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).
The testing of a new Bentley starter motor with a two-speed gear.
| Identifier | ExFiles\Box 62\1\ scan0259 | |
| Date | 6th July 1934 | |
| Hs{Lord Ernest Hives - Chair}/Wst.4/MA.6.7.34. BENTLEY STARTER MOTOR WITH TWO SPEED GEAR. We have now produced and bench tested the first Bentley starter motor with a two to one reduction gear between the motor armature and the Bijur drive to LEC.3892. The total gear reduction between the motor armature and the engine crankshaft with this scheme is 17 to 1. On the bench the motor was subjected to a stalling test but under these extreme torque conditions the cork clutch in the Bijur drive slipped badly. The brake load was therefore reduced to 117 lbs ft which was considered a reasonable margin over the most extreme conditions to be possibly encountered on the Bentley chassis in Winter and under these conditions the drive functioned without slip. As the clutch will now have to work under more severe torque conditions the design of this component might also come under review as it is now limiting the maximum torque performance of the motor. The gears are very quiet and the efficiency is high. After fitting to experimental chassis 4.B.IV. for test the motor was again tested and measurements shewed that it is now working over a range, with engine hot and cold, approximating its maximum B.H.P. point. This is very satisfactory, as it means that the maximum power developed by the motor is being utilized with consequent increased turning speeds. The motor is also working more nearly at its maximum efficiency which means less watt-hour discharge from the battery. Thus for an engine torque of 1000 lb inches whereas with the present Bentley motor the motor efficiency would be of the order of .25, with the extra gear ratio motor it would be .60. Expressed in current this is an approximate reduction of 120 amperes. We are allowing this motor to remain on 4.B.IV. for the 10,000 mile test. Hs{Lord Ernest Hives - Chair}/Wst. | ||