Sunday, May 20, 2007

Alignment woes...

So with the motor's pending arrival it is time to start thinking about fitting bits together - the gearbox will be a reasonably quick job to refurbish, it is time to start planning ahead on engine plates, spacing and drive trains.

Using a Norton gearbox, this will be the only part that will be fixed laterally. The engine, having its mounts narrower than the engine plates, has room to adjust side to side in order to align the clutch and engine sprocket. With the plans to use a belt drive, this has to be spot on to stop the belt wandering off. I will be using a double sided gearbox adjuster to stop the gearbox twisting under load. As well as the engine and gearbox being lined up laterally they must also be spaced suitably apart for the primary chaincase to fit, and using a belt drive, the belt must fit within spec - belts are not made in every conceivable number of teeth and the permutations are not limitless. The gearbox centre should also be below the centreline of the rear swingarm when the rear suspension is loaded. This is so that when the power is applied, the force on the rear sprocket is such as to pull it down more in contact with the road rather than pull it up away from the road. Also the nearer the gearbox shaft is to the swingarm pivot, the less the variation of the distance between the gearbox and rear sprockets as the suspension extends and compresses. This is kinder to the rear chain. So that is the gearbox.

The rear wheel has some movement side to side by fiddling with the axle spacers, and adjusting the rim offset to suit. Things to be careful of are compromising the rear brake plate torque stay mechanism, and the chain clearing the swingarm. The Gearbox sprocket also has some lateral adjustment by using shims or offset sprockets, so even though the gearbox is fixed, the sproket alignment is not. Of course, the same is true with the clutch. It is also true with the crankshaft sprocket.

So, if I haven't confused myself, I put in the gearbox, adjust sprocket to rear wheel, adjust rear wheel to gearbox, put in engine and adjust to gearbox, shim sprocket to get spot on and Bob's your uncle, I will have a drive train.

So with all this thinking about alignment, I am going to have to get my frame trued before I start putting things in it, or all will be for naught. I guess I am going to have to make my mind up on my rear wheel too. And who I am going to get my engine plates from. Should probably figure out my primary cases and order my belt drive while I am at it. And then I have to decide what sprocket sizes and chain guage to use. I guess I should quit worrying about alignment for now, and go back to collecting parts and upsetting my bank balance...

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