Monthly Archives: December 2020

Sleeve drive setup complete


Here’s the final sleeve drive assembly, complete with chain tensioner in situ. The distance between centres is as drawn, with the adjuster fully in to give the full travel as the chain wears. Shown in the orientation it will take in the engine on final assembly.

It looks right and with the 9 holes (3 sets of vernier adjustment) we can get to within a single degree of timing. Spot on!

The valve timing needs some thought still as the Hercules was supercharged, so the inlet opens late. Static timing can be set with the drive sprockets, however, the relative timing between inlet and exhaust can only be changed by re-shaping the holes in the sleeve. I only have one sleeve so that’s a one way operation.

How much is too much? You will only find that out after you’ve done it and there’s no going back. Hmmm..

Test bench.


So my trusty bench is going to become a test bench, for real! Nick asked whether the new gearbox would fit on the Churchill lathe. His idea is to make the control electronics and troubleshoot now, rather than when it’s all together in the bike frame. Makes sense to me.

However, while it’ll just about fit (the Churchill has a 12" throw) I don’t want to tie up such a useful machine for any length of time. A quick call to Matt and a spare motor was dropped round a few minutes later! Got to love having a good engineering mates community:-)

The motor is flange mounted and happens to rotate the same way that the engine will. So, with a bit if cobbling around I should be able to make a test bench and drive the torque converter (Tc). The first thing I will be able to uncover is the direction the Tc is designed to rotate! I have a sneaking suspicion that it’s the ‘wrong’ way, i.e. opposite to the engine. Time will tell…

Sleeve drive centres final adjustment.


The sleeve drive sprockets are machined up and the chain fitted. The distance between centres is critical and the chain length dictates that. The distance we’re chasing is 7 inches, which the chain adjuster helps – but the critical distance unfortunately falls between links.

The engine cases will need to be bored for the bearings, so the centres can be moved to provide a small offset. However, changing the centre of the sleeve drive crank will change (raise in this case) the maximum height of the sleeve. This in turn means that the barrel will need to be raised, lowering the compression ratio.

Important to nail this now before machining the cases. I think a maximum of .1" will bring the chain length, tension and adjustment within acceptable limits.