[Tom Line]

We started with grade 2's. The only type of nut we use is nyloc. Those worked for 1 competition, and started breaking and falling onto the field.

We went to grade 8 with nylocs. Those worked for 1 district, State Championships, then started snapping on the Newton field during the finals match.

We've replaced the grade 8's that had broken at Championships and are running that way. I don't expect a problem: we'll check it after the Tardec competition this Monday, after Marc later this month, and then after IRI next month.

However, I think that this may be a larger problem for high-torque drives that are used a lot. The side force from the fasteners simply isn't enough to keep the sprockets from working, and that eventially snaps bolts off or causes them to loosen (nyloc or not).

That's why I'm suggesting some sort of mating system between the sprocket and the hub of the plaction wheel.

Admittedly, our robot got a lot of use this year at 65+ matches plus practice field time. In addition, we had a high amount of skid-steer drag during turning. We went with the longest wheel base that the motors could turn so that it would be difficult for other robots to spin us. It was ALWAYS the bolts in the double-sprocketed wheel that failed first (the rear wheel was chain driven on the inside and had an outside sprocket that drove the next wheel forward). We had one sprocket on the inside and one on the outside and were using laser-cut spacers that were essentially copies of the Andy-Mark ones.