Originally Posted by n4zou

I have a bike with a 3-speed SA hub with a triple crank and FD. This gives me 9 speeds. I used an old RD with a broken cable clamp to take up chain slack. I just used the limit screws to lock it in front of the cog. My chain rings are 48-38-28. The only modification required was thinning the cog so it would accept 3/32 chain instead of 1/8 chain as the 1/8 chain is too wide for the front and rear derailleurs. I have a metal lathe so I chucked the cog up and machined one side and used a file to correct the profile of the teeth on the cog after machining it. You can find cogs ready made for 3/32 chain. Check your cog and see if 3/32 chain will run on it. I did a bike like this for a friend and the cog on his hub fit narrow chain nicely without modification. In his case it was a simple assemble and ride setup.
You can't use a SA hub with coaster brake! Using the coaster brake will destroy the rear derailleur.