I had to look it up cause I couldn't actually quite remember how I did it....
So I welded a piece of tube on to the tensioner arm, pressed a couple of bearings inside and had a 10 tooth sprocket running against the chain.
It's on the topside as the axle is in front of the drive sprocket, hence the "slack" part of the chain was on top.
From memory there wasn't much pressure on the chain, just enough to keep it from jumping.
Thankfully my welding skills have improved somewhat since those days.....
