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).
Straight 8 crankshaft vibrations, comparing performance with and without a damper on a Packard car.
| Identifier | ExFiles\Box 127\1\ scan0175 | |
| Date | 5th February 1934 | |
| To Eg. from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to Wor.{Arthur Wormald - General Works Manager} c. to R.{Sir Henry Royce} c. to Ey. c. to Da.{Bernard Day - Chassis Design} c. to Rly. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}22/KW.5.2.34. Straight 8 Crankshaft Vibrations. ---------------------------- Further to our report Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}11/KW.6.1.34, in which we gave particulars of the crankshaft periods on the Terraplane engine, the top period being in the running range but completely eliminated by the damper, we have now been able to test a Packard car under similar conditions. The engine is of 6.3 litres capacity and 5" stroke, has a nine bearing crankshaft with 2 1/4" dia. journals and 2.3/16" dia. pins. The crankshaft damper is an external dry friction damper on the lines of the J.3 one. The auxiliaries are driven by silent chain. The car in question was several years old, and was of no interest other than for the experiment in question. With the crank damper fitted no periods were detectable up to the maximum speed of about 4000 r.p.m. When the damper was removed a very slight half period appeared at about 1400 r.p.m. The top period at 2800 r.p.m. (60 m.p.h.) we ran through several times. It was more violent than on the 5 bearing Terraplane, but would never break the engine. The damper dealt adequately with it. A further very mild period existed midway between the half and top period. Our conclusion therefore concerning the crankshaft for a straight 8 engine is that the top period will inevitably be in the running range and is eliminated by a simple damper of either the dry friction or harmonic type. The crankshaft dimensions need therefore only be sufficient for the strength of the shaft. There is no reason why full balance should not be used. HS{Lord Ernest Hives - Chair}/h.Grylls. | ||