Every timpanist should know…
…How the Premier Timpani Clutch Mechanism Works.
The Premier clutch mechanism has three elements that work in conjunction with each other: The pedal, the fork pressing linkage, and the clutch block. It must be noted that they are not operated in isolation, they are part of the whole pedal assembly which in turn is part of the whole instrument. However the system can be simplified to the above three elements to empower a timpanist to be able to overcome most problems.
The pedal rocks back and forth around a fulcrum point, just like a see saw. Immediately below the fulcrum point is the barrel nut which holds the connecting rod to the fork pressing.
With the heel down the pedal moves the barrel nut forward.
It can be seen that the pedal is pushing the connecting rod forward, thus pushing the top of the fork pressing forward. The fork pressing also rotates around a fulcrum point, so it can be seen that as the top is pushed forward the fork prongs are pushed down.
This downward movement of the fork prongs enables the sleeves in the clutch mechanism to be pushed downward by their respective springs (not in the drawing for clarity). The bottom sleeve has a spring that is visible which pushes against the bottom of the clutch block. The spring around the top sleeve pushes against the chrome cap that is fitted on the top of the clutch block (not in the drawing for clarity).
The top sleeve has an angled face that pushes the ball bearings down and outwards away from the grip rod. However the inside of the clutch block is conical. As the sleeve pushes the ball bearings down, there is less and less room for them to go out, so they are in actuality forced down between the clutch block and grip rod. This wedging of the ball bearings is what holds the pedal arm in the desired position.
As the bottom sleeve lifts the balls, they become unwedged as they move up the conical shape of the clutch block. The angled face of the top sleeve can now push the ball bearings outwards away from the grip rod.
Because the ball bearing are being pushed away from the grip rod it is no longer held, therefore the tension on the head can be released lowering the pitch. Once the pitch is achieved, the pedal is rocked backwards by pushing the heel down. This action, as we now know, enables the spring on the top sleeve to wedge the ball bearings again, with the spring on the bottom sleeve pushing the sleeve down out of the way. Below is a photo of the complete assembly.
Now the system is understood, we can move onto the adjustment which is simplicity itself. The connecting rod between the fork pressing and the pedal is threaded so that its length can be adjusted. Making it shorter will therefore push on the balls and release a stuck pedal, making it longer will enable the balls to go down further thus preventing a slipping clutch.
There is a supplementary post to this one that explains how to release a jammed pedal which includes a video of me demonstrating how to do it.