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 to The British Thermostat Co. regarding incorrect calculations for a Bonnet Louvre Thermostat.
| Identifier | ExFiles\Box 156\1\ scan0127 | |
| Date | 19th November 1935 | |
| X1328 Exptl. Dept. Hs {Lord Ernest Hives - Chair} /Std.2/KW. 19th November,1935. Your Ref: WMH/GN.12.11.35. The British Thermostat Co., Windmill Road, Sunbury, Middlesex. For the attention of Mr. Martin-Hurst. Dear Sirs, I have received your letter of the 12th inst., together with your drawing No. B.G.A.3201, showing suggested arrangement for our Bonnet Louvre Thermostat, for which we thank you. The layout shows a neat way of doing what we require, but I regret to say that the bellows size and calculations relating to same are incorrect. The errors are :- (a) The stipulated load of 10 lbs. (push-pull) was to be at the end of the shutter operating lever; i.e., using the leverage ratio shown (4/1) the load to be exerted by the bellows at the bellows plate would have to be 40 lbs., not 10 lbs. as shown on the drawing. (b) The calculations appear to have been made on the basis that the bellows are in their free position when cold, and therefore would expand from this position when heated - a proceeding which the writer when at your Works was informed was thoroughly wrong. Actually you state in the list of data that the bellows take up their normal free position when hot - the calculations should therefore read as follows, for the spring loadings etc. selected by you :- | ||