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).
Engine balancers, flywheels, and crankshaft deflection.
| Identifier | ExFiles\Box 125\1\ scan0305 | |
| Date | 1st December 1936 guessed | |
| -3- damping more or less to wash it out. Sometimes a slight compromise is required sacrificing a little at the sixth to improve the third but if this is indicated more inertia will help. In general the greater the balancer inertia the less critical is its tuning and damping. However, we believe that if .200 lb inch seconds squared is used at first it will be found possible to reduce this value finally. We feel that an entirely satisfactory job is done when the total angular crankshaft deflection does not exceed .10 degrees. Characteristics of our spring type balancer for which we are enclosing drawings are as follows:- INERTIA - .135# inch secs squared TORSIONAL RATE - 85,000# inches per radian FREQUENCY - 125 - 135 cycles per second The only troubles we have experienced with the spring type harmonic balancer are: (1) Lack of lubrication and resulting corrosion due to external mounting and (2) Spring breakage in early designs which stressed the springs too highly. Installing the balancer within the case as you propose would care for (1) and keeping the initial spring stress (that due to deflection as installed) below 60,000#/square inch eliminates spring breakage. Obviously some form of separate damping would greatly simplify the task of tuning. The desired spring rate would then be secured with minimum stress and the required damping added independently. Perhaps you people will want to design something along this line. If any of this is not clear we will be glad to explain further to the best of our ability. FLEXIBLE FLYWHEELS We are very sorry that the drawings sent you did not make clear a very important part of the design. Please note that in our spider construction the torsional stress is distributed over a considerable amount of spoke and rim giving a considerably lower spring rate with correspondingly lower stresses. This spider design was worked out with photo-elastic celluloid models and a polarized light projector so that the stress might be as evenly distributed as possible. | ||