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

Thread Starter

gimpo

Joined Jan 27, 2016
124
1) Crimp connectors are used with stranded wire. Depending on the stranding, you have that many individual wires attached. So adding a few more doesn't hurt, given the constraint of total wire diameter.
Yeah, obviously I'm talking about stranded wires only. The only problem could be in the "insulation crimp" zone, since the total diameter increases dramatically. But solder keeps firmly the wires and solve the problem, as I understand.

2) As for solder, there may be specifications that forbid that. In aircraft, for example, when a crimped connection is specified, a soldered and crimped connection may not be. In general and barring such regulations, soldering probably doesn't hurt, but it may not help either to a well-crimped connection.
Bingo. You're again right. The major part of people against "multi-crimping" was referring their experience in a military "environment".
 

bwilliams60

Joined Nov 18, 2012
1,419
Use dual wall heat shrink tubing in this instance. This practice is quite common. Use a piece which covers the joint by about 3/8' on both ends. When you heat it up, the inner wall is an adhesive and sealant that seals the joint from moisture and does a very nice job of it. The outer layer then protects the entire connection. For peace of mind if you are really worried, place a second dual wall shrink tube over the first with extra tubing at both ends again. This connection will never see moisture. Have done this hundreds of times and never a comeback (that I know of :) )

Don't use silicones. They are too messy and hard to work with when heating the jacket.
 

#12

Joined Nov 30, 2010
18,223
I've seen that two layer tubing, but it's not what you find in most stores.
Do you remember the name of it?
 

profbuxton

Joined Feb 21, 2014
419
Properly made crimps do not require solder. Your pic shows a well made crimp. We regularly test our crimp tools for proper crimping. Shpuld hold a minimum of 10kgs pull tension.
 

Thread Starter

gimpo

Joined Jan 27, 2016
124
When the specs say, "no solder" you don't use solder.:rolleyes:
The aerospace industry probably uses proper crimpers, too.:D
As I wrote in the first post I don't love crimped connectors at all. I think that they are ok where/when no soldering tools are available (during a military operation for example), but they are everywhere today. So one has to embrace this "advanced" technology :(.
 

#12

Joined Nov 30, 2010
18,223
Dad always taught me solder a crimp for solid core
As far as I can tell, there ain't no such thing as crimping a solid wire because it refuses to become distorted.
You can attach a lug to the end of a solid wire, but the solder is the only thing with mechanical strength in that situation.
 

Thread Starter

gimpo

Joined Jan 27, 2016
124
Just a doubt about dual wall heat shrink tubing: it will leave enough room to plug the connector into his housing (e.g. AMP Superseal housing)? Or this solution is just for "open air" connectors?
 

Marcus2012

Joined Feb 22, 2015
417
As far as I can tell, there ain't no such thing as crimping a solid wire because it refuses to become distorted.
You can attach a lug to the end of a solid wire, but the solder is the only thing with mechanical strength in that situation.
Indeed but I didn't realise that when I first tried :oops: I had to redo a lot of crimps back then.

I do like to solder my stranded inline splices though like you, just seems more thorough :) If I do though I use these heat shrink tubes that have adhesive rings on either end to provide a fairly rigid but strong watertight seal to avoid flexing at the splice-cable intersection. Only drawback with them is they need quite a high shrinking temp. The kind of thing ETFE or silicon cable could only handle unfortunately. Think they were Raychem originally but not sure.

20160314_233619.jpg
 

AnalogKid

Joined Aug 1, 2013
9,380
As far as I can tell, there ain't no such thing as crimping a solid wire because it refuses to become distorted.
You can attach a lug to the end of a solid wire, but the solder is the only thing with mechanical strength in that situation.
I disagree. A properly calibrated crimping tool presents tons of force, and even steel wire distorts.

ak
 

Thread Starter

gimpo

Joined Jan 27, 2016
124
I've seen that two layer tubing, but it's not what you find in most stores.
Do you remember the name of it?
As I see, 3M produces something like that: 3M™ Heat Shrink Tubing MW, Multiple Wall, Semi-Rigid Polyolefin
As I understand, this tubes have an internal layer made of a completely meltable substance that will flow deeply when warmed. Nice!
 

tindel

Joined Sep 16, 2012
804
I've never seen a crimped connection soldered as well. I guess it doesn't hurt much if you can deal with the loss in bend radius due to solder flowing up inside the wire.
 

AnalogKid

Joined Aug 1, 2013
9,380
I recommend against soldering. The whole idea behind stranded wire and crimp connectors is that the wire can micro-flex in the micro-inches against the pressure point where nothing moves. This is what makes this connection technology so vastly more reliable in a vibration environment. In MIL systems we almost never solder a wire to a board or a connector contact. When we have to, such as solder-cup connector contacts dictated by other design factors, extra effort goes into the wire handling immediately near the connector to make sure the solder points never see any flexing. An example of this is a typical 38999-style circular connector updated to suppress electromagnetic pulse attacks, such as in MIL-STD 1310 and 3023.

