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Old 16th Jul 2019, 1:12 pm   #1
Nickthedentist
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Default Any hints for neat twisting when making DIY twisted flex?

Spurred on by this thread started by Joe:
https://www.vintage-radio.net/forum/...d.php?t=108785

I had another go at making some decent vintage-look flex today.

I used one of the inner stands of the Paracord to pull-through a 6' length of silicone-insulated single-core flex, repeated so that I had one black and one red. Easy so far!

But what I found hard to do was twist the two together neatly. No matter how hard I tried, there were portions where one core seemed to be wrapped around the other, rather than the two being evenly intertwined. The result is OK but I feel I could do better.

Any tips, please?
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Old 16th Jul 2019, 1:28 pm   #2
paulsherwin
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Default Re: Any hints for neat twisting when making DIY twisted flex?

Can you make a mechanical winder powered by an electric screwdriver or drill?
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Old 16th Jul 2019, 1:30 pm   #3
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Default Re: Any hints for neat twisting when making DIY twisted flex?

I use a hand drill and vice.
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Old 16th Jul 2019, 1:30 pm   #4
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Default Re: Any hints for neat twisting when making DIY twisted flex?

Not sure whether or not this is the effect you're after but I did this by clamping the wires in a bench vice and twisting with one hand over the other. Every couple of inches the wires should be pulled apart to tighten the twist. This is ordinary mains flex and not 'paracord' of course.

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Old 16th Jul 2019, 1:36 pm   #5
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Default Re: Any hints for neat twisting when making DIY twisted flex?

Always make a couple of foot more than you need

Vice and hand drill for me.

Get everything stretched until it shows a little permanent extension and is dead straight, get all strands equal in length tension.

Apply definite tension.

Wind away

Wind a bit too far

Keep tension od and let it unwind a little

If needed, increase tension wind some more. A stretch while wound up sets the twist.

Keep tension on and let it unwind gently

Undo and cut to length.

David
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Old 16th Jul 2019, 1:42 pm   #6
Lucien Nunes
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Default Re: Any hints for neat twisting when making DIY twisted flex?

To make a twisted cable properly, each core has to be able to rotate on its own axis as well as rotate about the axis of the finished cable. If that doesn't happen, you are fighting the internal lay of the conductor strands, either tightening or loosening it, and each will exert some kind of stress on the finished cable trying to straighten itself back out. With hookup wire you can get away with putting the cores in the chuck of a drill, tying the other end fast and giving it a spin, and the overall lay-up wins out. With something larger like this, where the cores and their jackets can move independently, the tendency to straighten is likely to be more troublesome. If you wind each core on a spool, mount the spools on something that can rotate, and then spin them pulling the finished cable out of the middle, it should come out nice and even.

Quote:
a 6' length of silicone-insulated single-core flex,
I would be cautious about using it for mains if it is the fragile high-temperature type that can be stripped with fingernails. Even with its normal sheath on, it is not recommended for portable appliances except where specially required, such as on theatre lighting fixtures that run very hot.
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Old 16th Jul 2019, 2:03 pm   #7
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Default Re: Any hints for neat twisting when making DIY twisted flex?

When I used to go to repair the cable bunchers at Lucas Rists, they did it by having the individual wires going through a die which rotated to twist the cores. At the winding end, where the single reel received the new twisted flex, the reel itself was twisted end over end as it was rotated. But of course, they were making batches of 1000m at a time, however the principle's the same.
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Old 16th Jul 2019, 2:09 pm   #8
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Default Re: Any hints for neat twisting when making DIY twisted flex?

What I do is secure one end in a vise and then wrap one core around the other keeping my hands about six inches away.

It difficult to describe in words so see: https://www.youtube.com/watch?v=isiVdzy-rkg
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Old 16th Jul 2019, 2:21 pm   #9
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Default Re: Any hints for neat twisting when making DIY twisted flex?

When I twist wires together over a long length, I usually twist each one first, like a super-long torsion bar. A hand drill is fine. I clamp both wires in a vice and twist each one separately, counting the turns of the handle, to make sure they are identical. It is essential to keep taut while doing this!

Then, when you put the two wires together and release tension, they will naturally twist together like two snakes in a passionate embrace. Clamping together in the drill's chuck enables you to control this and keep uniform.

For short lengths, as Lucien observes, each wire needs to rotate around its own axis and as long as the free ends can do this, twisting by hand works (I do it standing up, with the free ends hanging).
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Old 16th Jul 2019, 3:25 pm   #10
David G4EBT
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Default Re: Any hints for neat twisting when making DIY twisted flex?

I'd agree that you can't simply hold one end of the pair in a vice and simply twist them together over each other without applying torsion to the individual flexes. Each of the pair of flexes have to be rotated individually with one end of the pair held in the vice, then as rotated, twisted over each other. It's harder to explain than it is to do, but the sketch below might help, as might this video:

https://www.google.com/search?q=how+...TF-8#kpvalbx=1

Have fun!
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Old 17th Jul 2019, 11:13 am   #11
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Default Re: Any hints for neat twisting when making DIY twisted flex?

