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Old 4th November 2008, 12:28 AM   #11
jkeny is offline jkeny  Ireland
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Don,
I can't follow this without a diagram but I guess it's best to build it & see.

I always enjoy your postings here & your thinking outside of the box. Keep us posted on your progress, please.
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Old 4th November 2008, 06:32 AM   #12
Yvesm is offline Yvesm  France
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Potthoff says (col 3, lines 15 and next)

"... Belt 46 is now turned in the same direction as it was to place the wire onto [C shaped] belt loop ..."

This means, I believe, that the wire is unwound off the belt the inner turn first.

Seems feasible if there are only few layers stored on the belt loop.

Confused !

Yves.
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Old 4th November 2008, 09:29 AM   #13
jkeny is offline jkeny  Ireland
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No Yves, "....the end of the wire is then temporarily affixed to the core" on the line above line 15 signifies that the wire is unwound off the belt starting with the outer turn
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Old 5th November 2008, 02:36 PM   #14
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Looking at figure 2 in the Potthoff patent, I notice that the wire bundle is shown as a straight section thru the gap of the C. This would cause undesireable bending of the wire bundle for each turn of the "shuttle". (which could be 1000s of times for a Hi Z primary) A few fixes for this come to mind. First it depends on how much tension is applied to the wire during the initial windup on the "shuttle" as to whether the wire actually straightens there, so maybe it is not really a problem.

If it does prove to be a problem, a couple of fixes:

A thin metal section, shaped with the same curvature could be inserted into the C gap after insertion of the core. It would have a covering of Teflon adhesive tape over the outside curvature (this does exist, I have a roll, but it's expensive) to minimize friction. More elaborate, would be a machined piece of Teflon to fill the gap, but it could include a rounded edge for transporting the spill-off wire across with the same form factor as the rest of the C's spill-off edge.

Alternatively, a curved section of spring metal could be fitted to the surface of the cog belt, just like the bottom of a normal shuttle. It would have a gap in it for fitting thru the toroid initially, that could be taped shut (fiberglass based adhesive tape). This would rotate around with the wire bundle just like a normal shuttle, but forming just the bottom constraint.

On upper windings on the core, one might just use Teflon insulating tape between the layers, and let the existing lower winding shape provide the sliding support for the shuttle wire bundle passing by.
This would eliminate space consuming inserts as the winding window gets cramped. Although for high bandwidth OT work, one does not want to fill the core window, a long thin winding gives low leakage L.
------------------------------

Some undeveloped (and deranged?) ideas for making a toroid winder:

Seeing the Jovil mylar strip winding setup, gets me thinking that maybe something could be done using a fixed Teflon bobbin or shuttleless C configuration with a Mylar belt sliding along under (or over) the wire bundle for rotation of the wire. A continuous belt of this could easily be formed by taping together the ends after passing thru the toroid. Since large spools of Mylar are available, this may not even require a continuous loop belt, but could just de-spool and re-spool the mylar film continuously during a wind, capstan driven like a tape recorder.

The large 12 inch Jovil gear driven shuttles appear to bottom feed wire off the shuttle thru an inner slot (maybe a V bottom inside), and have the shuttle split in concentric sections somehow. One section appears to be gear driven, the other appears to be either friction dragged by a brake shoe in one case, or in the other case there is a second gear surface with maybe a drag or variable speed control motor connected. I think this scheme is driving the outside of the wire bundle and re-winding the slack wire during each turn back into the shuttle instead of letting it spill out into a slack loop. I notice that the specifications still allow progressive winding, like the smaller shuttles using friction plates (which this 12 inch spool does not have, nor need apparently)

The mylar tape winding shuttle scheme with rollers in the shuttle also gives me some ideas. If the shuttle is made of Teflon, no rollers are required (the Mylar stack has to rotate with respect to the shuttle and its bottom feed slot), so the shuttle can still be thin. Next, instead of a leather friction drag belt on the outside of the shuttle rubbing the top of the mylar wound stack (the shuttle itself is driven in their setup), this could be a driven belt around the whole loop.

This way the mylar does not have to perform a 180 degree turn coming out of the bottom feed slot, and rewinds on the shuttle when slack wire results. Now, replacing the mylar wound stack with wire, we have the equivalent of the Jovil 12 inch design. Bottom feeding wire from a V slot on the shuttle bottom thru an angled feed hole. Belt drive of the wire bundle itself on the top surface, the shuttle itself free wheeling or controlled by a computer controlled drive motor (variable speed during each shuttle rotation as it dispenses wire from its slot onto the toroid surface or rewinds slack wire back into the shuttle). No friction loop accumulator or edge spill-off needed here. Wire position is controlled continuously/accurately by the bottom feed hole.

Just for fun, I'm going to try getting a quote on a useable Jovil SMC-2 system (the minimum setup that can handle a 5 inch max OD winding), and for parts like the shuttle head or just a shuttle spool.

Don
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Old 5th November 2008, 03:26 PM   #15
jkeny is offline jkeny  Ireland
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Don,
I haven't read though your deranged? ideas section yet but some issues have been at the back of my mind:
- The circumference of the shuttle would have to be only slightly greater than the length of a full wind on the toroid otherwise each rotation of the shuttle will cause an accumulation of excess wire in the spill-off area.
- In other words unless most of the spilled-off wire is used up in a wind on the toroid it will simply accumulate because it can't be wound back onto the shuttle.
- Is this different to the continuous non-gapped shuttle which keeps the wire in the guide at all times?
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Old 5th November 2008, 04:26 PM   #16
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I suppose you could spool up a toroid of enameled iron wire,
if you really wanted to "Roll your own" from scratch. Aren't
needing frequencies a low-tech iron core wouldn't handle...

