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).
Magazine article discussing tyre temperature tests and a new Rapson jack fitting for Daimler cars.
| Identifier | ExFiles\Box 39\1\ Scan006 | |
| Date | 25th September 1920 | |
| THE AUTOCAR, September 25th, 1920. 544 Tyre Temperature Tests. stood at 144° F.{Mr Friese}, while the American tyre showed 146° F.{Mr Friese} Comparing these readings with those taken at the end of one lap, it was fairly obvious—indeed, it was only to be expected—that the internal heat in the Rapson tyre took longer to work through to the outer wall of the cover than was the case with the standard American cover and tube. Test Against a British Tyre. The great question to be settled was whether the temperature of the Rapson would go on rising to a point considerably above 144° if a high speed were maintained for a greater distance than five laps of the track. To settle this point, we proceeded to cover a second five laps, the interval between the two tests being only long enough to take the temperature of the Rapson and American covers, and to substitute for the back wheel carrying the American tyre a spare wheel carrying a new tyre of well-known British make. We did not actually take the temperature of the Rapson tyre before the start of the second five laps, but our halt was of very brief duration, and we do not think it likely that the temperature had fallen below 140° F.{Mr Friese} The first four of the second five laps were carried out at approximately 50 m.p.h., the last circuit being covered at something between 60 and 65 m.p.h. At the end of this test the temperatures were again taken, and we found that, somewhat contrary to our expectations, the Rapson read no higher than 147° F.{Mr Friese}, while the British tyre, which had started the test cold, showed a temperature of 157° F.{Mr Friese} From this it would appear that, while the heat radiation of the Rapson was slower than that of the other tyre, the Rapson maximum temperature, after prolonged spells of high speed work, is not likely to be greater than that of standard tyres. The Important Point. It is admitted by Mr. Rapson that his own tyres take longer to cool down than do ordinary covers and tubes, the longer heat retention being obviously due to the high temperature reservoir provided by the deflector. That, however, is not a very important matter, provided always that the maximum temperature attained by the Rapson tyre in use under ordinary conditions of running is not excessive. It is a very curious fact that, despite the presence of the deflector in the Rapson tyre, the heat generated should not be greater than it is proved to be by a thermometer test. We have never yet heard any explanation put forward as to the comparatively cool running of the Rapson, whereas, on the other hand, the alleged impossibility of running the tyre cool is one of the chief points upon which critics have based their adverse opinions. We hope that the tests referred to in the foregoing notes—tests, by the way, of our own choosing—as being best calculated to offer a fair comparison, may at any rate give pause to those who are tempted to imagine that the Rapson principle of construction is doomed to failure owing to overheating troubles. A RAPSON JACK FITTING FOR DAIMLER CARS. IN the issue of The Autocar dated May 15th, 1920, it was described the latest Rapson jack. This, it may be remembered, hooks on to fittings permanently attached to the front and rear axles, and thus is easily and securely located when it becomes necessary to jack up a wheel. Naturally the attachments to the axles vary somewhat according to the design of those components on various cars. In practice no trouble had been experienced by Mr. Rapson in adapting the axle fittings to various makes of cars until it became necessary to evolve a fitting for attachment to the rear axle of the large Daimler chassis. This at first proved a difficult problem owing to the position of the rear springs, brake drums, and large petrol tank, but eventually a design was evolved which was clamped to the back axle by the two U bolts securing the springs thereto, a support also going to the brake arm member, the whole weight of the car being supported from the axle casing. This proved a strong, but needlessly complicated fitting, for on inspecting the arrangement the Daimler Co., Ltd., informed Mr. Rapson that the brake arm was amply strong enough to support the whole weight of the car. Accordingly the design was simplified, and the fitting thus became a simple bracket to clip round the end of the brake arm, as shown in the illustration. From actual trial we can testify to the ease of jacking up so large a car. The jack handle is applied to the locating member, and the jack may then be lifted by the handle, and the hook-on head engaged with the fitting on the axle. On lowering the jack to the ground it is automatically extended, and it only remains to remove the handle from the locating member to the operating shaft and give a few turns in the ordinary way. The advantage of the special fitting is that it thus becomes impossible for the jack to slip and accordingly obviates possible serious damage. E2 [Image Captions] [Left image] The Rapson jack rear axle fitting for Daimler cars. [Right image] "The latest Rapson jack which hooks on to fittings attached to the axle. [Diagram Labels] INTERCHANGEABLE HOOK ON HEAD INTERCHANGEABLE HEAD INSTANTANEOUS ADJUSTING MEMBER SPRING RELEASE LOCATING MEMBER OPERATING SHAFT BEVEL GEARING ANTI-FRICTION THRUST RACE STEEL OPERATING SHAFT BRONZE BLOCK | ||