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).
Comparing the performance of different starter motors for the B.80 engine under cold conditions.
| Identifier | ExFiles\Box 124\1\ scan0261 | |
| Date | 20th October 1939 | |
| 10744 in elect. To Ev.{Ivan Evernden - coachwork} c. to Jnr.{Charles L. Jenner} Rm{William Robotham - Chief Engineer}/RC.{R. Childs}1/JH.20.10.39. re Starter Motor for B.80. We have not yet had the opportunity of testing a B.80 engine in the cold chamber. We hope to do this in the near future. Assuming the resisting torque of the B.80 to be 4/3rd. that of the Wraith, we estimate that under extreme conditions (8°F) it will lie in the region of 130 lb.ft. The speed at which the Lucas motor will turn the engine under the above conditions will be approx. 40 r.p.m. and the available voltage for ignition about 7.3 volts. Providing the battery is in good condition a start should be obtained. The efficiency of the R.R. 4.5" machine rapidly falls off under heavy loads and we estimate that under the above conditions the engine will be turned at 22 1/2 r.p.m. and the available volts for ignition to be approx. 6 volts. We doubt in this case whether a start would be made. From the above it is evident that providing the drive will stand up to the work, the Lucas motor is the more suitable for starting the B.80. Should the rubber drive prove unworthy we can go to a plain Bendix type of drive as fitted to S.S. Jaguar. If cold chamber tests prove the load to be greater than estimated and that the consequent speed and available voltage is insufficient we shall have to go for a bigger machine. There has been some talk of a 5" motor, and an R.R. version to DCD.1409 has been detailed. At the moment, we believe the Lucas machine can do the required work. Rm{William Robotham - Chief Engineer}/RC.{R. Childs} | ||