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).
Test report on modifications to the brush gear for the 40/50 and Bentley dynamo.
| Identifier | ExFiles\Box 168a\3\ img166 | |
| Date | 14th March 1935 | |
| MODIFICATIONS TO BRUSH GEAR ON 40/50 AND BENTLEY DYNAMO. The purpose of this test was to investigate the effect of the following modifications to the large shunt generator, these modifications being calculated to improve commutation and the general performance of the generator. (a) One brush per holder instead of two. (b) Larger cross sectional area brushes. (c) The spring of the negative brush reversed so as to be similar in position to the positive brush spring. (d) EG0 (Morganite) grade of brushes with same spring pressure as on 20/25 dynamo. Test Procedure and results. A standard production dynamo, Bentley type large shunt machine (Ex.std.33), was fitted with one pair of 20/25 size (1.0" x 0.300) EG0 brushes. The brush holders used were a pair of positive 40/50 size, modified to take a 1.000 x 0.300 brush with a single spring, the spring in both holders being pivoted behind the brush. Experimental brush gear. 1 brush/holder, 2 holders Both springs pivoted behind the brush. Brush width .300" Brush area - .300 sq.ins. Brush grade - EG0. B angle 14.7° Spring pressures 16 oz. 16 oz. (standard on 20/25) Standard brush gear. 2 brushes/holder, 2 holders. Negative spring pivoted in front of the brush. Brush width .280" Brush area - .280 sq.in. Brush grade - EG.2 B angle 15° Spring pressures 10 oz. 2 oz. Low Speed Heating Test. Experimental. 185 amperes at 13.0V, 1303 R.P.M. Standard. 16.3 amperes at 13.0V, 1270 R.P.M. | ||