BRITISH ANTARCTIC EXPEDITION 1910
Most of us know about the ordeal suffered by the British Expedition of the Antarctic in 1910 when they attempted to reach the South Pole, but not many know about the scientific experiments, geological work and zoology that took place. Their ship, The Terra Nova returned to England with over 2,100 plants, animals, and fossils, over 400 of which were new to science.
This article consists of items from the GPO archives, with respect to the proposed telephony connectivity at the base camp and to a couple of remote sites. The documents were inherited from The National Telephone Company.
Please note that the information herein details what was expected to happen on the expedition, but due to changes in the local conditions the base camp changed location and therefore the proposals below may not be accurate.
Evidently the phones worked as expected but at Midday the phone at Hut Point didn't work too well probably due to the top surface of the ice turning to water.
Another issue was that users could not talk and listen at the same time, so using the system was like using a walkie-talkie.
The instruments were also polarity conscious, so it must have been difficult to test and rectify faults at some of the distances involved.
The National Telephone Company Ltd
Telephone Installation for the British
A telephone installation was required by the expedition to enable communication to be maintained between their winter living quarters and their outside stations. Drawing No.10250 herewith shews the 5 stations to be connected and the mileages between them.
The Aurora stations (4 & 5) were required only to intercommunicate, while the Living Quarters had to be put in communication with both Hut Point and the Instrument Hut. The instruments at the Aurora Stations would have to be left exposed in the open; that at Hut Point would be in a Hut but would be liable to the lowest outside temperatures.
The minimum temperature previously recorded by Lieutenant Shackleton was -70° F. This was considered too low to make the use of dry cells advisable (See Correspondence 53726) so that either a purely magneto system had to be adopted or one using a common battery which could be installed either in the Living or Instrument Huts.
The lines, which would be of bare wire (metallic circuit), would be laid upon the snow at some considerable distance apart, not less than 6 ft. it being assumed that the clean dry snow would be a perfect insulator.
Several simplified circuits were tested to arrive at the most efficient and at the same time simple circuit. These tests were in each case made with two speakers only. The variation between the two results was never more than 3 miles with 9.5lb cable. This cable was used throughout. The figures given are between the average and the lowest figure obtained so as to be on the safe side.
The battery voltage was 18.
In all cases the current was arranged to polarise the receivers correctly.
As previously mentioned the wire are to be laid on the bare snow. The metals considered were iron, copper and aluminium or an aluminium alloy. Both iron and topper, to give the necessary equivalent, are considerably heavier than the aluminium and were therefore abandoned; very little information was available regarding the aluminium alloy and it was only slightly stronger than the aluminium it was decided to use this.
The following are some details supplied by the British Aluminium Company.
For information on the use of Aluminium wire for cables see - Report by the
Cable Department dated 26.6.09.
APPLICATION TO ANTARCTIC CASE
Owing to the low, temperature under which the wires will be working both the conductivity and tensile strength will be increased.
The increase of conductivity corresponding to -70° F is
about 20%, and the increase in tensile strength, assuming that the increase
below 16° C is equal to the decrease above this
As it is not certain if the above figures hold strictly for these low, temperatures, lower values have been taken to leave a margin of safety and of course the temperature will not be continuously as low as -70° F.
Tensile strength worked to - 36000 lbs per sq. in.
Those figures correspond to increases of 10% and 15% respectively over the normal values to approximately -40° F.
After tests it was noticed that two "limiting distances" are given the one based on the ohmic resistance of the line and the other on its equated length. The true value will lie somewhere between the two. The reason for this is that the allowance for the line is made up of two parts one due to the "cable" effect or pure attenuation and the other due to the reduction in the transmitter current. The tests was purposely made with 9.5 lb. cable to reduce the difference as far as possible since this cable has the highest figure of resistance per microfarad.
No.20 S.W.G. would be suitable for the purpose required so far as transmission is concerned but it was decided after consultation with Mr. Simpson the electrical expert to the Expedition, to use No. 19 S.W.G., chiefly for mechanical reasons.
The most suitable circuit among those tested is No. 4 using Ericsson G.T. 3a. H.M.T's.
The Instruments at the Living and Instrument Huts were made with fronts which were screwed on, to be permanently removed when the instruments had been fitted, and the other three with hinged fronts.
