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).
Crankshaft failure on an 'R'11 engine, detailing the conditions of failure, damage observed, and the crankshaft's running history.
| Identifier | ExFiles\Box 174\4\ img017 | |
| Date | 13th December 1930 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/RND. c. to Ag. c. to Mor. c. to Ry. E.{Mr Elliott - Chief Engineer} c. to RG.{Mr Rowledge} BROKEN CRANKSHAFT ON "R"11 ENGINE. -------------- We have recently had a case of crankshaft failure on an "R" engine when running under conditions of heavy detonation at 2000 R.P.M. on standard service fuel and Lodge A.2. plugs. The engine was fitted with 7.47 s/c. gears and 6/1 compression ratio pistons, and had been running for 85 mins. at 900. M.P. detonating at intensity 2.50 ft. when the failure occurred. This was marked by a pronounced vibration and very rough running. On stripping the engine down for examination, the crankshaft was found to be badly cracked. The crack started in No.2 crankpin (see sketch) and extended down the web and across the adjacent main journal to No.3 crankpin, the web of which nearest to the main journal was just showing signs of cracking. Running Life of the Crankshaft. ------------------------------- This crankshaft - (the original one) - had up to the time of failure completed 94½ hours running under varying conditions of load and speed. After acceptance and a small amount of flying at Calshot, (approx. one hour) the engine was used for double boost and valve spring tests at speeds up to 3500 R.P.M. High ratio gears were then fitted to the supercharger, (7.47 replacing 7.03), and the engine was used for development work in connection with "Miss England 11" which involved running up to 3000 R.P.M. After 37½ hours running tubular connecting rods were fitted to cylinders 1, 2, 3, and after an acceptance test and proof run at 3850 R.P.M. the engine was passed for development work. It was rebuilt with 5.5/1 compression ratio pistons and 5.9 s/c. gears after 47 hours and then run under "H" engine conditions viz; normal R.P.M. 2300 and max. R.P.M. 2900. Power and Constant speed Throttle Curves and Consumption Loops were taken and comparisons made between "R" and "H" engine crankshafts as regards intensity of detonation. The engine was then fitted with 6/1 compression ratio pistons and repeat tests made for comparison with the 5.5/1 figures. After 85 hours the high ratio (7.47) s/c. gears were again fitted with the object of carrying out tests to determine if there was some limiting point at which detonation caused pre-ignition to set in. The engine was run | ||