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).
Thermostat testing procedures, operating temperatures, valve operation, and bellows design.
| Identifier | ExFiles\Box 156\1\ scan0075 | |
| Date | 16th April 1935 guessed | |
| - 2 - Messrs. Rolls-Royce Ltd. attached to the valve spindle in such a manner that its position on the spindle can be adjusted. This requirement is not satisfied by your arrangement. The method of testing is to place the thermostat in water at the specified opening temperature, in your case 75°C. and to adjust the main valve head to be just in contact with its seat at this temperature, the head then being locked in position. The thermostat is then transferred to water at the higher temperature, namely 82°C, and a check is made to ascertain that at this temperature the by-pass is closed off and the main valve head has lifted at least the minimum amount specified. Objection has never yet been raised to the main valve opening too much. This arrangement gives a very simple method of ensuring that the opening temperature is exact. The general practice is to fix the maximum temperature at which the valve is to be full open, any thermostat which opens fully at a lower temperature being deemed satisfactory. In practice this arrangement works well, since it is only desirable to cut off the flow through the by-pass when there is a danger of overheating being caused by the existence of this flow, and once the temperature at which it is desired to close off the by-pass has been fixed, it is immaterial whether it closes off a few degrees earlier, providing that it does not close off later. We consider that a range of 7°C. from the opening to the full open position is too small, unless a greater length of bellows is to be fitted. From a bellows measuring 1" in the contracted condition a reasonable range is 11°C. If it is desired to reduce the difference between the opening and full open temperatures an even greater length of bellows must be employed. We shall be pleased to advise you on this point if you will confirm that you wish to maintain the temperature specified. The points which we wish to make quite clear can be summarised as follows:- | ||