Calculations of torque on the camshaft for a Wraith III engine, with and without a balancer.
| Identifier | ExFiles\Box 7\8\ X 607 Camshaft-page17 | |
| Date | 8th April 1938 | |
| Rm. {William Robotham - Chief Engineer} --- 607. BT {Capt. J. S. Burt - Engineer} /B.15/G.8.4.38. CAMSHAFT BALANCER - WRAITH III. The results of calculations made on the above are shown in the Table below. It will be seen that at high speeds (4,500 r.p.m) owing to the preponderating influence of valve inertia torque on the camshaft, caused by the high acceleration portions of the cams, the balancer has a negligible effect on the resultant torque exe(Aero Engine)rted by the camshaft on its driving gear, and so has no effect on tooth pressures. To be of any value at high speeds, a camshaft balancer would require to be of a different design, capable of balancing the inertia torque due to the valves. Peak values of Torque on Camshaft. At low speed lbs.ins. At 4,500 RPM. lbs.ins. Due to all engine valve springs, alone. + 25 - 29 + 25 - 29 Due to inertia of all engine valves, alone. - + 320 Due to gas pressures (60/lbs/sq.in. at release) on exhaust valves, alone. - - 60 Due to balancer alone ± 50 ± 107 Resultant torque due to engine valve springs and balancer springs at low speed (Gas pressure assumed zero since helpful) + 22 - 34 - ..do.. when one of three balancer plungers removed. + 11 - 16 - ..do.. " two " " + 15 - 13 - Resultant torque due to valve inertia, valve springs, and gas pressure, for whole engine without balancer at high speed. - + 335 - 370 ..do.. for engine with balancer. - + 325 - 355 Note: A positive torque in Table is one tending to assist rotation of engine, and therefore to cause gear tooth separation and noise. J.Mowbray. | ||
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).