Discussion: Making Your Own Coiled And Retractable Cables

idbruce

Hello Everyone

One of my current projects requires a coiled cable. In the past, I have altered coiled cables, by heating them and bending them to my will. Additionally, I have heated straight cable, which I coiled, to make my own coiled cables, with minimal success.

For my current project, I would like to make my own customized coiled cable, to satisfy my strict requirements, and I am looking to gather specialized information pertaining to this subject, so that it may benefit me and any others that may be interested. As I see it, it should all be a matter of heat and starting with the correct cable, however to do it correctly, torsion may be required, although I am not sure.

As for the cable, I suppose the investigation of various coiled cable companies and the materials they use, would reveal the proper type of cable to begin this process. However, I am certain that not all coiled cables are created equal. I would imagine that the best coiled cables are constructed from continous flex cable, but I could be wrong.

Any input you may have on this subject will be greatly appreciated.

Bruce

Phil Pilgrim (PhiPi)

A lot depends on the required wire gauge, number of conductors, and how rugged it has to be. For starters, I suppose you could fish a flexible cable through some precoiled plastic air hose.

-Phil

CuriousOne

I have been on coiled cable manufacturing plant. The cable is coiled imediately as it is made, process is quite different, so making same at home won't be that easy.

idbruce

@Phil

That might work for some peoples applications, however I must have (2) 18 ga. wires fitting through a 3/16 dia. hole., which is pretty tight. But let's say that diameter was not an issue, fishing the wires through coiled air hose might be quite difficult, although I am not sure. Conduit runs are limited to a maximum of 360 degrees from point to point, due to pulling and fishing issues. There are times when it can be quite difficult to get a nylon or steel fish tape through 360 degrees of bends.

@CuriousOne

I have been on coiled cable manufacturing plant. The cable is coiled imediately as it is made, process is quite different, so making same at home won't be that easy.

I would have never guessed that it was coiled immediately during manufacturing, however I am fairly certain that is can be accomplished post manufacture, as long as the temperature of elasticity is reached, but I am also certain there are other issues at play, such as strand count.

CuriousOne

Yes, sure you can do it in post processing. But just imagine, the inner diameter of coil is smaller than outer diameter. Insulation thickness is same around the wire, right? so, when coiled, where that extra insulation from internal side have to go?

Gadgetman

*Strikes a silly pose, holding a keyboard up into the sky*

By the Power of Google!

http://www.google.no/search?q=youtube+hows+it+made+coiled+cable&sourceid=ie7&rls=com.microsoft:no:IE-Address&ie=&oe=&gfe_rd=cr&ei=FNz6U4W6GY_K8ge08YHIBQ

idbruce

Since we are talking about reaching the temperature of elasticity for post processing, I can only assume the jacket and wire insulation would deform and distort.

idbruce

@Gadgetman

The first video from those results was quite impressive and informative, and just along the lines I was thinking. However, the reverse wind.... Who would have thought of that?

W9GFO

For many years I have coiled wires, especially servo cables, by tightly wrapping around a rod (such as a small screwdriver) then heating with a heat gun until it just starts to soften. I hold in place until it cools, then it's done. Makes things much tidier. A hair dryer can work too, but not quite as good as the heat gun - the coils don't retain as well. It does have the advantage that it won't melt the insulation, so in that regard it may be better.

idbruce

For Those That May Be Interested

From Gadgetman's list of links, this video was very informative (http://www.youtube.com/watch?v=wTmzg6WMnf0). Early this morning, I watched a portion of it again, only this time, I tracked down some vital information. As it pertains to the wire in that video, here is a link to the specifications : http://www.northwire.com/products/nwi-direct/retractile-power-cords/specifications

idbruce

I believe I am getting down to the heart of the matter.

Northwire (linked to in previous post) lists some of the cables utilized for coil assemblies as SJEOW, with a TPE jacket. So in reality, not only is the jacket TPE, but the conductor insulation is TPE also, or at least it can be, according to SJEOW specification.

TPE is the abbreviation of thermoplastic elastomers.

The following is a quote from Wikipedia - Thermoplastic elastomer (http://en.wikipedia.org/wiki/Thermoplastic_elastomer)

In order to qualify as a thermoplastic elastomer, a material must have these three essential characteristics:

1. The ability to be stretched to moderate elongations and, upon the removal of stress, return to something close to its original shape.
2. Processable as a melt at elevated temperature.
3. Absence of significant creep.

I now believe that it would be easy to form a coil assembly from SJEOW cable which has TPE as insulation for the conductors.

idbruce

Although I am not 100% certain, I think SJEOOW would also work, if constructed according to the video link above, and it is readily available from McMaster-Carr.

The following is an excerpt taken from the McMaster-Carr catalog which shows the thermal properties and insulation type. They also have other material which might work, but I think this is what I might try. However the diameter is much larger than I can currently accomodate, so I may have to do some alterations or come up with a different cabling method.

idbruce

Instead of ordering and waiting, I decided to attempt to make a coiled cord from some black 18 gauge SPT-1 zipcord I had laying around. According to the specifications that I found, SPT-1 has a PVC sheathing, but as mentioned, I decided to try it anyhow. So I wrapped it up around some 5/8" round aluminum bar stock and zip tied the ends parallel to the bar. I then heated in the oven at around 205 degrees fahrenheit for about 15 minutes, remove it, and allowed it to cool. After cooling, I reverse wound it according to the video.

The coils are now about 1-1/4" in diameter, but I must say that it works pretty well, and that it retracts back every time. It is not nearly as fine looking as one bought from a manufacturer, but it don't look bad. The main thing is that it works well and that it will do exactly what I want, while looking decent.

erco

That reverse twist is a very cool trick! I wonder if that was an accidental discovery, like some other things: http://www.impactlab.net/2010/02/21/19-accidental-discoveries-that-changed-the-world/

idbruce

erco

I was wondering that myself. I would guess yes.

idbruce

For those that may be wondering what the coiled SPT-1 cord looks like, you can see it here: http://forums.parallax.com/showthread.php/156588-Trying-Something-New-Today-My-Latest-Experiment-A-Linear-Slide-Carriage?p=1289543&viewfull=1#post1289543