Help soldering really thin cables to 7 pin Towbar socket/plug

[Adrianlle]

Evening. I am in the process of fitting reversing sensors and a camera to my Towbar bike rack. All going well so far. The plan is to split the 5 wire camera cable and 2 wire buzzer wire for the sensors using a 7 pin trailer socket and plug. That can then be connected at the same time as connecting the 13 pin plug/socket for the bike rack. The wires in the camera lead are really really fine however. So Im concerned that if they are just held fast in the 7 pin socket (but especially the plug) that they won’t be solid enough. That is because the wires are held by grub screws.
So I wondered what ideas people had for making a really strong fixing for each of the 7 wires in the 7 pin socket and especially the plug( which will get the most movement connecting it in and out) ? One idea I had was to try to solder each of the finer 7 wires into the brass hole for it and then screw the grub screw down while the solder is still setting. So any help from the electrical gurus out there much appreciated. Photo below if what I’m trying to explain.

 

[XxAnthxX]

Maybe crimp some terminal pins onto the ends of the fine cable?

 

[Mikeco]

Try a blob of solder on the end of the wire first like you see on some wired 3 pin plugs.

 

[Reallyretired]

I would suggest crimp terminal pins. They are useful for any wire that needs to go into a screw type fitting.

Cheap too, this would give you a few spare
https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=383251917207

 

[pappajohn]

One idea I had was to try to solder each of the finer 7 wires into the brass hole for it and then screw the grub screw down while the solder is still setting

Believe me, the solder will be solid before you put the iron down and Pick up a screwdriver.
Take a length of thicker stranded wire and wrap the thin wire around the thick stuff a few times then solder it.
That will give the screws something to bite on.
Cut off the excess thicker wire at the solder then repeat for the other thin wires.
When it's done and tested fill the plug with silicon through the gland end and allow to cure and it will also prevent 'movement' hardening and the soldered wire snapping
That will support and strengthen the thin wires and waterproof the whole plug at the same time.

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[MisterB]

you could try soldering the wires themselves so that the wire becomes 1 solid wire ( x7) rather than lots of very small strands?

i think thats the same as Mikeco suggested

 

[Adrianlle]

Crumbs- this forum! I idly check less than an hour after posting and I have more than half a dozen suggestions already! Crimping to round terminal pins sounds like one answer but Papa Johns suggestion sounds just as good with the advantage that the stranded wire gives more for the grub screw to bite in than a smooth pin. It also means I don’t have to wait another week for the terminals to arrive! The back filling with silicon also sounds like a good tip. So I will give that a go and let you know how I get on. Thank you one and all.

 

[pappajohn]

Make sure it works BEFORE using silicon.
Only one chance then its new plug time.

 

[Sandancers]

I'd always use Bootlace ferrules, like below. You can buy them online loads of places, but you need the correct crimping tool to go with them. So possibly not cost effective for a one off job. But if you plan a bit more wiring worth considering.

 

[Adrianlle]

Although I’ve crimped spades, rings etc as p

I'd always use Bootlace ferrules, like below. You can buy them online loads of places, but you need the correct crimping tool to go with them. So possibly not cost effective for a one off job. But if you plan a bit more wiring worth considering.

View attachment 384505

Although I’ve crimped various terminals whilst doing wiring mods on the Van I haven’t come across these before. Two silly questions. 1. How do I know what size to buy relative to the diameter of the hole they are going into / wire size ?2. What is special about the crimping tool? I have a crimper but didn’t know there were different sorts.

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[Sandancers]

The bootlace ferrules come in a variety of sizes, the picture I gave shows a tub containing a selection of sizes. The crimp tool is specially designed for them. These are like mine;

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=124167063293

But other versions are available.

 

[Adrianlle]

The bootlace ferrules come in a variety of sizes, the picture I gave shows a tub containing a selection of sizes. The crimp tool is specially designed for them. These are like mine;

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=124167063293

But other versions are available.

Thanks. In the meantime I’ve done some searches and can see the boot lace ferrules are really useful. Worth waiting a week for. What I’m not sure about is whether my Crimping tool will do or whether I’d be better off buying a kit from eBay that has both tool and assorted ferrules. See below the eBay tool and below that the head of my crimper. Any thoughts anyone?

 

[Sandancers]

Buy the kit ! The standard crimp tool used for the red / blue / yellow "normal" crimps will not go small enough for small bootlace ferrules.

 

[Adrianlle]

Ok. In for a penny....... Have ordered the kit. Thanks for help.

 

[Richard n Ann]

Yes the ferrules are the best option. If you just tin the wire and put that in, the solder slowly crushes over the months and the connection becomes loose.

A few years ago I remade the hook up lead plug and tinned the wires, a few weeks later I took the cover off the plug to check the tightness of the screws ? they were loose as buggery.

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[John Barrett]

Did you know that the little fibre wire clamp in a mains plug held in by two screws is euphemistically called 'strain relief'...

 

[tonyidle]

My best tip is to use a plug and socket more suited to the size of wire.

https://rover.ebay.com/rover/1/710-...0001&campid=5338547443&icep_item=193413605857

 

[Adrianlle]

Yes the ferrules are the best option. If you just tin the wire and put that in, the solder slowly crushes over the months and the connection becomes loose.

A few years ago I remade the hook up lead plug and tinned the wires, a few weeks later I took the cover off the plug to check the tightness of the screws ? they were loose as buggery.

