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).
Article reprint discussing the performance and fuel economy benefits of the 'R.P.' Adjustable Thermostat.
| Identifier | ExFiles\Box 156\1\ scan0010 | |
| Date | 2nd February 1929 | |
| Reprinted from “The Illustrated London News,” February 2, 1929. The “R.P.” Thermostat. In such winter weather as we are having now it is practically impossible to keep an engine’s temperature from fluctuating extravagantly without employing some special device. The latter part of my experiments have been with such a fitting, the “R.P.” Adjustable Thermostat, which the Houdaille Hydraulic Suspension Co., Ltd., asked to be allowed to fit to my engine. This is a thermostat of a new design, automatic in action, the opening and closing of its valve being controlled by the temperature of the water. I have found it, so far, most successful. It does all that is claimed for it—which is saying a good deal. It was fitted into the joint between the cylinder-head and the radiator (as close as possible to the former) in an hour or less, the operation being perfectly simple and straightforward. It costs 28s. 6d. for the thermosyphon type and 33s. 6d. for the pump type. The immediately noticeable results were that, on a bitterly cold day, with the thermometer only just above freezing point, the engine was in efficient running form within ten minutes of the start; that, after an hour’s wait in a windy square, it started up again instantly; and that all symptoms of “flat spots,” the effect of poor carburation, had disappeared. There was another result, with which I will deal later. What It Does. What happens is that, when the water is cold, the butterfly-valve is shut, thereby choking the flow of water from the water-jackets to the radiator. At the end of a minute or so, after the engine has started, the water warms up, and, as its warmth reaches the valve and the thermostatic coil-spring controlling it, it makes the valve begin to open, which means that the cold water in the radiator is allowed to flow to the jackets. As the heat increases, the valve opens wider until, at a point of temperature the owner can decide for himself, it is wide open. The moment the water in the jackets begins to cool down, even by four or five degrees, the valve begins to close, thereby restricting the water-flow and automatically warming things up again. The process is extraordinarily quick, as I was able to see by the help of a thermometer temporarily attached. I could send up the needle ten degrees in as many seconds by “revving” on third speed, and bring it back as swiftly by crawling on top, but each time the “correct” temperature was regained immediately after. A curious and, at first, rather a disquieting feature is that at least three-quarters of the radiator is found to be stone-cold whenever you stop. There is always a big reserve of cold water on which to draw in special circumstances, such as heat-waves and the Alps. Further, you can set the opening of the valve as hot or as cold as you like, by turning a milled disc on the outside of the thermostat. Greater Fuel Economy. The other result was the remarkable effect on the fuel-consumption. I drove the car over a week-end run I have used for years, every foot of the way as familiar to me as any road can be, and over the return journey of ninety-five miles, in and out of London, the consumption improved by no less than five miles to the gallon. It was cold, but still, and the roads were neither dry nor heavy. Twenty-three miles to the gallon had been the best I could get before, and with the “R.P.” I got an average of twenty-eight. Frankly, however, that does not interest me half as much as the other things. The engine is practically always running at its best now, instead of just sometimes. JOHN PRIOLEAU. | ||