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 regarding the performance specifications of calorstats, including travel, load, and the Hexane fluid used.
| Identifier | ExFiles\Box 156\2\ scan0208 | |
| Date | 13th March 1939 | |
| 105 1328 CONTRACTORS TO ADMIRALTY, WAR OFFICE & AIR MINISTRY BY APPOINTMENT TO THE LATE KING GEORGE V ENGINEERING & ALLIED EMPLOYERS' NATIONAL FEDERATION TELEPHONE: GLADSTONE 3333 (40 LINES) TELEGRAMS: SPEEDOFAC, PHONE, LONDON. CABLES: SPEEDOFAC, LONDON. CODES: MARCONI, COMMERCIAL, BENTLEY'S. S. Smith & Sons (Motor Accessories) Ltd CRICKLEWOOD WORKS LONDON, N.W.2 BRANCHES AT PARIS MILAN SYDNEY WELLINGTON AGENCIES AND SERVICE STATIONS THROUGHOUT THE BRITISH EMPIRE AND IN ALL THE PRINCIPAL COUNTRIES SHOWROOMS & DEPOTS 179-185 GT PORTLAND ST LONDON, W.1. 26-33, COX ST LIVERY ST BIRMINGHAM 14A JACKSONS ROW DEANSGATE MANCHESTER 21, DRURY STREET GLASGOW DUBLIN & BELFAST Please quote our reference: E.6 FGE/MM. Your Ref: Rm{William Robotham - Chief Engineer}/FJH{Fred J. Hardy - Chief Dev. Engineer}5/R.{Sir Henry Royce} March 13th, 1939. Messrs. Rolls Royce Ltd., DERBY. Dear Sirs, With reference to your letter of the 10th inst. the calorstats we have been supplying for some time past have been arranged to give a travel of .425" at a temperature of 75 deg. in accordance with your drawing. The load suspended at .425" travel averages 28 lbs. which is within ½ lb. of the mean load specified. We do not now take account of the temperature at which the instrument commences to open when not loaded as it is very difficult to control this point. We understand that the travel and load forms a better criterion as to the probable operation on a shutter. You will no doubt appreciate that variations will always exist on bellows apparatus which do not incorporate some means of adjusting the performance (such as a load spring), we have been at considerable pains to find out why these variations exist and find that the varying strength of bellows has considerable effect. The fluid used for filling is Hexane, but we understand that commercial Hexane includes fluids which distil above and below the temperatures at which Hexane is produced, and in consequence the boiling point ranges over a few degrees. The proportion of fluids of lower or higher boiling point no doubt varies and this would naturally give rise to varying vapour pressures at any given temperature and thus account for differences in performance. The performance is kept as close as possible. To avoid delay all envelopes should be addressed to the firm. | ||