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).
Letter to the Air Ministry comparing engine damping characteristics and discussing 'Harmonic Balancers'.
| Identifier | ExFiles\Box 25\3\ Scan201 | |
| Date | 18th December 1926 | |
| Expl: Dept: Hs{Lord Ernest Hives - Chair}/ACL1/LG. 18th. Dec. 1926 Air Ministry, Adastral House, Kingsway London W.C.2. Dear Major Carter, We thank you for your letter of the 30th ult. with the enclosed notes A.{Mr Adams} and B. which are very helpful. With regard to the relative damping of the 20 HP. and 40/50 HP., we agree that the angle of twist is not a good basis of comparison and have calculated the resonance factor for the 40/50 HP. on the lines you suggested :- 40/50 HP. inertia torque approx. ± 724 lbs.ft. at a speed of 3100 r.p.m. Assuming this to act at mid length of crankshaft would give a static deflection of ± ½º. The actual twist measured at the front end by means of the torsiograph was ± 1.725º giving the 'resonance factor' the value 3.45 ⏃ = 1.725/.5 It therefore seems that the 40/50 HP. engine possesses greater internal damping than the 20 HP. You will probably remember we discussed with you the question of the operation of the so-called 'Harmonic Balancer' employed by The General Motors Ltd. on Oaklands and Buicks and to which you make reference in your report No. E.3039. We have since communicated on this subject with Mr. W.O.Kennington, who is the technical representative of The General Motors Ltd. in this country and have received a visit from him. We desired to know the results given by this 'Balancer' in practice and if it was claimed, that, as well as eliminating the vibration at the main synchronous speed, it removed the effects of torque harmonics at sub-multiples of this speed. contd :- | ||