There are elements of this topic which have been touched on before but I admit I can’t find them so at the risk of duplicating stuff here goes.
I have no choice but to fit a centrifugal clutch in the beast, just not enough room for a T/C.
See if you can resolve the problem I have.
Basic Info you will need.
If you need more I will get it to you ASAP.
I am using a 428 chain and the smallest matching drive sprocket available on a centrifugal clutch has twelve teeth and that is what I am using.
It is driving a 60 tooth sprocket keyed onto a layshaft, giving the layshaft a reduction ratio of 5:1, (60/12).
A second gear, also keyed onto the layshaft has 31 teeth and this drives the diff on the rear axle which has a sprocket with 55 teeth. This is a ratio of 1.8:1 (55/31) therefore the overall ratio from engine to axle is 9:1 (5X1.
.
Now this seems very low I know but……read on Mc Duff.
I am using a tuned engine, just a little beyond stage 1 I think?
The engine mods are:
1. Tuned exhaust (F#).
2. High-lift rocker arms.
3. 30° valve seats with radiused valves.
4. New BIG re-jetted carb.
5. Stronger valve springs
6. Billet con-rod.
7. 4° advanced crankshaft timing.
8. Billet flywheel.
9. Governor removed (of course, nearly forgot that).
This lot should safely produce around 12 hp at 9,000 rpm.
The reason for this is not just to thrash Jimmy-de-Fish (:>)) but to get the beast moving sharpish off the line.
My new clutch will start to grab at around 1,800 rpm, and this means that the engine will be pulled down by the load because we are short of the rpm where real torque becomes available.
What do I do?
?
I think I am now approaching the bit that was done before and that is modifying the clutch so that it doesn’t start to grab until the rpm is much higher, overcoming the lack if torque issue. Say 3,000 rpm. These clutches seem virtually indestructible so I don’t think that will do any harm.
But how do we change the clutch so that it behaves like that?
The clutch in the T/C has springs which act on the weights and theses can be changed to make the clutch behave more in the way you want it to. Can’t do this with the ordinary clutch like wot I have got.
Thinking about it, the forces acting on the clutch’s friction surface are proportional to their weight, the internal diameter of the clutch housing and the engine rpm. (Check Google) The heavier the weights are the sooner the friction surfaces will contact each other for a given rpm, so the lighter they are the later they will grab………|Mmmmmmm.
Are we onto something here?
Well, thats my thoughts on the matter so far and now all I need is a spreadsheet which tells me how heavy the weights should be to begin biting at 3,000 rpm in a standard centrifugal clutch.
After that of course, you need an engine that can produce extra, useful revs to get the top speed out of it. This I now have.
First person to come up with a definitive answer will get a very special award, from me, at next years AGM.
Do you take sugar?
