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rogerdw
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Joined: 22/10/2019
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Posted: 03:25pm 11 Apr 2022

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I am at the stage of winding some toroids for a Warpverter and have finished the inner windings and now have to fit the outer heavy windings.

After getting a bit of a shock at the price of 70mm� cable (around $24/mtr x 15 mtrs

) ... I have been investigating bundling multiple wires together to build up to the diameter or cross sectional area I need.

Seeing others have already done this in the past, I spent a lot of time searching through the forum looking for other discussions about the topic ... and so that it's easier to discuss without having to spend ages jumping from page to page, wading through all the posts ... I pulled in these quotes and pictures from various threads. I hope you guys don't mind.

And having all this stuff in the one thread should make a great resource for anyone else wanting to try this method in the future.

-------------------------------------------------------------------

In a thread about multiple stranded primary cables by tinyt here ...

Madness said 9:1 Is do able Klaus, I have done it on a single core as well with home twisted wire. One key to it is to comb the wires out so they are all in parallel then I put small cable ties on to keep the bundle together until they are twisted. Once twisted remove the cable ties and fit a length of heat shrink over the wire and heat it. Works well but does require some grunting to get it twisted well.

Warpspeed said If you twist it when its straight, and then try to wind it around the toroid, you may be in trouble.
Wires on the outside of the bend will be a bit short, and wires on the inside of the bend may buckle and bulge outwards.
May be best to keep the wires parallel and wind it on like that. Each wire will assume some kind of radius around each bend, and the wires can slide over each other and be happy. Heat shrink will then bind the whole thing together in a neat bundle.
See how this goes, but I have not had a lot of success with really large twisted bundles of wires.

Madness said If they are not twisted they want to flatten out at the corners and take up a lot more space preventing getting enough turns on. When they are twisted it holds them together and different wires get to go around different radiuses sort of randomly. My own experience is that it works when twisted. There are 24 turns on the primary below and 9:1 ratio in turns as well as total wire cross-section. Also they all fitted snug against the inside of the core leaving plenty of space for mounting.

https://www.thebackshed.com/forum/uploads/Madness/2018-06-25_204350_20170423_083633.jpg

tinyt said Klaus, the rope trial winding also gives me a rough estimate of how long the winding will be (about 780 cm. + lead outs). The wire size I picked is much thinner than what I see being used here, still it needs to be 86 strands. Like Tony suggested, I don't intend to twist them into a round bundle. Will post picture whether it is a success or failure.

I like Gary's use of cable ties to secure the lead outs and use of a stand-off(long nut?) instead of a mounting bolt.

-------------------------------------------------------

tinyt said Pictorial toroid build progress: here ...

Here is a picture of the fixtures I used. The 3-post stand is where a put the toroid during winding.

The stand allows better access to the bottom of the toroid.

Last 3 turns to go. (toroid top view)

For the mounting bolt insert, I used left over flexible pvc electrical conduit with an OD of 0.82" (20.8mm), I sanded the surface and forced it inside the toroid. Since the pvc is flexible, it became out of round. So, I used an AA size battery, used masking tape to build up the diameter and inserted it in the pvc to restore the round shape. Then I applied epoxy to hold it in place. (toroid flipped for bottom view)

Because epoxy will not stick to pvc, I also applied J-B Weld polyurethane plastic bonder to the pvc insert. (toroid top view)

-----------------------------------------------------------

And then Tinker's approach ...

The following can be found here ...

Tinker said

Previous attempts shown on this forum to use small enameled wire for the primary did not appeal to me so I created my own version - proper spun 7 strand wire.

For this I required a 'spinning' gadget, this is what I came up with:

The 'spinning' side.

And the supply side.

Well, it actually worked - once I had figured out there was a trick or two how to use it

.

Here is a close up of my 7 x 1.5mm spun wire.

And now a picture of the first of the three in hand wound on. The white split PVC presses the wire out while the epoxy sets.

Cheers, Roger

Haxby

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Posted: 10:37pm 11 Apr 2022

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Thankyou Roger for consolidating the posts. Great job!

