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).
Torsional vibration tests carried out on a Terraplane crankshaft.
| Identifier | ExFiles\Box 21\6\ Scan110 | |
| Date | 1st January 1934 | |
| To Sg.{Arthur F. Sidgreaves - MD} from Ha/Gry.{Shadwell Grylls} X 4217 c. to Wor.{Arthur Wormald - General Works Manager} c. to Rg.{Mr Rowledge} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}11/KWS.1.34. Terraplane Crankshaft. -------------------- We have carried out tests to determine the severity of the torsional vibrations on this car. It will be remembered that the crankshaft has 5 bearings and is equipped with a rubber driver damper at the front end. When the damper is in position no torsional periods are detectable in the running range up to 4300 r.p.m. at which speed the valves bounce. For the purpose of our tests we substituted for the damper a light aluminium pulley, so that the dynamo, fan and water pump could be driven. Without the damper we discerned a half period at 1600 r.p.m., very sharp and slight, and a top period at 3200 r.p.m. of about the severity of the 20/25 half period when the spring drive damping is insufficient. Between these two periods there were two others of very small amplitude at 2000 and 2350 r.p.m. Removing the fan belt increased the severity of all the periods. After passing through the 3200 r.p.m. period we ran the engine (which has the same stroke as the Bentley - 4½") up to 5800 r.p.m., stronger valve springs having been fitted. The engine was remarkably smooth, a slight clatter appearing at the maximum speed obtained equivalent to 70 m.p.h. in 2nd gear. The conclusion we draw from this is that the top period of a 5 bearing 6-cylinder engine can be in the running range and is easily eliminated by a small crankshaft damper. Bearing in mind that the half period of a 6-cylinder engine is, in every case we know of, bad on a 7 bearing engine requiring a damper, and hardly detectable on a 4 bearing engine without a damper, we shall try and repeat the above tests on a 9 bearing 6-cylinder engine, such as the Nash or Chrysler. Hs{Lord Ernest Hives - Chair}/H.{Arthur M. Hanbury - Head Complaints} Grylls. | ||