Calculation of clutch lever ratio

[k.udhay]

Hi,

I recently got an opportunity to work on a clutch assembly. The clutch is an old model one which has six helical springs that keep pressing the pressure plate, clutch plate and engine flywheel against each other. The cross section is:

To give a brief working principle, when the release bearing presses the release lever (shown in fig.) towards right, the other end of it pulls the pressure plate on the opposite direction. The pivot is also shown in the fig. Like you can see, the lever ratio is mentioned as 1:4.6 clearly. But when I measured the dimensions 'a' and 'b' and found th ratio between them, I got a value 2.5. Can somebody explain me if there is anything wrong in what I have done pl.?

Thanks a lot.

 

[Navin A S]

The ratio of 'a' and 'b' is not necessarily the same as the lever ratio. The lever ratio is determined by the ratio of the distances between the pivot and the release bearing (a) and the pivot and the pressure plate (b). In other words, the lever ratio is the ratio of a/b multiplied by the ratio of the release bearing's force (F1) to the pressure plate's force (F2). If F1 = 2F2, then the lever ratio would be a/b * 2, which is different from the ratio of a/b.