6 wd, what wheels to power

[HarveyAce]

In the 6 WD configuration, is it better to power all 6 wheels with a chain or would it be better to simply power the rear two with the chain? The middle wheel is dropped.

[Billfred]

By powering all six wheels, 100% of your robot weight will be on driven wheels. This will, in most every case, improve your ability to push another robot.

(For more fun, you might want to spend a bit of time playing with JVN's excellent mechanical design calculator. While not a substitute for Really Knowing What You're Doing, it can find some interesting attributes of your planned design.)

[Vikesrock]

In addition to what Billfred said, there is a big issue wit powering only the rear two. A 6WD drop can rock a bit between being on the front 4 wheels and the back 4 wheels. If you power only the rear 2 wheels when you rock to the front 4 you will not be able to drive very well at all (the others may still touch some and give you slight traction). If you were going to power any set of two it should be the middle, but I second the recommendation to power all of them.

[skimoose]

With a drop center design, if you were only thinking of powering two wheels then it should be the center wheels as the rear wheels can leave the carpet. However, the whole point of 6WD is all six wheels are driven.

[Teched3]

Just to add that you should chain from the motor to each wheel individually. If you lose a chain (or more), you will still be able to maneuver.

[Mr_I]

We powered all six wheels; the KoP drive train has a dual sprocket at the transmission, so you can get two of the wheels on a side powered easily. (Just remember to swap the spacers on one of the axles, I'd recommend the non-middle one, so the sprockets align better.) Then all you'll need is a pair of sprockets and a loop of chain to reach between the middle and the other non-middle wheel.

The only other caveat is to make sure that the wheels powered directly from the transmission must have the same size wheel sprockets!

[Swampdude]

If you get a chance to watch the 2007 Einstien finals, you'll see our 6wd robot that is only driven on the rear 4 wheels playing defense quite nicely. And if you watch the Florida Regional finals of 2008 you'll see our 6wd robot with only the 2 center wheels driven do quite nicely as well. I think the key of 6wd is keeping the CG on those center wheels - or at least over the set of 4 that are driven. You also need to lower those center wheels at least 3/8". I think you should drive all 6 when you can't consistently balance the majority of your CG over the driven wheels. But if the bulk of your cg is consistently on your rear set of wheels, driving the front set won't help much. The magic of 6wd is only (1) of (2) sets of square wheel patterns on the floor at any time, vs a rectangular linear 4 wheel pattern adding drag during turns.