Date:         Thu, 8 Oct 2009 00:27:40 +0300
Reply-To:     Janne Ruohomäki <janne.ruohomaki@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Janne Ruohomäki <janne.ruohomaki@GMAIL.COM>
Subject:      Re: Stupid wire question...really... (temp 2 wire)
Comments: To: David Beierl <dbeierl@attglobal.net>
In-Reply-To:  <4aca7c2d.02c3f10a.6d05.105b@mx.google.com>
Content-Type: text/plain; charset=ISO-8859-1

On Tue, Oct 6, 2009 at 2:07 AM, David Beierl <dbeierl@attglobal.net> wrote:

> There are two issues involved.  The one I mentioned is simply that
> the shrink-wrap stiffens the wire so that bends near the connector
> prefer the more flexible section right at the connector.  You can see
> this effect in your own photo where the wires do a reverse bend right
> at the connector.  The short radius of the curve overstresses the
> tired insulation and it splits.
>
> The second is the problem that happens any time you have a sharp
> junction between two different stiffnesses.
...
> The closer you get to perfectly sharp
> transition, the closer the stress gets to infinite.
...
> In this case the change between terminal and wire is the critical
> one; flexing there will lead to the wire itself fatiguing and falling
> off the terminal.  The shrink-wrap contributes by forcing more bend
> to take place near/at the terminal than otherwise would.  In itself
> it's not enough of a difference to cause much of this type problem.

How about putting some low temperature heat glue inside shrink-wrap?
Glue with same or a little lower melting point than the shrink-wraps
shrinking temperature. At least if You have a bit bigger wire terminal
with plastic casing or piece of plastic tube around the end of the
wire it should be easy. I have sometimes cut some heat glue sticks
with a razor blade into (half of) a toothpich like pieces that I then
push inside the shrink-wrap. If You make piece of glue so that it gets
thinner on the other end and stick it to that the fat end is towards
the terminal and dont melt it so that it loses its form too much it
should result in quite gradual change in stiffness.

One thing is that I dont know how well these heat glues take the test
of time the other is that dismantling this is a bit harder if You have
plastic casing around the terminal and need to take the casing off.