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Old 5th November 2008, 08:02 PM   #21
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Quote:
Originally posted by smoking-amp
"If the empty core bobbin is a "C", you won't need anything
fancy to wind the copper through the donut hole.

The problem with C cores is that they don't have the low leakage L of a toroid to get the huge bandwidths.
Not a C core, just an empty C bobbin. For externally winding the
copper on the outside, and later internal spooling of the helical
iron core. No more absurd than anything else in this thread.

Obviously has to be some Teflon washers or whatever, for the
trapped bobbin to be turned... And an access gap through the
active copper windings, I don't know if that gap counts as a "C".

Packing the core in tight enough not to vibrate will be about
impossible, must assume the final step would then be potting.
I'm not attempting to be practical, just feeding the loons.
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Old 5th November 2008, 08:25 PM   #22
Yvesm is offline Yvesm  France
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There was a technic called "potato transfo" by here, forgotten now I suppose.

The copper wire was wound on a cylindric bobbin, then many steel wires was passed thru and bend so that they roughly join.

You know why they was so named

Yves.
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Old 5th November 2008, 08:56 PM   #23
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"could we revert to the standard circular shuttle and just make the shuttle cross-section small enough that it doesn't take up much more space"

Sure. I just think the Potthoff C design is a lot easier to make than the rotating shuttle designs. Take a look at all those guide wheels and bearings on the Jovil heads posted earlier. I am going to call Jovil to see if their shuttle bobbins and heads are available separately soon too. At least the bobbins might be affordable.

"an empty C bobbin. For externally winding the
copper on the outside, and later internal spooling of the helical
iron core."

This could be attempted, sure. Would need something like the mylar ribbon shuttle that Jovil has. But this would not get the metal wound up very tight this way. But then a little slack in the metal windup would lower the effective Mu some, so DC balance would not be such a problem for P-P. 1 mil thick permalloy tape would work great in a ribbon shuttle. (Hmmm...., on second thought, the Jovil ribbon shuttle bends the ribbon 180 deg. around a small roller. So that's NG. But, see my "deranged" version of this above, no 180 deg. bend using a belt drive on the outside of the ribbon stack. )

But why bother. There are R cores already. These are wound up cores with a circular cross section. Two round R bobbins each clip together over the circular cross section straight sections. These have a molded in gear sprocket on one end of the bobbin. You just use a gear drive to spin the bobbin on the core to wind the wire on. Result is a gapless toroid with two C core like bobbins on it.

An even simpler way would be to just use four sets of I laminations, interleave-stacked as a square, with winding bobbins over each one. This would get a little nearer to a toroid for leakage L than just two bobbins. Nothing special required at all.

But if you already just happen to have a toroid winder sitting on the bench... well...., its easier than any of these.

Don
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Old 5th November 2008, 09:20 PM   #24
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"There was a technic called "potato transfo" by here, forgotten now I suppose."

Sounds like this could work for SE with a huge effective air gap. Probably looked like a potato with roots sticking out. I'll bet it makes a lot of noise though with audio thru it.

Maybe re-arrange kenpeter's version to make a coil assembly shaped like a toroid, then use a toroid winder to wrap magnetic wire around it. Could call it the hairy smoking donut.

Don
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Old 5th November 2008, 10:52 PM   #25
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"Full manual approach ... for the fun. ....."

Looks like they used some type of bicycle rim for the shuttle there.
We need something like about 8 or 9 inches in diameter by 1/2 to 3/4 inch square cross section U shape. I've been trying to think of some common thing that fits the shape. Only thing I can think of would be some old IBM mini 9 track tape reel. How about some kind of dispenser reel for string, fishing line .... laundry line pulley, I guess a big pulley could be bored out in a lathe, but once we bring a lathe into this for machining, almost anything could be made from scratch anyway.
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Old 6th November 2008, 03:53 PM   #26
JLH is offline JLH  United States
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So is the whole idea of this thread to DIY a toroid winder, or is anyone exploring buying one used or new? How much are the small, low volume toroid winders anyway? Are they that much that DITY makes sense?

Rgs, JLH
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Old 6th November 2008, 06:38 PM   #27
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"So is the whole idea of this thread to DIY a toroid winder, or is anyone exploring buying one used or new? "

Well, the thread was inspired by the Potthoff patent as an easy way to build one. But any solution to toroid winding is fair game here. I have not been able to find a used toroid winder on Ebay so far, but I think there was some mention of a used one in some link for around $8000.

I just checked with Jovil manufacturing on new prices for progressive wind capable setups, and unless you've got BAILOUT access, probably not under consideration here:

For doing 5 inch max diameter coil winds, their model SMC-2 with a 9 inch winding head goes for $24,000. The 9 inch head alone for $7500. The bobbin alone for $700, the little tiny slider on the bobbin goes for $60.

A Chinese made version, the SMC-2E with a 9 inch head and lower quality is available for $15,750.

A cheaper model, the SMC-1E, (Chinese) with a 7 inch head (max. 3 inch coil diameter winds) is available for $13,500. The 7 inch head alone for $2500, bobbin alone for $400. (SMC-1E does not handle 9 inch heads or bigger though)

They said they will sell less than a whole machine, so you could buy a head or just a bobbin:
9 inch: $7500 / $700 or 7 inch: $2500/$400

I have priced the Teflon scrap on Ebay for building a bare bones Potthoff at around $100. But this requires further machining to build one. Probably a few hundred $ spent at a machine shop, unless you have a lathe or milling machine handy. (I do) Since Teflon is easy to machine, another option is a rotary table bolted on a drill press base, with a router head and a milling cutter. The big risk here is that one may have to do some experimenting and multiple tries before they get it right (spill-off friction/spill-over radius, spill-off wire capture across the C gap, friction in the loop-accumulator .....) The Potthoff patent is not a Heath Kit instruction manual.

One likely will also want to make some variants of the Potthoff for different belt widths. This would just mean an extra Teflon piece for the bottom of the belt groove and another cog belt. And some smaller cog-belt sprockets. A smaller width version would allow one to wind interstage xfmrs too.

Don
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Old 6th November 2008, 10:25 PM   #28
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Or one could go to Wall-Mart and buy a 26" bicycle rim.
A cloth covered hair scrunchie to prevent the wire from
coming off the wheel all at once. But that would be too
easy...

If you need a machine to spin it, Legos... and/or a rock
tumbler.
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Old 6th November 2008, 10:58 PM   #29
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"If you need a machine to spin it, Legos... and/or a rock
tumbler."

Mount the wheel horizontally thru the toroid above a flat table. Tie some cheese on a string from the wheel that dangles just above the table surface. Then tie a leash on a mouse and attach that to the wheel a few inches from the cheese. If its a really big toroid, you could attach a cat about a foot behind the mouse. High speed mode then.

Or just train some monkey to hand wind them for peanuts.
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Old 6th November 2008, 11:10 PM   #30
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Horizontally above a flat table of that slick cutting board stuff.
Now you are almost talking realistic.

Simpler answer to all the cat'n'mouse drive, patent search
"Rube Goldberg". Perhaps then you can save a part or two,
starting with string cheese.
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