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).
Reduction gears and a comparison of cartridge versus electric engine starters.
| Identifier | ExFiles\Box 27\3\ Scan221 | |
| Date | 15th May 1939 guessed | |
| 15. When necessary the plugs are returned to the makers to have a new tip welded on to the core. Reduction Gears Wrights are using a spur epicyclic gear with 20 small pinions. Mr Nutt himself said that he liked this design and that he would never revert to the Farman bevel type, but that when it became necessary to obtain ratios of .5:1 and lower, he would use a compound spur epicyclic gear. His chief objection to the bevel gear was that it could not be ground. Pratt & Whitney are using both spur and Farman gears with six pinions each. Starters The general opinion of engine people regarding Cartridge starters is not very definite although no-one would fit a Cartridge starter from choice. Wright said that the Coffman started engines satisfactorily but that they had had one rear half crankshaft twisted off when, as they said, the wrong cartridge had been put in. I was also shown a broken tooth from a 12-dog jaw which had been fractured only the previous day The single-breech mechanism is used and no development appears to have been done on the multi-breech mechanism in the States. The 'L' type Coffman Starter is fitted to the 18-cylinder 2000 HP Cyclone Duplex engine on show at the World's Fair. The Eclipse people had more decided views. They are making cartridge starters and supplying these to the Army and Navy, in fact quite a number were going through the shops, but they feel that the electric starter is definitely best. I heard from several different sources that the Army had decided that the Cartridge Starter was much too expensive, and they had just placed an order with Eclipse for electric starters to replace 315 Coffman starters which they had had in use for some time. In one year the cost in ammunition for these starters had practically equalled the capitol cost of the starters. Using 5 cartridges per day at from 22 to 31 cents per cartridge the cost would be 146,000 dollars per annum, whereas at 350 dollars each the capital cost of the starters would be 110,000 dollars. | ||