Feeding long cable runs down heatshrink tube?

Wiring best practices and loom building technique
Gadgetman
Posts: 34
Joined: Sat Sep 03, 2011 9:29 am
ECU Model: S80 Pro

Re: Feeding long cable runs down heatshrink tube?

Post by Gadgetman »

Never had a run tricky enough to need lube on the car, but yes we do use it at work occasionally on really long runs. (Helps cut down the pulling force you're applying to the cable too).

Best not just using Fairy liquid or whatever if doing it at home, you can end up building salts into the loom that way as it dry's. :o
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Feeding long cable runs down heatshrink tube?

Post by stevieturbo »

Painless actually sell some nice braided covering that is split down the middle. Well, it actually overlaps itself. So it's always easily opened for access.
Basil
Posts: 36
Joined: Fri Sep 16, 2011 2:28 pm

Re: Feeding long cable runs down heatshrink tube?

Post by Basil »

When I come to do the loom I may not actually need to pull through more than say 5 feet of shrink tube, thinking about it there will almost certainly be spurs off the main sleeving, so that will mean I only need to pul through to that spur, then I am into a different length of shrink tube. Thanks for the ideas, I did think that one wire at time was the way, maybe with a stiff wire leader. I hadn't considered pulling through as a bunch. I will be putting some spare cables in though, I have already experienced the joys of needing to add extra sensors and things to a lovely un-messed with existing loom ;)
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Feeding long cable runs down heatshrink tube?

Post by stevieturbo »

Well....you have plenty of spare cores in that 6 core anyway lol

Although if I'm reading right...you intend to heat shrink the majority of the loom ? That wouldnt be very flexible, and I dare say it, not the neatest approach ?

Some braided sleeving heat shrinked at any intersections or splits would be much better, and is quite the norm for high spec looms.

This type of thing

http://www.heatshrink-online.co.uk/heat ... eving.html

http://www.hilltop-products.co.uk/produ ... -sleevings
Neilw
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Joined: Sun Oct 16, 2011 2:04 pm
Location: Sheffield, UK
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Re: Feeding long cable runs down heatshrink tube?

Post by Neilw »

First of all, you need to be using the correct tubing - Raychem DR25. It's expensive, but for a reason - it's the best, as used in F1 etc. One of the many benefits of DR25 is that its quite elastic, which allows you to use a trick to feed wires down a long run. What you do is this:

1. Make sure the wires are evenly twisted - pro's use a 'contra-helical' twist pattern where each layer in the bundle is twisted around the previous layer in the opposite direction. Not easy, but not essential.

2. Make sure the twisted bundle is as straight as possible with no kinks.

3. Feed the bundle by hand as far as it will go, twisting the bundle as it goes can help, but eventually you will hit a block.

4. This is the trick - tightly pinch the end of the tube where the wires enter, then with your other hand run it down the tube to stretch it slightly. At full stretch, tightly pinch the far end, then let go of the first end. The DR25 will shrink back to its original length, pulling a new length with it. Repeat...

As I said, DR25 is best because it's elastic (and abrasion resistent, high temp, chemical/oil/fuel resistant etc.) but it does work to a degree with cheaper heatshrink. You must be careful though not to over stretch it otherwise its knackered!

Hope this helps,
Neil.
DTAS54
Posts: 30
Joined: Fri Jul 29, 2011 9:08 pm
ECU Model: S100 Pro

Re: Feeding long cable runs down heatshrink tube?

Post by DTAS54 »

I usually push/pull through an extra wire the first time passing wires through a long run of tubing. This leaves you a pull wire in advance.

In liu of that, sometimes using an existing wire to pull the desired new wires through, plus an extra to return the original back is easiest.

I've also found that quick soldering of the pull wire to the new ones is sometimes the least bulky way of getting the wires to pass..... Tape/twisting, hard wire with a loop etc are sometime too bulky to easily pull......

YMMV
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