AndyMark Plaction Wheels

[jfc358]

Has anyone else had problems with cracking of this wheel? We lost an entire segment of the rim, spoke to spoke, on one wheel yesterday and had to splint cracks in another. This appears to be happening when going over bump. Cracks seem to form on outside of facing side of wheel first and then propagate through wheel. Since the robot never comes down off of the bump completely square to the floor, the outside of one rim takes more of the impact. This is what we think is causing wheel to crack. At least that is what appears to be happening.

[Madison]

Our 6" plaction wheels started to exhibit cracking in the spokes almost immediately after we started going over bumps at competition weight.

Mistakenly, I ignored the crack in our competition robot wheel, as it was only on one half of one spoke. In semifinal match 1 at the Seattle regional, the wheel shattered into three pieces, splitting at each of the three bolts we were using to attach the drive sprocket.

We were able to swap in a wheel after using our time out and run semifinal 2, though because it was our front wheel, we couldn't make it over the bumps. We ran chain again before the finals and were back in full working order.

As mentioned earlier in this thread, we'd now recommend that all teams use all 6 bolt holes on these wheels.

[M. Mellott]

It seems like everyone is using the Andymark wheels with the standard 1" wide tread, but did anyone besides teams 3193 and 48 use PVC spacers to widen the 6"-diameter wheels to 2"? We had success with them using black nitrile treads from McMaster in our 8-wheel drive, but we too had issues with the tread coming off when we tried using staples like the original AM treads. Two 1/8" rivets (1/2" long) drilled into the PVC spacer worked great.

However, we found another issue: when mounting sprockets, you have to watch how hard you tighten the bolts on the hubs, as there is no support between the hubs because of the spacer. We found a couple cracked spokes, and we found one wheel had all six spokes one one side broken through after our last quarter-final match in Cleveland. If...I mean when we use these again, we'll definitely look to add spacers at the center of the wheel so that the hubs are not squeezed and stress isn't transferred to the spokes.