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).
Modifications to battery ignition dynamos for Exe, Vulture, Merlin and Kestrel engines.
| Identifier | ExFiles\Box 168a\3\ img285 | |
| Date | 22th February 1936 | |
| Es. and H/Bm c.-By Hw/Wst. By/RD. WST 86099. E.3/HP.22.2.36. re Battery Ignition Dynamos With reference to the ignition dynamos that will be used on the Exe engine, and Vulture, we now find as a result of development on armature construction that the present proportions are not practicable, and it will be necessary to increase the diameter of the armature, and hence the diameter of the carcase, to overcome the difficulties experienced with the windings. The trouble arises from the distortion of the formed coils in the taper slots leading to insulation damage and consequent breakdown. To avoid this it will be necessary to use parallel slots which will require the increase in diameter mentioned in the foregoing. To keep down the external diameter of the machine to the minimum limits the regulating resistance may be transferred from its present position on the pole pieces to an external unit where it will be easier to adjust, if required. With regard to the smaller dynamo for use on the Merlin and Kestrel, it is understood that owing to the operational speeds being below those originally contemplated the diameter of the armature will be increased by .5", and correspondingly shortened to obtain the requisite voltage without proportionally scaling up the output. This as By/RD. points out creates an unusual proportion for a dynamo which will mean that it will be relatively heavier than normal, but we should make up for this by saving weight in not having to add extra gearing in the drive. This will increase the diameter of the machine, and any schemes already prepared for the drive should be examined to see what modifications are required to accommodate this alteration. E.{Mr Elliott - Chief Engineer} | ||