This is the only picture I have of this thing. But the basic idea is visible. I finished it years ago and gave it to my friend. Who actually forced money on me.
I DC TIG welded the pipe to the heavy solid aluminum plate with helium inert gas. The twin belts run inside the pipe. When I was done, there was an aluminum face plate that covered the bearings and it keeps any parts from getting marred.
Next time I am over his house I will ask to take a picture of it.
I remember the only improvement I would have made, would be to put adjustable tension motor mounts on the motor. As the belts break in they need to be tightened or they rub on the inside of the tube if they flop around.
And I would have gone with slightly larger and heavier wall pipe. The reason although it performed well, I know the way I polish I would cause to much vibration in the pipe.
But this thing lets you polish big and weird shaped stuff. My friend Lou, polishes big stuff off large sail boats and big yachts.