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).
Notes on crankshaft balancers, detailing the procedure for fitting a damped harmonic type and the relevant frequency calculation.
| Identifier | ExFiles\Box 125\1\ scan0303 | |
| Date | 1st December 1936 | |
| December 1936 SUBJECT: NOTES ON CRANKSHAFT BALANCERS As the result of an investigation by General Motors Research of all the commercially practicable crankshaft balancers we have concentrated our efforts on the harmonic type. For engines like our V-12 and V-16 which have automatic chain adjusters and so provide a considerable amount of self damping for the crankshaft we find that the pure harmonic rubber balancer, having little internal hysteresis or damping, is satisfactory. But for engines having severe torsional periods the damped* harmonic is needed. This type when designed for steel springs is ideally adapted to installation within the case as you propose. We are enclosing complete details of such a balancer which we formerly used. Following is an outline of our procedure in fitting the damped harmonic balancer to an engine:- The engine selected should have been well run in and should have its chains and belts as loose as ever permitted so that the minimum of self damping is present. It is better to start with a relatively high inertia value for the balancer wheel - say .200# In Sec² (too much inertia does no harm and if unneeded may be reduced later). The springs are made from clock spring stock and it would be well to have available a selection varying in thickness from 10 thousandths inch to 30 thousandths inch before the work is started. For a first try select springs which will give a calculated frequency of 120 to 140 cycles per second. The equation we use is: F = (1/2π)√(C/I) F = Frequency in cycles per second C = Torsional Rate in Lbs Inches per radian I = Inertia in pound inches seconds squared * The damping is produced by the interleaf friction of the laminated plate type springs. | ||