Awesome. Thanks!

I see what you mean.

Thanks for explaining the "how" behind this.

Neil.

On Mon, Oct 5, 2009 at 4:07 PM, David Beierl <dbeierl@attglobal.net> wrote:
> At 06:46 PM 10/5/2009, neil N wrote:
>>
>> So adding shrink wrap would keep the original wire near connector from
>> bending as much, thus hastening the stock wire casings' demise? Not
>> clear about the "how" behind this, �but of course trust you're right.
>
> 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. �In electronics we call it an impedance
> mismatch; mechanical types call it a stress raiser. �In either case energy
> is concentrated at the junction between the two. �It's the reason why the
> transmission 3-4 slider fails, the reason why the old Zenith terminal CRTs
> used to break off their mountings from the rest of the case in shipping
> every single time, the reason why you have to bevel the edge when you're
> cutting a tire-tube patch to size. �The closer you get to perfectly sharp
> transition, the closer the stress gets to infinite. �It's also the reason
> why a windshield crack will keep on extending until you drill a little hole
> in front of it. �And related to why you need a great big hammer to move
> something, and a small one to deform it at the surface.
>
> 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.
>
> David
>

-- 
Neil Nicholson '81 VanaJetta 2.0 "Jaco"

http://tubaneil.googlepages.com/

http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines