Measure the pressure

At the weekend i took the clutch plates out of the motor and checked them out along with all the spares that i have. The verdict was that most of the clutch steels are warped or more precisely they have a cupped or dished profile, i split them up into good, bad, and somewhere between.
Only 5 are good.
And so there's a whole new set of both steels and fibers on the way, i went for the fibers too as mine are close to the wear limit but more importantly i have no idea how old they are, or what type they are. They are cheap enough individually but the whole pack is approaching £100 so the thing i really would rather not do is burn this one out. To reduce the possibility I've been doing some clutch calculations to work out what pressure the clutch springs can provide at any given Length of compression (installed height). It also means i can work out how much clutch base pressure i had on the last run i made at Shakespeare and replicate or add to it, as it was the best launch i had.

Working out spring pressure should be straightforward, especially if you have a decent spring tester..... which i don't. So i have to make do with what i can make and borrow - I'm sure the results will be the same they just take a lot longer to obtain. I welded up a jig of sorts and screwed it to the workbench, underneath i placed a set of scales. Working through 3 random clutch springs i measured and compressed, and remeasured in 0.2 mm increments, noting the pressure the spring was registering on the scales. After a couple of hours i had a table of closely matching measurements that i then took an average of. Hopefully the result was worth it, i now know the exact base pressure that one, or a combination of springs can give me with any installed height.
Once measurements of the clutch hub and pressure plate had been made i now have a method of working out the installed height of a spring according to clutch pack thickness.
All thats needed now is a selection of shims so that accurate changes can be made to the installed height.

The bike has had an oil and filter change, and valve clearances checked. The wheely bars are going for modifications this week too.... ready for the next race at santa Pod in just over a weeks time.