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).
Experimental work report on modifying a 40/50 plain shunt dynamo to improve its electrical performance and reduce high-speed sparking.
| Identifier | ExFiles\Box 60\3\ Scan185 | |
| Date | 25th January 1933 | |
| 86092 E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Wst. c. By.{R.W. Bailey - Chief Engineer} Wor.{Arthur Wormald - General Works Manager} c. Sg.{Arthur F. Sidgreaves - MD} Hs{Lord Ernest Hives - Chair}/Wst.1/KT.25.1.33. 40/50 DYNAMO FOR AUTOMATIC VIBRATOR CONTROL. We have carried out a considerable amount of experimental work with a 40/50 plain shunt dynamo on the bench in the direction of improving its electrical performance for use on the 40/50 chassis in conjunction with a C.A.V. vibrator regulator. We have aimed principally at improving its maximum output in respect to its maximum safe temperature rise, without affecting its cutting in speed or causing undue sparking with full output at high speeds. The suppression of sparking at high speeds is a new problem we are having to tackle, owing to the possibility with the headlamps on of full output being taken from the dynamo running at high speeds. We have found it advantageous in this respect to increase the field as much as possible and reduce the number of conductors in the armature, the idea being to reduce the effects of armature reaction [crossed out] in altering the neutral position of the brushes on the commutator. Working on these lines we used a standard 40/50 machine modified by fitting an old standard armature having 16 conductors per slot instead of 20 of 17. SWG. D.C.C. wire. The field winding consisted of as many turns of 20 SWG. D.C.C. wire as could conveniently be accomodated in the available space. The dynamo so modified gave a maximum output for safe temperature rise of 16.0 amperes at 13.0 volts, at a dynamo speed of 1200 r.p.m. The cutting in speed hot was 750 r.p.m. These figures are very satisfactory in view of the fact that the sparking at high speed was reasonable. A further modification we now wish to try consists of reducing the diameter of this armature and milling out the slots, so that the depth of the slot in the armature core is the same as the present standard 10 turns per coil armature. The length of the pole core could then be | ||