Which way do you think you will go?

rogerdw
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Posted: 11:18pm 11 Apr 2022

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Haxby said Thankyou Roger for consolidating the posts. Great job!

Which way do you think you will go?

Thanks Phil, I'm hoping the other guys don't mind me pulling together their quotes. I'm still finding stuff that's been written about ages ago that would have answered a lot of my questions if I had seen it before.

I think for the smallest two toroids I will use Klaus's (Tinker) method of twisting 7 wires of 1.7mm wire. They both have the primary winding wound on already, so just need the secondary.

My secondary windings on the larger two toroids are 7 x 1.7mm on the medium and and 6 x 1.8mm on the largest ... so 7 x 1.7mm matches very well for the smaller two.

It makes for a 60-63 amp secondary.

It's the larger two toroids that I'm trying to decide which way to go.

Warpspeed suggests that twisted wire will not wrap so well (and all good reasons suggested) ... and yet Madness said his experience was opposite ... and shows an example of his that turned out well. Tinker's idea of multiple windings of 7 twisted sets worked well for him too.

I do like the look of tinyt's primary winding ... that is so neat and it obviously worked well for him too ... though I don't know how he managed to keep them all tidy and in shape with such a sparse wrapping wire around them. It almost looks like they are epoxied together before being wound ... but that would prevent them from bending altogether.

My medium toroid primary needs to handle 102 amps, so 11 or 12 of 1.7mm would cover that ... but of course the big one at 307 amps would need 34 x 1.7mm.

I did wonder if I were to drill some disks like Tinker did ... to keep the wires parallel ... and then wrap them in mylar tape to keep them all together ... then wind that.

I have ordered some adhesive mylar tape ... though if I was able to use the non adhesive tape ... the wire would be able to move more easily inside the bundle as it is bent around the toroid.

Anyway, I'm probably over thinking this as usual and just need to choose one method and get on with it.

In the meantime, Klaus, could you describe a little more about your method of twisting the 7 wires together please ... eg. did you anchor the eyelug end and twist the wooden disk ... and were the spools feeding it tensioned up to prevent them unwinding too easily etc etc. Thank you.

Cheers, Roger

Murphy's friend

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Posted: 08:46am 12 Apr 2022

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Thanks for your research & summary Roger, its a great idea.

If you are using 1.8mm wire I suggest not using more than 7 strands at a time. Gaspo here twisted 21 strands (I think) into one cable and found he could no longer wrap it around the core - it got way too stiff.
If you want to use many strands all in one go then Tiny's method is the go but stripping the enamel of so many thin strands, even with that you beaut expensive power tool, was not to my liking.

I used the same 7 strand method primary for the 3 bigger transformers, just used smaller diameter wire for some.

Roger you guessed the way I did it by myself pretty well. Its doable but this job becomes *very* much easier when done by two persons. The following is the two person method.

1.measure one turn around the core, I used standard 3 core electrical flex which is very close to twisted 7 strand 1.8mm wire diameter.

2. multiply that by your number of turns and add one meter for twisting losses and end termination (better get this right than one turn too short

).

3. cut 7 strands to this length and de enamel & tin one end of each.

4. wind 6 of those strands on those little spools (they were originally 3mm plumber solder reels), any sturdy spool will do as long as it can fit on your jig and also is wound on easily (I used my lathe, a very low speed drill might work too - wear leather gloves when feeding the wire on). Start loading the spool from the untinned end, important!

5. fit those 6 loaded spools on the jig and feed the wires through the 2mm hole.
Pull them out so all wires are the same length for perhaps 15cm. Feed the 7th wire through the center hole, it can be loosely coiled around itself at this time.

6. arrange the wires so that 6 sit side by side (no cross over from the exit hole) around the central 7th wire. This job can be tricky at first, use cable ties or fuse wire to hold them together. When satisfied that all the 7 wire's tinned ends are parallel and form a proper 7 strand cable, solder them together.

7. for the twisting I had a home made worm drive reduction with 3 socket screw 'chuck', it was powered by an ordinary battery drill. I do not know if the drill could do the job directly, the worm drive made easy work for it and weas also nice and slow so the amount of twisting could easily be checked.