Agree with the need to allow each wire to rotate, not simply laying them next to each other and twisting.

For significant lengths, allow the two wires to hang freely from a height, such as down a stairwell. Take care that they do not become tangled at the bottom.
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Old 17th Jul 2019, 12:17 pm   #12
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Default Re: Any hints for neat twisting when making DIY twisted flex?

My method is to cut the 2 'singles' and thread the ends through holes in a piece of wood, which is held in a vice.

Then put the 2 protruding ends into an electric screwdriver, and off you go! Pull gently to draw the singles through the wooden holes as you twist.

The 'tails' behind the wood can rotate on their axes as necessary - just don't go too fast with the screwdriver or the tails will whip about and tangle themselves.

[The same approach can be used with enamelled-copper or Kynar/PTFE-covered wire when making up 'bifilar' wire for winding baluns].
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Old 18th Jul 2019, 4:41 am   #13
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Default Re: Any hints for neat twisting when making DIY twisted flex?

I was taught a trick many years ago that requires an offsider.

Take the two pieces of wire and clamp them in the ( manual hand ) drill chuck. Offsider then holds the two wires about 6"/150mm away from the chuck, and at about 60 or 70 degrees apart. Wind the drill, and as the wires twist, offsider allows the wires to slip through their grip as the wire winds up. For some reason this "breaks the grain" of the individual wire cores in each wire, and allows a VERY neat twist that will hold its shape and doesn't "bunch up" as the cores try to return to their origional positions. This works with thin and thick multicore cable (see note), even silicone covered super multi strand like that used in modern battery powered aircraft, helicopters and quads.

"Multicore" is what I call a piece of cable that has a single outer cover of some type, be it PVC, silicon or cotton, and a "bunch" of strands within. It's no longer available here, but the classic 10/010 is what I mean. TEN strands of TEN thou copper wires, sometimes tin plated, sometimes not.

It has worked for me over more than 50 years. It's one "trick" I was taught as a kid when making heater wiring.

Joe
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Old 18th Jul 2019, 5:39 pm   #14
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Default Re: Any hints for neat twisting when making DIY twisted flex?

If I need it, I use a cordless drill and a vice. Works for me. That's for PVC sheathed cables with multistrand copper. I was taught this at work. We now use so much of the stuff we buy reels, from Leoni who used to be Rists. Probably the same place, Newcastle u Lyme.
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Old 18th Jul 2019, 9:22 pm   #15
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Default Re: Any hints for neat twisting when making DIY twisted flex?

I have used a technique similar to #13 for making about 2 m of twisted flex from 2.5mm stranded wire, for use with a battery charger. I cut the two conductors to length, clamped the two end in a vice, and then twisted them together by hand, starting from the vice and working back I wound the wires into small coils secured with masking tape to avoid getting them tangled, leaving a foot or so free. when all the free part has been wound, another foot is unwound and so on.

I still have a couple of 100m drums of thin twisted pair cable from my days at Plessey many years ago so haven't needed to make any of that size.
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Old 19th Jul 2019, 10:07 am   #16
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Default Re: Any hints for neat twisting when making DIY twisted flex?

Quote:
Originally Posted by joebog1 View Post
I was taught a trick many years ago that requires an offsider.

Take the two pieces of wire and clamp them in the ( manual hand ) drill chuck. Offsider then holds the two wires about 6"/150mm away from the chuck, and at about 60 or 70 degrees apart. Wind the drill, and as the wires twist, offsider allows the wires to slip through their grip as the wire winds up. For some reason this "breaks the grain" of the individual wire cores in each wire, and allows a VERY neat twist that will hold its shape and doesn't "bunch up" as the cores try to return to their origional positions. This works with thin and thick multicore cable (see note), even silicone covered super multi strand like that used in modern battery powered aircraft, helicopters and quads.

"Multicore" is what I call a piece of cable that has a single outer cover of some type, be it PVC, silicon or cotton, and a "bunch" of strands within. It's no longer available here, but the classic 10/010 is what I mean. TEN strands of TEN thou copper wires, sometimes tin plated, sometimes not.

It has worked for me over more than 50 years. It's one "trick" I was taught as a kid when making heater wiring.

Joe
I don't know about "break the grain" but the individual wires will be free to "untwist" themselves as they pass through the fingers of the helper. It's a sort of passive version of a machine to turn the individual cores at the same rate as they are twisted together which allows the twisted result to be "dead" and not try to untwist.

Sounds like what you call "multicore" I would call "multistrand". A core I would regard as being an individual insulated wire in a cable. (Over?)thinking about it I suppose "multicore cable" is a bit of a tautology.
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