Don just need to figure a machine to fill up this "core" bobbin
with iron, while copper primary and secondary windings are
already wrapped over the entire mess...

If the empty core bobbin is a "C", you won't need anything
fancy to wind the copper through the donut hole.
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Old 5th November 2008, 04:30 PM   #17
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"The circumference of the shuttle would have to be only slightly greater than the length of a full wind on the toroid otherwise each rotation of the shuttle will cause an accumulation of excess wire in the spill-off area."

I wrestled with this issue myself, but finally concluded it is a non issue. 1st, either gapped C or continuous shuttles handle this the same way.

Imagine a really huge shuttle diameter, one with circumference vastly greater than a single turn length on the core. Seems like there will be way too much wire pulled off the shuttle when the spill-off is at the far side. But now imagine the same situation after winding one turn. There is still the same huge length of wire pulled off the shuttle forming the wire spoke to the back.

What happens is the 1 turn wound uses up a little of this each time, and the spill-off feeds just enough more, at some small angle just before reaching the far point again, to make up for the loss. The huge loop formed in the friction pad/loop accumulator simply gets pulled all the way thru to form the next long wire spoke to the back again next time. The spill-off can not (should not anyway, I notice there IS an EMERGENCY OFF switch on the Jovils) pull wire off until the wire has gone tight again (so only after the complete loop is pulled thru).

Obviously, an excessively sized (diameter) shuttle does cause the wire to get dragged around thru the friction/accumulator many times, but only one loop is ever present in it if it is operating correctly. This again highlights the need for correct control of friction in the spill-off and accumulator section and to variations of this with wire size.

Just a comment on the Jovil belt drive shuttle heads. At first I thought the belt wrapped around the shuttle was to obtain sufficient torque for turning the shuttle with large wire. But I now believe this is to increase friction at the spill off point for large wire. Ie, the wire has to pull-off between the shuttle and the tight rubber belt over it.

The angle range of the belt covering can also be put to use for controlling the spill-off force versus shuttle rotation angle, but I'm not sure they made use of this. One would like the required spill-off pulling force to be high while pulling the loop thru the core, but to be low while replenishing the wire in the loop for the next turn once its pulled up tight on the core.

Don
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Old 5th November 2008, 05:08 PM   #18
Yvesm is offline Yvesm  France
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Quote:
Originally posted by kenpeter
I suppose you could spool up a toroid of enameled iron wire,
if you really wanted to "Roll your own" from scratch. Aren't
needing frequencies a low-tech iron core wouldn't handle...

Don just need to figure a machine to fill up this "core" bobbin
with iron, while copper primary and secondary windings are
already wrapped over the entire mess...
. . .
Yes, but that's another attracting/exciting part of this funny game

Don, be prepared to insert someting else than a mylar tape between windings to control stray capacitances

Yves.

Full manual approach ... for the fun.
http://www.audiyofan.org/forum/viewtopic.php?t=6822
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Old 5th November 2008, 05:11 PM   #19
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re kenpeter:
"just need to figure a machine to fill up this "core" bobbin with iron, while copper primary and secondary windings are already wrapped over the entire mess..."

How about using Teflon covered steel wire wound in a BIG loop, then held flat on one side to wind the coils on. Then pull on the Teflon covered steel wire end until the whole thing shrivels up to a small round toroid.

"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. They can do a little better than an EI if the windings are split (both primary and secondary split, this means ALL sections ie, the P-P halves too) between the two sides of the completed assembly.

To get low leakage L requires very long thin winding profiles so that the leakage paths are very long and comparable to the high Mu core pathes. The toroid is the master at solving this. It not only gets the long profile right, but even makes the leakage paths cancel by symmetry (provided each winding covers the full core). (unless the toroid hole gets significantly filled in with wire, then circular leakage paths form around the inner hole wires, which are shorter in circumference than the high Mu toroid path.)

Notice that toroids do not require interleaved windings either. With a progressive toroid winder, one can wind super performing toroids easier than EI or C cores. Just one automated progressive layer wind for each winding.

Don
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Old 5th November 2008, 06:59 PM   #20
jkeny is offline jkeny  Ireland
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Quote:
Originally posted by smoking-amp
(unless the toroid hole gets significantly filled in with wire, then circular leakage paths form around the inner hole wires, which are shorter in circumference than the high Mu toroid path.)
This is another thing I also had in mind - based on the above point - we need to have a sufficient toroid hole left after winding so 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 than the bare wire bundle? I know this imposes a limitation on the smallest size core that can be used.

Just how many times do we need the ability to wind a toroid that has a smaller hole than the shuttle cross-section? Maybe for these rare occasions the final windings could be hand wound?
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"Imagine a really huge shuttle diameter,....." - here's my logic on this situation - lets say the toroid needs a 1000 turns then the shuttle is loaded with 1000 turns of wire. When we have wound the 1000th turn on the toroid all the wire must be off the shuttle but this is vastly more wire than is needed to wind around the toroid so where is the wire located?
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