[Doug G]

Originally Posted by dlavery

"..... the easiest solution is to just measure the mechanical drag. Connect a spring scale to the front of the robot, pull it over a known distance in a measured time increment, and calculate the force needed to do the task (disconnect and remove the motors so you don't have any back EMF concerns). The difference between the measured force and the theoretical force will be the measured drag.

If you are trying to do this for a future build, and are not characterizing an existing machine, then the problem is slightly harder. The best suggestion is to still measure one of your existing robots, as that will give you a ballpark estimate of the drag on a robot built with your production capabilities. Then add 10-15% to give a conservative estimate.

Salik,

I suggest you do just as Dave suggests. We have an accelerometer and a force probe that can easily measure the Force required to travel at various speeds and accelerations (hmmm.. 2nd Law) using the two robots from past years. Then compare the results to the theoretical torque output by those transmissions. This should get you close to a mechanical drag coefficient.

Regarding the efficiency of the chain drive. Can anyone comment on the differences they've experienced between a direct gear driven setup vs. a Chain driven setup? I remember the Bionic bulldogs (60) using a direct gear drive in 2001(?) and 2002 and then went to chain in 2004. I suspect the efficiency of a chain drive depends on the size of chain and how well it's tensioned.