That’s reassuring to hear now I’ve splashed out on the 14 quid! The reason it needs to be a 7pin trailer plug is that I have 7 wires to carry across from the camera/ buzzer from rev sensors I’ve fitted to the bike rack across to the Van. I want to avoid a multiplicity of different plugs. Having a 7 pin socket alongside the existing 13 pin makes for easy coupling/ uncoupling of the bike rack. In fact there is already another 7 pin socket on the other side of the Towbar where the plug from the bike loop for the Growler plugs in ( Vanbitz). I imagine that too has v fine wires coming into it and is what gave me the idea of how to get the camera / sensor buzzer wires from the bike rack to the cab. Anyway, once the ferrules/tool arrives I’ll see if the design works !! All the spadework is done bar the 7 pin coupling and seems to work bar cutting the cables and wiring the coupling........

 

[tonyidle]

That’s reassuring to hear now I’ve splashed out on the 14 quid! The reason it needs to be a 7pin trailer plug is that I have 7 wires to carry across from the camera/ buzzer from rev sensors I’ve fitted to the bike rack across to the Van. I want to avoid a multiplicity of different plugs. Having a 7 pin socket alongside the existing 13 pin makes for easy coupling/ uncoupling of the bike rack. In fact there is already another 7 pin socket on the other side of the Towbar where the plug from the bike loop for the Growler plugs in ( Vanbitz). I imagine that too has v fine wires coming into it and is what gave me the idea of how to get the camera / sensor buzzer wires from the bike rack to the cab. Anyway, once the ferrules/tool arrives I’ll see if the design works !! All the spadework is done bar the 7 pin coupling and seems to work bar cutting the cables and wiring the coupling........

OK . To make the terminations robust lay a piece of decent wire alongside the thin stuff for a couple of inches. Strip 15mm or so of both, twist together, and solder. Slip heatshrink over both leaving the soldered end exposed. This will reinforce the last couple of inches of the thin wire. Trim the soldered end to suit the termination.

 

[Adrianlle]

OK . To make the terminations robust lay a piece of decent wire alongside the thin stuff for a couple of inches. Strip 15mm or so of both, twist together, and solder. Slip heatshrink over both leaving the soldered end exposed. This will reinforce the last couple of inches of the thin wire. Trim the soldered end to suit the termination.

Thanks. That sounds a good workplan and it will enable me to use larger diameter bootlace ferrules too.

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[Sandancers]

Thanks. That sounds a good workplan and it will enable me to use larger diameter bootlace ferrules too.

No, it's not good practice to crimp onto solid cores.

 

[mitzimad]

adding a crimp seems wrong to me you then have two joints i would double the wire back on its self into the screwdown terminal

 

[tonyidle]

A ferrule shouldn't need to be crimped for a screwed termination. It simply slides over the conductor and is squashed by the screw to prevent the screw from cutting it.

35mm Uninsulated Cord End Terminals - CUT35-25

35mm Uninsulated Cord End Terminals

www.cablecraft.co.uk

 

[Sandancers]

A ferrule shouldn't need to be crimped for a screwed termination. It simply slides over the conductor and is squashed by the screw to prevent the screw from cutting it.

35mm Uninsulated Cord End Terminals - CUT35-25

35mm Uninsulated Cord End Terminals

www.cablecraft.co.uk

Why would they sell crimp tools then ? We always had to crimp the ferrule or you didn't pass the tests !!

 

[Adrianlle]

Oh dear- what have I started here!

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[hilldweller]

Oh dear- what have I started here!

Situation normal for FUN.

I'll add to it, I'd say totally wrong connector for video signals which need a properly screened cable from end to end. If the video is not sharp you know the connector is wrong.

 

[Adrianlle]

Situation normal for FUN.

I'll add to it, I'd say totally wrong connector for video signals which need a properly screened cable from end to end. If the video is not sharp you know the connector is wrong.

I’m keeping my fingers crossed about that aspect ! I’ve experimented with breaking a 4 pin camera extension cable. The video line in that has an uninsulated sheath wire wound around it presumably to screen it. I’ve therefore cut and extended that in a big loop so that is some distance from the live video wire. I’ve then cut the video wire itself and rejoined it using a terminal block. The picture from that is good - certainly good enough for a reversing camera. So I’m hoping the 7 pin connection will replicate that - it’s the one pin of the 7 that I have a question mark over in my mind though. But I will only know when it’s connected up. That’s part of the reason why I want as good a connection ad possible between the video wire and the plug/socket.

 

[tonyidle]

Why would they sell crimp tools then ? We always had to crimp the ferrule or you didn't pass the tests !!

My badly thought out reply. I assumed the OP meant the blue (or yellow, or red) thingies that end in a straight piece. The ferrules I had in my head were the ones pictured in the link. For this use they don't need to be crimped (in fact crimping would probable damage them). Within the confines of a 7 pin trailer plug / socket I can't imagine trying to fit the other type. Those pre-insulated connectors of any configuration were never intended for use on motor vehicles anyway. Horrible things.

 

[Adrianlle]

Bootlace ferrules and tool arrived and worked a treat for joining the fine wires to the new trailer socket/ plug. Thank you for the suggestions. Also pleased to say that the design works! Rear view camera on the bike rack and 4 parking sensors on the bike rack- 2 in the number plate and 1 in each corner of lamp cluster ( heart in mouth taking hole saw to those!). The resulting 7 wires get to the cab via the new trailer socket alongside the existing 13 pin one. V good picture. All works fine in yard and can’t foresee any probs in use. What I haven’t yet done is squeeze silicon into plug as in Papa Johns suggestion. Sounds a good idea but any thoughts on that from others ? At the headunit end I have installed a video change over switch so that the 2 inputs take a feed from the bike rack camera and the Rev lens of the twin roof camera. That enables me use either depending on whether the bike rack is being used or not. Also still have the looking straight back lens as other part of roof twin camera. Golly, taken some time though- just as well we are in lockdown !Some photos below.