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

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fausto99
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Re: The Joy of Crimping; a terminal case...?

Postby fausto99 » 15 Oct 2020, 5:53pm

simonineaston wrote:...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...


Way back when I was servicing TVs in my summer vacs a thing called wire wrapping "came in". It was touted as the most reliable way of interconnecting circuit boards. A solid core copper wire was tightly wrapped around a square section pin with a small rotating hand tool. The joint was claimed to be airtight and so free from future corrosion and the wire was supposed to virtually weld itself at the sharp corners of the pin.

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

Postby Brucey » 15 Oct 2020, 8:01pm

2_i wrote: …. I used to solder the connectors myself, but a good crimp is cleaner, faster and does not undermine the strength of the insulation around the connector. You can compensate for the latter with some heatshrink but it ends up being messier both in terms of labor and end result. At this point I am completely sold on crimping with a good tool. I am still toying with the idea of plastic housings for the terminals, like on motorcycles on cars, but maybe bikes represent a too rough environment for those. (Yes, my projects are extended enough for this to become an existential problem :roll: )….


I guess I'm in the same loop more or less. I've ridden thousands of miles with connections made the best way I know how but this doesn't lend itself to easy serviceability etc. So more widespread use of crimp connections on bikes is not something I have embraced before. One of the things that worries me most about crimped connections (on bikes) is the prospect of corrosion; hence using some kind of gloop ( like waxoyl) on the terminals. I think the plastic shrouds in my photos won't do any good at all when the wire is one way up (they are not a tight fit) but provided the male blade faces down and is shrouded from above, the plastic shroud on the crimped terminal may help prevent water ingress (eg into the structure of the wire) whilst also helping to retain the gloop/corrosion-proofing.

FWIW if required to say what might be a 'gold standard' for lamp wiring seen in production bicycles, I'd have to go with the Dynohub lighting setups found on Raleigh bicycles in the 1950s. These typically used crimp or soldered connections on the exposed wire ends, normally with mechanically mated push-fit terminals inside the headlamp shell, where the joints are protected from the weather. Even though the terminals were unplated brass and were assembled dry, contact corrosion inside the headlamp shell is rare. If necessary the connections inside the headlamp shell can be remade by the roadside; the only tools required would be to open the headlamp shell (small screwdriver) and to strip the wire insulation back a little. Everything else can be done with fingers. Because the connectors are cylindrical, the female parts are not difficult to clean should corrosion occur; the male connector ends up with wire strands on the outside, so the wire strands make direct connection with the female terminal. IME the whole arrangement is pretty reliable 'as is' but with the addition of a little waxoyl it can be made proof against corrosion; gentle warmth (~60C) is enough to cause waxoyl to penetrate the wire bundle near the terminal, which means that subsequent penetration of (salty) water into the wire bundle and subsequent corrosion within the wire itself is stymied. Vaseline works pretty well but it doesn't 'wick' into the wire bundle like hot waxoyl will.

I don't expect any crimp connections I make -no matter how fancy the tool or terminal is- to be 100% proof against corrosion; all I can hope for is that whatever corrosion proofing gloop is used will work well enough that it will make corrosion-related failures a rarity.

I have found myself attending to features such as

- 'drip-loops', i.e. where the wires always enter (say) a lamp housing from below, even if the wire approaches from above, and
- other methods of strain relief, such as making a flexible 'pig's tail' of wire where the steering flexes the wire running to the rear light,

as well as more obvious things such as reducing the chances of wire snagging/rubbing, and leaving enough length in the wires such that they can be reterminated should the need arise, etc.

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

Postby 2_i » 15 Oct 2020, 10:05pm

Brucey wrote:One of the things that worries me most about crimped connections (on bikes) is the prospect of corrosion; hence using some kind of gloop ( like waxoyl) on the terminals. I think the plastic shrouds in my photos won't do any good at all when the wire is one way up (they are not a tight fit) but provided the male blade faces down and is shrouded from above, the plastic shroud on the crimped terminal may help prevent water ingress (eg into the structure of the wire) whilst also helping to retain the gloop/corrosion-proofing.


I make my own boots out of a transparent heatshrink, grabbing the wire that is above and extending the protection down, no matter which is male/female. Onto the contacts I put Nyogel 760G that seems to be the car industry standard. There exist truly waterproof automative connectors in the 2.8mm version, but I suspect that they are not practical with 22AWG, exerting too much weight and maybe not even fully grabbing its diameter. My newest discovery are polyolefin bonders, Henkel AA 3035 and Permabond TA4610. They are expensive and require a bit of application infrastructure but these are dream adhesives that can seal any kind of gap in any kind of intractable material, gluing pretty permanently polyethylene with neoprene and stuff. Just crazy! However, sometimes you don't want to make it overly perfect, since indeed you may end up having to do the service under conditions where you only have your fingers at your disposal and maybe a pocket knife. I lack experience with waxoyl, but I suspect that it is a sticky substance that might leave room for manipulations.

