[Qbranch]

Before you start, really do consider tires if this is for a FIRST robot. We used tracks in '04 and '06, and found tires to be far superior ('08). 6WD or a 6x4 have proven to be great drive trains.

For us, a sliding/clamping tensioner proved very effective. Our favorite and lightest tensioning scheme was on our '06 robot. The last wheel mount point was on a seperate piece of aluminum which has a slot milled out of both of it's sides which slid in and out of a groove milled into the main part of the frame rail. So, to tension, you just took something like a screwdriver and pried the tensioner away from the frame rail hard as you could, then tightened two bolts that clamped down the tensioner (the two sides of the tuning-fork-like cutout in the end of the man frame rail). As a note, the only problem with our '06 robot's track system was in the design of it's bearings: the design of the bearing mounts had too loose of tolerances, which allowed the end sprockets to deflect slightly, allowing the track to work itself off if hit from the correct angle while doing a turn. As a redesign, simply taking more time to make each bearing pack would have eliminated this problem.

We used BrecoFlex both in '06 and '04 on custom FDM sprockets.

-q

p.s. If anyone wants a picture of the tensioner clamp system, just let me know and I'll see if I can dig up one or two to post.