h a l f b a k e r yIncidentally, why isn't "spacecraft" another word for "interior design"?
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This idea stems from one common problem associated with brushed dc motors, brush wear. These brushes push against the sides of the rotor and deliver power to specific contacts thereon thus switching electromagnets on the rotor on and off. My proposed alternative system would use a mostly plastic ball
bearing to both support the end of the rotor in the motor and to provide power to the electromagnets thereon. essentially the rolling elements inside the bearing transmit electrical energy from the stator to the rotor without the two rubbing against one another. The conductive balls have plastic ones between them so as to prevent current from short circuiting from one end to the other. this would eliminate brush wear and thus make the motor far more reliable. its doubling as a bearing would decrease the complexity of larger motors.
Ball bearings would decrease the size of the contact area to a single point. roller bearings might be better for high power applications.
[edit] after doing some more research it would appear that some people have m=been looking into using liquid metal conductors for exactly this purpose. Also carbon brushes are one of the more expensive components in electric motors. This might actually work [/edit]
How electric dc motors work
http://electronics....orks.com/motor2.htm
Explanation + Pictures [RichardT, Mar 09 2010]
Dc motor wear
http://ecmweb.com/m...ntaining_dc_motors/
This article deals exclusively with rotor wear as high end motors treat brushes as consumables [RichardT, Mar 09 2010]
http://en.wikipedia...d_DC_electric_motor
Wikipedias article on brushed DC motors [RichardT, Mar 09 2010]
US 530,717
https://patents.goo...en?oq=US+530%2c717+
[xaviergisz, Mar 10 2010, last modified Feb 19 2018]
US patent 5,714,825
https://patents.goo...en?oq=5%2c714%2c825
motor with "ball-point pen" type brush [xaviergisz, Mar 10 2010, last modified Feb 19 2018]
The homopolar motor
https://en.wikipedi...icity_and_magnetism
WKTE [8th of 7, Feb 13 2018]
Diamond Roll-Rings® (formerly from Roltran)
http://www.diamondr...ings_explained.html
Mentioned in my anno. A type of roller bearing designed to be an alternative to slip rings, with no sliding contact [notexactly, Sep 15 2019]
Wikipedia: Gear bearing
https://en.wikipedi...g/wiki/Gear_bearing
Mentioned in my anno. Like a roller bearing, but with gear teeth instead of smooth rollers [notexactly, Sep 15 2019]
Wikipedia: Scrollerwheel
https://en.wikipedi.../wiki/Scrollerwheel
Mentioned in my anno. Like a rolamite, but rotary rather than linear [notexactly, Sep 15 2019]
Mike's Electric Stuff: Ball-Bearing Motor
http://electricstuff.co.uk/bbmotor.html
Mentioned in my anno [notexactly, Sep 25 2019]
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Strangely (gut feeling), I thought the opposite was
the way to go; fast wearing brushes that are easily
replaceable. Somehow use the disintegration of the
metal brushes to supply free electrons to the circuit. |
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I like it, there could be potential for reduced friction, but if it works better totally depends on execution. Forget the plastic stuff, that is trouble. Plan on these not conducting quite as well, on account of a smaller contact area than a seated brush and because bearings are made of harder metal that doesn't conduct as well. The roller bearing would probably have to be larger than the brush version to compensate for this. It will also run hotter and perhaps need lubrication, which could be a can of worms. Deterioration due to arc pitting is not too big of an issue for brushes because it happens at the corners, and the face is renewed as the brush wears. For your bearing this may be a much more significant issue.
An advantage the bearing has in this area is the lack of dust generated, which causes nearby bearings to wear faster and can even cause shorts/arcs on the commutator.
