[sanddrag]

I'd say the simplest very effective (fairly fast and fairly powerful) would be what 696 did in 2003 and 498 did in 2004. http://www.team696.org/forum/image.php?iid=164 You gear down the Chia 3.5:1 to match the drill in high gear. Then you gear down the drill whatever (ours was 4.8:1) to the wheels (we used 8 inch). It all uses chains and sprockets and kit pillow blocks. All you need to machine is shafts and spacers. (I suppose if you have keyway shaft you could cut and grind that to length to make it even less machining) Since it has multiple pillow blocks and mounting points and stuff that lie on the same shaft (and since we used compressable nylon spacers underneath), binding and misallignment became an unavoidable problem. Also, aligning and tensioning the chains was always a problem too, as was high current draw. But, this was a very easy to build very fast, powerful, and RELIABLE setup. There was a lot of maintainance due to sloppy contruction on our part, but the only time it actually failed is when we threw a chain (to the wheel) by hitting a wall at full speed. another drawback was the weight - with steel sprockets and chains and shafts and 5/8 bearings and thick pillow blocks, it was no lightweight. However, I think if it was mounted rigidly in good alighment with properly sized parts (like 498 did in 2004 improving on our 2003 design), it would work very well. It is very easy to make, and it will definitely work - and work fairly well too.

If you are looking for a great little lightweight gearbox with a nice low output speed and are up for a bit of machining, I too would recommend the 716 2003 Single Speed. Both 696 and 980 as well as others used it with great success in the 2004 season. It is a bit more involved to make than the above (it was the most machining we'd ever done for anything) but is still quite simple. The gearbox itself was (and still is) flawless all season long. We made a few changes to the original design but nothing major. One thing we did have problems with however was the reliablity of the Bosch drill transmissions in low gear. I think we had to perform a swap maybe four times over a scrimmage and two regionals.

If you have any questions on any of the above, let me know.