The connections of the instruments are shewn in Drawing No. 10251. It will be seen that each instrument contains a generator, bell and condenser, and H.M.T., the bell and condenser being permanently across the line. One instrument is fitted with a key to enable it to work to either of two stations. The H.M.T's used were Ericsson G.T. 3a's. The specification for the instruments is numbered 32I.
The expedition did not wish to have the wire in larger
sections than 100 lbs. and it was therefore wound on drums in 100lbs. lots.
The wire was drawn in lengths corresponding to 25lbs. and four of these
jointed with aluminium McIntyre sleeves wound on each drum.
Line Wire & Accessories.
6 Drums. (Supplied by the Western Electric Co.)
100 x Aluminium McIntyre Sleeves.
2 x Jointing Clamps - S.L. 1 for sleeves.
TESTS OF APPARATUS
Before being despatched all the instruments were connected up as nearly as possible to correspond to the actual conditions and ringing and speaking tests made.
The battery used was 24 volts as it was stated that this was what would be used.
Speech was easily commercial between any two instruments when 30 S.M. of 20lb cable was in circuit. The resistance corresponding to this is 2650 ohms.
The largest line the expedition would have would be 13.5 S.M. and 2950 ohms.
The ringing was good between all stations.
The following tests and notes thereon are mainly taken from a report of Test Department on a sample of this wire. The tents were made to ascertain whether the wire would be suitable for the Company's use in cables.
Resistance (electrical) of a 12 yards length = 0.392ohms at 63.5° F = 57.5ohms per mile.
Weight of a 12 yard length = 393.7 grains = 7.816 lbs. per mile,
After tests it was found that the average breaking load is 49.2 lbs. = 39,100 lbs. per sq. inch.
A total tension of 40 lbs corresponds to a stress of 31,800 lbs. per sq. inch and tension of 45 and 50 lbs. to stresses of 35,800 and 39,800 lbs. per sq. inch respectively.
NOTES ON TESTS
The average breaking load for ten specimens is 49.2 lbs. =
39,100 lbs per sq inch. The average number of twists is 34 per
This system has bean arranged to work off one common
battery of 12 accumulators giving 24 volts. No local cells
The following conversations only can be made:-
The instruments are numbered 1 to 5 and should be fitted as
The connections of instruments 2, 3, 4 and 5 are shown in Fig (1) and those of instrument No. l in Fig. 2 Drawing 10251. Wiring diagrams of these instruments are shown in Drawing 10161.
The instruments are already connected up inside and it is only necessary to make connection with the terminals fixed on the outsides of the oases.
Terminal Blocks for terminating the outside wires on are supplied and also a coil of office wire for making connection between these terminals and the Instruments. No holes have been drilled for screws to fix the instruments, in order to minimise the risk of water entering. They can be drilled where convenient.
The aluminium wire is to be jointed where necessary by means of McIntyre sleeves, 100 or which are supplied. Those sleeves are tubes of aluminium which are slipped over the ends of the wires and then twisted 3 or 4 tines by means of the special clamps supplied. A ample joint is enclosed.
Before placing the wire under terminals or in the sleeves it should be cleaned by being scraped with a knife.
The instrument terminals are marked A & B. When connecting up two instruments the two terminals marked A should be connected together and also the two terminals B.
The following rules must be followed when using the installation:-
LIST OF APPARATUS SUPPLIED
The above apparatus is all that is required for the installation but the following spare parts are also supplied.
These are in a case labelled "spare parts".
In the cane of No. 1 instrument the bells and condenser are connected permanently to the lines and the transmitter and receiver controlled by the springs on the generator in the same way on the bell and condensers in the other instruments.
See that the armature of the bell in properly pivoted and that the bell hammer in free to strike the gongs.
See that there are no loose or broken wires on or in the instrument.
Should the generator handle at any time turn stiffly and in Jerks and no
reply be obtained from the distant end, the line would probably be short
circuited. To verify this
disconnect the line wires from the instrument. If the handle then turns
freely, a short circuit should be looked for on the line, starting from
Bad hearing may be caused by a buckled receiver diaphragm. To ascertain, remove receiver cap and examine diaphragm, change if necessary. Remove any dirt or metallic particles from pole pieces of magnate before replacing. Caro must be taken to put back the ring on the under side of the diaphragm.
If unable to speak or hear at instrument No. 1 examine switch and see that it's springs are making proper contact in the various positions.
If instruments are perfectly silent and no sound can be hoard on blowing into transmitters when both keys are pressed examine battery connections for a broken wire.
The Terra Nova
Last revised: December 02, 2020