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).
Calculation of the natural frequency and synchronous speed of a Lorraine Dietrich crankshaft.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 47 | |
| Date | 22th April 1927 | |
| 3 PERIODICITY OF LORRAINE DIETRICH CRANKSHAFT. [DIAGRAM] FLYWHEEL, I₁, e₁, NODE, CRANKSHAFT, I₃, e₂, L, I₂, FAN PULLEY THE POSITION OF THE NODE IS GIVEN By e₂ = L [I₁ + ⅓ I₃] / [I₂ + I₁ + ⅔ I₃] WHERE:- OVERALL STIFFNESS OF SHAFT = C = 28350 lbs ft/RAD. I₁ = .3767 = FLYWHEEL I₂ = .001437 = FAN PULLEY I₃ = .04322 = INERTIA OF CRANKSHAFT .01058 = '' BIG ENDS .00587 = '' DUE TO PISTONS. .05967 TOTAL OF SHAFT ASSEMBLY ∴ e₂ / L = [.3767 + .05967/3] / [.001437 + .3767 + 2x.05967/3] = .39659 / .417917 THE INERTIA OF THE PART OF CRANKSHAFT OF LENGTH e₂ WILL BE — .05967 x .3966 / .4179 = .0566. THIS INERTIA IS REPLACED BY ONE THIRD ASSUMED ACTING AT THE FRONT END = ⅓ x .0566 = .01887. TO THIS IS ADDED THE INERTIA OF THE FAN PULLEY. ∴ INERTIA OF FRONT END (EQVT) = .01887 + .001437 = .020307. lbs ft². THE STIFFNESS OF A LENGTH OF SHAFT e₂ WILL BE APPROX. — = 28350 x .4179 / .3966 = 29900. lbs ft/RAD. ∴ FREQUENCY = 1/2π √ (29900 / .02031) = 193 Oscns/Sec. WITH THREE OSCILLNS OF THE DISTURBING FORCE PER REV. THE SYNCHRONOUS SPEED WOULD BE 193 x 60 / 3 = 3860 R.P.M. THIS IS IN CLOSE AGREEMENT WITH 3800 R.P.M OBtd BY EXPT. AWH | ||