Tuesday, 15 October 2013

Old telegraph poles near Smethwick Junction

16th September 2013

As we cruised along the Birmingham Canal New Main Line I spotted some old telegraph poles near Smethwick Junction.

It looks as though some of the insulators are stuck to the pole, but one of the cross members has swung round.

The second pole shows things a bit more clearly.

Was it the case that the wires were uninsulated, hence the ceramic insulators on the poles?

And I wonder when the cables last saw service.


Davidss said...

re "Was it the case that the wires were uninsulated, hence the ceramic insulators on the poles?"
I worked on such wires as an apprentice, when going the rounds doing different jobs within the GPO, as it then was.
IIRC the standard gauge wire was '40lb', being the weight of 1 mile of wire.
I suspect there were various insulators available, but the standard term was 'a 16' or '16s' (plural).
There was an awful lot of documentation around the correct use, rigging, and termination of such wires. The poles you show are for local use. The arrangements for open wire trunk routes (long routes between towns) were something else again.
Remember there were always two wires per single circuit or phone number.

Now what are you going to do with with that information :-)

Halfie said...

Davidss, thank you for that. I'll tell you what I'm going to do with that information, and that is to ask you some more questions!

Was the wire a single strand per conductor, and was it steel? I can't imagine pure copper being strong enough for long runs. Or was it stranded, with a few copper strands around one steel strand?

When would the poles have been erected, and when would the communication circuits they carried last have been used?

Would they in fact have started off as true "telegraph" lines before carrying speech?

Davidss said...

There was no stranding or steel in the design.
The wire was considered 'copper'. Clearly trace elements could have been added to make it stronger or harder, but it was still considered 'copper'.
Strength is difficult to assess, because I cannot recall the diameter, merely 40lb (per mile) for normal wire, and 70lb (per mile) for heavy duty wire, such as when the route ran through trees. I don't know if the heavier wire was used on long routes to reduce resistance, but I don't think so, as a general rule.

"When would the poles have been erected?"
Not certain, but you can tell when the tree became a pole, by the markings engraved in it, seen at or below head height on any installed pole. (Assume an average adult male). I wouldn't like to guess how long a pole may have remained in the stack before it was put into use. This might have depended on its stature and length, and therefore the demand for that size and type of pole.
An 11 metre Light pole near my house was erected by BT in 2005, and is marked 03.

The engraving will show who owned the pole (GPO, PO, BT, Electricity or Railway (abbreviated)). Poles were either L(ight), M(edium), or S(tout). The type used would have depended mainly on how many wires it was expected to carry, and their alignment. A pole on a corner, if carrying 'many' wires, needs a stay to stop it bending sideways over the years, and this staying induces stresses of its own, possibly needing a thicker pole.

The type chosen could also have reflected it's overall length, where additional height was required to clear factory buildings, or to give wire clearance at road crossings.
Lengths were measured in feet, so 30L would indicate a 30 foot Light pole. Obviously later poles were measured in Metres, so 30L became 10L, more or less.

The engraving would contain a year indicator, normally 2 digits, as you would not expect a pole to last over 100 years.
There may well be a coded mark to indicate who had supplied the pole.

The most important mark is the most unobtrusive, being a horizontal line. This is 10 feet / 3 metres from the end of the pole. Measuring from this mark to the ground tells the person about to climb the pole how much of it is in the ground. Local ground conditions make a big difference here. Soft ground could see 6 feet of pole in the ground. There is also the danger of someone 'improving' a drainage ditch and scooping away 2 feet of soil. 12 months on and the lineman wouldn't know about this, so referring to the line can be a life saver.

"when would the communication circuits they carried last have been used?".
Can't say.

"Would they in fact have started off as true "telegraph" lines before carrying speech?"
I doubt it. I'm not sure when pre-telephone pure telegraph circuits were in use, but I'd expect them to go to Telegraph Offices, with the messages transcribed on to paper for onward delivery. Would any business in Smethick have been big enough to warrant its own telegraph office, before telephones became common? I doubt it.

Halfie said...

Fascinating stuff, Davidss. Thank you. I'll look out for that horizontal line now.

otd strans said...

What a great post about
Steel telegraph poles