Joining 1.0, 1.5 and 2.5mm^2 cables

[Dave Plowman (News)]

Yes. And difficult to tell since covered in plastic. I only now buy them from TLC.

[John Rumm]

I have met a number of Wylex style rewireable fuse CUs where the terminals were no longer "tight" - even if there were no obvious signs of overheating as such.

[John Rumm]

IIRC I got mine from CPC, and they have been fine.

[Dave Plowman (News)]

But were they ones you installed yourself so know they were tight to start with?

As I said, I've come across plenty faults due to terminals not being tightened properly.

[John Rumm]

Not usually... but then again they have often been loose enough it would be hard to believe that they were originally left like that (and also where the wire ends show deformation from the original clamping pressure)

I have installed CUs and then a year later checked tightness on all the termination screws. Even when properly tightened originally, applying similar torque again will sometimes get a bit of movement.

Yup also a typical failure mode, but some relaxation and creep of terminations also seems common.

[Fredxx]

I have long considered the loosening of terminals is down to thermal expansion and cycling. We are led to believe that copper suffers very little creep.

Using:

The difference between expansion coefficients for copper and brass is around 2 x 10-6, so for a worse case 50C temperature rise it should give rise to an expansion difference of 0.1%

Whether that is enough to overcome any pretensioning or if movement is the killer I'm not sure.

[tony sayer]

In article <qvsmjd$d3b$ [e-mail], Fredxx [e-mail] scribeth thus

Your doing something wrong, used thousands over the years not one has been a problem.

However you do need decent ratchet crimpers, the pliers type ones are useless!..

[Dave Plowman (News)]

I've seen lots and lots of problems with pre-insulated terminals DIY fitted on cars.

[Adam Funk]

Well, the one I had a problem with was for the kitchen lights. One morning they wouldn't light & I noticed that walking on the bathroom floor (directly above) made them work. We moved in a little over 20 years ago, so it must have taken at least that long for it to work loose.

(Obviously all that makes sense.)

[Brian Reay]

Are you using a decent crimp tool ie not one of the simple ones which are just two bits of flat metal with notchs?

I wouldn't say I've never had problems with a crimp joint made with a proper crimp tool but certainly they are few and far between. The number plate lamps on our motorhome were intermittent and I noticed them on a trip so returning to the dealer was really practical. I nipped up one of the crimps (lated replaced- I don't carry a crimp tool so a nip had to do for the time being) which cured it but that is the only one I recall in years.

Conversely, Scotch-loks are the invention of the devil and I only use then for quick lash ups etc to try things.

[Dave Plowman (News)]

I'd not dream of using pre-insulated crimps on a car. I use the correct ones and have the correct crimp tool.

It's well worth carefully cutting off the insulation from a pre-insulated type and seeing the actual crimp. A decent crimp uses a heart shaped die which makes the crimp grip the conductor all round. The pre-insulated type merely flattens it. Which might be OK on solid core mains cable, but not ideal with multi-strand. Of course it will work OK when new, but some years down the line?

[tony sayer]

In article [e-mail]>, Dave Plowman (News) [e-mail]> scribeth thus

Yes as most use those useless cheap crimp pliers!

With the ratchet ones they just do not move ever again!!

[Adam Funk]

I can't find the e-mail with the order details, but this definitely looks like the one I have, which I know I got from TLC:

The picture shows an adjustment wheel held in place by a small screw. When I got the crimper, it was on the lowest setting, & I got good results (i.e., really can't pull the wires apart) by adjusting it up one position. (I suppose it adjusts further as the jaws wear out.)

[tony sayer]

There're the good ones:)

[Adam Funk]

Good, thanks!