Because the rear axle has no way of adjustment and the engine is fixed there has to be some way of tensioning the chain. It shows you in my plans how to build this very clever idea. First I had to drill all the "adjustment holes" in two pieces of strip steel. Then weld two more pieces of strip to make the shape as in the piccy oppersite.

Then out came the trusty old modellers lathe again. (I'd used it earlier to make the king pin,wish bone & swing arm bushes.) I had to turn two pulley guides out of Acetal bar. This stuff is a hard wearing nylon used widely in engineering for bushing e.t.c.. It's quite expensive for what firstly appears to the eye as "plastic rod" !!! Anyway it machines beautifully, and in no time at all I has the two pulleys complete with bearings inserted.

You can see how the tensioner is assembled in the piccy. It "squeezes" the chain till the slack is taken up. Note how the tensioner frame is pivoted. The clever bit is, as the top row of chain tightens up as the engine starts to drive the wheels, the tensioner frame moves up, moving the bottom pulley up, and taking out all the slack in the chain on the bottom row. The exact oppersite happens when the engine goes into "over run" when slowing down - the bottom of the chain goes tight and pulls the top of the chain tight. Simple but bloody effective I'll think you'll agree.