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).
Manufacturing variations in gauge glasses and proposed solutions to improve accuracy.
| Identifier | ExFiles\Box 61\3\ scan0098 | |
| Date | 11th September 1930 | |
| Messrs. Rolls-Royce Ltd. Date 11/9/30. Page 2. the bend in the flexible tube between the inside of the instrument frame and the zero mark on the dial. We have found in manufacture that it is almost impossible to guarantee that there is no variation in the glasses coming off the machine, and that some show a decidedly longer taper than others. We cannot, with safety, raise the full mark on the dial any higher than it is now. Therefore the only absolute cure is the reduction of the scale by some 1/8" bringing the scale to 2" instead of the present 2 1/8". In the meantime careful selection and throwing out of all glasses showing an excessively long taper can improve matters greatly, but it does not really give us a chance to eliminate the trouble completely. We should be much obliged if you would make a simple test to confirm our findings which we have very carefully investigated and feel confident that you will find what we say is correct, viz., that given a gauge glass with an exaggeratedly bad taper portion projecting above the zero mark, and a good glass with the taper portion scarcely reaching the zero mark, if these two gauges are tested under identically the same conditions of pressure, a variation in reading throughout the scale of less than the thickness of one of the dual lines is to be found. The liquid must be set at the zero mark in each case to make the conditions equal. Admittedly it is difficult | ||