The Joy of Crimping; a terminal case...?

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Brucey
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The Joy of Crimping; a terminal case...?

Postby Brucey » 13 Oct 2020, 9:17pm

Or 'crimp my ride'.....?

It is cold, dark, dank and gloomy out, which means it is dynamo season again. 'Tis the season to make sure that all the wires are connected nicely to all your lights. I confess that in the past I have been a bit paranoid about bad wiring and unreliable lights; this means for many years I have preferred to open up my lamps and solder wires to the relevant parts of the lamps permanently. If I can manage it, the only breakable connections in a good dynamo light system might be at the generator itself; additional connections are just extra places where faults can develop, and are best avoided.

The above approach has served me well. But this doesn't make for quick or easy installation. Nor does it allow for quick and easy lamp replacements in the event of breakage, failure, or just wanting to mess about and try different things out.

After connecting the headlight to the generator, the most common wiring task in a typical hub generator system is connecting the rear light to the headlight. It is absolutely vital that this connection is made as reliable as possible; if your rear light goes out as you ride you may not notice and this leaves you vulnerable to dozy drivers. Most commonly the connections to the rear light are made at one or both ends using 2.8mm blade terminals; male in the lamp housings, female on the wire ends. The best way of making these connections is probably to use good quality crimp terminals on the wires. Some B&M lights come with a length of wire for the rear light that is correctly terminated at one end. But you might need one a different length or to have the terminals at both ends.

Since I happen to possess suitable crimping tools for these terminals, I thought it remiss of me not to break them out and use them.

The most common type of crimp terminal is probably the 'Engex' sort that has a red, blue, or yellow sleeve around the strain relief part of the connection. These terminals are crimped over the coloured sleeve and can provide a good connection in many instances.

Image
Terminals can have a full insulating sleeve or (as above) not. 2.8mm female blade type shown.

However inevitably there are problems; the 'red' type is the smallest size commonly available yet it will accommodate 1.5mm^2 conductors. Which is a bit OTT for running a rear light which takes 100mA tops. It is not certain that the skinny wires used in dynamo lights will be crimped well at all. The strain relief isn't as good as many terminals. You can't easily inspect the quality of the crimp after it has been made (you can't see where the insulation ends because it is hidden). You can't easily apply waterproofing (eg Vaseline or waxoyl) to an assembled connector. However the real show stopper for bicycles may be that the coloured sleeve is so fat it sometimes makes it impossible to fit the terminal to a lamp.

If you want to use these terminals you can make a reasonable job of it by crimping the terminals, cutting the red stuff off, inspecting the crimp better, and then using heat-shrink insulation on it.

Needless to say terminals of this sort are not used by B&M and other good lamp makers; they use better quality crimps which are made using more sophisticated tooling.

My best tool for this job is a Molex 69008-0953 crimp tool which I have had for years; it wasn't cheap when I bought it originally but I recently looked it up and was horrified at the current replacement cost; I am sure that there must be cheaper alternatives. Anyway, this tool is designed to crimp Molex type 2478 terminals to 18-24 AWG wires. It happens that there are many terminals (other than Molex-manufactured ones) which are compatible with this tool. These vary in design, material, plating, and whether or not they come with insulation or whether you are meant to use heat shrink. They vary in cost and quality, from pennies each to a more significant cost per item. The ones I have used here were not expensive ones.

Image01854.jpg
phosphor bronze (L) and brass (R) terminals


The terminals are crimped at both conductor (electrical connection) and insulator (for strain relief) by two sets of jaws, in a single operation.

I have taken a series of photographs in which I have tried to show how crimping works and what might constitute a reasonably acceptable crimp quality.

Image01851.jpg
simple figure-8 bell wire for the rear light


Image01852.jpg
use of automatic wire stripper is important when there are not many strands in the wire


Image01853.jpg
nice clean strip, no broken strands


tbc
Last edited by Brucey on 13 Oct 2020, 10:59pm, edited 2 times in total.
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Brucey
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Re: The Joy of Crimping; a terminal case...?

Postby Brucey » 13 Oct 2020, 9:23pm

below is a series of photos taken 'one click at a time' as the tool is used; you can see the strain relief part of the crimp being made

Image01855.jpg
click one


Image01856.jpg
click two


Image01857.jpg
click three


Image01858.jpg
click four


Click four was the first click at which the wire started to be 'nipped' by the crimp

Image01859.jpg
click five


you can see the strain relief 'ears' pierce the insulation here; this isn't always recommended but where it is, it improves the grip on the wire and provides a secondary connection to the wire.
Last edited by Brucey on 13 Oct 2020, 9:48pm, edited 4 times in total.
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Brucey
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Re: The Joy of Crimping; a terminal case...?

Postby Brucey » 13 Oct 2020, 9:23pm

Image01860.jpg
click six


Image01862.jpg
the completed crimp


In practice the terminals would be waterproofed (eg using Silicone grease, Vaseline or waxoyl) before the insulating sleeve is fitted.

