REMARKABLE RADIO 'PED REPAIR LORRY.
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First Practical Demonstration of Direct Use Automobile Industry. Saving Time Intercommunication in Connection with the iing the Efficiency of a Repair Lorry.
DI:RING the past year The Commercial Motor has kept in close touch with developments in wireless transmission and reception of messages that might be applied specifically to the automo-bile, and we are now able to publish exclusive details of the first system of a private wireless communication system between a vehicle on the open road and its headquarters. This installation has been erected by the Park Motor Co., Ltd., of Wells Street, Jermyn Street, S.W.I, for employment in connection with their breakdown van. The vehicle is equipped with a sensitive receiving apparatus, and the garage has its transmitting plant, so that while the vehicle is away from headquarters its driver can still receive messages and instructions.
By the courtesy of Mr. J. A. Woodhams, of the Park Motor Co., we were recently given an opportunity of making a thorough examination of the working of the set, and were asked to put it to any independent test we thought reasonable. The following description of the test and the apparatus contains several informative facts for those who are interested in the development of radio in connection with the commercial motor, as we have been given permission to publish full technical details of the set.
Arranging Unexpected Test Call.
The test we arranged was of the -following nature. We presumed that the repair van had gone o.ut inanswer to a telephone summons from an owner who had broken clown, and that while the'vehicle was away the garage received another request for assistance from a vehicle that was broken down in approximately the same locality as the first. This is a very' common situation and it is one in which time and. money can obviously be saved if a message can be got to the repair lorry in order to prevent it returning to the garage before going on to the second job — and thus making an unnecessary double journey.
The Park Motor Co.'s wireless repair wagon arrived outside our London offices in Rosebery Avenue at about 12.45 one afternoon and, unknown to its driver or " mechanic J" Mr. Woodhams telephoned to the garage in ermyn Street and told them to get into touch with the van by radio and instruct its driver to proceed to a breakdown (imaginary) outside the main entrance to the Zoological Gardens in Regent's Park. It so happened that
2L.O., the London Station of the British Broadcasting Co., was carrying out some tests at the time, and the fact that the message, transmitted by the amateur station in Jermyn Street, was received three miles away in the van at a point only about a miles distant from the powerful transmitting station of the B.B.O. is in itself definite proof of the fact that, given a sufficiently selective arrangement of tuning, messages can be tranemitted with certainty by radio under very adverse conditions.
So soon as the message had been received, the van set off to Regent's Park, where, for its benefit, we had staged a " breakdown " of a small van. In the meantime, we had given instructions to the garage in Jermyn Street to tell the driver of the van to return to the garage so soon as he had finished in Regent's Park.
Now, when transmitting and receiving messages by radio, it is not only expensive, but also unnecessarily wasteful, to keep the receiving set' working all the time. Also the cost of a man who is constantly ' listening-in " would not be negligible. Therefore, an arrangement had been made that communication was to be established definitely every quarter of an hour, two synchronized watches being used. Thus, on the hour, quarter-past, half-past, and quarter to, the operator on the repair van listened-in, and actually he received the message to return to the garage so soon as he had finished in Regent's Park while the van was in motion and was being driven along Euston Road at a normal speed. By this time 2L.O. had closed down its tests.
Bringing the Crane to the Rescue.
, Arrived at the " broken down " car, the very ingenious crane carried in the lorry was rigged up on the tailboard (see illustration) and the front part of the sinall van was lifted in proof of what could be done had it been in dereli.ct condition. An inspection of the repair van showed that there was ample tackle for carrying out any ordinary repair job on the road. Incidentally, froin the time of driving up to the breakdown only 74 inins. were occupied in rigging the crane and hoisting the ear ready for towing. The tackle is quite suitable for dealing with cars of up to two tons.
Thereafter,' as a further radio test, a long transmission was made, during which messages were very clearly received both on a Western Electric loud speaker (with power amplifier) and on two pairs of 'head-phones (using one 1-1.-F., one detector, and one L.-F. valve only). In short, .the demonstrationwas in every way satisfactory and proved that it certainly is practicable to maintain communication between a moving vehicle and its headquarters.
Mr. J. A. Woodharns and his brother, Mr. W. F. Woodhanis, have devoted considerable time to the development of radio in connection with automobiles, and may be regarded as pioneers in this connection. Their transmitting set consists of a two-Osramvalved choke-controlled transmitter worked off " Ever-ready" dry batteries. The actual circuit was built up from parts obtained from Messrs. Gambrel', and undoubtedly much of the clarity of the reception of the speech was due to the fact that dry cells were used. The total potential employed is about 1,000 volts, and the batteries have been found to stand up remarkably well to their work. The aerial current is carried to a single-wire T aerial above the garage, and, considering the damping effect, of the buildings in the vicinity, this tramknitting station must be remarkably efficient. The receiving set consists of a movable aerial mounted on top of the van and made up of four copper strips slung by insulators between two poles. The actual receiving panels were supplied by Messrs. Gambrell Bros., of Southfields, and incorporate four valves (one H.-F. working on the popular tuned anode system, a detector, and two L.-F. valves) using the high-efficiency Gambrel' coils and a grid potentiometer to control os6llation. Osram valves were fitted, including a V24 for high-frequency amplification, and R valves for detector and L.-F. Forty-five volts high-tension potential was applied to the H.-F. and 60 volts to the other valves. This current was also obtained from "Ever-ready " dry cells. The masts for the aerial were made by Messrs. Simpson and Blythe, makers of the wellknown Turret mast, and a Western Electric loud speaker was used. •
. We consider this privately conducted demonstrae Lion to be very enterprising indeed, and it reflects great credit on Messrs. the Park Motor Co. The reception range of the outfit has been shown to be well over 20 miles, and the fact that messages can be received " through " the broadcasting wave up to a considerable distance is very promising indeed, and is, we should say, a unique achievement.