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 the extreme 'Third Degree' durability testing methods for new car chassis and components.
| Identifier | ExFiles\Box 160\3\ scan0238 | |
| Date | 3rd February 1939 | |
| February 3rd, 1939. The Autocar 181 'THIRD DEGREE' Details of the Methods Employed by the Rolls-Royce and Bentley Experimental Division to Wring the Stark Truth Out of New Designs The "rack"—a modern version of a medieval punishment applied to a car for brake test purposes. By MONTAGUE TOMBS With Illustrations by F.{Mr Friese} Gordon-Crosby UNLESS you have witnessed it you could scarcely conceive what excruciating tests are performed upon metal in the processes of “proving” the soundness of new type cars and components by the Rolls-Royce and Bentley experimental engineers. There is a passion for the truth in that historic factory in Derby—home truths, and the truths about other people’s products, too. Neither time nor expense is allowed to stand in the way of getting at the truth. Hence the pinnacle upon which that reputation without parallel so securely rests. In America a suspected person is liable to be subjected to a process called the “Third Degree.” In England the process has its counterpart in the treatment given by engineers to metals and metal structures. And in the Rolls-Royce factory it is raised to a fine art. New chassis are, in effect, until they have proved their innocence. The picture is not overdrawn, it is the truth. But the process is, in fact, no more severe than conditions which are met in the daily life of a car used in rough country. The difference is that the worst that may occasionally happen on the road is made to happen continually on the rack, so that it is got over fairly quickly and the weak spots found, traced, and eliminated. That is how the perfect car is sought. The spectacular apparatus referred to as the rack is officially described as the bump-test equipment. At one side, concealed below the surface of the floor, is a pair of 4ft. diameter drums capable of being rotated at various speeds by an electric motor. The top of each drum is level with a gap in the floor, and the front wheels of the chassis to be tested are set to rest upon the drums. The rear wheels are chocked to secure the chassis. Bolted to each drum is a cam three inches high. When the drums are rotated, the cams strike the revolving front wheels repeated blows equivalent to running the car continuously over a series of enormous pot holes. Some idea of the severity of this test is given by the fact that with the surface of the drums running at 18 m.p.h. each cam strikes the tyre with a force of 2,100lb., and imparts an upward acceleration to the wheel of 600ft. per sec. per sec. One of the principal objects is to prove the strength of all parts of new suspensions or steerings, since a failure on the road might endanger the life of a tester at his work. The test produces a great many more results than that, however. It is amazing to see how massive - looking components twist and turn, weave and vibrate, from one end of the frame to the other. "A chassis . . . subjected to relentless heavy blows . . . which cause it to writhe and twist and shudder." | ||