And back to the original question - some industries such as aerospace and submarines have internal rules prohibiting the 2-wire technique in most situations. For more normal environments, UL has rules about ground wires but not other stuff.

ak
 

Marcus2012

Joined Feb 22, 2015
417
As I see, 3M produces something like that: 3M™ Heat Shrink Tubing MW, Multiple Wall, Semi-Rigid Polyolefin
As I understand, this tubes have an internal layer made of a completely meltable substance that will flow deeply when warmed. Nice!
Nice stuff, 135ºC shrink temp is a bit :eek: though
 

Thread Starter

gimpo

Joined Jan 27, 2016
124
If I do though I use these heat shrink tubes that have adhesive rings on either end to provide a fairly rigid but strong watertight seal to avoid flexing at the splice-cable intersection. Only drawback with them is they need quite a high shrinking temp. The kind of thing ETFE or silicon cable could only handle unfortunately. Think they were Raychem originally but not sure.
Hi Marcus, I have tested that heat-shrink tubes just today! Result? I was totally disappointed.
I was planning to use them massively in my projects, but after today I have to regret. The resistance to pull-force it's ridicolous, you can get the wires off by applying a modest force with your hand. I tried several wire sizes, from AWG 26 to AWG 20 and several hot air-gun temperatures but the result was absolutely poor...
Maybe I've used low-quality heat-shrink, I don't know... but I suggest you to put this "thing" in the trashbin.
 

Marcus2012

Joined Feb 22, 2015
417
Hi Marcus, I have tested that heat-shrink tubes just today! Result? I was totally disappointed.
I was planning to use them massively in my projects, but after today I have to regret. The resistance to pull-force it's ridicolous, you can get the wires off by applying a modest force with your hand. I tried several wire sizes, from AWG 26 to AWG 20 and several hot air-gun temperatures but the result was absolutely poor...
Maybe I've used low-quality heat-shrink, I don't know... but I suggest you to put this "thing" in the trashbin.
I can't say I've had a bad experience with them to be honest but maybe I wasn't putting it under any pull force at the time. Thinking about it I can see that happening because there isn't much of an ability to stretch lengthways as they go quite rigid once shrunk.
 

Thread Starter

gimpo

Joined Jan 27, 2016
124
I recommend against soldering.
Yes, but maybe you missed the point. When you want to crimp two wires in the same crimp connector then the solder can provide extra-help against pullout forces, since the insulation crimp cannot firmly grab two insulated wires together.

And back to the original question - some industries such as aerospace and submarines have internal rules prohibiting the 2-wire technique in most situations.
Ehmmm... why?
Could be some paranoid fear against breaking the rule #XYZ that would cause braking the rule #ZKY in the manual #WHZ? I mean... I know something about military furnitures and I know the general fear about doing something not stated, validated and signed on some document... :D
 
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Thread Starter

gimpo

Joined Jan 27, 2016
124
I can't say I've had a bad experience with them to be honest but maybe I wasn't putting it under any pull force at the time. Thinking about it I can see that happening because there isn't much of an ability to stretch lengthways as they go quite rigid once shrunk.
I strongly suspect that the main reason of the poor mechanical performances is the low-temperature solder used in such applications, it does not depends on the quality of the manufacturer. I mean... one cannot get a solder melting at so low temperature and, at the same time, having strong mechanical characteristics. If you take a run on wikipedia you will see that the best is SnPb solder melting at 187 C° (and it has extremely high tenacity too).
 

tcmtech

Joined Nov 4, 2013
2,867
Well being I rarely follow standard convention wherever possible I crimp and solder followed by having the wire itself properly supported near the connector so that it can't wiggle or flex.

Never had a properly crimped soldered and supported connector fail yet due to mechanical issues.

I've seen too many crimp only pull apart simple due to either being under crimped or over crimped or that have had enough corrosion set in that the wires rotted right out the connector.

Never seen a soldered connection do that and if they are corroded to that point there are other environmental issues that need addressing that are not connection related.

Sure my crimp and solder connections might not meet military spec but then they have to work in much harsher environments like being owned by old farmer's.
The military has strict maintenance schedules and standards whereas old farmer's don't and tend to run things until they die (either the machine or the old farmer. Whichever drops dead in the field first) on a zero maintenance equals zero operating cost or less if they can get away with it maintenance schedule.:p

BTW on extremely abusive high power applications like inside starters or high current DC motor or generators I have often went to the extreme of silver brazing connections. ;)
 
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