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Unread 26-01-2017, 00:14
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Bob Steele Bob Steele is offline
Professional Steamacrit Hunter
AKA: Bob Steele
FRC #1983 (Skunk Works Robotics)
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Re: Polycord and polycord pullies

We use hex shaft and cut the disks for the poly cord out of 1/8 polycarbonate. We cut them on the waterjet but you could probably find a different way to cut them and then use a hex broach for the hole. (These are for driven pulleys or idler pulleys on a live axle) We are presently using 3 - 1/8 inch center pieces and two 1/8 inch outer pieces with a difference of 3/16 so that the round drive belt is 1/16 proud. This gives us a 3/8 spacing in the middle of the pulley with the two side plates....

Are you using a dead axle for them or a live axle? idlers can just spin on a dead round axle (with or without bearings if you use something slippery like UHMW for the pulleys.... )

In the past we have also used a piece of PVC pipe and glued on more PVC pipe cut from connectors as spacers between the belts. We put a hub inside the pipe on both ends and ran an axle through it. This worked OK but was not optimal although it was pretty cheap to make. The belts all drive together but you will have to put a sprocket on one of them connected to the motor (with chain) to put power to the whole assembly.
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