# How to calculate (mechanical) clutch forces

1. Feb 16, 2016

### kanibal

Hello
i am working on a small clutch cable testing machine this machine can give the lifetime of clutch cable
i need some assistance to figure out how much forces i need to apply on this mechanism , and because the cable related directly in the clutch i'm asking if the force in the clutch in the same us what we give to the pedal example : if i push the pedal with 200 N how mach force is applied in to release the clutch it is the same 200 N or more and why !

this is the mechanism i made

2. Feb 16, 2016

### gjonesy

Simple solution is to attach a load cell to the clutch pedal and press it down slowly and release it slowly, it will give you force in PSI at its peek in both directions of travel. Just repeat till you have a base line and average it, then adjust the machine accordingly.

3. Feb 16, 2016

### JBA

With regard to the above question the force on the clutch is first increased at the clutch pedal assembly. The force you place on the pedal is multiplied by the ratio of the clutch arm length between the pivot and the pedal and the clutch arm length between the clutch cable connection and the pivot.
ie. F clutch cable = F foot x L foot pedal / L cable connection
Additionally, the actual force on the clutch may also be increased over the cable force by a similar design on the throwout fork between the clutch plate bearing contact point(s) and the clutch cable attachment point

4. Feb 16, 2016

### gjonesy

Its worth noting that the PSI will peek and then drop as the clutch pedal is pressed due to the (release point) on the diaphragm spring. I am assuming that "peek" is what you are looking for. When the throw-out Bearing is pressed against the diaphragm spring passed the middle point of travel it (breaks) and becomes easier to push once its passed that point due to less resistance in the spring.

5. Feb 17, 2016

### kanibal

thank you both of you for the answer

How the machine would look like if I asked you making this machine if possible with a simplified drawing to make it easier to understand

6. Feb 21, 2016

### Rx7man

Looking at your drawing, and making some rough guesses.

If the ratio of the distance from the clutch pedal 'pad' to the cable attachment point is 3:1, that will be the mechanical advantage you have on the cable, so 200N of force on the pedal will be 600N of force on the cable.. Then once more you look at the mechanical advantage the cable has on the throwout bearing.. Most designs similar to what you show have about a 3:1 ratio again, so the 600N of force on the cable is multiplied to 1800N

@qjonesy I think you mean "peak" (Maximum) not "peek" (take a look at)