Found what I was looking for that was tucked away, my Hyperdrive parts. A belt drive transmission seems like a good place for it to get used. So I drilled up my outer hub with 4 more holes so I can use a 3 screw spur pulley mount pattern.
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Then I found 2 problems. The Hyperdrive spur pulley uses an 8 hole pattern so I can't use 3 screws, and it also uses the larger diameter pattern. Doh!
So I drilled up my last MRP Ripper outer hub with a 4 screw pattern. Problem solved.
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The Trackmaster got disassembled and reassembled with the motor plate on the opposite side, so I don't need a reverse rotation motor because of the Hyperdrive setup.
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I still need to put together a pressure spring assembly for the slipper. But for now, everything seems to fit together correctly.
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It seems like these Hyperdrive spurs are only intended to be used with a 6 gear hub setup. That just adds to the fun

Also, it sounds really excellent when it spins up!
Frankensteined RC10T3 / Franky Jr RC10GT-e (x2) / A+ stamp / Toy Story RC / Graphite replica / B1.5 BFG 5LTi / Clonewald / Hyper Hornet
"I love the effort, but it sure looks like you took the long way around to a tub again"