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Heat shrink

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Finished the course but still have the following question -

How do you feed a bundle of wires through a length of heat shrink tube?


There are a couple of problems people face when feeding cable through heatshrink, I'll cover a few of them.

1, Most people use a size of heatshrink that is too small for the bundle that they are feeding, if you are using 2:1 ratio heatshrink, I have found that a bundle that is greater than 60% of the internal unrecovered diameter of the heatshrink will be difficult to feed through over more than ~15cm.

2, Not lubricating the bundle/inside of the heatshrink be for feeding the bundle through. There are specialised lubricants available to assist with this, or you can also use products like WD-40, I have even seen dishwashing detergent being used. Just cut a small piece of the heatshrink off first and expose it to the product that you are planning on using, and make sure that there are no adverse reactions between the heat shrink and lubricant.

3, Not using a puller, I use TIG welding rods as a feed through longer (~1m+) lengths of heat shrink, I have also used string with a knot on the end that I blow through the heatshrink with compressed air to pull wiring through longer lengths (I have done 22m on a trailer with a single piece of heatshrink, 10 20G wires in the bundle using this technique)

4, Not being patient! I see it a lot, people trying to force a bundle through, and not being smooth, leading the the wires kinking in the heatshrink, this leads to having to back them out again, and then restarting, when you kink the wires, they will always tend to do so again in the same place as well.

5, Not having the leading wires in the bundle securely bound and in a tight bundle, so that they can't spread and hook into the heatshrink.

6, If you have heatshrink that has been shipped flat, you need to recover the heatshrinks internal opening, I do this with compressed air, holding one end of the heat shrink close, I give short, sharp bursts of air into the open end of the heatshrink, this opens it up and makes it a lot easier to feed through.

Hope that helps.

Thanks. Some good ideas in there, should make life easier in future.

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