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).
Examination of the Lorraine Dietrich crankshaft and its synchronous speeds, including vibration and torsion stiffness tests.
| Identifier | ExFiles\Box 25\3\ Scan236 | |
| Date | 1st March 1927 | |
| X6324 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACH. c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/ACL1/LG2.3.27. LORRAINE DIETRICH CRANKSHAFT AND SYNCHRONOUS SPEEDS. X3588 We have had the opportunity of examining the crankshaft of the Lorraine Dietrich and there appear to be several features worthy of note. The chief point of interest is perhaps the fact that it is an example of a four bearing crankshaft which appears to possess a high natural period of vibration or one in which the master period occurs at a high speed. We understand that the Buick crankshaft which also has four bearings has its synchronised speed at 4800 r.p.m. As far as we could estimate from road tests the synchronous speed appeared to be about 3750 r.p.m. This was reached by running the car on low gear. The engine is now being fitted to a test bed so we shall shortly be in possession of more information regarding its synchronous speed and harmonics. On the road a vibration at approx. half the higher vibratory speed was very evident and would no doubt be the one having the six cycles per rev. which occurs on the Goshawk at 1600 r.p.m. when the slipper drive is not employed. We made a test of the torsion stiffness of the shaft and found this to be 75% stiffer than the std. Goshawk. Torsional deflection curves together with drgs. of the crankshaft and conn. rod are appended. contd :- | ||