At the top - Ringing the DS from Whitetop - Hello, Mr. Duncan !
NW Mailing List
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Wed Oct 23 13:52:55 EDT 2019
“Thanks to Senator Link for posting his very interesting photo of the ring combinations posted in the Green Cove Grand Union Terminal Station.”
In case you don’t remember . . . the other famous Mr. Link (O. Winston that is) took a wonderful photo inside White Top Union Terminal station showing Mrs. Gladys Harriger at her agent’s desk. The photo (best version I have is plate 24 in ‘Life Along the Line’, also a smaller version is in ‘The Last Steam Railroad in America’ p.109) clearly shows two crank telephones, four message lines coming through the wall, and NO telegraph confirming just as you said in an earlier post . . .
“Well, Mr. Thieme's photo of the remains of the Whitetop turn-table also answers another question: How many communications circuits were on the Abingdon Branch? There are four insulators on the pole. Since we know that the Abingdon Branch, being built quite late, was operated by telephones rather than by telegraph, and that a telephone circuit requires two wires, we may deduce that there were two telephone circuits on the Branch.”
John Garner, Newport VA
From: NW Mailing List [mailto:nw-mailing-list at nwhs.org]
Sent: Monday, October 21, 2019 10:28 PM
To: N&W Mailing List <nw-mailing-list at nwhs.org>
Subject: Re: At the top - Ringing the DS from Whitetop - Hello, Mr. Duncan !
Thanks to Senator Link for posting his very interesting photo of the ring combinations posted in the Green Cove Grand Union Terminal Station.
Let us think for a minute about the problem of ringing from a magneto phone (crank phone) on the Abingdon Branch, and raising the Train Dispatcher in Roanoke by the appropriate combination of long and short rings. (Or in the other direction, ringing from Roanoke to a station on the Abingdon Branch.)
Our question will be: Can a magneto cranked at the West Jefferson depot ring a telephone bell in the Train Dispatcher's office at Roanoke?
The track mileage from West Jefferson to Roanoke is 213 miles. Double that number to get the number of miles of copper wire in the two-wire phone circuit: 426 miles.
Assume this 426 miles of wire is No. 9 gauge Copper, which has a resistance of 4.12 Ohms per mile at 68 degrees F. The resistance of the wire alone in this circuit will be 1713.9 Ohms.
Next, we must also account for the ringer coils which will be ringing the bells in all stations when the operator at one station cranks. How many stations will that be? According to the list Mr. Link posted, it will be 14 bells on the Abingdon Branch, plus one set of bells in R Office, the Train Dispatcher at Roanoke, for a total of 15 bells. That is to say, every time the agent/operator at one of the stations on the Abingdon Branch cranks his phone, 15 sets of bells will ring.
Each set of bells in a railroad magneto telephone has a resistance of approximately 900 Ohms (I metered a set of ringer coils.). Multiply that resistance times 15, and you get 13,500 Ohms added into the circuit just by bell coil resistance. Add 13,500 Ohms of total BELL COIL resistance + 1713.9 Ohms LINE WIRE resistance, and the total resistance of the telephone circuit is from West Jefferson to Roanoke is about 15,214 Ohms... if the weather is warm. In frigid weather, resistance goes up markedly.
Now, let us look at the device which is powering the ringing of all these telephone bells. It is a little hand-cranked magneto inside the oak box mounted somewhere inside each depot, constructed from 5 (or 6) horseshoe magnets and a coil of wire spun by the crank. The whole thing weighs just over 10 pounds. By actual tests I just made, the voltage output of the magneto is about 90 volts AC when cranked at a comfortable rate. When cranked quite hard, voltage output goes up to about 105 volts. When cranked full-bore, as furiously as I can crank, voltage hits 120 volts AC for a brief (but unsustainable) period of a few seconds only. For the purpose of this discussion, we will take 100 volts as the output of the magneto.
Now, let us see if that magneto output is adequate to ring a bell in Roanoke, after passing through the resistance of all the bell coils and line wire.
Each set of bells (by tests I just conducted) needs approximately 20 milliamperes of current (that is 0.020 amps, or 1/50th of an amp) to operate. Can the (assumed) 100 volt magneto output at West Jefferson, working through all the line wire resistance + bell resistance of all the stations along the route, develop the needed 20 milliampere current at the Roanoke end?
Current = Volts divided by Resistance. So, doing the substitutions for this circuit, current will = 100 (volts) divided by 15,215 (resistance.) Current will = 0.00657 amps, or less than 7 milliamperes. Result: The magneto cranked at West Jefferson will cause only 6.67 milliamperes to flow in the bell coils at Roanoke... only about 1/3rd of the current needed to ring the bell at the Train Dispatcher's desk.
Therefore, I believe that "ringing" was only effective BETWEEN the stations themselves on the Abingdon Branch. If one of the operators on the branch needed to speak with the Train Dispatcher, or if the Train Dispatcher needed to put up a Train Order to one of the stations on the branch, the Operator at Abingdon was probably asked to *get the Train Dispatcher on the line,* or *get the Operator at Whitetop on the line,* or whatever.
The actual voice circuits (talking circuits) could have been made to work between Roanoke and West Jefferson by the addition of load coils or an amplifier. It is only the bell circuit which is being discussed above.
A final observation. When the Virginia-Carolina RR constructed the railroad between Abingdon and Todd, NC, what did they use for line wire? Could they have used the much cheaper Iron wire, rather than Copper? Iron wire could be had for only 1/3th the cost of Copper wire, but it had 448% more resistance. No. 9 Iron wire has a resistance of about 18.5 Ohms per mile. Figure 75 route miles Abingdon to Todd, and multiply that times 2 to get total wire miles in the telephone circuit, and multiply that by 18.5, and you see that an Iron wire telephone circuit of that length would have far too much resistance for a voice circuit to operate between Todd and Abingdon without amplification. Therefore, the VC RR almost certainly used Copper line wire.
The N&W probably began using amplified telephone circuits at the same time it began implementing telephone train dispatching. Prior to that, my guess is that the Train Dispatcher for the Abingdon Branch was probably located in the Abingdon depot. Roanoke could have telegraphed with the Abingdon Branch stations, but the Abingdon Branch was built with telephones only, and no telegraph.
Attached is an article from the October 16, 1909 issue of Telegraph Age magazine, indicating that the N&W had just the month before implemented voice Train Dispatching circuits on the Radford Division (River side) and Pocahontas Divisions. My guess is that those original voice circuits were operated with the old "line loading" technology (load coils,) as the vacuum-tube telephone amplifier was not marketed until about 1912.
So, if you are ever walking along the Virginia Creeper Trail and pull up some Copper wire from the cinders, there is a good chance that wire was original to the Virginia-Carolina Railroad.
ALL OF WHICH IS SUBJECT TO CONFIRMATION OR REPROOF BY MR. TOMMY DUNCAN, WHO WORKED THOSE JOBS.
(Please, don't anyone ask me for help in setting up railroad magneto telephone circuits. I am a straight-telegraph person and know not a fig about telephones. They are far too modern for my interests. The best I can do is send you the century old circuit plans for hooking them up.)
-- abram burnett
CEO, The Turnip Telegraph Co., Inc.
Sent to You from my Telegraph Key
Successor to the MAGNETIC TELEGRAPH LINE of 1844
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