A ball bearing motor

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Rich Feldman
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A ball bearing motor

Post by Rich Feldman » Fri Apr 20, 2018 11:46 pm

As a side effect of Tyler Meagher's motor & pump cleanup, I had a cleaned up motor armature, about the size we would find in a Dremel tool. viewtopic.php?f=10&t=12189#p79527 Thought it would make a nice-looking ball bearing motor.

That took longer than necessary, because of excess attention to distributing current around the bearings' outer races. Maybe 50 to 100 amperes.
Online accounts range from incredibly lame:
bbm1.JPG (13.58 KiB) Viewed 1522 times
to probably good & practical:
bbm2.JPG (21.59 KiB) Viewed 1522 times

My bearing OD of 0.866 inches (22 mm) made it unlikely to find round copper, brass, or aluminum parts with the right size hole, so I made some. First a piece of brass from a scrapped valve, bored out on the Sherline lathe. Press fits are touchy -- a thousandth or two makes the difference between too loose (no contact pressure) and too tight (reducing the diameter of pressed-in bearing race). Then a piece cut from a coupler for 3/4" copper pipe. Its ID is 0.875 + gap for solder; measured to be about 0.887. Both got soldered to 8 AWG feeder wires.
Of course the copper sleeve is much too loose, with average radial clearance of more than 0.010 inches. Could have cut a longitudinal slot, at least 2 pi x 0.010" wide, and squeezed the sleeve down onto the bearing with a hose clamp. Instead I filled the gap with bits of 28 gauge copper wire.
bbm3.JPG (15.44 KiB) Viewed 1522 times
When pressed onto bearing by hand, the wires crush slightly and the circle distorts slightly toward an octagon shape. The thin wires won't mind carrying 10 or even 20 amps each, across their diameters. :-)

Here it's out for a spin. Current and voltage measurements to follow.
Mike echo oscar whisky! I repeat! Mike echo oscar whisky, how do you copy? Over.

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Richard Hull
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Re: A ball bearing motor

Post by Richard Hull » Mon Apr 23, 2018 4:34 am

I made this "Marinov" Ball bearing motor back in 1994 and displayed it at one of the old Telsthons before they became the HEAS conferences.

Typically runs at about 2.5 volts @ 50 amps just and aluminum shaft in two brass pillow blocks I milled out and inset ball bearings. Runs fine on AC or DC and can spin in any direction you choose even regardless of DC polarity, if running on DC. It just doesn't care what you feed it beyond a gang o' amps.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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