Image01863.jpg
with the sleeves in position


If possible the terminals will be set facing down, so that water won't penetrate the connection so easily.

Image01864b.jpg
What Molex recommend it should look like
Last edited by Brucey on 13 Oct 2020, 9:50pm, edited 2 times in total.
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Brucey
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Re: The Joy of Crimping; a terminal case...?

Postby Brucey » 13 Oct 2020, 9:30pm

more crimp details;

Image

crimps look most convincing when the conductor 'fills' the terminal properly, which is unusual in bike lighting;

Image

You can see that to get the 'funnel' shape requires that the terminal is set precisely in the tool, and the wire needs to be similarly accurately prepped and positioned.

There are many possible faults (of which mine show some.. :oops: .)

Image

Image

Image

cheers
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2_i
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Re: The Joy of Crimping; a terminal case...?

Postby 2_i » 14 Oct 2020, 1:10am

I use Knipex 975214, with a loader:
Image
and the crimps come out looking exactly like in those advertising photos :D . At times, I go to my tool area and attach a terminal to a wire just to admire the perfection of this tool.

Brucey
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Re: The Joy of Crimping; a terminal case...?

Postby Brucey » 14 Oct 2020, 7:54am

the loader is a nice idea for some applications, locating the terminal so leaving just the wire insertion to worry about. You can see what is going on much more clearly with chunky wires and terminals; the one in your picture looks like a standard Lucar type (3/16" or 1/4"?) terminal. The 2.8mm crimps and wire etc are about half the size, so are about twice as fiddly to work with. On critical parts, I normally inspect crimps under a binocular microscope.

It is not shown in my photos, but the Molex tool has an additional element, being a spring loaded shutter that comes down on the terminal body (between the conductor crimp and the connection itself) and locates it, provided the terminal is of the correct manufacture. By the first or second click, the terminal (regardless of type/polarity) is accurately located and cannot move. The shutter also acts as a depth stop so that an accurately prepped wire end (not mine, not in cheap bell wire with squishy PVC insulation... :roll: :lol: ) will be inserted to the correct depth.

All this is done without having 'used' a female terminal on the loader blade. I don't think this is definitely a big deal but it might be significant n some cases, depending on the application, how many cycles the terminal is designed for, and how it is plated; for example there is arguably no point in using gold plated terminals if you are going to scrape the plating off the working surfaces of the terminal on a loader blade.

It is indeed a little engineering miracle to see a crimp being made using a decent tool. I may take some better photos if I get the chance.

cheers
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boblo
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Re: The Joy of Crimping; a terminal case...?

Postby boblo » 14 Oct 2020, 8:54am

Good or bad, I've always soldered the joints then used needle nosed pliers to set the strain relief and heat shrink to insulate. Clearly I haven't got a set of crimpers and I've no need to buy any for the couple of dozen connectors I've soldered in my lifetime...

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simonineaston
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Re: The Joy of Crimping; a terminal case...?

Postby simonineaston » 14 Oct 2020, 9:38am

I'm not really adding anything of value to the conversation here, but during the course of the recent refurb I done to a Dyson vaccy, I noticed that the in-line fuse was put in place by a pair of crimped terminals. I was going to unsolder the failed component before I spotted that its leads had been crimped into place, rather than soldered. As the rest of the product is a miracle of modern engineering ( or at least it is, in my view, sheltered tho' that is!) I fell to wondering what the benefits of a crimped joint were, above those of a soldered joint - at least from a manufacturing point of view. I concluded: less energy required (no permanently on soldering 'irons', no chemical (flux), no fumes, better mechanical joint... pretty much win win :-) Until you come to replacing the item, that is!
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

Brucey
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Re: The Joy of Crimping; a terminal case...?

Postby Brucey » 14 Oct 2020, 9:48am

re Boblo's comment: soldering is a very good method; a soldered connection will (if there is no corrosive flux residue) usually take longer to corrode than a purely mechanical connection. But not everyone has a soldering iron and it does take longer to use. Also, it is arguably of reduced benefit to solder a push-on connection, since under adverse conditions the push-on connection will likely be the point at which the thing goes open circuit anyway.

If you do solder such terminals, there are a few things to watch out for, including;

a) that the solder doesn't run up the wire too far (i.e. past the strain relief); this reduces the flexibility of the wire, so that if it is flexed in service, it becomes vulnerable to premature failure.

b) that the strain relief is actually doing some good. If the strain relief is crimped before soldering, the usual outcome is that the insulation melts, and the strain relief loses its grip.

So it is probably best if the soldering is done first (with a heat sink to prevent the solder from running up the wire) and then the strain relief is crimped (once everything has cooled down). If you do solder after the strain relief is crimped, it isn't a bad idea to recrimp after soldering.

