Joining festoon cable

[SimonH2]

During the storms a while back, we had a couple of fence panels blow out, and put a lot of strain on a set of festoon lights as they went - and the lights stopped working. I finally got round to investigating, and it looks like it's broken the joint where the flat festoon cable joins to the round feed-in cable. Simple enough, chop out the moulded joint and re-do it with one of those inline joints. But ...
The festoon cable is rectangular - about 1/8" thick and 1/2" wide (3mm x 12mm for those that don't understand real measurements ), with square edges. That's not going to fit well, or seal well, in any standard stuffing gland.

The best I can think of is one of the flat-form glands that Remora do (I've got a couple of 4mm2 ones left over from a job) - but by the time you get anywhere big enough (I think one of the ones I have might do), it's 25mm thread and the inline joints are only 20mm. I'd rather not use something like a Wisker box as it'll stand out like a sore thumb.

Any suggestions on how best to do this joint ?

 

[plugwash]

Would a gel-filled joint be a solution? something like

Raytech 2-Entry 2-Pole IPX8 Mini Gel Joint Green

Order online at Screwfix.com. Pre-filled joint designed to snap shut to ensure safe electrical connections. Accommodates 2-core flexible cables up to 4mm straight through, or 2-core 1.5mm cables branched or 4-way. Reuseable and suitable for permanent submersion or burying. Can fit 2 x Wago 221...

www.screwfix.com

 

[SimonH2]

Hmm, looks like it could be just the ticket - and I've a Screwfix just up the road.
Only thing is it isn't clear if there's any strain relief. Guess I'll have to pop up and ask if I can have a look at one.

 

[ericmark]

I would use epoxy lined shrink sleeve, but depends on your skills.

 

[SimonH2]

Why didn't I think of that first The annoying thing is, I know I have some heatshrink big enough ... somewhere. But I've moved twice since I last knew where it was
My usual method is to use hot-melt glue - either applied from the gun, or slice a bit off the end of a stick. Short of a proper moulded joint it's the nearest I can get to moisture proof. But it sure is sticky where it extrudes out of the end of the heat-shrink.

 

[SimonH2]

Job jobbed.
Soldered cores, glue & heat shrink. Glue and heat shrink over the top. Luckily my brother had some black that was just the right size - big enough to fit the flat cable, small enough to shrink down tight on the feed in cable. Less visible than the original joint
But, what a p.i.t.a. prepping the flat cable. Three layers - basic insulation on the cores, then a spacer like the 300Ω aerial feeder (to keep the cores exactly where they need to be for the lampholders to pierce them), and then a sheath over the top of that. And all stuck together so you have to carefully shave back the sheath till you see the core colour show up.

 

[Sureitsoff?]

Nice and neat

 

[SimonH2]

I would use epoxy lined shrink sleeve, but depends on your skills.

BTW - do you really mean epoxy, or hot melt ?
I've only ever seen hot melt lined heat shrink, never heard of epoxy.

 

[ericmark]

It said epoxy, but not a clue what was really inside it. It did two things, one it sealed it, and two it gripped it, but the kits only gave one just enough, so you had to be rather neat when cutting before the splice.

 

[bernardgreen]

Joint kits like this use two part epoxy resin

https://docs.rs-online.com/3952/A700000007765393.pdf

 

[SimonH2]

Indeed, those cast joint kits do use two-part epoxy. I think Ericmark is meaning glue lined heat shrink - hence me questioning "epoxy lined". This is similar to regular heat shrink, but the tube is lined with a layer of hot melt glue which melts and fills* the voids when you shrink the sleeving, as well as gluing the sleeving to the cable.
Regular heat shrink is mostly 2:1 shrink ratio, but I've noticed that glue lined is typically 3:1 (or even 6:1).
For this job, I had a bit of plain sleeve just the right size, so used the hot melt glue gun to fill in the gaps first - then it remelts and (if you've got enough in) extrudes out of the ends when you shrink the sleeving. It takes a bit of practice to get right - too much of a bulge and you struggle to get the sleeving over it - and you have to wait for the glue to cool down, otherwise a) the sleeve sticks to it, and b) the heat can start the sleeve shrinking, before you've got it in place (guess how I know that )
* Depending on how big they are, as said, there isn't generally much glue.

 

[DetlefSchmitz]

As it happens a quick search finds Epoxy Heat Shrink Sleeving. The epoxy resin is activated as part of the shrinking process.