Importance of "Marine" rated wire

[SBM1234]

Rather than blindly following my advice, take a look at this 4-page site, heavy on pics, light on print. This gives you an excellent background into what and why...

http://www.pbase.com/mainecruising/w...ination&page=1

The author is one of the guys who I consider as an expert on the subject. I do not hav ethe $6K wirth or crimp tools he does, but after reading this, I think you will be able to form a pretty educated decision.


Phil
Kicker

A guy who writes that the corrosion risk is increased when using solder doesn't seem to me to be an expert, but I digress.

[Dandy]

This company does a pretty decent job of offering quality wire, tooling and terminals. They carry decent stock levels and ship quick. We use them for odd connections for custom builds at work.

http://www.waytekwire.com/products/

[philwsailz]

132575328_AWjoaGIo.jpg

Seems that the shear stress imparted on the strands by the crimp could potentially exceed the yield strength of individual strands and cause failures. In a high cycle fatigue situation, the cyclical bending loads applied to the crimped end of the wire would likely cause individual strands to part (particularly those on the OD of the bundle) that are at or near the limits of their yield strength due to the shear stress imparted by the crimp. When the connections are soldered, the load is spread among several of the strands and there is no shear stress imparted by the crimp so it seems that this would be a more robust connection.

If the element of human error is removed from the failure statistics, one would expect the soldered connections to outperform the crimped connections.

A proper crimp will never introduce shear. It is a wholly compressive application of force. Take a 3/4" piece of copper tube. Stick your finger in it. Now put the tube in a vise and start cranking. Your finger is not cut off, it is crushed. This is a fairly accurate analogy, except that your finger will not cold work into a polishable homogenous mass like is shown here

[SBM1234]

'Shear' as I used it was one of the stresses acting on the wire. Not the actual cutting of the wire.

Total stress on a crimped wire = shear + bending (cyclic)

Total stress on a solder wire = bending (cyclic)

The individual strands (especially those on the outside) are under more stress in the crimped condition than in the soldered condition.

[philwsailz]

In the above image, if the copper strands had been soldered prior to crimping, we would see that the barrel of the crimp connector did not make uniform contact all around, but rather likely we would see two "holes" through the barrel of the connector, basically at 90-degrees to where the crimp pressure was applied. Assuming a worst-case scenario where a soldered wire end became a perfectly cylindrical feature that the connector was crimping to, we would actually see only a tiny area of contact between the connector and the soldered wire end. Think about it. From a geometry standpoint you would have a large cylinder contacting a smaller cylinder in two places 180-degrees from each other. The resulting intersection would geometrically be two lines..... with infinitely small area....

[philwsailz]

'Shear' as I used it was one of the stresses acting on the wire. Not the actual cutting of the wire.

Total stress on a crimped wire = shear + bending (cyclic)

Total stress on a solder wire = bending (cyclic)

The individual strands (especially those on the outside) are under more stress in the crimped condition than in the soldered condition.

What happens where the solder stops? You got a bunch of flexible wires emerging from a single brittle one.... From a shear + bending standpoint, your solder joint turns a bunch of tiny strands of wire that individually do not exceed their modulous of elasticity into one large strand of wire that is quite brittle by comparison...

[SBM1234]

In the above image, if the copper strands had been soldered prior to crimping, we would see that the barrel of the crimp connector did not make uniform contact all around, but rather likely we would see two "holes" through the barrel of the connector, basically at 90-degrees to where the crimp pressure was applied. Assuming a worst-case scenario where a soldered wire end became a perfectly cylindrical feature that the connector was crimping to, we would actually see only a tiny area of contact between the connector and the soldered wire end. Think about it. From a geometry standpoint you would have a large cylinder contacting a smaller cylinder in two places 180-degrees from each other. The resulting intersection would geometrically be two lines..... with infinitely small area....

That is not how to properly solder connections.

[SBM1234]

What happens where the solder stops? You got a bunch of flexible wires emerging from a single brittle one.... From a shear + bending standpoint, your solder joint turns a bunch of tiny strands of wire that individually do not exceed their modulous of elasticity into one large strand of wire that is quite brittle by comparison...

Yet they still have less of their yield strength utilized than at the compressed connection of a crimp due to the lack of combined stresses.

[philwsailz]

Do this experiment in order to be convinced of what I am saying.

Take two 3" pieces of 16AWG wire and strip the insulation off.

On the first piece of wire, solder it up solid the entire length.
On the second wire tin each end to 1/2" so you have "handles" Leave the middle 2" un-soldered raw stranded wire

You now have your test specimens.

Taking the first sample, Grab it by the ends and bend the wire at the middle from straight to 90-degreesd and back. That is one cycle. Do this repeatedly until the wire breaks. Note the cycles.
Now repeat with the second sample; grab it by the ends, and bend it to 90 degrees and then return. Note the number of cycles.

Something tells me you don't actually need to do this test as by now it will be quite clear that the second sample probably will never break....

[philwsailz]

That is not how to properly solder connections.

That is not how you do power connection for an amplifier either, as you said you did.... a tinned wire stuck into an amp's power or speaker terminals will provide an equally poor connection...

Sorry, man, I don't want to be the cyber bully behind the keyboard... Tone is lost, so know I just consider this debate...

[chpthril]

If we have moving strands in a crimped connection, we have a cable that will eventually pull out. Doesnt a quality commercial grade crimp basically do the same? Compress the individual strands into 1 at the point of the crimp?

[philwsailz]

If we have moving strands in a crimped connection, we have a cable that will eventually pull out. Doesnt a quality commercial grade crimp basically do the same? Compress the individual strands into 1 at the point of the crimp?

I think... (this is where I will cite an earlier post where I shared I could be on the fence... I do solder sometimes) I think that the difference comes down to this. When you turn a mass of stranded wire into a soldered bundle you introduce elongation when the soldered bundle bends. Think about it; in a soldered bundle the strand in the middle is only in bending, but the outer strands are now being stretched to allow the bend. You quickly work-harden the outer strands where they are soldered together. In a crimp the strands are all still independent where they exit the crimp connection' they can move with respect to each other as the bundle is bent. This prevents the elongation of the outer strands.

I think that IF you executed a crimp, then you heated the crimp to the pont you could flow solder in from the ring-end you could do a soldered crimp that did not put so much solder in the joint that it flowed out the wire end. In that case a post-crimp soldered crimp might not create a problem where the wire exits the crimp. How many of us will repeatably add "just enough" so that it doesn't wick all the way through though???


I love debating, and its not like we are talking space shuttle wiring.... I had a buddy's son who soldered harnesses for the aerospace industry. You wouldn't want his job. Ever considered what a bubble inside an electrical connection will do in the vacuum of space?

[carcrz]

Hahaha I think I opened the wrong can. I didn't mean to start another Oil debate.

So, what about soldering a crimped connection?

[Dandy]

I suggest either simply using wire nuts or if that is too expensive, twist and tape - electrical if you have it, Duct if you don't

[philwsailz]

I suggest either simply using wire nuts or if that is too expensive, twist and tape - electrical if you have it, Duct if you don't

Uggh. Don't get me started.... My Monterey cruiser I bought last June has wire nuts all over the place.. 16 or so on the stereo at the moment and I have been removing them from the engine compartment...

I will have all the wire nuts out of the boat prior to boating season this year...