FWIW you can get less expensive crimp tools which have the correct jaw shape to work with the terminals shown. However these tools typically only have one set of jaws, no provision for locating the terminal accurately and no depth stop, so it is more difficult to make a really good crimped joint (esp regarding the 'funnel' shape).

cheers
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Brucey
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Re: The Joy of Crimping; a terminal case...?

Postby Brucey » 14 Oct 2020, 10:05am

simonineaston wrote:…. I noticed that the in-line fuse was put in place by a pair of crimped terminals. …... I fell to wondering what the benefits of a crimped joint were, above those of a soldered joint - at least from a manufacturing point of view. I concluded: less energy required (no permanently on soldering 'irons', no chemical (flux), no fumes, better mechanical joint... pretty much win win :-) Until you come to replacing the item, that is!


There is nothing stopping you from using side-cutters on the whole fitting (i.e. cutting the tag on the fuse unit, leaving the crimped joint on the end of the wire) and then installing a new fuse by soldering, if you want to.

Manufacturers of crimps (as you might expect) claim that their crimped connections between the wire and the terminal are more reliable than the connection between the (say blade type) terminal and the other part. Part of the reason for this is as per my post above. So crimps make sense when there is a (demountable) mechanical connection nearby, or persistent vibration, hence widespread use in cars etc. They may make less sense when used for a permanent connection as per your fuse.

Possibly the wiring harness for a vacuum cleaner is assembled by a subcontractor and then installed in the vacuum cleaner factory. Crimping may lend itself better to automation on parts like these. The fault charts I posted above are relevant to machine-crimping; several of the fault conditions can only occur when crimps are belt-fed into a machine, such that the crimp is sheared off the end of the belt before the joint is made. Hence there are fault conditions involving cutoff tabs at either end of the terminal. Hand-crimping uses loose terminals and those tab faults can't occur; plenty of others can do though!
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Brucey
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Re: The Joy of Crimping; a terminal case...?

Postby Brucey » 14 Oct 2020, 11:19am

some more photos

Image01866.jpg
Molex tools HT1919 (top) and 69008-0953 (bottom)


the upper tool is an (old) inexpensive single-action crimp tool, having 'A' and 'B' jaws for strain relief and conductor crimps respectively. Using this tool it is impossible to make the correct 'funnel' shape with some (smaller) terminals, because the jaws are wider than the crimped part of the terminal and foul the shoulders on the terminal when you try and offset enough to leave a 'funnel' shape. A similar tool is currently sold by GC/Waldom (even sharing the same HT1919 designation).

The clever 'shutter' action in the posher Molex tool is shown below;

Image01865.jpg
terminal located by the shutter element at the rear of the 69008-0953 tool.


Both tools are meant for use with Molex type 'KK' terminals (amongst others). These are larger than the 2.8mm terminals and more familiar to some as about the same sort as those used in 'Tamiya' plugs and sockets.

cheers
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resus1uk
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Re: The Joy of Crimping; a terminal case...?

Postby resus1uk » 14 Oct 2020, 6:33pm

After years of soldering for radio, model railways and auto electrics, I'm still not good at it. I have had better results with crimping. A good quality crimper is needed.
My dynamos are connected with the 2.8 connectors. No failures yet.
For the car, big crimps for battery jump leads and charging. Powerpole connectors give indexed connection.

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simonineaston
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Re: The Joy of Crimping; a terminal case...?

Postby simonineaston » 14 Oct 2020, 6:49pm

After years of soldering for radio, model railways and auto electrics, I'm still not good at i
Me too! I can do it, but it never looks good. That's why I'm so impressed by folks who can do lovely-looking welds and brazes.
10436625455_6cb4ae680b_o.jpg
wow!
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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andrew_s
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Re: The Joy of Crimping; a terminal case...?

Postby andrew_s » 14 Oct 2020, 8:49pm

Brucey wrote:My best tool for this job is a Molex 69008-0953 crimp tool which I have had for years; it wasn't cheap when I bought it originally but I recently looked it up and was horrified at the current replacement cost

How much? Google shows it as discontinued, but I got the impression that it was northwards of £400. That, or the ~£140 for @2_i's Knipex is well over what I can justify to myself for occasional dynamo wires.

I've always soldered, like @boblo, but having been inspired to look properly, would something like one of these be worthwhile?
https://www.amazon.co.uk/ATPWONZ-Crimpi ... ref=sr_1_6 (£17)
https://www.amazon.co.uk/TTAototech-Cri ... ef=sr_1_18 (£14)

slowster
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Re: The Joy of Crimping; a terminal case...?

Postby slowster » 14 Oct 2020, 9:13pm

Image

Judging by the image above and the one below from Peter White's website It looks like the Knipex tool jaws do not result in the ears around the exposed wires being flared out at one end to produce the 'funnel' shape. I presume the benefit of the funnel shape is more significant in the context of very high volume/automated production and/or safety critical applications such as aviation, where the risk of failure must be absolutely minimised, whereas the benefit for bike lighting would be too small for it to matter.

Image