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

[rogerzilla]

The problem with crimping is that it needs a tool which is far too expensive for a once or twice a lifetime job. Cheap crimpers don't work.and a bike shop in the UK will look at you blankly if you ask them to crimp your rear dynamo connectors.

I crimp as best I can to make the cable secure and then solder as well to ensure continued conductivity.

Really, B&M should come up with a screw connector or something else that uses simple tools.

[JakobW]

SON sell a GHW crimping tool, which SJS have for a mere £45: https://www.sjscycles.co.uk/tools/schmi ... ping-tool/

TBH most of the rear lights I've got (Spanniga/B+M) use bare-wire connection anyhow, which I can generally fix on the road in a minute or two. I do use a readymade loom, because it's got the spade connectors for the front light soldered on. I don't think I've ever had a light die on me whilst underway; I've always picked it up when wheeling the bike out of the shed and fixed it then.

[Brucey]

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.

I think the chances of failure arising through lack of the funnel in this case are slight. The crimp looks OK to me otherwise. It is a 4.7mm crimp presumably destined for a SON hub generator. However there is a problem, which is wire size. Unless you splice in a new bit of wire don't get any choice about the wire that goes from the headlight into the crimp connections for a SON hub.

The Knipex tool jaws are marked "0.5, 1.0, 1.5" which I would take as being the mm^2 conductor sizes. The Molex tools are rated for 14-26 AWG for the HT1919 (using different sized crimps) and the posher tool does only skinny wires; 24-22 AWG with one set of jaws and 20-18 AWG with the other.

24 AWG is 0.20mm^2
22 AWG is 0.32mm^2
20 AWG is 0.52mm^2
18 AWG is 0.82mm^2

Now, 0.5mm^2 is fat enough for 5A current. Unless your dynamo wires are somewhat oversized, they won't be any larger than that and they might be a fair amount smaller. The upshot of this is that if you use the Knipex tool with skinny wire the conductor crimp may not be fully compressed onto the conductor, hence no 'funnel' perhaps. You can also perhaps see in the photo that the wires have been twisted before crimping; this is a common dodge if the wire cross-section is slightly on the small side; what tends to happen is that the bundle gets mostly gathered into one side of the crimp and is usually more secure than it would be otherwise. Another dodge with skinny wires is to strip more of the wire and to both twist and double the conductor over before crimping onto it; this fills out the conductor crimp.

Re tool cost; My posh Molex tool cost about £100 when I bought it; at the time it was cheaper than a new wiring harness for my motorcycle. It had gone up to more like £300 when I looked a couple of years ago.

Some B&M rear lights have both blade connections and bare wire terminals; these ease the lot of anyone trying to wire the lamp up, because a piece of wire with crimps at one end only (which is what you tend to get) is all you need to wire the rear light.

cheers

[slowster]

Now, 0.5mm^2 is fat enough for 5A current. Unless your dynamo wires are somewhat oversized, they won't be any larger than that and they might be a fair amount smaller. The upshot of this is that if you use the Knipex tool with skinny wire the conductor crimp may not be fully compressed onto the conductor, hence no 'funnel' perhaps. You can also perhaps see in the photo that the wires have been twisted before crimping; this is a common dodge if the wire cross-section is slightly on the small side; what tends to happen is that the bundle gets mostly gathered into one side of the crimp and is usually more secure than it would be otherwise. Another dodge with skinny wires is to strip more of the wire and to both twist and double the conductor over before crimping onto it; this fills out the conductor crimp.

That makes me wonder about the larger 4.8mm connectors for Son hubs, the ears of which I presume are sized for wider diameter cable than the 2.8mm connectors typically used on rear lamps. If so, assuming the same diameter cable is used for the dynamo and rear lamps, the quality of the fit/crimp of the cable in either the 2.8mm connector or the 4.8mm connector (or both) must be sub-optimal. But again I presume that for bike lighting it still doesn't greatly matter.

Given the various alternative connections that Son offer for their dynamo (female spade connectors, coaxial adapters, and SL/steckerlos hubs which require a fork made with special fittings), I suspect that they are not entirely satisfied with any of them. Their coaxial cable is better, or at least more robust, than the skinny twin core cable used by B&M, but the need to remove the outer cable, peel away and twist the outer wire and fit heat shrink to it before fitting the connector seems a very crude bodge, even though in most cases it's not a task customers need to do themselves, because Son sell rear cable looms with the connectors already attached, albeit only in one length (190cm).

[2_i]

I paid USD 130 for Knipex 975214 and USD 35 for the loader. The price for the tool itself was pretty good but the loader, I think, can be had cheaper in Europe. That's very often the strategy in farther away markets: to entice with the price of the main tool and recover the profit with accessories.

The crimps I get from the Knipex have the flares and look very much like in https://www.ttieurope.com/content/dam/tti-europe/resources/Literature/SupplierGuides/1473-TE-Connectivity-Good-Crimping-v3Web.pdf. I will post photos later after I hopefully take care of the day job.

