Heat shrink tubing

3338 Views 17 Replies 11 Participants Last post by Brian Considine, May 16, 2008

Robert Stokes

Discussion Starter · May 14, 2008 (Edited by Moderator)

This is not really a DCC question but this appeared the most appropriate place for it.

Yesterday, I was fitting a decoder into a loco. To insulate the solder joints I was trying to use heat shrink tubing. I used my wife's hairdrier on it for a couple of minutes but this didn't seem to work properly. The tubing may have shrunk a little but it was still loose. I had assumed that it would shrink until it was a tight fit.

Does it not really shrink all that much? Do you need a significantly higher temperature than a nairdrier and if so how? Was a couple of minutes not long enough?

Thank you in anticipation.

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dwb

· #2 · May 14, 2008

In my experience heat shrink tubing shrinks by about 50%. I use a hairdryer on it's hottest setting, use the nozzle attachment and hold it close to the tubing. I don't think I've ever needed to use it for as long as two minutes, maybe 30 seconds?

I buy my heat shrink from Farnell by mail order. They sell several different starting diameters and I think publish the technical specifications as well.

Hope this helps

David

SPROGman

· #3 · May 14, 2008

QUOTE (Robert Stokes @ 14 May 2008, 18:54) <{POST_SNAPBACK}>This is not really a DCC question but this appeared the most appropriate place for it.

Yesterday, I was fitting a decoder into a loco. To insulate the solder joints I was trying to use heat shrink tubing. I used my wife's hairdrier on it for a couple of minutes but this didn't seem to work properly. The tubing may have shrunk a little but it was still loose. I had assumed that it would shrink until it was a tight fit.

Does it not really shrink all that much? Do you need a significantly higher temperature than a nairdrier and if so how? Was a couple of minutes not long enough?

Thank you in anticipation.
If you don't have a proper hot air source (many gas powered soldering irons can be convereted to one) then just put an old bit on your soldering iron and hold very close. With the tubing I use I can actually touch the tubing without it melting and it shrinks down nicely. Try on a spare piece to start with.

Andrew Crosland

John Webb

· #4 · May 14, 2008 (Edited by Moderator)

I recall most heat-shrink tubing needs around 80-100deg C to give a quick shrink. Needs care that the heat is directed onto the pvc insulation which starts to melt around the same temperature!

The sleeve holding the bit in place on my Weller soldering iron held just under the wire gives me rapid shrinkage for the odd bit, but I invested in a temperature-controlled industrial hot-air gun some years ago and this set to 100deg does the job very nicely when I have a quantity to do.

By the way, if you use large self-adhesive clear shrink tubing, it is very easy to permanently mark the outside of a multicore cable at its ends by using such tubing to hold a label in place.

Regards,
John Webb

Chinahand

· #5 · May 14, 2008

Hi Robert,

I don't use anything as sophisticated as any of these. Just a throw-away gas cigarette lighter passed quickly 3 or 4 times close to the heat shrink tube does the job in about 3 seconds.

Regards,

Expat.

Doug

· #6 · May 14, 2008

If the item is small and a heat gun is not practical, I turn off my soldering iron and lightly tap the heat-shrink tubing with the hot, but cooling iron. It works fine.

I use a Black & decker heat gun for large applications - this thing gets really hot - I think it's used for paint stripping. A couple of quick passes on the low heat setting is enough to get the tubing or covering to shrink.

Robert Stokes

Discussion Starter · #7 · May 14, 2008

Thanks for the replies. I'll try one or two.

poliss

· #8 · May 14, 2008

Why not use the 'barrel' of a soldering iron as in this youtube vid?

Brian Considine

· #9 · May 15, 2008

QUOTE (Doug @ 14 May 2008, 21:18) <{POST_SNAPBACK}>I use a Black & decker heat gun for large applications - this thing gets really hot - I think it's used for paint stripping. A couple of quick passes on the low heat setting is enough to get the tubing or covering to shrink.

Same here - most of the heat shrink I use has about a 50% shrink rate, although I do find that it can vary. I've also found that it's a bit like soldering - a decent amount of heat for a short time is better than not enough for a long time !

Robert Stokes

Discussion Starter · #10 · May 15, 2008

Thanks for the video Poliss, especially as I think that my soldering iron is exactly the same type as the demonstrator was using.

Richard Johnson

· #11 · May 15, 2008

QUOTE (Robert Stokes @ 15 May 2008, 17:42) <{POST_SNAPBACK}>Thanks for the video Poliss, especially as I think that my soldering iron is exactly the same type as the demonstrator was using.

