soldering short cable

[roberta1000]

Re the crimp question (yes - I know the OP doesn't have enough space). Crimps are electrically better than soldering all things being equal partly because there won't be any ongoing corrosion and partly because they wont weaken the original wire even if its flexed a bit. Solder joints do both of these.

And each to their own but there is no way I would do a solder joint like this. Too little space to make a good joint, no way to remove the flux residues, hit or miss with the insulation (barrel of the soldering iron my foot!). Screw fittings or crimps for me even if it means a bit of cutting back.

 

[plugwash]

A soldering iron works very well for heatshrink (use the side of the bit just behind the area that solder will stick to) far more control than with a heat gun and if you've just done a solder joint you have it there and handy..

but I would use fine stranded wire for the extentions to reduce the potential for stress on the joint and make it easy to solder, Soldering solid core to solid core is a pain.

flux residue shouldn't be a problem if you use a solder with a non corrosive flux like rosin.

 

[Softus]

FYI - 1 cm of a 2.5mm² conductor has a surface area of 56mm²....

And two conductors whose only contact is a hooked part will have a contact area of what?

 

[THRIPSTER]

BAS,

I make that 26mm squared for a single conductor?



Softus,

so two conductors = 56mm squared surface area, mechanically secure, not liable to significant mechanical movement and surround by a nice wet soldered joint - I see no problems.


Regards

 

[Softus]

so two conductors = 56mm squared surface area

Two conductors, each with a contact patch of x, are touching, and you believe that the contact patch is 2x?

I think not.

 

[JohnD]

unless they are twice as long, hooked over and bent double?

Anyway, I prefer the Stranded wrapped round solid idea.

 

[Softus]

I could have crimped 100 connections in the time anyone has taken the time to work out the surface area of the best method of soldering.

 

[stargazer]

And that is one of the reasons electricians prefer crimping – it’s much quicker than soldering.
Nothing wrong with that, but soldering is a viable alternative for a diligent DIYer prepared to take the time to do a careful job.

 

[Softus]

I agree - nothing wrong with soldering. If you get on with it and do it.

BTW, how many electricians does it take to work out the wrong surface area of touching conductors?

 

[THRIPSTER]

Softus,

Two bare copper conductors stripped back one centimetre hooked and bent over and covered in solder - and you believe they are are not effectively in contact - I think yes.


Ans: One electrician and you

 

[Softus]

Two bare copper conductors stripped back one centimetre hooked and bent over and covered in solder - and you believe they are are not effectively in contact - I think yes.

Where have I said that the contact is not effective? Or that I'm an electrician?

What I have said is that nobody has correctly worked out the contact patch area, despite having taken enough time to crimp 100 effective connections.

The most amusing theory of all is that you can double the contact area of one conductor by touching two together. Priceless.

 

[THRIPSTER]

Softus,

One conductor surface area = 25.49 sq mm (cross sectional area plus 1cm cylinder surface area based upon a radius of 0.3978mm) rounded up to 26mm sq mm to allow for leaching of the solder along the conductor. I stand to be corrected on the calculations though.

Two conductors makes a total surface area of 56 sq. mm covered in solder. Or do you believe that that the only electrical conduction takes place through the copper where the conductors touch and that there is none through the solder?

 

[plugwash]

why would anyone put a lot of effort into trying to calculate something that depends heavilly on how the particular joint went and doesn't matter much anyway.

it's not really possible to calculate how much direct copper to copper contact there will be in a soldered joint. It really depends on how tight the joint was before it was soldered, there may not even be any.

but it doesn't really matter. We are talking about soldered joints here not joints stuck together with an insulating glue.solder is a good conductor of both heat and electricity. While it is not quite as good a conductor as copper that really doesn't matter too much.

 

[THRIPSTER]

Plug,

Just spotted the topic and calculated out of interest really - if my calcs stand up then a surprising surface area of copper is covered in a good conductor and, as you say, if the joint is well made then there is absolutely no problem. My point would be that the contact areas between the copper conductors in a soldered joint is not the most important thing. The important things are that the joint is (a) mechanically strong and (b) is a well made soldered joint.

Would be interested if anybody calculates differently though.

 

[ban-all-sheds]

BAS,

I make that 26mm squared for a single conductor?

Pi x r² = 2.5

r² = 2.5/Pi = 0.796

r = 0.892mm

d = 1.784mm

c = 1.784 x Pi = 5.6mm

5.6mm x 10mm = 56mm²

So 2 x 2cm bared & bent over, including the ends of the conductors is a total surface area of 229mm²...

(Actually a bit more because of the deformation of the cylindrical conductors where they bend, but I think we can ignore that)