SA Front Dynohub Problems
I apologize that I am a bit of a rookie in terms of knowing how my bike works inside and out. With that in mind...
So I picked up one of these old front dynohubs (from e-bay, sigh), but I'm having issues. First of all, after carefully disassembling it for cleaning, I noticed that there are no ball retainers, so I tried my best to just repack the balls (also there were 9 in there, while the schematic says 8 1/4" in a cage). Second, whenever I rotate the axle, the cones tighten/loosen. The bearings on the non-magnet side seem well supported, but the ones on the other seem to easily fall into the middle. Is this tightening caused by the bearings near the magnet side falling into the middle and not providing support against the cap?
Here's a blow-up of my hub, and I apparently don't have the ball cages: http://www.users.globalnet.co.uk/~hadland/sa/sagh6.pdf
Edit: I also noticed that the ringed edge of the cap is not perfectly straight and wobbles slightly like a warped record.
Is this thing a piece of junk, or can it be fixed? Are replacement parts even available?
Last edited by jasminereeds; 06-25-10 at 04:11 PM.
I've never played with one myself, but a bit more information via the late Sheldon Brown and Chris hayes can be found here: http://sheldonbrown.com/dynohubs.html
You should be able to replace the balls/retainers with nine 3/16" or 1/4" steel balls (check to see which is proper) without a problem. The dyno side cone gets threaded onto the axle and then the dyno armature is tightened up with the washer and dynohub side cone locknut. That gets put together real tight. Then, put the dyno side balls into the race in the shell, spaced evenly and well lubricated with appropriate grease. They will stay in position as you lower the axle/dynohub assy into the hub shell mating the cone nut with the balls. Hold it together so that the cone can't fall away from the balls and secure the axle on the dyno side into a vise or other method of holding the axle. Lube up the race on the non-dyno side and put the balls in place, insert the grease retainer (LB405) and screw the cone down onto the axle until it firmly contacts the balls. Then, adjust the cone for proper preload. This is a little tricky with a dyno hub as rotating the magnet around the armature causes magnetic, not friction resistance. Play with the tightening and loosening until you have just enough contact to eliminate any side play at the rim. Not too tight, just tight enough. Then hold the cone in position with a 16mm cone wrench (which you may have to grind to get a perfect fit as the flats may be slightly recessed into the hub shell) and tighten the cone with the lock nut (LB155). If you hold the axle tight and spin the wheel, it will rotate well. Trying to feel for proper cone tighteness at the axle doesn't work well because of the magnetism.