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 specifications and performance testing of a dynamo, including cold condition and heating test results.
| Identifier | WestWitteringFiles\G\October1921\ Scan4 | |
| Date | 17th October 1921 | |
| Contd. -2- In the cold condition, a voltage of 12.4 is attained at 790 r.p.m. The carcase diameter is 5". Weight of dynamo inclusive of pulley but exclusive of suspension 21 lbs. (our suggested limit being 25 lbs). Armature diameter 2.50" Active length 2.50" Overhang of armature conductors at driving end 1.25" Overhang at commutator end, including commutator spokes 1.55" Carcase length 5.00" The brush hear is similar to that of the 2D machine. The quality of the brushes is L.C.3 Morganite. The air gap is rather large - .0325" approx. Field circuit resistance at 18°C -5.4 ohms No. of slots - 13. No. of commutator bars - 26 Armature resistance at 18°C - .78 ohm. Commutator diameter - 1.6" Brush useful length .625" Brush contact area .425" x .325" = .138 sq" On the heating test, we found that running the machine at maximum ampere output with the same brush setting on which the output curves were taken, which was found by trial to be the best allround setting (though makers had set the brushes, for some unexplained reason, fully retarded), the final carcase temperature was only 73°C with an ambient temp: of 20°C. The maximum continuous ampere output corresponding to this temperature was 8.2 at 14.6 volts, the speed being unduly high - 2780 r.p.m. The calculated temperature by rise of field resistance was only 90°C. We found that maximum temperature occurred at the speed at which maximum output was obtained, but that for variations of brush position, the Contd. | ||