Widget for joining 3-core mains flex

[Palindrome]

MikeC wrote:

"Alex Coleman" <no@no-email.com> wrote in message
news:Xns9949BC38CC60671F3M4@127.0.0.1...

On 03 Jun 2007, Owain <owain47125@stirlingcity.coo.uk> wrote:


Coleman wrote:

[...]

Then stop bodging things and install a proper, permanent socket
where it is needed.

Owain


Bit drastic?


I didn't see the beginning of this thread, but a technique that I frequently
use when joining wires is as follows. Look at the diagrams in Courier New
font, or they won't make much sense.

-------------- -------------------
Cable +---- wire_1 --------------------+ Cable
sheath +----------- wire_2 -------------+ sheath
+-------------------- wire_3 ----+
-------------- ---------------------

Firstly, strip a piece of the outer cable sheath off and put it to one side
to use later.
Then cut the wires as shown in the diagram. Bare the ends of the wires, and
solder the two ends of wire_1 together, and the same for the other wires.
Because the wires were cut to different lengths in this way, the soldered
joints are not close to each other, and cannot short together.

Now take the piece of sheath that you put to one side, slit it down the
side, and put it over the new joints. At this point, the cable should look
almost as if it had never been worked on.

-------------- ------------------------------------------------- -------------------
Cable | This is the piece of sheath that you | Cable
sheath | kept to one side, now used to | sheath
| cover the joint |
-------------- ------------------------------------------------- ---------------------

Now wind some electrician's tape around the full length of the sheath that
you have inserted, and an inch or so beyond each end. Better still would be
if you had slipped a piece of heat-shrink tubing over the wire before
soldering it together. The heat-shrink tubing should be about two inches
longer than the piece of sheathing you used to cover the joints.
_________________________________________________________________
---------/ / / / / / /
/-----------
/ / / Taped up with electrician's tape / /
----/ / / / / /
/____
/ / / / / / /
/
----------/_________________________________________________________________/------------

I have used the same technique on multi-wire cable - most recently on an
Ethernet cable that I had to cut to get through a small hole, then join
together again, because I didn't have the tool to put the connector back on.
In this case, with 8 wires, the total length of the connection was about 4
inches.

Fine for signal cables.

Lethal for mains flex.

The method provides virtually no strain relief for the conductors. Which
a continuous outer sheath provides as well as insulation.

Subject to even a modest pull, the conductors or soldered joints will
fail, potentially leading to a bare live conductor.

Any means of jointing mains flex has to provide strain relief for the
conductors comparable to that provided by the outer sheath of the
original cable.


--
Sue

 

[John Rumm]

Palindrome wrote:

Fine for signal cables.

It would also be ok for fixed house wiring in the uk, although
heatshrink would be a more appropriate sleeving material than insulating
tape.

Lethal for mains flex.

Yup. If you had some form of enclosure with cord clamps though then it
would be fine.

Any means of jointing mains flex has to provide strain relief for the
conductors comparable to that provided by the outer sheath of the
original cable.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

 

[nog]

On Sat, 02 Jun 2007 20:23:15 +0100, Coleman wrote:

On 01 Jun 2007, <meow2222@care2.com> wrote:

On 1 Jun, 12:13, Palindrome <m...@privacy.net> wrote:
Bob Mannix wrote:
meow2...@care2.com> wrote in message
news:1180694680.834209.209690@p77g2000hsh.googlegroups.com...

Coleman wrote:

I am in the UK. I want to ask for info about joining 3-core
mains flex on an appliance that may have to carry up to 3,000
Watts.

I usually extend the mains flex by soldering but the finished
join is too bulky when winding the flex or pulling it around a
corner.

When I make my 3 joints I slightly offset each one so that it
is not beside another one. This helps make a slimmer overall
joint but it makes for a longer joint (about 2.5 to 3 inches)
and with insulating tape it is still too bulky.

(A) Is it safe to use heat shrink insulating tubing for each
join and have each join beside the other? Then I might use a
single layer of insulating tape to bind over and protect the 3
joins.

(B) Or is there some widget which can help with this? Perhaps
a small moulding which is made up of three very small metal
tubes held by moulded plastic to be close together but not
touching. I could put a wire into each end of a metal tube and
then solder the wires into it. (It's just an idea.)

Any info?

http://wiki.diyfaq.org.uk/index.php?title=Twisted_Flex_Joints

But that is about twisted flex joints (the key is in the name
) ) rather than soldered joints, which is what the OP was
talking about. Hardly ideal but still not twisted flex joints
and therefore not subject to the dangers described in the
article.

I would suggest that soldered joints covered with normal heat
shrink and insulating tape, "lack tensile strength, abrasion
resistance, general robustness, spillproofness (they can make a
small spill live), good insulation, petproofness & small
childproofness."

The marginal advantage of soldering the joints has to be balanced
against the greater risk of failing during flexing, as the
soldered joint will form a flexure discontinuity and stress
points.

Of course, soldering with acid flux would be an even greater
problem.

--
Sue

I also thought it was pretty obvious what also applied to soldered
joints. Solder is weak stuff too, though I've not seen any
significant failures from soldering pretwisted flex (at LV). But
not everyone twists enough before soldering.



ISTR there was a time when the different twists had their own names.
Maybe they still do.

Wasn't something like "Western Roll" one such name???

You're thinking of the Western Union splice:

http://www.tpub.com/content/neets/14176/css/14176_46.htm

The Western Roll is a high jump technique which preceded the Fosbury Flop.