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 Dennis Bros Ltd discussing issues with thermostat bellows caused by hard water and proposing an alternative design.
| Identifier | ExFiles\Box 156\1\ scan0332 | |
| Date | 25th November 1937 | |
| ALL COMMUNICATIONS TO BE ADDRESSED TO THE FIRM AND NOT INDIVIDUALS TELEGRAMS: DENNIS GUILDFORD TELEPHONE: GUILDFORD 1575 (7 LINES) OUR REF. JM{Mr Morley}/CS. YOUR REF. RM{William Robotham - Chief Engineer}/SJDS/JH. BY APPOINTMENT HEAD OFFICE AND WORKS DENNIS BROS LTD COMMERCIAL VEHICLE AND FIRE ENGINE MANUFACTURERS GUILDFORD SURREY ENGLAND A B C CODE 5TH EDITION LIEBERS 5 LETTER BENTLEYS MARCONI DENNIS ESTABLISHED 1895 25th November, 1937. BENTLEY'S SECOND. Messrs. Rolls Royce, Ltd., Derby. Dear Sirs, We are in receipt of your letter of the 23rd inst., querying information given to your Mr. Matthews when he visited our works recently. As suggested, we have experienced a considerable amount of trouble with the ordinary bellows type thermostat where the bellows are in contact with the cooling water. In several districts, such as Kent and Essex, where hard water is normally used, an excessive lime deposit is formed in the cooling system, and quite independent of the corrosive action which is found when this water is used we have had many cases where thermostat bellows have been prevented from operating in a satisfactory manner. We desire our engines to work with the temperature as high as possible, and yet this very action has the effect of causing the excessive deposits to be formed, and as the bellows are very often expanded to the full extent, the deposit which is then formed covers the whole of the convolutions and after a time prevents the bellows from closing satisfactorily. Repeated operation under such conditions will rapidly cause failure of the bellows. We have customers who now specify that they will not have the normal type of thermostat bellows on any of their vehicles and they insist on their drivers operating a diverter or bypass valve in order to maintain the cooling water at a satisfactory temperature. To attempt to meet these conditions, we have reverted to the type of bellows where the convolutions are formed internally and do not come in contact with the water. This type of bellows has been used for some considerable time by various accessory makers, and we feel sure that you are fully aware of the design. When this type of fitting is used, any deposit which is formed merely adheres to the plain external body of the thermostate, and in this manner, we hope to be able to prolong the life of the bellows. (Cont:) Handwritten text: 1328. THERMOSTAT FILE STEADMAN Side text: CUSTOMERS' VEHICLES DRIVEN AT OWNER'S RISK ONLY. | ||