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 titled 'Third Degree' detailing rigorous testing methods for new engines, frames, and brakes.
| Identifier | ExFiles\Box 160\3\ scan0228 | |
| Date | 10th February 1939 | |
| The Autocar February 10th, 1939. 210 'THIRD DEGREE' Concluding the Article on the Methods Employed by the Rolls-Royce and Bentley Experimental Division to Wring the Stark Truth Out of New Designs By MONTAGUE TOMBS With Illustrations by F.{Mr Friese} Gordon-Crosby ONE of the largest sections of the development department of the Rolls-Royce-Bentley organisation is a form of clinic for engines. It is the engine test, and the test beds are equipped with every modern measuring device—indicators, exhaust-gas analysers, air-measuring apparatus, multiple thermometers, the Stroboscope, vibration analyser and recording meters, and one hundred and one truth-seeking instruments. Endurance running of engines goes on almost continually. One of the standard intensive tests consists of 25 hours’ running at full power, 15 per cent. over speed, which has been found to produce the same results as 15,000 miles on the road. Many hundreds of hours of such tests are completed in the year’s work. Exactly what is accomplished by this research work is illustrated by the fact that during the past fifteen years the power output per pound of engine at Rolls-Royce, Ltd., has been increased by 200 per cent. Every Combination Tested In most of the progressive car factories the engineers have “something on the shelf” in the way of new engines, but I was considerably surprised at the extensiveness of the Rolls-Royce “shelves.” There is hardly a known and promising combination of valves, valve gear, combustion chamber, and so forth, that has not been made and subjected to exhaustive tests. I saw one such combination which, when applied to the 4¼-litre Bentley engine, would raise the maximum b.h.p. at any given compression ratio by as much as 20 per cent. It has never been put into production because it produces minor effects at the other end of the power range which would not preserve the silkiness associated with that famous car. Supercharging has been thoroughly investigated up to the final point of comparative tests on the road. Another particularly interesting feature of the “clinic” is a section devoted to research on single cylinders, consisting of a crankshaft and crankcase upon which different types of single cylinders may be dropped. This unit is also equipped with variable valve lift and timing. Single-cylinder running is confined mainly to the investigation of combustion chamber design, but reliance cannot be placed upon the results until they have been confirmed on a complete multi-cylinder engine. If the weighbridge is not exactly a spectacular method for extracting the truth out of road springs and frames, it is not the less effective. It consists of a rectangular platform with a weighbridge at each corner to accommodate each wheel, or a support in lieu thereof, with large screw-down jacks at the ends. Chiefly it is used for determining the rate of the frequencies of road springs, and their working deflections. The chassis is pulled downwards by means of the jacks, and the increase of load for any increase in spring deflection may be accurately measured. Frame deflections for different loads variously applied may be measured in the same way, a process extremely useful in developing frame designs. “Water Clock” Braking Quite another phase of brake testing is employed for research into brake mechanism as a whole. When it is desired to duplicate constantly the effect of a driver using his brakes for medium-length hills, the whole car is mounted on drums which it drives under its own power, as during the testing of b.h.p. at road wheels. Then a contrivance is brought alongside which takes the place of a driver’s foot and which applies the neat little servo-motor characteristic of Rolls-Royce brakes. This device is a form of water clock. A stream of water is directed into a small tank, balanced on trunnions, and having on one side at the top a shallow annexe. The weight of this tank and its water content is arranged to provide The illustration in the heading is the “skid pan” on which cars are tested for steering accuracy. A 26 | ||