Wiring and connectors

**LINK**

There is a serious corrosion problem with almost all the motorcycle-bullet sleeves currently on the market. The ones sized just over 4mm diameter, not the Japanese sizes. The originals had a tinned brass sleeve, but for some years they seem to be tinned steel. OK when new, but in the damp, the sleeve rusts inside. Nothing to do with flux, just the weather and the space - damp gets in, with salt in the winter, and the mixture of brass bullet and steel sleeve causes electrolytic corrosion. This creates resistance in the joint, and then the corrosion really gets going.

There are some bronze-coloured sleeves which are not double-ended, the sleeve has a crimp or solder fitting at one end. They seem much better. Personally, I do not have a professional factory crimping machine, so I do the best I can with hand crimpers, and then fill the joint with solder. It works for me.

Any theory about heat shrink keeping the water out does not fit with my experience, and the idea that copper wire will harden with heat is contrary to the science - honest!

Regards - Tim (ex BSA, ex Norton, ex Hesketh)

Absolutely Correct. Back in the 1970s we thought we were being clever crimping and then soldering connectors on rally cars. It proved to be a disaster, the crimped and soldered joints failed very quickly with the vibrations. The crimped only joints never gave any trouble.

Peter

Temperature does not harden copper its movement (vibration) that does

I have worked on mains electric kit that had to be used in a wet environment, I used adhesive heat shrink and had no leakage.

Very likely vibration causes work hardening too, but I was referring to a form of Age Hardening where the application of heat below annealing temperature causes precipitation within the grain structure. Apparently it can happen at room temperature! The Copper's purity makes a difference, and solder compromises that by mingling Lead, Tin and whatever else in the Solder with Copper near the surface. Not the same as annealing, in which Copper is softened by heating well above soldering temperature and then quench cooling. The effect is small.

If work hardening due to vibration was the major cause of failure, crimped and solder joint would behave the same. They don't: vibrated soldered joints are more likely to fail than vibrated crimps.

Dave

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Not quite true, Dave

… Your closing statement is valid, but the preceding sentence is not.

Peter’s explanation is good … at a micro level, vibration fatigue failure has a lot to do with the ‘stress-raiser’ created by filling the crimp with solder.

[stated from memory … If I can find corroboration, I will report back]

MichaelG.

This paper doesn’t actually address the specific issue under discussion here … BUT it is very informative, and I think the final image nicely illustates my point.

**LINK** : https://www.osti.gov/pages/servlets/purl/1356221

MichaeG.

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On the other hand … here’s some evidence of ineffective crimping:

https://www.osti.gov/servlets/purl/1288669

Edited By Michael Gilligan on 12/04/2022 07:27:07

it all comes down to the skill of the person doing the job soldering requires some. any fool can squeeze a pair of pliers

Multi strand wire and fluids are never happy bed fellows ! Ask any one who had a Landrover TD5 engine ! engine oil would cappiliary from the engine to the computer under the seat along about 8' of wire. Noel.

A further factor is the attachment of the bullet (etc) to the insulation itself, and the nature of the insulation. Decent solder-type connectors (including bullets) include a clamp around the insulation of the wire. This is more effective if the clamping is done after the soldering has cooled - otherwise any clamp is filled with melted insulation which can be cut through. Yes, this does slow down the attachment process, but adds the stiffness of the insulation to that of the wire in vibration cases. In my mind, doing this sort of connection 'properly' is part of the discipline - it used to be called craftsmanship.

Modern harness wire for vehicles tends to be insulated with a stiff version of PVC - with less, or different, plasticiser. This results in a stiffer wire, and one of smaller diameter - easier to feed through small spaces. The behaviour of rubber insulation is quite different from this more-rigid PVC.

Regards, Tim