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).
Table comparing calculated and observed critical speeds for various engines.
| Identifier | ExFiles\Box 137\4\ scan0004 | |
| Date | 28th February 1928 | |
| TBR. 28/2/28 EXAMPLES OF CALCULATED CRITICAL SPEEDS. Fig 4 Column Headers: ENGINE. C/SHAFT STIFFNESS LBS.FT./RAD I OF C/SHAFT SLUGS-FT4 I OF BIG ENDS 6 x r² I OF PISTONS ETC. 6 x r²/2 I OF SPRING DRIVE HUB. EQUIV INERTIA Ie I OF FLYWHEEL IF CALC. FREQ. PER SEC. CALC. PERIOD RPM OBSERVED PERIOD RPM ERROR %. Row 1: ENGINE: I-C-I. C/SHAFT STIFFNESS: 14,750 I OF C/SHAFT: .01403 I OF BIG ENDS: .00525 I OF PISTONS ETC.: .00520 I OF SPRING DRIVE HUB: - EQUIV INERTIA Ie: .008161 I OF FLYWHEEL IF: .4371 CALC. FREQ.: 215.5 CALC. PERIOD RPM: 4310 OBSERVED PERIOD RPM: 3850 ERROR %: 10.5% HIGH Row 2: ENGINE: STD. 20HP. C/SHAFT STIFFNESS: 16,350 I OF C/SHAFT: .016823 I OF BIG ENDS: .007779 I OF PISTONS ETC.: .004710 I OF SPRING DRIVE HUB: .005814 EQUIV INERTIA Ie: .01859 I OF FLYWHEEL IF: .6911 CALC. FREQ.: 164.8 CALC. PERIOD RPM: 3296 OBSERVED PERIOD RPM: 3300 ERROR %: 0 Row 3: ENGINE: 20 HP. WITH DAMPER WHEELS LOCKED SOLID TO NOSE. I OF BIG ENDS: " I OF PISTONS ETC.: " I OF SPRING DRIVE HUB: .02212 EQUIV INERTIA Ie: .03190 I OF FLYWHEEL IF: " CALC. FREQ.: 116.5 CALC. PERIOD RPM: 2330 OBSERVED PERIOD RPM: 2450 ERROR %: 5% LOW Row 4: ENGINE: STD. PHANTOM. C/SHAFT STIFFNESS: 45,000 I OF C/SHAFT: .06738 I OF BIG ENDS: .02513 I OF PISTONS ETC.: .01616 I OF SPRING DRIVE HUB: .01437 EQUIV INERTIA Ie: .05059 I OF FLYWHEEL IF: 1.384 CALC. FREQ.: 152.8 CALC. PERIOD RPM: 3056 OBSERVED PERIOD RPM: 3250 ERROR %: 6% LOW Row 5: ENGINE: LORRAINE-DIETRICH C/SHAFT STIFFNESS: 28,350 I OF C/SHAFT: .04322 I OF BIG ENDS: .01058 I OF PISTONS ETC.: .00587 I OF SPRING DRIVE HUB: .00144 EQUIV INERTIA Ie: .02132 I OF FLYWHEEL IF: .3767 CALC. FREQ.: 188.2 CALC. PERIOD RPM: 3764 OBSERVED PERIOD RPM: 3750-3800 ERROR %: 0 Row 6: ENGINE: STUTZ-8. LARGELY FROM CALC. FIGURES C/SHAFT STIFFNESS: 54,400 (MEASURED) I OF C/SHAFT: .0565 (CALC) I OF BIG ENDS: .00576 I OF PISTONS ETC.: .01088 I OF SPRING DRIVE HUB: - EQUIV INERTIA Ie: .02417 CALC. FREQ.: 237.8 CALC. PERIOD RPM: 3570 OBSERVED PERIOD RPM: 3800 ERROR %: 6% LOW | ||