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).
Performance analysis and discussion of the B.80 Engine's starter motor and battery system.
| Identifier | ExFiles\Box 133\3\ scan0224 | |
| Date | 2nd July 1940 guessed | |
| - 2 - B.80 Engine (cont) Flywheel to pinion ratio = 10.25 Starter Motor "driving" torque = 124 / 10.25 = 12.1 lb.ft. Starter Motor Speed (SC.126 C.A.V.) = 750 R.P.M. Starter Motor current. = 475 A.{Mr Adams} Starter Motor Volts (CAV. 75 AH Battery) = 7.5 V.{VIENNA} ? Input in H.P. = 4.77 H.P. Output in H.P. = R.P.M. x T / 5252. = 750 x 12.1 / 5252 = 1.72 H.P. Efficiency. = 1.72 x 100 / 4.77 = 37%. Cranking Speed = 750 / 10.25 = 73 R.P.M. ----------------- The current consumption of the above motor is high, nearly twice that of the R.R. or Lucas Machine. That we are only allowed a gear ratio of 10.25 : 1 instead of the standard 16 : 1, aggravates conditions, and puts our standard battery out of consideration, since the volt-drop when passing 475 amps, would be 9.5 volts, leaving 2.5 volts across the motor. The C.A.V. performance curve shows a drop of only 4.5 volts at 475 amps, using a 75 A.H. battery. We are now making enquiries for the details of this battery. However, since we are not limited with regard to battery size, we think the SC.126 motor will be suitable. If possible, the gear ratio should be increased so as to lighten the burden on both the battery and starter motor. We will let you have further particulars with regard to the battery when we hear from C.A.V. Rm{William Robotham - Chief Engineer}/RC.{R. Childs} | ||