Cheers

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

Postby Brucey » 15 Oct 2020, 10:35pm

that is interesting stuff. Waxoyl is a corrosion proofing substance with a solvent carrier and a wax base, so can be applied as a fluid and sets as a soft wax. Even when the solvent has gone, it can be liquefied by heating and will creep into all kinds of tiny crevices. It is not perfect by any means (e.g. it will melt if the ambient temperature gets above about 50C, as can be seen when some of my bikes have been in the back of the car on a sunny day, ahem...) but it isn't bad stuff.

Below is an almost successful experiment;

Image01874.jpg


a comment in a previous post set me wondering; what happens if you try and make a 'funnel' in the strain relief? The result when I tried it (by offsetting the terminal slightly in the tool jaws) was that the wire went in a bit too far and the strain relief tabs started to shear. Back to the drawing board, eh....? :wink:

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

Postby 2_i » 16 Oct 2020, 1:02am

Brucey wrote: Waxoyl is a corrosion proofing substance with a solvent carrier and a wax base, so can be applied as a fluid and sets as a soft wax. Even when the solvent has gone, it can be liquefied by heating and will creep into all kinds of tiny crevices. It is not perfect by any means (e.g. it will melt if the ambient temperature gets above about 50C, as can be seen when some of my bikes have been in the back of the car on a sunny day, ahem...) but it isn't bad stuff.


My checking fails to show any way to acquire Waxoyl cheaply in the US for trials. That suggests that is not critical substance in terms of composition or properties, with equivalent ones available from local manufacturers. In any case, I mix together something myself that contains light and heavy components and is very effective in terms of protection, but it is not as heavy as Waxoyl might be, so not good for sealing the connectors.

Cheers

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

Postby 2_i » 16 Oct 2020, 1:43am

slowster wrote:
2_i wrote:OK, here are the photos for Knipex.

I see that there are funnels both to the ears around the exposed wire and also to the ears around the insulation. That indicates that the locator accessory has positioned the connector in the tool such that it protrudes 1mm-2mm beyond the face of the other side of the tool (so knowing that it should be easy to achieve the same result without the locator accessory). Presumably that is by design, unless the connectors you used were longer than standard, although Knipex's own photograph above of the tool with the locator attached oddly does not show the crimped connector to have a funnel.


Before I got the locator and was positioning the connectors by hand, I was ending up with pretty similar results. The locator, though, makes the operation less stressful for those connectors that fit in well. As to the funnels, I measured the respective parts of the bottom Knipex die with calipers and both the conductor and insulation parts subtly narrow along their lengths.

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

Postby Brucey » 16 Oct 2020, 6:46am

2_i wrote:...My checking fails to show any way to acquire Waxoyl cheaply in the US for trials....


You can buy it in the USA via the link on this page

https://www.waxoyl-usa.com/products/corrosion-protection/120-4/rnw5004-120-4-500ml-aerosol.html

No surprise that it is distributed via Land Rover dealers; it is a vital ingredient in getting a Land Rover to last like it should.

There are other similar products such as Dinitrol, Dynax etc., but I have never done a back to back comparison so I have no means of comparison. These products can also be used inside steel bike frames; in the case of waxoyl simply warming the frame will cause any excess to run out, leaving a thin coating inside.

If you are thinking of a homebrew, be aware that Waxoyl contains chemical corrosion inhibitors (see MSDS for some details) which is a good part of how it suppresses corrosion. Unless this component is included the mixture won't be effective.

I have also considered using products such as Owatrol oil; this 'wicks' well so ought to penetrate the wire bundle and help to protect it against corrosion. However it also cures to a hard layer, meaning that it could interfere with the blade connection itself. By contrast a soft wax coating like Waxoyl is normally displaced in a sliding connection at normal contact pressures, well enough that it doesn't interfere with the electrical connection itself, whilst still protecting the arrangement from corrosion.

