mechanical vs hydraulic clutch physics
mechanical vs hydraulic clutch physics Why is it that hydraulic clutches are easier to use than cable clutches? By my reasoning
Pedal force * pedal travel = throwout bearing force * throwout bearing travel
should apply to either type of clutch (work in = work out). So assuming pedal travel and the pressure plates are the same, the pedal effort should be the same. Am I missing something? Or are cable clutches limited to a shorter pedal travel for some mechanical reason? Something doesn't add up.
Pedal force * pedal travel = throwout bearing force * throwout bearing travel
should apply to either type of clutch (work in = work out). So assuming pedal travel and the pressure plates are the same, the pedal effort should be the same. Am I missing something? Or are cable clutches limited to a shorter pedal travel for some mechanical reason? Something doesn't add up.
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The main difference is that modern, axial-slave hydraulic clutches are designed to move the pressure plate a smaller distance than older, mechanical actuator clutches. Greater precision makes a better clutch but proper installation is more critical.
Last edited by Gary Z; May 25, 2006 at 03:35 PM.
It's not as simple as your equation states. You develop a lot higher forces with hydraulics than simple mechanical advantage. Pedal travel is still the same between the two.
pedal force = throwout bearing force/slave cylinder piston area * master cylinder piston area * master cylinder moment arm / pedal moment arm
and
pedal travel = throwout bearing travel * slave cylinder piston area/master cylinder piston area * pedal moment arm/ master cylinder moment arm
multiply the two equations together and you get
pedal force * distance = throwout force * distance
How is it not as simple as that? The fact that you're using hydraulic advantage (is that a term?) instead of leverage doesn't change the "work in = work out" relationship.
Originally Posted by Gary Z
The main difference is that modern, axial-slave hydraulic clutches are designed to move the pressure plate a smaller distance than older, mechanical actuator clutches. Greater precision makes a better clutch but proper installation is more critical.
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Originally Posted by P Mack
Interesting...does the precision you're talking about have to do with pressing all the clutch fingers evenly? Or if not, what part the system has more precision?
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Verdad Gallardo That's more friction than I would have thought. I'd still say that even the 30% less force releasing the mechanical clutch is still more force than it takes to push the hydraulic in. I guess it's a combination of friction and more pressure plate travel.
gary'sright about them being more precise. nowadays if you surface a flywheel more than .025" you have to shim the flywheel. with mechanical linkage you didnt have to do that because they traveled farther. and since hydrolic (i.e. modern) throwout bearing only require 10 thousandths to engage a clutch, the leverage is much greater.if you dont need as much pedal travel for example you can set you pivot point higher= less force required to engage. also the size of master cylinder piston versus slave piston, has an effect on leverage also, so there are a lot of factors involved that all change depending on the car.
