I spent the day replacing my Shimano freewheel based intermediate drive with a Shimano freehub type. The freewheel holds only 5 gears and they are fairly heavy. The freehub is a newer, lighter hub made to accept the best gear clusters money can buy. I had an old Shimano Dura-ace cluster that I thought would better serve my HPV including a total of nine gears, and a smaller low gear for more speed.
It was a messy job - You have to take apart the freewheel to remove the pawls. Pawls are the little 'clicks' you here when you spin your wheel backwards. They allow you to drive the wheel when peddling one way, but spin when peddling the other. Since I am simply using this hub to hold my gear cluster for an intermediate drive, I don't require the locking-in of the pawls. When you pull apart the freehub, no less than one million tiny ball bearings spill out and roll everywhere. The only way to hold them in place during the reassemble is to coat the bearings with enough grease to stick onto the side of the bearing wall. I removed the pawls and put it back together, then put on my nine speed cluster and tried to figure out how to fasten the whole thing to the frame of the bike. I'm using an old axle as a bolt and simply bolting the entire thing including the derailleur onto the frame. Seems to work just fine.
Since the large gear is a bit smaller than the old freewheel 5 speed, I had to move the cluster further to the left to get the chain centered above the drive gear on the wheel. In so doing, my handlebar stem now hits the chain during a right hand turn. As part of the solution, I cut down the stem to lower the handle bars and I will add a metal chain guide to hold the chain onto the big gear during a sharp right hand turn when the stem wants to pull the chain off the gear.
Tomorrow, I'll finish the chain guide and start work on breaks and shifters for the front and rear derailleur. I might try to clean-up and simplify the handle bar system also.
Sticking the bearings back onto the freehub.
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