Crimping two wires together on the same crimp-connector it's criminal?

tcmtech

Joined Nov 4, 2013
2,867
This thread just keeps giving! :D

I have never found duct tape to be conductive so should we start a another 100 post discussion on what tape is best for what and who disagrees? o_O
 

MrAl

Joined Jun 17, 2014
8,562
Hi,

I just realized we havent talked about "welded" connections yet :)

Not what the Chinese often called welded (which is really soldered) but actual real welding where the wire and metal to be connected to are both melted in a small spot and the metals fuse together. So actual welding, but more like spot welding.

Welding is the preferred method for battery cells like NiMH where they have to be wired together. That's beause the very quick heating does not have a chance to damage the internal part of the cell. Of course welding would have the same flexing problem that solder has, in that the wires could break off, so we should probably discuss that again too.

The wires break off because the interface between any single strand of wire and the solder or weld blob is sharp, and that causes the same small section of wire to flex over and over again if the wire moves. This section could be as short as 1/16 of an inch which means a very very small bend radius, when if the wire had a flex sleeve that radius would be much longer like 1/2 inch or even 1 inch or longer. That tiny portion of wire metal flexes back and forth that that is what causes the break. This could be called a micro movement.
The interesting thing is that if we can change that micro movement into a larger movement where the stress is distributed over a longer part of the wire, it would mean less breakage. Also interesting is if we can increase it just a little with a shock absorbing material, then when the wire flexes the softer material 'gives' just a little and prevents the wire from breaking. When a smaller diameter wire is crimped, the insulation part is crimped also and that is what gives it a more break resistance structure. The crimp on the insulation, combined with the length between the bare metal part of the crimp and the back end of the crimp (where the insulation is crimped) gives the crimp both a little flexibility (at the insulation crimp) and a little more stress length. That helps prevent the break.
There are other ways around this too though. For larger connectors and larger alligators clips, we can wrap the wire around the end once or twice with the insulation still on it, and then just solder the bare end. The wrap gives the wire flexibility when it is flexed or tugged on. This has worked for me in the past on things like large automobile type alligator clips. It actually becomes hard to break the wire off.
 
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