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Clutch Release

A website dedicated to the construction of an accurate 1/2 scale replica of a 1937 Aero Douglas Motorcycle


Clutch Release Mechanism

The clutch release mechanism is very simple in operation.  It only has 3 main components being a cam ring, thrust washer and roller ring.  The roller ring has three equally spaced rollers protruding around it's circumference, these rollers are free to rotate but axially captive.  This ring slides over a boss on the crankcase and is held from rotating by a pin protruding into one of three slots at the back of the ring giving adjustment.  The cam ring has three slots milled at a gradient into it which when placed over the roller ring and rotated, provide the thrust which
disengages the clutch with an extremely light action.  There is a thrust washer which is located between the cam ring and the centre boss of the clutch so that i can operate when the clutch is rotating. 

The first part of the mechanism to be made was the cam ring.  This was machined from a billet of steel in the Myford lathe.  Everything was turned ready for parting off before the chuck was unscrewed and placed onto the dividing head on the mill.  The slot was cut using the table in the x and y then the head rotated through 120 and the task repeated.  The ring was then taken back to the lathe, parted off, t
urned around and finished.  A specially shaped arm will be tig-welded on the outside when i can get hold of a tig welder.  This arm will hold the bowden release cable. 


The thrust washer between the cam ring and clutch boss is a special custom made affair and is made from brass with individual 1/4" rollers held in the drilled holes by punched deformations each side of the hole and washer.  The scale version uses 1/8" balls removed from scrap ball races and thrust washers.  The holes were drilled in the part turned billet using a vertical dividing chuck before being parted off and deburred.  An old centre punch was given a rounded point and used to create two dimples 180 degrees around each hole on each side deforming the brass enough to keep the balls captive.  I practiced a few times and even then a few balls found the floor.  For such a simple component it was very rewarding to make.