Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[burakkucat]

The following extract, taken from The Post Office Electrical Engineers' Journal, Vol 62, Part 3, October 1969, Page 195, may resonate with certain Kitizens. 


GPO's World First in Aluminium

The Post Office has scored another world "first", in collaboration with British industry.

In its campaign to reduce costs and hold down charges, the GPO is now using aluminium instead of copper in cables linking the customer's telephone with the local exchange. This is expected to save about £500,000 a year.

The changeover began about eight months ago. By the end of this year all cable laid for subscribers' lines in local network extensions is likely to be in aluminium.

Although aluminium has been used experimentally before, Britain is the first country in the world to lay it for telephone lines in everyday use.

Prompted by increases in the price of copper, the Post Office began experiments in the 1950s -- and ran into difficulties with jointing methods and corrosion. Patient research continued, in close co-operation with manufacturers, until the breakthrough came in the mid-1960s.

The jointing problem was solved by using a new crimping tool to compress the wire ends inside an insulated connector without stripping off the plastic insulation. A new method was developed of preventing corrosion in underground cables by packing them with petroleum jelly, greatly reducing the likelihood of faults. [1]

Further experiments established the most suitable grade and tensile strength for the aluminium conductor, while factory and field tests proved that aluminium cable could be made and laid using normal methods. The first bulk-produced aluminium telephone cable was laid in South-East England and further quantities are now ready for installation in the Midlands, the East and the South-West. Northern Ireland and Scotland will be next.

Aluminium cable costs about 10 per cent less than copper cable. Aluminium is not such a good conductor as copper but, since the metal is much lighter, this has been easily overcome by making the wire thicker. At Coventry, the Post Office is carrying out trials with aluminium wires thinner than previously thought possible: this may lead to a further reduction of costs. Bulk is a major factor in designing the larger cables that run between exchanges and distribution points and the possibility of using the thinner aluminium wire in these cables is also being examined.

A pneumatic machine for making better joints faster, developed by GPO research staff and a British manufacturer is now undergoing field trials which include tests on its suitability for aluminium cables. [2]

[1] Developed by British Insulated Callender's Cables Ltd; process now used by all British telephone cable makers.
[2] The Plessey Co. Ltd.

[Black Sheep]

Ha ha ........... 'Ball Crystal 1A' was not a stores item back in the day. 

[JGO]

Wasn't it Babbage who said show an Englishman a device to do one job better and he wants it to do something totally different !   This still is as true as when he said it.

 

[sevenlayermuddle]

It strikes a chord with many modern-day cost cutting ideas, from letting cars drive on the hard shoulder of motorways, to NHS plans for 'watching and waiting' rather than healing.

The one clue I'd suggest, then as now, if it is a 'world first' as described by the GPO, then it is worth careful consideration.   There may be good reasons why nobody else is doing it.

That said, I have no idea whether other countries adopted Aluminium cabling too.   Anybody know?

[Jaggies]

I remember Raymond Baxter on Tomorrow's World (in monochrome) showing fibre-optic cable and saying the the GPO (or whatever they were called that week) wanted to introduce it to replace copper phone lines.

I believe the government of the day put the kibosh on that one...

I believe there are some remnants called TPON still out there - http://www.samknows.com/news/tpon-copper-overlay-update-186.html

A slightly more recent TW, and only slightly annoying because of over-use of "information super-highway", can be found here -
http://youtu.be/V8cnP-RtRHU

[roseway]

"By the end of this year all cable laid for subscribers' lines in local network extensions is likely to be in aluminium."

Thank heavens they didn't achieve their objective.

[Black Sheep]

 

[JGO]

The one clue I'd suggest, then as now, if it is a 'world first' as described by the GPO, then it is worth careful consideration.   There may be good reasons why nobody else is doing it.

That said, I have no idea whether other countries adopted Aluminium cabling too.   Anybody know?

I seem to remember reading that a large part of the National Grid is Aluminium plated Steel , anyone confirm ?
My point is that the technique works for its designed purpose - whose fault is it if some ignorant accountant decides it is "magic" applicable to everything ? 

[c6em]

Correct - for the overhead High voltage cables on pylons.
No idea what the low voltage local distribution overhead stuff is in rural areas.

[Berrick]

You see this idea everywhere in cabling today as it is about half the price of the good stuff.

Copper Coated Ally for ethernet, copper coated steel RG59. IF ally and steel are soooo good at conducting for the given purpose why do they add copper   

[JGO]

Copper Coated Ally for ethernet, copper coated steel RG59. IF ally and steel are soooo good at conducting for the given purpose why do they add copper   

Skin Effect;   At high frequencies current only flows near the surface, so anything ( or even nothing ! ) will do inside.  Forget 50Hz practice ! 

[Berrick]

Dont know enuff about skin effect so would have to agree with you JGO.

I would say I was thinking more about PoE when I posted my comments. Nothing inside wouldn't be any good here

[c6em]

Skin effect means that as the frequency rises the currents starts to flow only in the outer diameters of a wire.
So the centre of the conductor and what it is made of becomes irrelevant.
At very very high frequencies the conductors are made of hollow tubes of something with a coating of silver on the outside.
Due to skin effect the only place the current flows is in the silver.

[JGO]

Further to c6em's comment, a hole down the centre conductor is handy at high power to water cool 1" coax cable;  at that size you don't need a steel core for mechanical strength but  at 100kW even 0.1 dB cable loss is appreciable.
 

[4candles]

The following extract, taken from The Post Office Electrical Engineers' Journal, Vol 62, Part 3, October 1969, Page 195, may resonate with certain Kitizens. 

It surely does. 

Ha ha ........... 'Ball Crystal 1A' was not a stores item back in the day. 

'They' should have asked those of us at the 'sharp end' - we said it was a daft, short-sighted idea. But of course they never did.