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 selection of bearings, shaft materials, and mica for commutators.
| Identifier | ExFiles\Box 181\M7\ img014 | |
| Date | 12th August 1912 guessed | |
| -4- Messrs Royce Ld., (contd) very practical, and I do not like to recommend anything of a more complicated nature. Should ball thrust bearings be required and only for small end pressure I recommend the type and general arrangement as used at Birkacre and recent experience confirms this, but when for heavy pressure as in the case of worm thrusts grooved washers & large balls should be used, here the running portions require that the ground groove shall run very truly otherwise trouble arises. With reference to the plain bearings, although I am definitely in favour of white metal bearings of the genuine tin babbit alloy, I think it is sufficiently good for us to use bronze with a large percentage of lead (say 10% to 15%) which is undoubtedly less expensive and has some practical advantages. The shafts in all cases should be of high elastic limits and rather hard steel except in the case of the large forged ones which should be of a milder steel, and I should prefer to have the coupling forged solid and be fitted with white metal or composite bearings i.e. bronze bearings with white metal patches. In these larger pieces of work composite bearings would be a practical proposition, and in all cases these large machines should be so built that any deflection of the shaft does not disturb the commutator or the windings , a good system being similar to that which has been so well tested on the Wrigley generators. With reference to mica between the commutator bars, I am of the opinion that Mr Bentley's practice of using Canadian silvered amber mica is perhaps the most satisfactory of all, and should, owing to its giving such good satisfaction, | ||