As are most multi-pin connectors found on cars in recent years. However, on my old Rover SD1, they didn't include the crimps from the harness to the said multi-pin connectors, and some have gone high resistance.
Wonder if the cable and connector had been coated in tin, etc, rather than plain copper and plain brass would have extended their 'life'?
The regs certainly allow for the earths of a ring to have a different topology than the live conductors in some cases, e.g. when provided by steel conduit or by the mineral insulation copper cover. I'd have to delve into the regs to see if that only applies in these cases. Generally cross connecting CPC's can only result in improvement to the earth fault loop impedance, and it is required in certain places, e.g. in all the circuits used in a bath/shower room.
No, they suffer more from galvanic corrosion between them than you save from reduced oxidation. In the car context, plated terminals are less troublesome for their life, then fail. Plain brass are a higher resistance for most of it, but their usable "life" is longer.
It's a thin layer. So although the resistivity/length is indeed high, the actual resistance added is negligible. Only if you start getting a loose connection where the area drops down to a fraction of a screw area do you start to see appreciable heating.
Hi,
I'd not worry about now it unless they're taking a lot of current and/or near anything flammable, or the wires might get moved or disturbed or have flammable stuff placed near them.
Often a safe and lasting 'bodge' is very acceptable :)
Though if I was a tradesperson I'd find another way of joining the cable or some use crimps designed for solid core.
What do the IEE make of using 'auto' crimps? Maybe this has been discussed on their forum. I'd expect if everyone started using ones designed for solid core the prices would come down.
cheers, Pete.
Excellent, thanks. I'm sure we could get an answer to the meaning of life here.
As I said, the pre-insulated types sold by TLC and others as presumably for mains use appear no different from the ones sold by Halfords presumably for auto use.
There's a kind of spot welding going on there. If you unwrap one of those joints you have to tear the wire away from the post at each corner.
Hi,
They may be fine for mains use but a lot of people assume that includes solid core T&E, and I expect they're only intended for stranded mains cable, eg conduit cable.
If you look up some tech info on these on the RS site they all talk about use with stranded cable and not solid core.
Even so if I was a tradesperson I'd even buy branded ones for use with stranded mains cable, saving a few pennies by using unbranded ones isn't worth the risk.
cheers, Pete.
Not sure which ones you're looking at on RS, but the ones I've seen say that they are suited for solid or stranded wires.
Specifically - part code 842-107 ("Plasti-Grip Butt Splice Terminals" - I looked at the blue one!). Click on the Tech Info button. Then select the "General info on Plasti-Grip" link. When the PDF opens, look at the bottom of the page - and you'll see that it's certified as UL Listed for "Terminals, Butt & Parallel Splices XX-YY Solid or Stranded" with a note saying that Standed wire is only supported when using "Tetra-Crimp tooling".
D
Sounds good! I take back what I said earlier then.
Hopefully an inexpensive rachet crimper would be just as good as the recommended tool :D
But the UL test for pullout doesn't look that hard to meet:
I'd still avoid the most cheapo terminals and crimpers though.
cheers, Pete.
I still see no reason why it should make any difference. Why should a crimp 'designed for stranded cable' work any less well on solid?
Hi,
I've seen photos of burned out crimps on a forum somewhere, plus there have been reports of problems on this ng:
AFIAK for a crimp to be guaranteed to work well in the long term there needs to be a good 'gas tight' seal between crimp and wire. Evidence of this would include the wire being crimped so that there are no air gaps between it and the crimp.
With a plastic insulated crimp and solid core wire I can see less chance of this happening, especially if the wire is the minimum size for the crimp and the crimper is only closed enough to release the ratchet.
The problem is that a crimp may be mechanically secure and give a low resistance connection, but if the connection can oxidise over time it may go high resistance and heat up or even start arcing, as mains connections have a greater chance of arcing than low voltage connections.
I'd be happy to use insulated crimps in a low volume situation with known crimps and crimper where I've proved to myself that they crimp completely, but still there would have to be no possible fire hazard if they overheat. Even so I wouldn't recommend it to someone else.
AMP also market their 'solistrand' type crimps, if the plastic insulated ones were just as reliable would there be a need for another type? :
Has anyone cut open a few sample crimps made with different sizes of solid core and crimp to see how well they're made?
cheers, Pete.
In article , Pete C writes
FWIW we've used crimps on vehicle installations for many years with no problems at all. However it seems to me that an awful lot is down the crimps used, and even more the what you use to crimp them. The only really good crimped joints are those that are done with the heavy duty ratchet type crimpers. The ones that work with a simple "scissor" action as it were, aren't that clever.
Some of the crimps on the factory loom on my 20 year old Rover are giving trouble. They've gone high resistance.
BTW, my rather expensive crimping tool for Lucar non insulated connectors isn't a ratchet type - merely cantilever.
I agree re: the [insert name of cheap DIY emporium] type of scissor action crimpers, however, I am most impressed with the pair of AMP branded crimpers I obtained, they are scissor action, but relatively long handles and very short 'crimping arms' make for very high pressure, and they're thicker stock than the usual, [circa 1/6 of an inch] with very well shaped work areas, thus crimping MUCH better on both insulated and non-insulated terminals.
In article , Dave Plowman (News) writes
Amazing its still on the road with it being a Rover;))
Well ours cost around 30 odd quid, but they do the job very well indeed:))
You have a good point; but detailed reading of the AMP datasheets both at the rswww.com site and at AMP/Tyco's own site reveal claims that their Plasti-grip and PIDG ranges are designed for solid as well as stranded wire. However, AMP's tooling isn't exactly cheap - if you buy it fullprice (at rswww.com, for example) you're looking at a hundred notes for the cheaper flavour, and 250 for the certified one! Much other documentation on crimps is all around their use on *stranded* wires, and that's the overwhelmingly common case in practice.
I tend to agree with you - random crimpology using bargain-bin crimps and a plier-style tool is not what I'd call 'good workmanship'; and I generally prefer to have cable connections genuinely accessible, and would rather replace a run with a new piece than join two ends somewhere out of sight...
Stefek
If you want _really_ expensive, look at the tools with on-board load cells and data loggers. Last few times I've been to Bideford it was to get to Lundy, not to work at AMP, but they used to have a fair few machines on that site running some of my code - both crimpers, and the press tools that made the crimps.
Ah, real-time data loggers under DOS - now there's a pointless stick to beat yourself with. Rewriting the font generator to get analogue graphics out of a text-mode colour display too - it was like coding on a damned Spectrum!
Yes - I was only covering hand tooling, not the bench-installed MIL-STD-traceable gubbins!
At least under DOS you're close to the bare metal, and can lock out interrupts reliably. Try doing that with Windows ;-)
or, indeed, the geeks who combined two separate video modes on the Elite screen to run the upper three-quarters in a hi-res monochrome mode and the status-display in lower-res more-colours mode. And you tell that to the DirectX9 games writers of today, with their Z buffers and anisotropic shaders and multiple pipelines, and they won't believe you...
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