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).
Summary of examination and tests for a new brushholder design.
| Identifier | ExFiles\Box 166\1\ img079 | |
| Date | 9th July 1936 | |
| To E.{Mr Elliott - Chief Engineer} c. to By /RD. 86093 Hs{Lord Ernest Hives - Chair}/Wst.1/JH.9.7.36. New Design of Brushholder. In connection with a discussion with By/RD. this morning, on the new design of brush gear, R.R. Sch.904, the following is a confirmation and summary of the essential points raised as a result of an examination and tests :- (1) The brushholder as designed in R.R. Sch. 904 is an improvement on the existing design. (2) From bench tests carried out, there is no visible difference in sparking and commutation generally, between the heavy pressure arm, as designed, and a much lighter arm, obtained by reducing the section of the lever, and the mass of the head. This portion of the holder, therefore may be made as light as desired, consistent with mechanical strength. (3) In order to keep the line of pressure on the brush, within the holder, the centre of the pressure arm pivot, must be lowered. This involves altering the position of the holder-securing hubs. (4) To eliminate all danger of the lever end of the spring fouling the commutator, the anchorage at this end, should be raised. (5) It appears to be necessary to give some attention to the clearance in the holder-securing holes, and also the method of procedure to be used in fitting the holders to the bracket; in view of the desirability of having :- (a) A small clearance (.025" to .030") between the bottom of the holder and the commutator. (b) The bearing wall of the holder at a trailing angle to the commutator of from 5° to 10°. (6) The pressure applied to the brush should be 14 + 3 ozs. | ||