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).
The high-speed performance test of a Phantom II car (27-EX) at Brooklands, which resulted in a broken crankshaft.
| Identifier | Morton\M19\ img207 | |
| Date | 13th July 1931 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to By.{R.W. Bailey - Chief Engineer} ORIGINAL Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey}6/WJ.13.7.31. 87771 8788 PHANTOM 11 IMPROVED HIGH SPEED PERFORMANCE. We have taken 27-EX. car to Brooklands to ascertain the improvement in high speed performance due to employing "R" engine type cams. On the previous Brooklands test on this car the maximum lap speed obtained was 83.5 m.p.h., the engine being fitted with R.R. twin choke carburetter and 4.9:1 compression ratio head; the available horse power (at the flywheel) being 135 HP at 2500 R.P.M. and 131 at 3000 R.P.M. This power is increased to approximately 149 at 2500 R.P.M. and 156 at 3000 R.P.M. by using "R" engine type cams (at110°) and resulted in putting up the lap speed to 88.78 m.p.h. The best speed over the half mile being 90 m.p.h. The conditions were not good, there was a strong head wind on the railway straight (used for 1/2 mile test); under ideal conditions we should expect to be able to lap at 90 m.p.h. and increase the half mile speed to 91 or 92 m.p.h. In addition to the weather conditions a great deal of rear wheel spin was experienced on the rough portions of the track (near Vickers sheds and on the railway banking); the rear springing is entirely inadequate for speeds over 85 m.p.h. (standard springs were fitted), for future tests it is essential that high rating springs are used. Apart from wheel spin continual buffer hitting took place, it was not possible to eliminate this by tightening up the single Hartford shock absorbers to their maximum loading. Accelerator tests were carried out. The results shew a slight decrease from standard up to 40 m.p.h. but above this speed the acceleration is very much improved. The engine in this car is fitted with a crankshaft (E.79738) having 2.1235" dia. crankpins, 2.245" dia. journals, stiffened flywheel flange and four balance weights to LeC.2874. The main torsional period is well within the car speed range and was very violent, owing to its violence it was not reached more than twice on the gears. On top gear it became prominent at 90 m.p.h., becoming very bad at 92 or 93 m.p.h. (the speedometer registered up to 98 m.p.h. only). Every time wheel spin was evident the engine was running momentarily on the main crankshaft period (approximately 3400 R.P.M.). After completing the acceleration tests it was decided to obtain some tractive resistance figures by coasting from 90 m.p.h. downwards in top gear and in neutral. Three tests were completed in this manner but when trying to restart the engine after the third test it was evident that something had broken. Upon examination of the engine it appeared that the crankshaft had broken to the rear of No.6 crank; it was possible | ||