Hi All,
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As the old clutch fork was worn to death and had previously been built up with braze,
I needed to make a new one,
The arm that operates the fork/clutches moves in an arc, so the fork must be able to move up and down in its slot as the arm operates
I measured the distance between the operating arm and the clutch engaging boss, then finding a suitable piece of phosphor bronze just the right size in the "come in handy" box, I set it up 5mm off centre in the 4 jaw chuck and machined it as in the photos
I took a light cut to mark the highest point on the outer diamater where the pivot pin would be fitted before parting the piece off.
I marked where the pin was going to go and drilled to suit the 3/8in. pin, and milled a small flat area around the pin hole
I then set the piece in the vice and centered it up, I set up a boring head to the diamaters then off set the piece + and - 0.040in and bored the hole and outer shoulder eccentric, then reversed it to do the other side
Then cut the fork off in the mill
I silver soldered in the pivot pin and triall fitted the fork
I did not have enough eccentricity to allow the fork travel the required distance
So a further setup to increase the eccentricity was needed, as in the photos, another 0.020 either siide was enough !!
To refit the parts !!!
The engagement boss must first be sat on the gearbox floor,
then the fork is fitted in place by removing the clutch operating arm from the outside of the lathe allowing the inner arm to pivot further towards the drive pulley end of the gearbox
Wriggle the fork and boss into place into the pivot arm,
Fit the chuck end clutch assembly into place and bring the fork and boss up to meet it,
Make sure the inner ramps line up with the clutch rollers and pop the boss onto the clutch and engage the clutch, it should all stay in place
Grease the thrust washer that fits between the clutches and stick it in place to the clutch already fitted
the pulley end clutch and gear can now be wriggled into the casing and the drive spindle fitted from the outside,
Line up the inner ramps with the clutch rollers before engaagine the spindle into the splines
All going well the drive spindle should slide all the way through easily
Then fit the bronze thrust washer, the steel washer with pin and the allen screw
I used some threadlock fluid on this screw.
The plug with the centrifugl brake centre can then be refitted and the retaining grubscrew tightened
The next post will be about repairing the drum brake which had suffered from someone with size 14 boots
John
