[Joe Johnson]

This forward/reverse thing comes up very often.

Let me just say that I am skeptical still.

In general, we have not bothered with such things. I have gotten 12V speed-torque curves (actual test data) from the manufacturer (not only do I call these guys constantly begging for them to donate motors to FIRST, but my day job more or less involves using motors and gears to make doors open, grind coffee beans, etc...) which tells me that at least at 12V, there shouldn't be much of an effect (less than 10% difference from forward to reverse as I recall).

BUT...

Jim Zontag of the Killer Bees, Mike Gray of the HOT Team, Raul-the-Magnificent of Wildstang, and a host of other folks wise in the lore and magic of FIRST tell me that I am just plain wrong on this issue.

What is a rookie to do?

Well, I suppose that if you are using 4 Wheel Drive or Tank Drive, you shouldn't worry much about it at all. In years when we have had 4 wheel drive, our robots go straight with only 1 side driving. In order to turn we had to drive one motor one way and the other motor the other way -- really. In such cases, it seems hard to argue that a small effect like we are discussing will make any noticeable difference at all.

If you are using 2 wheel drive with castors or have somehow compensated for the scrubbing effects of multi-wheel drive (for instance by using 6 wheel drive with the center set of wheels 1/4 inch lower than the outer wheels), then your robot will not be so intent on going straight. In these cases, if it is easy for you to turn the motors around so they are going the same direction, I say do it. Why not? If it is not easy, finish your robot early and get enough driver time so that they can compensate.

I know I am muddying the waters a bit, but I think it is important for folks to realize that it is far from clear what to do in this case.

Experts disagree...


Joe J.