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).
Motor temperature conditions and static torque tests for engines.
| Identifier | WestWitteringFiles\G\June1921\ Scan57 | |
| Date | 22th June 1921 | |
| Contd. -3- EFC1/T22.6.21. As regards the temperature condition of the motors under test, this does not enter into it so much as in the case of the dynamo performance, as the motor is usually in a nearly cold condition when used. To equalise the condition as much as possible, however, our successive readings are taken with gradually decreasing loads, the heaviest load being taken first. Static Torque Test. On the experimentally made motor a static torque test was taken, the result of which is given on the photostat sheet as a curve showing the relation of motor armature torque to amperes. In taking this curve frictional effects were eliminated in the usual manner by taking the average of readings of maximum and minimum torques possible without motion in the forward and backward directions respectively. It will be seen that the torque figures corresponding to given amperes are, as would be expected, somewhat greater than with the motor in a running condition. A table of quantities for the rolling of engine is shown on the sheet for comparison and shows a motor torque of 55 lb-inches, with a motor current of 111 amperes. The static torque with a motor current of 111 amperes will be seen to be 529 lb-inches. A loss of torque of about 3% is due to the epicyclic gear. Of the remainder, some is due to bearing friction, some to windage, some to eddy currents in the core, and some to torque necessary to overcome armature hysteresis when running. An estimate of the stalling condition of the motor has been made and indicated on the sheet, in which a 90% overall torque efficiency has been taken (instead of 87% for the running condition). In the static torque test the exact useful flux per pole at various excitations has been calculated and indicated in the form of a table. A motor is being arranged with the field coils two in series and two in parallel to be tried on an experimental car. We propose to make a brake efficiency test of the present standard motor arranged in this manner, as you have suggested for the American cars we might make this alteration only to the motor. A standard R.R. starter motor was arranged to start the Goshawk engine with a reduction ratio of 12 to 1 (epicyclic gear on the motor representing 6 to 1 of this reduction). It was found that with the engine cold the motor takes 96 amperes and runs the engine at a speed of 85 R.P.M. with a motor terminal voltage of 9.5. Reference Contd. | ||