Surprises about electrical conductivity

Robert, One thing I'm absolutely certain of is when they finally ran the phone line up the two mile road to the little comunity of Marrysville in PA, where we lived at the time, in the 1940s (late, after the war) they used steel wire plated with copper. I collected some of the scraps hoping to use it. :-( ...lew...

That is because the actual joint is "gas tight" and hence wont corrode. ...lew... (who has made a lot of wirewrap connections)

I do remember that tunnel, and also a "town", if you could call it that, stretched out along a mile or more of road which had houses and shops on both sides of it.

But, what I can't forget was stopping along that road to grab a Coke with whatever college buddy I was driving across the country with, and being immediately surrounded by very young native american kids begging for handouts.

Being about 19 at the time, and I suppose having led what you'd consider a sheltered existance around the cities of San Francisco and Boston, I'd never experienced child beggars before or after that, here in the USA, though I've sure seen plenty of them elsewhere in the world since then. I'm always saddened by it, wherever it happens, though I understand that it's just local industry in some places.

Yes, that mountain reminded me of a volcano, with a spiral road with RR tracks running around the inside. From the observation point we could see the dust puffs from blasting going on here and there on the inside walls, I remember it seemed like there was one of those explosions every few minutes.

But not forgotten by me...

During that same trip through Utah a large wooden water pipeline ran alongside a road we were on, and I couldn't resist having my traveling companion take this silly photo of me at a spot where some AH must have taken a potshot at the pipe.

Thanks for the mammaries...

Jeff

It's all relative, though, Pete. Iron (or steel) at room temperature is about 12. Yet you don't think of that as being a poor conductor. Or the mercury used in a mercury switch, which is under 2. They are actually pretty decent conductors, with silver being an incredible one. Unless you compare it, of course, to a superconductor down around absolute zero....

John Martin

Lew sez:

True. But I was describing long haul transmission lines on cross arms of wood poles. The only ones I was familiar with from AT&T and RR experience were #9 hard drawn copper. I think that was used most all over the U.S. for open wire.

I think you are referring to what was generally called "parallel". Parallel consisted of 2 copper plated steel conductors of 17 - 18 AWG, laying side-by-side (not twisted) thus the name parallel; covered with a heavy rubber insulation. Parallel was flat and typically held in reuseable "P" clamps, although it could be "served up", or wrapped with soft copper to form a hook for hanging as well. P clamps were easy and fast to hang on poles in "J" hooks as I remember. Parallel was typically used only for short haul stuff such as house drops. Being flat, it lacked the cross-talk rejection characteristics of transposed open wire, or twisted pair.

Bob Sw>

Mufilira, Luansha, Kitwe, Ndola and the surrounding areas of the CXopperbelt in Zambia had/have many large open pit copper mines as well. Spent a few years over there in the seventies.

Skin effect is almost totally irrelevent at 60 htz, and most of that old knob and tube wiring was bright tin plated. Copper plated aluminum would be a corrosion nightmare.

You just described "C Rural" wire - they still make and use it today for long runs of one phone line. The big advantage being it will go

300 to 600 foot spans between poles depending on the ice and wind loading factors, just like the power line on the top of the pole.

If they try using regular residential drop wire (1 or 2 pair) it can't handle that long of a span without inter-setting additional poles, and for one house it doesn't pay to hang a steel strand and lash a normal 25-pair Alpeth cable to it.

This is called "CopperWeld" wire. Basically drawn by inserting a billet of steel inside a billet of copper. Then the billet is drawn down into wire. At the end the copper is still on the outside, and the steel is still on the inside!

Very strong stuff, which is why it's used (self supporting) for subscriber's drops.

The same kind of cored wire is made using copper on the outside, and niobium on the inside, for superconducting magnets. In this case though they put ten or fifteen niobium slugs inside the copper billet before drawing it down. When one is done there's a three mill diameter copper wire, with a dozen or so niobium fillaments visible in the cross section. Etch away the copper with nitric acid, and you get a microscopic niobium brush!

Jim

That stuff makes great ham radio antennas. Err, so I've *heard*.

That's copperweld wire, not plated. It's drawn down from billet with the same steel/copper cross section to start.

Jim

No this was a two mile run of open wire with one on each side of the pole. To about 4 or 5 people party line. Some other rememberances: A budy and I had a short pair of climbers (only up to the ankles OUCH) and a pair of earphones which we taped into the line ocaisonally. :-) ...lew...

Bob - read my note- I said old failing abandoned - telegraph/telephone. This was in the High desert and mountains north.

I well know the TDR and Smith stuff - Long Lines used to send me stuff when I was a kid. I was in El Paso and my dad was ATT/WESTERN - Long Lines adopted my class and myself on the side I guess.

The lines ran from El Paso to New Mexico. High winds required concrete weights to hand on the wires to keep them from sailing in the wind - pulling out the poles. Some lines had 2 large fruit can size weights. So strength was needed. It was cut by scoring and snapping. The wire required about a 3' minimum diameter. I suspect they were 100 years old at the time - maybe 75. Likely used between forts and during the war. The one with Black Jack in charge vs. Mexico bandits.....

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Robert Sw> Respectively beg to differ, Martin. The standard telephone wire was #9

Blame it on Edison. I bet it was for DC.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Lew Hartswick wrote:

Cool! I always wondered how they made that damned telephone wire. New why---it was obvious---for strength.

Harold

What a handsome guy! I bet you drove the chicks crazy!

it's an interesting view in google earth.

Ah, but the resistance across anything is:

length/(area*conductivity)

The cross sectional area of a solder joint between two copper wires laid side by side is huge compared to the cross section of any given point in the wire and the length is very short. Even with lead, the joint would conduct better than the rest of the wire...

That's also why the lead car battery terminals someone else mentioned are not a problem (large cross-section). If your battery terminals are getting hot, it's because the contact surface between the post and the terminal is corroded or loose.