Thread: AndyMark Plaction Wheels
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Unread 27-03-2010, 19:53
RRLedford RRLedford is offline
FTC 3507 Robo Theosis -- FRC 3135
AKA: Dick Ledford
FRC #3135 (Robotic Colonels)
Team Role: Mentor
  
Join Date: Jan 2010
Rookie Year: 2009
Location: Chicago, IL USA
Posts: 286
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Re: AndyMark Plaction Wheels
We are running a chain driven 4x 8" -wheeled tank setup with dual-CIMed AM supershifter gearboxes on each side. As we entered the semi-finals of the Midwest Regional, we were losing staples and had to super glue the tread ends of one wheel. Then later in the semifinal, after not paying enough attention as to why only one chain was getting progressively looser after each match, we ripped a sprocket off that wheel, shearing bolts and shattering the sprocket, plus breaking the chain at the master link. Even though we had all six screws, they were low grade screws and several were slightly short and did not fully engage the nylon inside the Nylock nuts.

Because we have the dual sprockets on out gearboxes, with one chain to each wheel, our two rear sprockets are spaced away from the side of the wheel to line up properly with the dual sprocket of the gearbox. These spacers were not done right, and allowed too much flexing of the screws which finally worked themselves loose. This was the cause of the chain loosening, and by not zeroing in on the cause the problem went to self destruct stage.
We have now replaced all our KOP sprockets with new 22-tooth ones that do not have the six radial slots in them. We have replaced all our chains with 100% riveted chain (no master link & 50% higher working tension)). We have 1/2" diameter precision nylon spacers between sprocket and wheels. Screw heads are allen socketed (not slotted) so they can be seriously tightened. We now use Locktite blue on the the Nylock threads too.
As for tread to wheel attachment, after roughing up the plastic surface with abrasive paper, we are gluing the Roughtop treads onto the plastic wheels with GOOP Shoe Goo urethane adhesive. We use large hose clamps to compress tread material against the wheel overnight. This produces an almost inseparable bond.
We also decided to have spare upgraded wheels with sprockets mounted ready to go in case of failure. Handling the torque output of this drive setup demands that all components be made with top notch materials.

-Dick Ledford