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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article from 'The Autocar' magazine detailing tyre temperature tests carried out at Brooklands Track.

Identifier  ExFiles\Box 39\1\  Scan005
Date  25th September 1920
  
X.1238

THE AUTOCAR, September 25th, 1920.
543

TYRE TEMPERATURE TESTS.
Experiments Carried Out with the Rapson and Other Tyres on Brooklands Track.

Mr. F.{Mr Friese} L. Rapson and his Rolls-Royce on which the tyre temperature tests were made.

EVER since the first tests of the Rapson tyre were described in The Autocar, a good many motorists have found it very difficult to accept Mr. F.{Mr Friese} L. Rapson's claim that in running conditions this tyre, reinforced as it is by the thick rubber deflector, does not tend to become hotter than a normal cover in similar conditions of usage.

Taking the Tyres' Temperature.
This question of heating was naturally one which presented itself to us when first we investigated the tyre, and we were able to announce, as a result of fairly prolonged trials on the road, that the Rapson tyre did not become hotter than others, its temperature, indeed, being less high than that of another first-class make of cover and tube used on the opposite driving wheel during the tests. Our opinion, however, was formed after merely laying our hands on the two tyres from time to time, and it has been suggested, very naturally, that some test of a far more precise nature was required.
With a view to obtaining more convincing data, we accompanied Mr. Rapson to Brooklands a few days ago and carried out trials along the lines we desired. In these the temperature of the covers was not judged by the sense of touch, but by carefully calibrated thermometers. Mr. Rapson's Rolls-Royce (running weight 2 tons 9 cwt. 1 qr. 17 lb.) was used for the tests, there being for the first trial an 895x150 mm. Rapson "unpuncturable" tyre on the off driving wheel, while a well-known American cover and tube of the same size were fitted to the near back wheel.

How a thermometer was used to take the temperature of the various tyres.

On the outer wall of each cover was a large rubber patch, which was solutioned to the rubber of the cover in such a way that it was possible to insert the bulb and about 2in. of the stem of a glorified clinical thermometer between the inner side of the patch and the wall of the cover. We reproduce a photograph of one of the thermometers in place, and we think that readers will agree that this was a satisfactory method of arriving at the temperature of the wall of the tyre. Two thermometers were used, and we satisfied ourselves that the readings given by both were identical.
Before any temperatures were taken we drove one complete circuit of the track, which measures 2.76 miles on the 50ft. line. Our average speed for the circuit was 58 1/4 m.p.h. We then stopped and at once inserted the thermometers beneath the patches on the driving tyres. The temperature of the Rapson, after due time had been given for the mercury to reach its highest point, was 101° F.{Mr Friese}, the temperature of the American tyre was 124° F.{Mr Friese}

After a Five Mile Run.
Immediately these readings had been taken, the thermometers were withdrawn, and we set out on a five laps run, of which the first four were covered with the speedometer needle ranging between the 48 and 55 m.p.h. marks, and the last at approximately 60. It should perhaps be mentioned here that we carefully tested the speedometer against a stop watch over the half mile, and satisfied ourselves that it was recording the speed correctly. At the end of the five laps, we again stopped, and once more took the temperatures of the two driving tyres. The Rapson

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