[2_i]

OK, here are the photos for Knipex.

[Brucey]

Nice photos; what size wire are you using there? The conductor crimp is well-compressed and you can see the 'funnel' is more developed as a consequence. They certainly are not undercrimped; any more and they might be considered 'overcrimped' because there are signs of the 'reverse face extrusion shoulders' appearing in the conductor crimp.

I've not used that particular Knipex tool but in other tools of this type which are properly designed, the tool is adjustable so that the jaws can be made to close a little bit more or a little bit less on the last click. In this way you can allow for wear or intermediate wire sizes.

The SON/GHW tool sold by SJS is similar in principle to the more basic Molex tool I have; with care you can make a nice job of crimping using this type of tool, provided it fits the connectors properly (the combination I have of cheap crimps and the Molex HT1919 tool isn't ideal in this respect).

cheers

[slowster]

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.

[Brucey]

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)

yes I think either of those tools should do a decent job for the money (although the claimed range of wire sizes is slightly different for each tool). And the inclusion of some terminals is a welcome bonus, even if you might only ever use the 25 or so female 2.8mm blades (assuming you get 150 terminals, and equal quantities of six types). There is no loader and no depth stop, but that just means you need to pay attention when using the crimper.

If I wasn't already 'tooled up' that is probably what I'd buy if I intended to do a few bike lights and didn't want to do it some other way.

cheers

[iandriver]

Have to admit, a nicer job than my method of:

1. Heat end of wire with a fag lighter and nip off required amount when outer is hot enough to be plasticine like.
2. Clamp on with pliers.
3. Apply heat shrink outer with same fag lighter.

My version works as an emergency repair also

[Brucey]

if you need to do a roadside 'get you home' repair to a rear light connection, e.g. with a faulty female terminal, one way is to cut and trim the wire, then replace the (now loose) terminal over the blade, whilst trapping a few conductor strands between the blade and the female terminal. A proper repair can be carried out later.

I usually carry a small section of Stanley knife blade (well wrapped) in my puncture repair outfit for this kind of use.

FWIW if you carry a cigarette lighter this is useful for other purposes (such as flashing off solvent from rubber solution in cold weather). In theory you should also be able to solder connections using a cigarette lighter, provided you have some flux-cored solder with you. However I don't recommend that you try this for the first time in the dark by the side of the road; it is less easy than you might expect. Also between the fact that modern lead-free solder is a bit crap anyway, and the stuff you are trying to join is likely to be a bit manky, this further reduces the chances of success.

cheers

[iandriver]

I've often noticed quite a few of the male connectors have a hole in them. I've never quite bothered to look for the exact purpose of it. Perhaps a perfectly matched female would have a dimple on it so that aligns with the hole and holds the connector in place. Something I've never really thought about in any great detail. The hole seems to be a common feature though.

[Brucey]

I wasn't thinking of this when I bought my cheapo terminals; they have the dimple in the wrong place, and tend to get stuck when half-engaged because of it. However 2_i was thinking more clearly than me; his 2.8mm terminals have the dimple in the correct place to match the most common type of blade connector used in bicycle lights.

cheers

[ChrisP100]

I work on aircraft components, which often involves crimping of ring-tongue PIDG, in-line splicing and Plessey pin's & sockets. Not very often spade's, unless on related non-safety critical ground equipment.

I have to do a batch of yearly test crimps of various sizes which are sent to a lab for inspection and testing for damage and strength. This checks both my technique and a sample set of tools, so that any damaged tools can be identified and either repaired, or withdrawn from use.

[2_i]

Nice photos; what size wire are you using there? The conductor crimp is well-compressed and you can see the 'funnel' is more developed as a consequence. They certainly are not undercrimped; any more and they might be considered 'overcrimped' because there are signs of the 'reverse face extrusion shoulders' appearing in the conductor crimp.

I've not used that particular Knipex tool but in other tools of this type which are properly designed, the tool is adjustable so that the jaws can be made to close a little bit more or a little bit less on the last click. In this way you can allow for wear or intermediate wire sizes.

The particular crimps are 2.8mm/0.110" TE Connectivity/AMP #42068, for 22-18 AWG. The wire is 22 AWG from NTE. I like to use NTE wires because their insulation is slimmer than from other suppliers, yet comparably resilient and withstanding the temperature better when any soldering is involved. Because this insulation is slimmer than typical for 22 AWG, the crimp's range is pushed a bit on the insulation side. The Knipex pliers have an adjustment of the crimping pressure and it is supposedly calibrated at the factory and I actually went down a notch lower compared to the original.

At this point I try to push for 2.8mm spades to be the standard connector for bikes under my care for the obvious reasons that it is the right size for the currents on a bike and that it is already common for lamps. 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 )

Cheers