Why does 13A plug and socket system have flat pins when most others are round?

[marconi]

(A sad admission: as a lad I collected plugs by make and colour and displayed them on a shelf in my bedroom - I liked for example the style of the 'Rock' make. I had therapy and am now recovered but some interest remains. Who remembers makes such as Rock, WG, Nettle, Wylex, Empire, Walsall(?)?)

Does anyone know why the designers opted for square pins rather than continue with round pins, as other plug/socket systems eg. MK commando have done.

And why did the old plugs have an aperture above the earth pin?

 

[Pete999]

(A sad admission: as a lad I collected plugs by make and colour and displayed them on a shelf in my bedroom - I liked for example the style of the 'Rock' make. I had therapy and am now recovered but some interest remains. Who remembers makes such as Rock, WG, Nettle, Wylex, Empire, Walsall(?)?)

Does anyone know why the designers opted for square pins rather than continue with round pins, as other plug/socket systems eg. MK commando have done.

And why did the old plugs have an aperture above the earth pin?

Did you ever come across the 13 Amp ones with the live piin being the fuse DS I think was the maker, as in Dorman and Smith, my Parents had these in their House when I was a Lad

 

[Midwest]

Was it not, so that the old round pin sockets could be plugged into the new format?

 

[KEV 1 N]

(A sad admission: as a lad I collected plugs by make and colour and displayed them on a shelf in my bedroom

When I was 2, I had an annoying habit of switching on / off sockets with items plugged in. To combat it, my dad had the idea of putting a bit of 5A fuse wire across L and N in a plug and left it plugged in but switched off....the trap was set! Soon there was a flash bang, and apparently I never touched the sockets again!

I remember being about ten, and on my travels came across an old plug (efe) brand it was.....the reason I remember the make was, after carrying it around in my pocket all day, when I got home I opened it up....to discover there was a family of earwigs inside it!

 

[telectrix]

And why did the old plugs have an aperture above the earth pin?

to get your R2, of course. before break-out boxes were invented. .

 

[Pete999]

Was it not, so that the old round pin sockets could be plugged into the new format?

Is that aimed at my post Murdoch?

 

[Richard Burns]

It was probably so that the new improved style of plug was substantially different from the boring old pointless plug and certainly not interchangeable so that only the new ring circuits would have the new sockets. I think Wylex did make a flat pin plug so they probably pushed for their style.

 

[Midwest]

Was it not, so that the old round pin sockets could be plugged into the new format?

Is that aimed at my post Murdoch?

I'm Midwest, he's Murdoch. ​

 

[marconi]

I wondered if they thought at the time a better contact (more surface area in touch and lower resistance) would be made between socket and plug for a square pin than a round pin. But if that were so then I'd have thought round pins would gradually die out.

 

[Midwest]

Wikipedia;

'An early MK plug to original version of standard. Note the unsleeved Line & Neutral pins, and the inspection hole for the purpose of making the connection of an earth conductor visible with the cover in place (as required by BS 1363:1947 clause 15)'.

 

[marconi]

So, the aperture/inspection hole is for safety check? Do you know why they thought a visual check without taking off the plug's top was necessary ?

 

[snowhead]

You need to get hold of "Post War Building Study No. 11 – Electrical Installations’"
It doesn't appear to be on the net for free download.
Apparently it shows the reasoning behind the 13amp plug / socket and ring circuit and more.

The I.E.E had 22 meetings (no surprise there then) in the forties and came up with the above document which led to the development of todays wiring systems.

 

[Midwest]

It was the decision to accept the MK socket as the default design, it was called 'Multy Kontact socket';

Museum of Plugs and Sockets: British BS 1363 plugs and sockets - https://www.plugsocketmuseum.nl/British1.html#BS1363history

and then read about BS1363

Our History - http://www.mkelectric.com/en-gb/AboutUs/Our_history/Pages/default.aspx

From Google.

 

[snowhead]

Finally an answer, from here, "Socketman";
13 amp plug question - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum - https://www.vintage-radio.net/forum/showthread.php?p=563154&posted=1

Getting back to the original point about the hole, clause 15 of BS 1363:1947 is quite clear, it states "The connection of the flexible conductor to the earthing plug pin shall be visible when the cover of the plug is in position". I can confirm that I inspected a copy of BS 1363:1947 held in the National Library of Scotland earlier this year, and took notes on that very point.

 

[westward10]

You are not alone Marconi, a colleague of mine collects unusual 13A plugs poached when doing PATesting. He has all sorts and makes even a couple of double-pole fused ones.