8. to do the job the soldered wire ends were inserted and clamped in my 'chuck'. The 7th (central) wire was stretched out for its full length, a fishing line swivel attached to it and then tied off via some string to my fence. It is *important* to keep the central wire straight and that it can freely turn so the 6 wires are neatly spun around it.

9. to proceed, one person holds the disk jig and walks slowly backward, pulling the wire out at the same time while the other person powers the twisting drive.
Here is where the worm drive came in its own, it was clamped to a post and so took all the pulling force while the drill operator just had to hold the drill.

10. we found very little friction was required at the spools, we actually had to lessen it by reversing the spools so they fed 'over the top'. The wire does not need to be tightly twisted, just so that each strand is close around the center strand.

!important! do fit cable ties around the finished cable end as the spools are getting almost empty and do *not* let one wire run completely off its spool until the finished cable is tied off as close as possible to the jig exit holes. This prevents the wires unraveling due their inherent tension. When the jig is finally pulled off, the cable's tension will turn its end a few rapid times so keep the fingers away from it.

To wind this cable around the core do *not* pull the full length through it at each turn. Instead make a 'hoop' of it by forming a few loops (about 600mm diameter) first around the core. After securing the start of the winding to the core, start winding by rotating that 'hoop' a little if more wire is required.
This is harder to describe than it would be observing it but those who wound their secondaries by the hoop method would have no trouble following it.

My single person method fixed the soldered end (I soldered the lug on there) to a post and the disk was rotated by hand as it was walked back and pulled. Its a good exercise if one is inclined that way, I liked my power twisting method a lot more

rogerdw
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Joined: 22/10/2019
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Posted: 03:06pm 12 Apr 2022

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Murphy's friend said Thanks for your research & summary Roger, its a great idea.

If you are using 1.8mm wire I suggest not using more than 7 strands at a time. Gaspo here twisted 21 strands (I think) into one cable and found he could no longer wrap it around the core - it got way too stiff.
If you want to use many strands all in one go then Tiny's method is the go but stripping the enamel of so many thin strands, even with that you beaut expensive power tool, was not to my liking.

Thanks very much Klaus, I also hope the thread can be helpful for any others investigating the options.

Now that you've mentioned it, I reckon I had read about Gaspo's attempt some time in the past. I wonder how Madness got away with it ... maybe he only gave it a light twist and Gaspo made his pretty tight. Either way, I'm more inclined to use Tiny's method if I do go down the track of 20 or 30 strands.

Your directions are awesome, really detailed and make sense, so I can definitely see myself using this method for the smaller two toroids which each need one lot of 7 strands.

Once I've done those I'll have a better idea which way to tackle the bigger two .. whether multiple lots of 7 strands ... or Tiny's method.

I had been a little extravagent and bought one of those auto wire strippers ... so that job is not so daunting. It makes a good job of it.

I'll also probably need to strip another toroid to get enough wire to finish the lot, but it'll certainly be cheaper than paying retail for new cable.

Thank you again for going to the trouble of explaining the process so well.

Cheers, Roger

Godoh
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Posted: 08:09am 13 Apr 2022

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One other option rather than making your own stranded cable is to use fine strand Solar panel cable.
I bought a 100 metre roll of 6mm twin solar panel cable for about $145 off Gumtree.
It is insulated and rated to 600 volts DC. Current carrying capacity in air is supposed to be 60 amps plus.
I wound my transformer for my 8010 based 24 volt inverter with 6 of these cables in parallel.
Overkill I know but it does not run hot. I have a thermostat that turns the fan on in the inverter at 40 degrees C, and where I live it rarely comes on.
Of course my inverter is really only capable of about 3kw. Even though the original PowerJack transformer claimed to be an 8Kw inverter. Of course Taiwanese watts are not the same size as ours.
It may not be as neat as the amazing examples that you are showing in this article but then it powers my house and that is enough for me.
Pete

Murphy's friend

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Posted: 08:33am 13 Apr 2022

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rogerdw said Either way, I'm more inclined to use Tiny's method if I do go down the track of 20 or 30 strands.

Your directions are awesome, really detailed and make sense, so I can definitely see myself using this method for the smaller two toroids which each need one lot of 7 strands.

