[TR] TR3 clutch pressure

[Michael Marr]

> You won't do it with air, I'd bet.  The difference between air and fluif 
> is that one is compressible, the other is not (for our purposes).  You can 
> put air pressure in until the cows come home, and I wouldn't think you 
> could move the arm enough to see anything.

I disagree - you could certainly do it with air, if you have enough 
pressure.  The relative compressibility of the two fluids is immaterial - 
pressure is pressure.  The problem is, your home air compressor will 
probably produce not more than 125 psig and this will not be enough.

> If you do the arithmetic...I guess it takes about 300 pounds to compress 
> the springs on the pressure plate.  I guess the piston in the slave 
> cylinder is about 3/4" in diameter, making the area somewhere around 0.44 
> square inches.  There may be some mechanical advantage in the fork lever, 
> but I don't think it's a lot.  So you're looking at maybe 600 pounds per 
> square inch in the pipe, delivered from your pedal.  Can that be right? 
> (The pedal, of course, has a huge mechanical advantage.)  Don't forget the 
> losses due to friction!

Yes, I would guess it is in the 300-600 psig range - I came at it from the 
opposite direction, however.  I assume that the effort required to operate 
the clutch pedal is about 50#, the mechanical advantage has got to be 4 or 5 
to 1, so, if the clutch piston is .44 sq ins then the pressure in the 
hydraulic system would be 400-500 psig.

Mike