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).
Paper on the application and development of resilient mountings for automotive engines to reduce vibration.
| Identifier | ExFiles\Box 126\4\ scan0137 | |
| Date | 1st September 1933 | |
| X1056 Wyman We ought to try the Chevrolet rear mounting on our cars Resilient Mountings as Applied Rem to Automotive Engines NVR/L By Alex Taub Development Engineer, Chevrolet Motor Co. VIBRATION formerly was classed as such without much thought as to the determination of its sources, Mr. Taub states, and then came isolation of the various causes. The first two vibrations to be segregated and vigorously attacked were the secondary inertias of reciprocating units and torsional vibration. The development of the six-cylinder engine was among the earliest attempts to eliminate secondaries, and it was also the earliest producer of torsional vibration. Dynamics, combustion roughness, torsional roughness and structural weakness, are a few of the contributing causes of engine roughness. Consideration must be given to all these factors if an engine is to be considered inherently smooth, and each is analyzed. Engine mountings should have low resistance to rotation about the longitudinal principal axis and to rotation about the vertical axis through the center of gravity, together with minimum shift of affective principal axis and vertical axis. The kind of material used in engine mountings should be determined after considering the overall characteristics of the mounting and the durability of those characteristics. THE purpose of this paper is to provide a means of looking backward over the trail of the development of resilient mountings. We expect to bring out, at least, for those interested, a few fundamental principles that we believe cover the business of proper mountings. We will briefly touch their history, from mechanical to rubber, including rotations of the engine movement, frame rigidity and material specifications. The observations included herein are personal and do not represent the opinion of any group; as such, they can be taken for what they are worth. The data are based upon a review of the work others have done in the industry with reference to the elimination of engine sensation, this review being aided by experimental work. We wish also to acknowledge the cooperation of various engineering organizations throughout the industry for data furnished to me for study. Resilient mountings have been used in various industries for many years, the primary use being for insulation against noise and vibration. The earliest attempts in our industry were intended for insulation. Examination of correspondence from various engineers indicates how similar the history of all concerns really is. Originally, the engine was set down in the frame with or without brackets and bolted down at convenient spots. Later, springs were added at the front to limit the crankcase distortion as well as to minimize vibration. In some cases three-point mountings were used; however, other organizations frowned on this practice because it “sacrificed” frame rigidity. Sub-frames came in for consideration. In one particular case, the Studebaker Corp. produced a car with a flexibly mounted sub-frame which rocked fairly freely. Fabric liners were introduced between mounting brackets and frame and these liners were gradually changed to ever-increasing flexibility by adding to and/or softening the material used. To further increase the local flexibility, rubber in tension was introduced. Engine movement or “flop” on the road became a factor, and the need for designing frames to stand on their own rigidity became apparent; then, an accomplished fact. With the frame stiffened and the front-end weaving covered by special designs that eliminated radiator, head-lamp and fender movements, engines could be and were mounted with increased flexibility. An entirely different investigation was introduced and merged into the mounting picture, which merger brought about consideration of the position of the mountings. This other investigation had to do with the business of vibration and its source. In the early days, vibration was classed as such without much thought as to the determination of its sources. Then came isolation of the various causes. The first two vibrations to be segregated and vigorously attacked were (a), secondary inertias of reciprocating units, and (b), torsional vibration. [This paper was presented at the International Automotive Engineering Congress, Chicago, September, 1933.] Vol. 34, No. 4 136 | ||