Thank you for your kind words Roger. What, IMO, makes Tiny's method hard is that he had to pull the entire wire bundle through the hole at each turn with that fancy plywood jig.
Less strands of a thicker wire can form a self supporting large 'coil' that can be pre fed through the core hole. No more wrestling with a long wire snake.

I'm still laughing when I remember reading about Gizmo's first toroidal core winding. He used welding cable (or heavy gauge earth wire) and had to pull the wire end out through the door for each turn.

Anyway, with 20-30 strands you need to tame them before winding. Lots of cable ties can be a bother as you need to cut each off as it is wound around the core. Perhaps spiral wrapping with thin string is better, you can leave that in place.

tinyt
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Posted: 02:22pm 13 Apr 2022

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Murphy's friend said ... Perhaps spiral wrapping with thin string is better, you can leave that in place.

That's how I remember doing it. However, I did not leave the string but instead cut it as I wind the bundle. The notched fixture is just to evenly space the bundle around the toroid. I remove it before each turn and put it back as shown on the picture after each turn to help in positioning the bundle on the outside of the toroid.
Edited 2022-04-14 00:29 by tinyt

rogerdw
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Posted: 03:13pm 15 Apr 2022

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Murphy's friend said
What, IMO, makes Tiny's method hard is that he had to pull the entire wire bundle through the hole at each turn with that fancy plywood jig.
Less strands of a thicker wire can form a self supporting large 'coil' that can be pre fed through the core hole. No more wrestling with a long wire snake.

Yes, I'd have to agree. I should have thought that through a little better ... I was really only refering to his approach of leaving his wire bundle straight ... and not twisted. To get to the required mm� I will need to use heavier wire at around 1.7mm diameter, so hopefully that will be more self supporting.

Quote Anyway, with 20-30 strands you need to tame them before winding. Lots of cable ties can be a bother as you need to cut each off as it is wound around the core. Perhaps spiral wrapping with thin string is better, you can leave that in place.

That's where I was wondering if I might try wrapping the bundle with mylar tape ... the same stuff as is used to insulate between windings of the transformer. That is very thin and should allow reasonable movement of individual wires inside the bundle as it is wrapped around the core.

I also ordered some self adhesive mylar tape off ebay, in case that may work better. I need to experiment.

Quote I'm still laughing when I remember reading about Gizmo's first toroidal core winding. He used welding cable (or heavy gauge earth wire) and had to pull the wire end out through the door for each turn.

Sounds like one of the toroids I unwound ... I put it in the middle of the lawn and pulled the wire out without winding it onto a shuttle. I did go back to the old way for the next one though.

tinyt said

Murphy's friend said ... Perhaps spiral wrapping with thin string is better, you can leave that in place.

Ahh, I picked up that you removed the string as you wound it ... but didn't realise you were just sliding the template on and off and using it as a locator. Certainly would have made it far easier to do than trying to thread it through the small holes.

So many neat ways of doing things.

Cheers, Roger

rogerdw
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Posted: 03:29pm 15 Apr 2022

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Godoh said One other option rather than making your own stranded cable is to use fine strand Solar panel cable.
I bought a 100 metre roll of 6mm twin solar panel cable for about $145 off Gumtree.
It is insulated and rated to 600 volts DC. Current carrying capacity in air is supposed to be 60 amps plus.

Thanks Pete. I have been looking out for any other options ... but am fairly limited because of the small holes left in my toroids. I've been going back and forth with one of Warpspeed's favourite calculator pages ... the circles within circles page ... to see if some of these other options might work.

I did get a call from my scrapee mate on Thursday who knew I was looking for various size heavy cable ... he had a hundred and fifty meters of about 5mm� three core cable (new) ... really like oversize extension cord. Really heavy insulation ... but it was aluminium wire.

He wanted $175 for it all ... but I couldn't see a use for it for myself in the near future, so I reneged on the offer. I could have cried as I drove off because he was cutting it up into manageable pieces. What an absolute waste. I've thought of about a hundred uses for it since I've come home ... but it's too late now.

Cheers, Roger

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