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 operation of a choke valve, its disadvantages, and a proposal for an improved bi-metal unit with manual seasonal settings.
| Identifier | ExFiles\Box 123\1\ scan0040 | |
| Date | 6th March 1940 | |
| -3- Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager}7/MOL.6.3.40. It will be seen that immediately the engine fires, the kick piston comes into operation and opens the choke valve approximately 27°. These figures were taken every ½ minute with the engine running at 1,000 r.p.m., but when the car is driven on the road, the engine warms up much quicker and consequently one gets off the choke quicker. The only apparent disadvantage to this scheme appears to be the heating of the bi-metal strip electrically, for instance if the ignition is switched on and the engine not started almost immediately, the choke valve would be gradually opening, and with a still cold engine, difficulty in starting would be experienced, or as a second instance, if the engine has been started in the correct manner, and the car subsequently driven down a long gradient, the choke again would be well open with the engine still cold and a consequent lean mixture. To overcome this particular point we require a bi-metal unit which will do the work without electrical heating. We would also suggest that a Winter setting of the choke may be too strong for Summer conditions, and some form of manual control should be incorporated to give a definite Winter and Summer setting. We attach herewith a photograph of our "mock-up" scheme. Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager} | ||