We used them last year on "SPYKE" our robot. You can see them on each of the sides. It had great pulling/pushing power. We would put people on the stretcher and take them up and down on the ramp last year. We would use them again this year but we want to be quicker. And we put some heat sinks on them with fan to keep them cool.
http://www.geocities.com/mhsfullmetaljackets/spyke.html
Tony
Captain 393