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).
Calculating starter motor torque for the B.80 'Marine' engine based on data from the B.60 engine.
| Identifier | ExFiles\Box 133\3\ scan0223 | |
| Date | 1st July 1940 | |
| 1128 To JNR.{Charles L. Jenner} from Rm{William Robotham - Chief Engineer}/RC.{R. Childs} Rm{William Robotham - Chief Engineer}/RC.{R. Childs}1/SW.1.7.40. re Starter Motor for B.80 'Marine' Since we have not been able to obtain the "resisting" torque of the eight-cylinder engine under extreme conditions, i.e., at a temperature of 8°F, we shall have to approximate by assuming that it will be 4/3 times that of the B.60, for which, we have some data. B.60 Engine. (R.R. Starter Motor. Std. B.V. Battery) Starter Motor current (Temperature: 8°F) = 240 A Voltage across starter = 7.2 V.{VIENNA} Input = 240 x 7.2 = 1728 W. Starter input in H.P. = 1728 / 746 = 2.316 H.P. Effic: under the above conditions = 44%. .. Starter output in H.P. = 2.316 x 0.44 = 1.02 H.P. Speed of Starter armature under the above conditions = 920 R.P.M. Motor "driving" torque = (1.02 x 5252) / 920 lb.ft. = 5.82 lb.ft. Armature to flywheel ratio = 16.02 : 1 (for R.R. Motor) .. Engine "resisting" torque = 5.82 x 16.02 lb.ft. = 93.2 lb.ft. Cranking Speed = 57½ R.P.M. MARINE. B.80 Engine (C.A.V. SC.126 Starter. C.A.V. 75 AH. Battery) Engine resisting torque = 93.2 x 4/3 = 124 lb.ft. | ||