Ah, the number of spectacular failures we’ve had.
In 2006, the Pi’s rookie year, the team had a belting company sponsor us. The team decided on treads, and the company supplied us the softest durometer natural rubber they had. At 30 lbs the robot was pushing people across the carpet. At 120, when it turned, the treads went straight and the robot stepped right out of them. They pulled the treads mid-competition, refit wheels, and never went back. However, they had a single match where they hadn’t finished yet, so they put the bot out on the field without any wheels. No one said they had to move, right?
In '07, we had a spring counterbalancing the arm. The spring was strong enough, but the 1/4 bolt holding it wasn’t really. I wasn’t there for the catastrophic failure of approximately 400 lbs. of spring tension. Thank goodness. Gas shocks are your friend.
'07 banebots. 'Nuff said. Never went back - but we’re giving them another shot this year. We have Andy Mark planetaries already here as a backup, because when you buy from Andy Mark you just know it works.
In '08, we went for a 6 wheel omni wheel setup. 4 oriented front to back, and two sideways. Unfortunately, we didn’t have the foresight to make any spring loaded. Ever tried to make every leg on a 6 legged stool touch the ground at once? Our drivetrain was quickly rebuilt and frankly was never where it should have been that year.
Also in '08, we built a forklift. We ordered Bishop Wisecarver ball bearing linear rails. They strung us along for 4 weeks, telling us the parts were coming, before finally telling us we’d never see them. We built the entire 3 stage lift system out of igus slides, and used them in a manner I’m pretty sure that Igus never intended. To this date, we don’t talk about Bishop Wisecarver without nasty glares.
In '10, we tried a linear kicker. Linear bearings from Mcmaster car on precision ground steel rods. Total stroke of 6 inches. 3 inch wideup with a 3 inch slowdown after hitting the ball. It worked great on paper. In reality, we shot 1/4-20 bolts across the room into a couple 4x8 plate glass windows.