Electrathon America Forum

Jim,
WHS does not do it 'precisely' but we can get pretty close. We set up a 'blank' rear sprocket in a lathe with a thin ~1" piece of 16 gauge sheet metal between the teeth of the sprocket and the 3 jaws of the lathe (jaws on the outside gripping on the outside of the sprocket). Then we check the existing 1" hole to see that the hole is centered in the lathe using a dial indicator. From there we machine out the center hole until the freewheel just snaps into it. Drop in the freewheel, drill 4 - 1/4" holes that match up to the teeth on the freewheel. Put in 1/4" button head cap bolts and nuts. We use washers that are flattened on one side to catch the teeth on the nut side so the bolt can be very close to the center of the freewheel and bolt it together. Sometimes we need to grind off the outside of the button round bolt head bolt and one side of the nut so they don't put pressure on the inside of the freewheel or it will not 'spin' correctly. If the student is good with the lathe they usually come up with a nearly 'precisely' centered sprocket without much change in tension as the sprocket turns.

Another problem is that some of the freewheels themselves are not concentric and they cause problems or the motor sprockets that we purchase are not completely concentric. So again we seldom are 'precise' but can be close enough that the change in tension is minimal and does not cause a problem. I tell my students to be sure that they check for it and adjust their motor so that it is not 'too tight' at the tightest point and hopefully it is not so loose it falls off and the loosest point.---GOOD LUCK