6WD vs 8WD

[kramarczyk]

Originally Posted by Hawiian Cadder

... the goal of having the outer wheels raised is to make them act more like omni wheels. for the purpose of the argument imagine all we care about is drive systems with omni wheels on the corners.

You may want to look further into this assumption.

As you raise the wheel (or increase the center wheel drop) you decrease the load on those wheels. Yes, it decreases the sideways slipping force on the wheel, but it also decreases the tractive force in the same proportion. The first point is that it never really behaves like a omni wheel, just as a wheel with less traction.

The second point is that the load drops off across the distance of your wheel dropped (teams range from 1/16-1/4") which makes it hard to tune. I worked with an adjustable drop 6WD for a few years and we discovered that 2-3mm drop was what worked for us as optimum. Outside that sweet spot we began to get significantly different driving performance. We also discovered that a 1/2 day of matches was enough wear on gum rubber treads to get us outside this range. We eventually decided that it was not worth the effort and decided to let the wheel off the ground and allow the robot to rock between the two 4 wheel systems. It was much simpler in the long run and allowed us to apply our resources elsewhere. I know the 2011 kitbot configuration has enough lift to accomplish this.

You may want to spot check with teams to see if all of their wheels are actually on the ground or just really close. How might having one set of corners off the ground affect the logic you used above?