I assume this is why liquid metal was tried as it does not suffer from arc pitting, but most all of those designs suffer from gravity constraints. |
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As for as maintainance life goes, I'm not sure if it would be extended or not considering these other factors. In those cases going for max life, the increased complexity of magnetically transmitting power to the rotor fields without physical contact is worth the increased cost. Depending on application it really isn't too substantial. |
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for roller versions, you could distort the contacts slightly like herringbone gears so that one end of the roller contacts the contact first.In addition to this that end of the roller could include materials that increase resistance to current flow along with a thin coating of a conductor like tungsten. This resistant roller end would act to lessen spark voltage and to wear less from sparks. |
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Hold on. The rotor is rotating, but the wires feeding
the motor are not. So there has to be a sliding
contact somewhere. The roller can transfer that
motion nearer an axis of rotation, but I wonder at
the cost/benefit trade-off. |
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You do realize, [RichardT], that the balls in a ball bearing travel around at one half the speed of the borne rotating part? |
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Elimination, or at least reduction of sliding friction is the entire principle behind this idea. basically you are using the rolling elements in the end bearing to transfer electricity between the two contacts. |
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The rolling elements will be traveling slower than the rotor but the idea is to have enough of them that when one stops connecting two contacts another moves into place. You would need at least four conducting rollers for a three contact motor, five for a four contact motor and so on. That ensures all rotor contacts are connected to the stator contacts by rollers. There would of course be some variability to the motor timing. the rolling elements would slip a little every turn, but overall it should work. |
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Ball bearings wear out eventually, but they should last
longer than carbon brushes, I think, and they won't add as
much friction. A motor already has two bearings, so just
replace one with one of these commutative bearings, and
that's a friction advantage over two bearings plus brushes. |
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Ceramic ball bearings exist. Those should be used for the
insulating ones rather than plastic, because they'll last
longer. |
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// You do realize, [RichardT], that the balls in a ball
bearing travel around at one half the speed of the borne
rotating part? // |
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If they have the same diameter as the borne rotating
part. They work exactly like planetary gears. |
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// replace one with one of these commutative bearings // |
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No, because then you need some sort of external switching to achieve the polarity reversal. |
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The point about opposed brushes on a segmented commutator is that they automatically switch current polarity with rotation. It makes the whole system extremely simple. |
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Now, if you use slip rings and sense the armature position, you can switch the polarity externally and have lower brush erosion, but then you might as well build a stepper motor - no brushes at all - or use a PWM controller to synthesize an AC drive waveform, which is of course what brushless motors do. |
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Synchronous motors are great, but they're constant-speed devices. |
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When it comes to converting electrical energy into mechanical rotation, it's all been tried before. |
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// using liquid metal conductors for exactly this purpose. // |
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There was this bloke called Michael Faraday, he used mercury as the conducting element, about two hundred of your Earth years ago ... <link> |
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Brushed DC motors are very, very cheap to make. That's why, for all their faults, they're still around. |
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I thought the point of this idea was that the bearing would
act as a commutator, not just as a slip ring. That's why it
has both conductive and insulative parts, right? |
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Does anybody know a good Chrome extension for
recovering form inputs lost due
to browser crashes, forced OS updates, etc? I used to use
Lazarus, but it was
never very good, and I don't think it's available anymore.
Anyway, I had written
but not yet submitted an anno here describing the
possibility of using Roll-Rings® [link], gear bearings [link],
or similar as a motor commutator (with the
gear bearings having the advantage of no slip, meaning
that they could be made
conductive and insulative on a sectoral basis, instead of
on an individual basis,
so as to provide a commutation function), but I lost it
because of a forced OS
update that I hadn't been notified about in advance. |
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// a good Chrome extension for recovering form inputs lost due to browser crashes, forced OS updates, etc? // |
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Yes. Switch to Linux, a real OS - not a jumped-up video game with delusions of adequacy. |
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<Chorus of Borg voices chanting "_luser ! _luser !"/> |
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//Yes. Switch to Linux, a real OS - not a jumped-up
video game with delusions of adequacy// |
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Windows often goes through a late-life upgrade.
This is about to happen to Windows 7. When MS
stop "supporting" it, life is likely to be simpler
regarding updates and restarts. |
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I'm on Windows 10. I've tried to install Linux on this computer,
but it never worked properly. Couldn't get through the whole
boot process for some reason, IIRC. |
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It just occurred to me that a scrollerwheel [link] (not to be
confused with a scrollwheel) could also be used for this. You
could have a band with an insulative web and two parallel
selectively-conductive tracks along it. I feel like it might be
possible to design such a motor such that if the scrollerwheel
slips, the torque of the motor would somehow cause it to slip
back to its proper phase relationship. If not, just put holes along
the edge of the band and teeth on the rollers, like camera film
uses. |
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[notexaclty] I'm using Typio on Chrome to recover text typed
into the browser but not submitted before the browser
crashes, etc. I can't compare to Lazarus since I never used
it, but it seems to work well. |
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Gear bearings seem just about perfect for this. Since the
relative positions is locked, you wouldn't need plastic or
ceramic spacer bearings. There would also be no
variability of when one a roller bearing connected or
disconnected each commutator segment since the
position of each gear bearing is predictable. It seems like
having teeth could optimize a larger contact area as well. |
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You might also combine the gear bearings with the gold
plated spring copper rings from Roll-Rings. If a roll ring is
locked together with each gear bearing, it seems like the
spring copper could provide a larger contact area, while
the gear bearing keeps it positioned accurately. |
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// [notexaclty] I'm using Typio on Chrome to recover text
typed into the browser but not submitted before the
browser crashes, etc. I can't compare to Lazarus since I
never used it, but it seems to work well. // |
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Looks good (much nicer UI than Lazarus), and
seems to be at work already (just
installed). Thanks for the recommendation. |
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It has occurred to me (after [bs0] brought it up elsewhere) that
these bearings we're talking about here would be susceptible to
acting as ball-bearing motors [link], which may or may not be
desirable in the context of bearing the shaft of a larger
electromagnetic motor. It would certainly be undesirable for the
bearing to seize after a few seconds of operation, as ball-bearing
motors tend to do, but that's with relatively unlimited current, and,
in this application, the 'actual' motor (the electromagnetic one) will
limit current. But if that motor stalls, that will make it draw more
current, and it will also stop the bearing's rotation, resulting in more
heating at the same spots on the bearing balls/gears and races,
which could lead to seizing and then an inability for the motor to
rotate even after the stall is resolved, until it has been turned off
and allowed to cool. Maybe it would help to make the bearings out of
a material with a very low coefficient of thermal expansion. |
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