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).
Letter from S. Smith & Sons discussing the operational forces on a thermostat valve and proposing modifications.
| Identifier | ExFiles\Box 156\1\ scan0088 | |
| Date | 10th May 1935 | |
| S SMITH & SONS (Motor Accessories) LTD. CRICKLEWOOD WORKS, LONDON, N.W.2. CONTINUATION NO. 1. May 10th, 1935. Messrs. Rolls Royce, Ltd. The pull on the valve will be lessened as the thermostat is heated until at 75 degrees the valve will commence to open. These are the effects which would take place providing that no external forces are acting on the thermostat or the valve it is to operate. Our experience is, however, that there are such forces to consider, for instance, water pressure will tend to open the valve against the pull of the cold thermostat unless the water pressure is also acting on the bellows unit in like degree (i.e. tending to keep it compressed.) It will thus be seen that for the valve to operate effectively the force of water acting on the valve tending to open it should be balanced by a similar force acting on the bellows and tending to compress it, and you will thus see that the water pressure, the area of the valve and the mean area of the bellows are very important considerations. The disposition of the valve and bellows in relation to water pressure and its direction of flow are also important. Since the water circulating pump of a car engine can develop a pressure of up to 20 lbs at high speed and corresponding lower pressure at lower speeds, you will no doubt appreciate that unless the forces are balanced the behaviour of a thermostatic valve subjected to varying pressures will be erratic, and in view of the above we should be much obliged if you would let us have a sketch showing the application of the thermostat which is projected. With regard to the thermostat E.86612, it will be necessary for us to modify the screw plug shown in order that exhausting and filling can be better arranged. We would also suggest spanner flats on the external boss which is tapped 5/16", to avoid strain on the bellows when assembling the valve stem. Yours faithfully, for S. SMITH & SONS (MOTOR ACCESSORIES) LIMITED. F.S. Estfad | ||