Rebuilding the driven variable sheave

[T-rustyfix]

In October of 2021, the driven sheave on my ‘73 1200 sheared off its drive lock pin. I replaced it several times, and those also broke. The sheave was wobbling on the shaft and the play around the pin from the cast iron was slamming the pin ends until they broke off. It was clear that it needed attention. I was in the middle of a foundation dig, but she went up on blocks anyway and I took her sheave out. For two weeks, I used my friend’s abandoned shop and junkyard to put together a plan and engineer an improvement for this component. He had an old 14” metal lathe and a smaller 6” lathe and enough tooling laying around to get the job done. A decent portion of my time was spent wading around in his piles of “useful items”, and searching the junk yard for this or that. Recently, here on the forum there has been a discussion regarding this issue, do I decided to start a thread on the details of this repair. Thankfully, I took pictures to share what I was doing with my kids, so here you go.

 

[T-rustyfix]

Previous repairs had been attempted by my father, as the welds on the cast next to the drive studs show. A small amount of grease in the zerk on the sheave next to the spring was part of our daily maintenance. A greasy belt often caused slippage however, which I was determined to prevent during this repair.

 

[T-rustyfix]

I used a piece of 1” thick steel sheet to make a 6” “donut drive” this transferred the power directly from the shaft to the drive studs. The pin is replaced with a hardened 6” bolt The shaft was bent and eaten up, so I used a press to bring it straight again and welded more material to build it up and smooth it off. In hindsight, I should have just bought a piece of 1.25” round and drilled a hole in one end and a key way on the other. I made custom bushings and installed o-rings to prevent grease from going to the inside of the unit and getting it on the belt. I also drilled journals to supply grease to the drive studs from the center shaft.

 

[T-rustyfix]

Here is the shaft repair. The shaft must be smooth to keep the grease in between the shaft o-rings on the sliding half of the sheave.

 

[T-rustyfix]

The final product. Note the grease coming to the exterior from the drive stud.

 

[jonesallu]

THAT is fantastic work. Your donut is a champion idea! Greatly appreciate you sharing it so you can help others save their machines.

Al Jones