Friday 27 November 2020

The Chain Tensioners

As with the AJS K7 restoration and the AJcette project a Weller chain tensioner is required. The only difference with the V-Twin engine is that 2 are needed but, otherwise, the principles are identical to the earlier single cylinder K7 engine.

The first task was to generate and fix 2 strips of ertalon 4.6. This comes in round bars and must be machined into flat strips before it can be used.

If this were a piece of steel it would be possible to clamp it at both ends and machine one side in a single operation. Unfortunately the flexibility of the material does not allow that and it requires clamping in the middle and machining the flat in 2 operations on each side. After one side has been finished it can be turned over and the other side machined.

And, eventually, there are 2 flat strips of ertalon 4.6 ready to be fixed to the timing case.

On previous engines, these were fixed with copper rivets. This method of fixing could not be used here because of the difficult access to the lower fixing holes on the front cylinder that prevents riveting, namely that the rear cylinder part of the case gets in the way. In fact it was not even possible to drill holes easily due to the difficult access and these lower holes were spark eroded.

Each hole was tapped carefully turning the tap with a spanner from the inside of the casing, the strips were drilled and countersunk and attached to each surface with brass screws and a specialist adhesive.

As with the K7 and AJcette, the springs and blades were made by Alberta Springs and, with blade pivots and the spring tensioner retaining guides, aka the reaction dampers

The complete Weller chain tensioner could be installed

At this stage, there was still a dummy shaft and sprockets for the drive to the camshafts and the next task was to make the  bearing housings and camshaft to fit inside the Velocette camboxes.

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