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

Postby simonineaston » 16 Oct 2020, 8:38am

While we're on the subject of electrical contacts and stuff that ends up on them, I was puzzled by the following: As readers may recall, I've recently stripped & reassembled a Dyson vacuum cleaner (a model DC49, for the curious...). As I did so, I discovered a component that allows the mains supply to pass from the rotating cord retractor to the motor. It consists of two concentric slip-rings (see photo). Looking closely, I could see a dark soft material (barely visible in the photos, I'm afraid) which I assume is there delibarately and I imagine is for lubrication purposes - the cord retractor rotates, every time the vacuum cleaner is used & the user pulls the cord out. Then I thought, "Wait one cotton-picking moment - isn't that lubricant going to spoil the contacts' ability to conduct electricity?!"
I turned to a search engine for guidance but was not able to find anything very helpful on the subject of greases and conduction, except a whole bunch of arguments - can you guys shed any light?
IMG_1921.JPG
body of cord retractor
IMG_1920.JPG
spindle, with slip-rings
byyeee,
SiE

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

Postby Brucey » 16 Oct 2020, 8:54am

as per my previous post moderate contact pressures breach soft films and soft films can have lubricant properties. Possibly the dyson unit uses grease loaded with something conductive; any particles trapped in the interface will conduct nicely, but conduction between tracks is inhibited by simple separation.

In clean contacts the actual area of contact is given by considering the contact pressure and the yield strength of the materials. This means asperity contact only, unless the contacting faces are extraordinarily flat, and if they start out that way, they don't stay that way in the real world. Contacts spark, wear, oxidise etc. Often a lubricant will suppress some of the wear mechanisms, by improving the contact, or suppressing sparking. Often simply excluding oxygen from the contact area is enough to do some good, so materials which are electrical insulators -but also exclude oxygen- can improve certain types of contact, provided the contact pressure is enough to breach the film and allow some direct contact.

Similar conditions exist in windscreen wiper motors, i.e. a set of moving contacts which carries reasonable current. Such contacts are almost invariably lubricated.

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

Postby simonineaston » 16 Oct 2020, 9:00am

Funny stuff, electricity... Perhaps I'll drop James a line & ask him if he can put all that r&d he did for the car to use, in the form of a Dyson e-bike (thinks: balls for wheels??). His stately pile in Old Sodbury is near where I used to work.
byyeee,
SiE

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fausto99
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Re: The Joy of Crimping; a terminal case...?

Postby fausto99 » 16 Oct 2020, 11:06am

simonineaston wrote:While we're on the subject of electrical contacts and stuff that ends up on them, I was puzzled by the following: As readers may recall, I've recently stripped & reassembled a Dyson vacuum cleaner (a model DC49, for the curious...). As I did so, I discovered a component that allows the mains supply to pass from the rotating cord retractor to the motor. It consists of two concentric slip-rings (see photo). Looking closely, I could see a dark soft material (barely visible in the photos, I'm afraid) which I assume is there delibarately and I imagine is for lubrication purposes - the cord retractor rotates, every time the vacuum cleaner is used & the user pulls the cord out. Then I thought, "Wait one cotton-picking moment - isn't that lubricant going to spoil the contacts' ability to conduct electricity?!"
I turned to a search engine for guidance but was not able to find anything very helpful on the subject of greases and conduction, except a whole bunch of arguments - can you guys shed any light?IMG_1921.JPGIMG_1920.JPG

Again going back to my tv servicting days when the channel changer was a large many contact knob in the turret tuner, we used to use silicon grease after cleaning the silver plated contacts to stop them from going black again. Similarly we used to use petroleum jelly on car battery contacts to prevent furry growths caused by stray acid. Neither inhibited the flow of electricity!

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

Postby simonineaston » 16 Oct 2020, 11:15am

Neither inhibited the flow of electricity!
Cool! That's the answer I wanted :-) I guess they pop a little splodge of graphite-loaded goop onto the contacts at assembly, to reduce the wear on the slip-rings.
byyeee,
SiE

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

Postby slowster » 16 Oct 2020, 12:56pm

I think (most?/all?) heat shrink tubing is coated inside with a glue which melts when the tubing is shrunk and thus creates a seal at the non-connector end.

Image

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

Postby 2_i » 16 Oct 2020, 3:24pm

Brucey wrote:
2_i wrote:If you are thinking of a homebrew, be aware that Waxoyl contains chemical corrosion inhibitors (see MSDS for some details) which is a good part of how it suppresses corrosion. Unless this component is included the mixture won't be effective.


My mixture contains ACF-50. I developed it out of frustration with chains rusting in winter due to the short-lived (~2 weeks) protection provided by commercial chain lubes under our conditions. By experimenting with components and proportions I arrived at times until the next rust of up to 6 months, this on a chain. In most other places I apply my mixture and never get back. Of course it is hard to be entirely original and Waxoyl may be similar.

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

Postby alexnharvey » 16 Oct 2020, 3:31pm

slowster wrote:I think (most?/all?) heat shrink tubing is coated inside with a glue which melts when the tubing is shrunk and thus creates a seal at the non-connector end.

Image


You can choose glue lined or not, degrees of shrinkage and so on. If you want to be able to separate the connector glue lined heatshrink would not be very useful.