So in the wheels post, I mentioned how I had made some lexan wheels. Lexan is a name brand for polycarbonate plastic sheets. They are tough and durible. I wanted to write this so that other members that did not read the post can maybe see some of the things that I did and maybe use them themselves.
Well I found that Mcmaster-carr will sell 1/4 inch belting by the foot, so you can basically make the wheel as large as you want and still be able to apply the traction control that I was talking about. The link for the mcmaster site is here: http://www.mcmaster.com/#timing-belts/=1kftrd
I used the singel sided with the trapazoidal teeth. What you use is entirely up to you. The belts that I used were already prejoined and that is why I had to use a mill and mill down a piece of plastic to the right diameter so that I could put the belt in it. They have various sizes, that way if you have large wheels, you can get larger belt and have the added traction. I am not sure how they will hold up on rough dirt terrain, but it is a viable option. I also had the idea that if you used a mirrored plastic wheel with the mirror on the inside, you could use like a photoeye or some other decector and draw a line on the wheel if you need to monitor the number of revolutions. I found mirrored plastic on this site: http://www.estreetplastics.com/Plexiglass_Acrylic_Mirror_Sheets_1_4_thick_s/54.htm
unfortunately they only come in 1/8 and 1/4 inch sheets, but the possibilities are boundless!!! When you use a mill to make the circles, you have to center the piece on the chuck. What I used was a socket headed capscrew and used the centering tool pressed into the screw to make sure it was center. Then I milled it down and viola, I had a nifty wheel. I screwed the horn for the servo into the wheel itself. That way it would turn duh!!! If you have any questions, I will check this post and try to answer them. I think that the sheets are resonable priced, but for those on a budget, I guess you could use a file and file the edges of the plastic away until you got to the circle you wanted.