***Sorry, can't help it - what a truly shocking example of an installation that video is - a really scruffy install I'd be totally ashamed to show anyone!
* using exactly the wrong tool to strip fine decoder wire
* stripping too much insulation back
* wires not measured to be the right length for the install and bent up everywhere
* not insulating the ends of the wires he cut short
* Not cleaning the iron tip between joints (it should be shiny!). All it takes is a wipe on a damp sponge!
* Lingering far too long with the Iron on the joint becaue the tip isn't properly clean and transferring heat properly
* Using far too much solder on the joint for the same reason
* ....and the way he prepared the black wire with several threads of copper missed is the cause of many many unexpected shorts.

An OK demo using the Iron for heatshrink though

Richard
DCCconcepts

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poliss

· #12 · May 15, 2008

Looking forward to seeing your videos of how it's done properly Richard.

ben1

· #13 · May 15, 2008

QUOTE (Richard Johnson @ 15 May 2008, 17:31) <{POST_SNAPBACK}>***Sorry, can't help it - what a truly shocking example of an installation that video is - a really scruffy install I'd be totally ashamed to show anyone!
* using exactly the wrong tool to strip fine decoder wire
* stripping too much insulation back
* wires not measured to be the right length for the install and bent up everywhere
* not insulating the ends of the wires he cut short
* Not cleaning the iron tip between joints (it should be shiny!). All it takes is a wipe on a damp sponge!
* Lingering far too long with the Iron on the joint becaue the tip isn't properly clean and transferring heat properly
* Using far too much solder on the joint for the same reason
* ....and the way he prepared the black wire with several threads of copper missed is the cause of many many unexpected shorts.

An OK demo using the Iron for heatshrink though

Richard
DCCconcepts

Hi
And I thought that video was complicated!

I can't imagine what yours would look like if you did one!
Regards,
Ben

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Richard Johnson

· #14 · May 16, 2008 (Edited by Moderator)

2

QUOTE (ben100 @ 16 May 2008, 01:00) <{POST_SNAPBACK}>Hi
And I thought that video was complicated!

I can't imagine what yours would look like if you did one!
Regards,
Ben

***It'd be no more complicated at all Ben - just properly done.
And
***No Poliss, I won't be posting one as I don't own a video camera. I spend lots of time teaching such things already and don't have time to become a video producer for the sake of Ego

. Besides, if you followed my comments you'll already know how it should be done.

For you its important - N scale is very unforgiving of scruffy installs, long stripping which needs too much heatshrink there's no space for, bare wires which are pressed against metal chassis and lots of wire that has nowhere to go!

A tidy installation is reliable & always works best!

Basically my point is simple:

Its as easy to do it right as wrong, and many of the blown decoders and most faulty installs I see suffer from problems created by just such issues, so I really think that if someone is going to present themselves as an expert, the very least they should do is do the job properly and tidily.

Richard
DCCconcepts

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Brian Considine

· #15 · May 16, 2008

QUOTE (Richard Johnson @ 15 May 2008, 16:31) <{POST_SNAPBACK}>An OK demo using the Iron for heatshrink though

Richard
DCCconcepts
After reading the comments I just had to watch the clip & agree with Richard.

railstimulator

· #16 · May 16, 2008 (Edited by Moderator)

I have to agree that the demonstrator's techniques are not to be recommended. If he did work like that in my repair workshop he'd be sent for remedial training.

1) You should never cut thru wires with a modelling knife, a pair of wire cutters should be used.

2) As the unit carries a warning about static which can damage it, each wire should be cut individually

3) Stripping back wires by scraping is not the correct way. A pair of purpose wire strippers should be used. Stripping by cutting through the insulation with a knife or even wire cutters will nick the conductor (if solid) which reduces it cross sectional area or in the case of multistrand will/may result in the lose of a strand or two. this will reduce the current carrying capability. A nicked solid wire is weakened at that point.
In his case he is reducing the wire CSA by scraping.

4) Where he does appear to be applying flux he doesn't pre tin the wires.

5) His soldering technique is not very impressive.

6) Shrinking of the heat shrink should be done by a heat gun to ensure equal shrinkage.

7) the unused wires from the chip should be covered with a heat shrink tube which extend over the end and then shrunk. This will ensure that they do not get shorted.

Ok it just one of his toys but personally I treat my toys with more TLC

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SPROGman

· #17 · May 16, 2008

And why does a Jinty have a "diode board"? They look more like inductors to me. I associate diodes with directional lighting, unless they're a bodge to reduce the voltage to the motor.

You should never put a chipped loco straight on the main track and run it. Always try programming on the programming track first, where the current is limited and you have less chance of doing any damage if the installation is faulty.

Andrwe Crosland

Brian Considine

· #18 · May 16, 2008

QUOTE (SPROGman @ 16 May 2008, 12:25) <{POST_SNAPBACK}>You should never put a chipped loco straight on the main track and run it. Always try programming on the programming track first, where the current is limited and you have less chance of doing any damage if the installation is faulty.

Andrwe Crosland
Another good point & well advised too.

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