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Saturday, September 16, 2017

Beogram 8000: Fabricating a Fix for the Tangential Arm Drive Problem

Since I have the two broken pieces of the tangential drive bearing for the Beogram 8000 I thought of a way I could fabricate a repair. Any attempt to glue the tiny broken tab back onto the bearing by itself would be pointless. There isn't enough surface to attach it so that it wouldn't just break off again.

I re-installed the rear rail, drive screw, bearing and bracket to check what the clearances are around the bearing. There is plenty of room to add some reinforcement to the broken side of the bearing in the fix attempt.

What I needed was something I could epoxy all the way around the broken side of the bearing. My solution for that was to find a flat nylon washer to fit the job. After some experimenting I found that a #10 (SAE) size washer would be a good candidate. 

To glue the nylon washer to the broken side of the bearing I needed a clamp. It turns out that an M5 - 0.8 screw, washer and nut work perfectly as both a clamping mechanism and a secure mount for the bearing. The tangential drive screw is also an M5 - 0.8 threaded part.

I glued the washer onto the bearing first and let it begin to set up.

The broken sliver of plastic that was the bearing tab snugly snaps into the space between the washer and bearing. All I needed to do was add some epoxy there and everything will bond up nicely.

I let that dry for a couple of hours then removed the repaired bearing from the makeshift clamp. A test fit shows promise that this solution will work.

Tomorrow I will re-assembly the various Beogram components and see how close I am in having this turntable back in operating condition.

The best solution for this problem will still be to create a 3D replacement part. I was lucky in this case to have the broken tab piece to fully build the bearing part back up. Had that tab piece been unavailable (as is the case with some of my other spare Beogram 8000 units), I would have probably tried to build and wall there with some epoxy. Fortunately I didn't have to deal with that scenario.

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