculation to estimate the speed of our kit-built competitors was 6.3 ft/sec.