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. Ltd. regarding disappointing test results of a thermostat scheme on a Bentley car.
| Identifier | ExFiles\Box 156\1\ scan0204 | |
| Date | 1st July 1937 | |
| Experimental Dept. Rm{William Robotham - Chief Engineer}/Std.1/JH. 1st July, 1937. The British Thermostat Co.Ltd., Teddington Works, Windmill Road, Sunbury, MIDDLESEX. For the attention of Mr.Martin-Hurst. Dear Sirs, We have now completed and tested a scheme for using your thermostat (drawing BGA.3357A) on our Bentley car, and also an alternative scheme using your thermostat BGA.2073A. Attached drawing LeC.5655 shows the first scheme and the second scheme consists of substituting a BGA.2073A thermostat for that shown on LeC.5655 (BGA.3357A) and taking a permanently open bypass pipe from the casing surrounding the thermostat bellows, the bypass pipe shown on LeC.5655 being dispensed with. The results with the scheme as drawn are disappointing, we find so far that if the clearance around the head of the valve (between valve and machined guide in casting) is less than about .018 - .020, sticking of the thermostat occurs with consequent erratic temperature control. However if this clearance is used the warming up period is very long, 15 minutes approximately, and the running temperature is below that which the thermostat should give, actually about 72°C instead of 80°C. We are modifying the guide in an endeavour to prevent sticking while using a clearance of the order of .008" - .010", but are not very hopeful about the scheme, since even if it works when new, with a clearance as small as .010 it seems likely that sticking would occur as soon as some corrosion etc. took place. Our conclusions are that in order to get effective working of the thermostat to BGA.3357A, the valve head clearance (diametral) must be so small that the scheme is not likely to remain reliable in service. | ||