Author Topic: ball bearings as sliprings.is it a good idea??  (Read 1539 times)

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snake

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ball bearings as sliprings.is it a good idea??
« on: April 19, 2009, 03:01:06 PM »
hi,i did a research about constructing sliprings and i saw a guy using ball bearings as slip ring.what do you think about that?is there any disadvantage?
« Last Edit: April 19, 2009, 03:01:06 PM by (unknown) »

Janne

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Re: ball bearings as sliprings.is it a good idea??
« Reply #1 on: April 19, 2009, 09:38:12 AM »
Sounds like a good plan if you intend to weld the balls to the races..


With small currents it might work, but I wouldn't try it.

« Last Edit: April 19, 2009, 09:38:12 AM by Janne »
Nothing's as easy as drilling a hole in the wrong place

Ungrounded Lightning Rod

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Re: ball bearings as sliprings.is it a good idea??
« Reply #2 on: April 19, 2009, 10:09:38 AM »
Look up "electrodynamic machining".


Putting a current through a bearing, especially when immersed in a dilectric fluid such as greese, is an incredibly efficient and rapid way to mill away metal from the surface of the bearing and suspend it as fine dust in the dilecteic fluid.


An arc through the fluid melts a tiny pit where it lands - mainly on the positive electrode, and vaporizes a path through the dilectric.  When the arc extinguishes the vapor condenses with extreme rapidity (because of the low temperature of the surrounding dilectric) and the arc path collapses - with a cavitation-style shock wave.  The shock wave blasts the dilectric into the pit and splashes the still molten metal (or whatever) into the dilectric, where it immediately congeals as nanoscopic grit.


Repeat thousands of times per second.


There is a whole machine tool industry built on this:  Using the end of a wire as a drill, the side as a bandsaw, or a shaped carbon rod as a funny-shaped-hole drill.  (There's a releated device called a "tap disintegrator" that is used to remove broken taps from a workpiece without damaging the workpiece by removing the center of it.)  These are used for things like:  Drilling precise holes in jet and diesel engine fuel injectors, cutting precisely-shaped strain-relief slots into cast tungsten jet engine blades (so several can be cast as a unit), machining the cylinders of diesel engines for cargo ships, cutting dies (in extremely strong metal creating a near-mirror finish), forming molds for casting plastic, etc.  It can cut anything that conducts electricity (including diamond:  By flashing a small amount of metal onto the surface to prvide the initial electrode then conducting through the graphite formed as the hole progresses.)


This was accidentally discovered in Russia in WW II:  They were having trouble with lifetime of ignition "points" in engines for trucks and tanks.  An engineer got the idea of oil-cooling the points.  Lifetime went from months to days.


(By the way:  I wrote the core of the motion-control software for one of those tools - the one whose first job was "bandsawing" those strain-relief holes.)

« Last Edit: April 19, 2009, 10:09:38 AM by Ungrounded Lightning Rod »

Flux

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Re: ball bearings as sliprings.is it a good idea??
« Reply #3 on: April 19, 2009, 10:21:39 AM »
slip rings are not really necessary. If you do use them then there are no short cuts, most half baked ideas will be a total failure. using sleeve bearings is not without significant problems, ballraces will be a total disaster.


Unless you have decent machining facilities and are prepared to use reliable brush holders then keep the weather out avoid slip rings like the plague.


Ball races can be destroyed by very tiny circulating currents within machine shafts, any attempt at transmitting finite power will scrap them in days.


Flux

« Last Edit: April 19, 2009, 10:21:39 AM by Flux »

Blutoy

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Re: ball bearings as sliprings.is it a good idea??
« Reply #4 on: April 19, 2009, 10:58:51 AM »
Yea, what Ungrounded Lightning Rod said...
« Last Edit: April 19, 2009, 10:58:51 AM by Blutoy »

wooferhound

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Re: ball bearings as sliprings.is it a good idea??
« Reply #5 on: April 19, 2009, 11:29:13 AM »
Most of us don't use sliprings because it adds considerable complexity to the design and is high maintenance too. The easy super simple and reliable method is to run your Down-Wire up over the turbine and down the pipe that is holding the turbine above the tower. The turbine would be allowed to turn into the wind using a slightly larger diameter pipe slipped over the support pipe at the top of the tower.


Then at the bottom of the tower you install disconnect plugs which you can unplug at anytime to untwist the wires. In practice this works really well in most locations because the turbine will rarely do 360 degree turns and the wire will only need to be unplugged and untwisted about once a month.


Here is another story about using Steel Bearings as a slip ring

http://www.fieldlines.com/story/2003/10/6/2127/58788

« Last Edit: April 19, 2009, 11:29:13 AM by wooferhound »

snake

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Re: ball bearings as sliprings.is it a good idea??
« Reply #6 on: April 19, 2009, 11:44:48 AM »
this sounds good.thanks friend
« Last Edit: April 19, 2009, 11:44:48 AM by snake »

betwixt

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Re: ball bearings as sliprings.is it a good idea??
« Reply #7 on: April 19, 2009, 12:29:15 PM »
You might also find this interesting - if impractical!


http://www.electricstuff.co.uk/bbmotor.html


It's a wonderful web site for weird ideas and loony experiments.


Brian.

« Last Edit: April 19, 2009, 12:29:15 PM by betwixt »

Batdude

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Re: ball bearings as sliprings.is it a good idea??
« Reply #8 on: April 19, 2009, 02:48:15 PM »
If you really need something that will allow rotating contact there is a device that is mercury filled that does this. I think someone shared about it on this site.


batdude

« Last Edit: April 19, 2009, 02:48:15 PM by Batdude »

domwild

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Re: ball bearings as sliprings.is it a good idea??
« Reply #9 on: April 21, 2009, 12:11:19 AM »
Very interesting technique! Never heard of it before. Heard of depositing hard metal surfaces onto softer automotive cylinder surfaces via arcing but not actual machining.


Cheers

« Last Edit: April 21, 2009, 12:11:19 AM by domwild »

Ungrounded Lightning Rod

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Re: ball bearings as sliprings.is it a good idea??
« Reply #10 on: April 21, 2009, 05:20:16 PM »
It's been around for a while.  I did the software back in '84 or so - when things were moving from special-purpose electronics to computer control.
« Last Edit: April 21, 2009, 05:20:16 PM by Ungrounded Lightning Rod »

BigBreaker

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Re: ball bearings as sliprings.is it a good idea??
« Reply #11 on: April 23, 2009, 05:51:02 AM »
Mercotac is the company.  Current may be a limiting factor, especially for a 12V machine.
« Last Edit: April 23, 2009, 05:51:02 AM by BigBreaker »