# Calculating force applied from an expanding disk

1. Apr 5, 2015

### knight92

Hello,

I need to calculate the force applied within a clutch pack by an expanding disk. Can you guys tell me if there is anyway to do this? I am working to find the torque capacity of a centrifugal clutch using the equation:

Torque Capacity = 2/3 * COF * n * F * Radius Gyration
where COF = coefficient of friction of clutch
n = number of friction surfaces
F = force applied (Applied by the expanding disk)

This clutch I am dealing with contains an expansion disk. The expansion disk has weighted shoes placed on ramps inside it and the weighted shoes are held in by springs which provide a tension of 80 Newtons. Once the clutch rotates at a certain speed, due to the centrifugal force the shoes start sliding up the ramp acting against the spring tension. The weighted shoes are tapered which means as they slide up the disk expands. Now because I know the spring tension I know how much force is experienced by the weighted shoes. If there are six of these around the whole expansion disk, is there anyway I can get an estimate of the force applied to the whole clutch pack? Please see the images I have attached for more detail about the mechanism (Fig1) and the clutch pack (Fig2). Will I be right in assuming since there are six of these around the disk then 80*6 = 480 Newtons is the total force applied to the clutch pack?

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2. Apr 8, 2015

### Simon Bridge

1. the spring tension is not a constant - it changes as the shoes move.
2. use a free body diagram to work out the forces on the shoes - when they are in equilibrium, the forces sum to zero.
3. isolate the force you are interested in.

"force applied to the clutch pack from what?
Since the force from each spring is equal and evenly distributed in many directions the net force on the disk is going to be zero.
The forces all act radially so they do not exert a torque.
So you need to clear your thinking ... that does "force applied by expanding disk" mean? Where does it act and how?