Well I hope everyone had a great Christmas and a good New Years celebration. I slept through the latter.
I have been fitting the sprocket with the Worksman freewheel acting as a carrier. Pics are easier than words in this case(a hard thing for me to admit).
I bored out the center hole of the sprocket to a friction fit on the freewheel.
As you can see this entered into the original bolt pattern of the sprocket. I decided to use these "partial" holes as locators for four pins(turned down some socket head bolts) tapped into the freewheel sprocket. A slight taper on them helps with location.
I would also use four sets of teeth to bolt the sprocket to - thus the sprocket carrier term. Since the teeth aren't that long, I brazed up some half step spacers to complete the surface under the mounting nuts. They are a combo of a smaller and larger washer. I could have ground them to the same diameter but just didn't care to. All in all this will give me eight points of contact with the freewheel. I then used an indexer to locate eight holes symmetrically around the sprocket and made eight 1 1/2" holes.
Here's how it all fits together.
A quick word on sprocket/chain sizes. It is often said that any #40 or #41 sprocket/chain combo works. Indeed these are both 1/2" pitch but the roller width of a #40 chain is 5/16" and is too wide for the 1/4" #41 sprockets. It would work but these are shortcuts that make for a hack job that will soon fail. A loose floating chain will at best wear out quickly. There is a .0065 inch difference in the roller diameter but that will be okay. In my case the narrower the chain (as long as it's motorcycle size) the less trouble with interference with the seat stay or bottom bracket.
My advise would be go with the common #41 sprockets that are common with the jackshaft kits and use a 420 motorcycle chain. This keeps the pitch at 1/2", the width to 1/4", and the rollers to 5/16" Everything matches perfectly, is the narrowest reasonable combo, and is stronger than needed for such a project. An alternative would be to use true #40 sprockets(wider than the kit sprockets at nearly 5/16") and #40 chain for a thicker look that is still stronger than the #41 option.
Remember without cush drives on these things, chain wear could be an issue. Whatever you do, don't run a solid rear cog(without freewheel) as the motor breaking will likely unscrew your cog from the hub in quick order likely with violent results.
