
The Ball-Bearing Electric Motor (2003) - fn42
http://electricstuff.co.uk/bbmotor.html
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nippoo
Sadly the premise that it operates on a thermal principle has been pretty much
debunked - it operates on electromagnetism, due to the induced EMF when the
ball bearing rotates through a magnetic field caused by the current through
it. Here’s a paper describing the effect (which has been experimentally
verified)...
[http://www.physics.princeton.edu/~mcdonald/examples/motor.pd...](http://www.physics.princeton.edu/~mcdonald/examples/motor.pdf)

I built one of these at university as a research project and it works well
(albeit drawing a huge amount of current!). Interestingly enough it works just
as well in either direction, depending which way you give it an initial push -
the polarity of the DC terminals doesn’t matter at all!

~~~
tzakrajs
I don’t see how anyone could have ever thought it was anything but
electromagnetism. What a strange inversion of thought.

~~~
mikepurvis
The parent is replying to the article itself, which describes in glorious
detail the apparent principle of operation. The youtube video linked
downthread also has a description with the same thermal expansion explanation.

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nippoo
Sadly the premise that it operates on a thermal principle has been pretty much
debunked - it operates instead on electromagnetism, due to the induced EMF
when the ball bearing rotates through a magnetic field caused by the current
through it. Here’s a paper describing the effect (which has been
experimentally verified)...
[https://news.ycombinator.com/item?id=20415755](https://news.ycombinator.com/item?id=20415755)

I built one of these at university as a research project and it works well
(albeit drawing a huge amount of current!). Interestingly enough it works just
as well in either direction, depending which way you give it an initial push -
the polarity of the DC terminals doesn’t matter at all!

------
kordlessagain
Roobert33 on YouTube demonstrates this:
[https://www.youtube.com/watch?v=f1xnQ9gWy1o](https://www.youtube.com/watch?v=f1xnQ9gWy1o)

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ggm
I sort-of feel that anything which uses electricity purely for a thermal
effect, is actually in the carnot engine space and not actually "electric" in
any meaningful sense of the word. They could have modified a stanley steamer
to boil water electrically, and made similar claims (ball bearings aside)

But undenyably very .. cool?

~~~
Taniwha
Well he does claim it's a thermal engine, not an electric one .... and it
runs, um, not-cool

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seiferteric
I wonder if you could put a current regulator on it that would provide the
minimum current needed to achieve a certain RPM. Seems like the heat issue
could just be that after it reaches its maximum speed, the excess current is
just wastedin ohmic heating.

