A Beogram 4002 DC motor arrived from Australia for restoration. It exhibited the usual RPM variations due to dry bearings. This shows the motor as received:
I extracted the bearings for oil infusion under vacuum. This required disassembling the motor:
The bearings are the two small donuts on the black pad.
I immersed them in engine oil and pulled a vacuum:
Immediately vigorous bubbling started from the bearings, indicating that the vacuum drew the air from the porous Oilite brass material to make room for the diffusion of fresh oil into the bearing.
These bearings were particularly 'thirsty' and it took about 72 hours until the bubbling stopped. After the bubbling stopped I extracted the bearings
and put the motor back together for an RPM stability test. I used my 3D printed assembly tool for installing the top bearing:
I installed the motor in one of my Beogram 4002s for measuring the RPM stability over 24 hrs using my BeoloverRPM device:
This is the curve that I measured:
This is as good as it gets with the Beogram 4002 DC motors. This motor is ready for its trip home to Australia!
Thank you Rudy for restoring my DC motor. It's back in place and my Beogram 4002 is now spinning at a constant speed. Your videos have helped me no end in repairing my 4002, I feel very lucky to have accidentally found you via Youtube.
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