Homebrew copper crimp connections

[Joules]

At last some play time.... I wanted to get some crimps and a crimping tool for the 25mm sq. welders cable I picked up for our solar PV install.  Ok, the crimps aren't too expensive, but the crimping tools are.  Hmmm, that cable looks just about right to fit in some Microbore copper pipe, and thats how my DIY crimp was born.  Easy to keep on hand and the copper pipe comes in for loads of different jobs.  I dare say the same technique could be applied to different cables using different copper pipe sizes...  Just watch your copper isn't too thin if it's carrying heavy current.

http://homepages.tesco.net/jenesis/ESF/DIY%20Cables%20and%20Crimps/Cables%20and%20Crimps.html

Now it might be that some would advise tinning this lot after crimping, only time will tell on that one.  Very simple and quick to do once you have made a few.


                                                          Joules

[frotter]

Good bodgery! i must say though that i would lean toward generous soldering myself.....

 

[ajstoneservices]

would lean toward generous soldering myself.....

.

especially around the exhaust

[Ivan]

Nice tip. I've done similar myself - using 15mm water pipe for car starter cable. A friend, suggested it. He recommended using a small diameter solid steel pin running in the same plane as the wire, and using a mole wrench as a crimping tool. Seemed to work!

[camillitech]

Most impressed

Paul

[guydewdney]

Ah ha!

My area of expertise. I used to design electrical connections for the military, rail, space and aerospace industries (until about 7 years ago)

In the nicest way, the crimping technique you are using is insufficient. I have no problem with the rest of your system - in fact, I have done the very same. I found that blunt drills worked best for copper drilling.

When I have had to bodge a crimp, I have tried to keep to the same form as a 'proper' crimp. To this end, I use a nut, or similar thick walled small cylinder that fits neatly round the outside of the tube. Cut it in half to end up with a C shape. I then find a drill shaft, or similar (bolt?) that is about 1/2 the diameter of the copper tube.

Hold nut in vice (or on anvil)place tube in C shape. Place bar on top, in line. Twat with a big hammer, or squash as hard as you can with a vice.


The theory:-
You are trying to create a sealed, pure copper environment. A squished tube into an oval (as above) causes the wires to splay out. You are not going to have a very even distribution - ie theres going to be loads of wire in the middle, little in the outside. Therefore, an air gap - air gap = corrosion = bad connection (not now, but in a while). The better way is a ferrule style crimp - where the copper tube is compressed from all sides (like a hydraulic fitting) - but this is difficult to bodge. The indent system as I described, keeps the wires closer to the original centre of the wire, reducing (but not totally eliminating) the splay effect.

Soldering a properly done crimp is a waste of time. The solder cannot get into the joint. If you are going to solder, dont bother crimping!



On a similar note - the red/blue/yellow crimps you get are fine, IF you use the proper 'ratchet' tool (15 quid). Never ever use the pressed steel plier things unless in an emergency. Never ever use scotchlocks for anything other then temporary connections (god awful things those)

[northern installer]

Agree with that Guy! if you cant use the correct crimping tool and crimp/cable combination,(which is a precision tool),
solder it! useful for other bodge work too,like several cables into one crimp etc.
Scotchlocks  one of our employees recently discovered these nasty little things in a house installation during a test and inspection;and people wonder why we ended up with part 'p'    the householder said 'they sell them in halfords so they must be ok'             POOR CONNECTIONS CAUSE FIRES!

[Joules]

OK boy's,
           having taken what's been said, I'm open to suggestions on improving my bodge....  Soldering is out the question as I don't want to damage the insulation or introduce flux, which in itself can cause corrosion, by it's very nature.  I do have a hydraulic press here, so the option is available to sit and make a nice 4 anvil press tool, but the fun is in the bodging here.  I will cut open one of my crimps and see what state the cores are in.  I was pretty confident as the core are a close fit in the copper tube, but we shall soon see.  A better crimp tool would probably be a good start.


                                          Cheers  Guys         Joules 

[guydewdney]

the way we use to inspect a crimp was to sit it in araldite (or similar goop) until hard. Then used a diamond ultrafine grit rotating table thingy (I forget its name) - basically a polisher - to grind away the sample so you can see inside the crimp itself.

you will then see somthing like this:-



the lines inside the (four way here) crimp are the surface corrosion of each individual conductor - ie the not shiney bit of copper. As you can see, theres no air gap, therefore no more corrosion (which creates bad connections, which increases resistance, which heats up, which burns down idiots houses who use scotchlocks in a mains wiring situation  darwin???

heres another



as stated here http://www.thinlayeranalysis.co.uk/Crimp%20connector%20cross%20section.html the pressed steel plier things are carp. the wires are loose in places....


Ill shut up now - as Im sure you lot are bored to tears

[martin]

no, actually this sort of thing is fascinating - it's not just saying something doesn't work well, you're showing WHY and how............

[northern installer]

 Solution 1,hire a crimping tool and use correct size crimps
Solution 2,back in the good old days,there only was solder,I have done up to 400mm2(or imperial equivalent) this way,tin all the lugs first,use rosin flux only,tin the cable,put it in the lug pointing down,sweat the lug until full,using coed solder;dont move until solder has set,then dowse in a jamjar of water;when cool,clean off flux with meths,and tape over the bare /burnt bit with pvc tape 

[Joules]

He he....   I'm impressed too....  However I just cut my crimp and polished the cores with emery....  Bear in mind I have now broken the crimp so the cores are no longer restrained, hence some slippage of the cores.  I had a very tight packed bunch, so for my money the crimp worked.  Long term, I will keep a close eye on the cables I have in use.




                                                         Joules

[billi]

Joules

that looks good to me ..... like a good compressed salami 

Any how for myself will take a bit more care about connecting wires , batteries , PV , windgenerator and still have to do propper connections for my PV 10mm sq

So what would you use to extend copper cables from a windgenerator or pv ?  (saltwater waterproved ?)

Should i use a copper ferrule (have them ) to connect the two ends of the cable and seal with epoxy ?
I donot mean these crimps attached to the batteries

billi

[northern installer]

Hi Billi,if the cable joint is on the surface,put it in a waterproof box,ip65 rated,cables led in through a stuffing gland,crimp inside the box,and anoint all with petroleum jelly before the lid goes on,nb,cables enter from the bottom only,and put a 6mm drain hole at the lowest point(one drain is worth a dozen gaskets)
if its underground,use a cold cast 'sausage' joint

[billi]

cheers NI