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).
Specifications and test results for a motor, concluding it is unsuitable for the Goshawk engine.
| Identifier | WestWitteringFiles\G\October1921\ Scan17 | |
| Date | 17th October 1921 | |
| Contd. -2- WFC1/T17.10.21. well finished. One each end of each pole core is a brass plate with projections which are bent over to secure the field coils in position. The main terminal connections and connections to the brush holders seem O.K. There are two brushes only at 90° each with two pigtail connections, the brush material being of C.M.3 Morganite. A slight adjustment of the brush position is provided by slotting the stud holes over the end plate. Hoffmann ball bearings are fitted. The brush holders on the commutator end plate are similar to those of the Smith 2D dynamo. Further particulars of this motor are as follows :- Weight of armature including long spindle and driving end plate 6.3 lbs Air gap .075" 1.9 mm. No. of wound poles - 4. Arrangement of coils - all in series. The armature is electrically sandwiched between two pairs of field coils, this being done for convenience of connections. Resistance of field circuit. ohms (cold 18°C) - .0213 No. of armature slots - 13 No. of commutator bars - 13. Armature resistance ohms (cold 18°C) - .017 Commutator diameter - 1.50" Useful length - .90" Brush contact area - .75" x .375" = .281 sq." Ratio of field resistance to armature resist: - 1.18. On brake test on the bench this motor gives very poor results and we fear it would be quite unsuitable for application to the Goshawk. Our estimate of the motor torque required to roll the Goshawk engine (cold) was 66lb-ins (see calcu- lations in connection with the R.R. Goshawk 11 starter motor). R.R. 235A (100 T) (S.H. 798. 10-12-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2947 | ||