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 The Packless Gland Co. Ltd. discussing thermostat design, its perceived shortcomings, and potential improvements.
| Identifier | ExFiles\Box 85\4\ scan0059 | |
| Date | 5th July 1934 guessed | |
| - 2 - Messrs. Rolls-Royce Ltd. You will notice that a ball valve is mounted in the head and this is arranged to allow air to pass through the thermostat when the radiator is filled, and to close off the hole when the water flow attains a pressure of approximately 3 lbs./sq.in when mounted vertically, and 1 1/2 lbs./sq.in when mounted horizontally. We feel that this thermostat, while being satisfactory for the general run of cars, is of too cheap a construction for inclusion in a vehicle such as you manufacture. We are therefore enclosing Drawing No. BGA. 1743C. showing an alternative type where the by-pass is conducted from the annular space surrounding the valve stem, this by-pass being closed off when the bellows is fully extended. Both these types work very satisfactorily but an improvement could be made to that shown on Drg. No. BGA. 1743C by increasing the length of the bellows. This modification would ensure that in the event of bellows failure the thermostat would open fully, at the same time closing the by-pass off completely. In the design shown this does actually occur, but for reasons of economy and space the length of bellows was cut down to a minimum so that when a puncture occurs there is only a very small margin of safety between the valve closing off fully and not closing off quite fully. If there is any further information we can give you we shall be very pleased to do so on hearing from you. Yours truly, THE PACKLESS GLAND CO. LTD. W.Martin-Hurst. | ||