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).
Design considerations for the Bentley 50 thermostat and fan drive system.
| Identifier | ExFiles\Box 156\1\ scan0350 | |
| Date | 17th December 1937 | |
| To Da.{Bernard Day - Chassis Design} from Rm{William Robotham - Chief Engineer}/Std. c. By.{R.W. Bailey - Chief Engineer} Rm{William Robotham - Chief Engineer}/Std.1/MH.{M. Huckerby}17.12.37. 1044 1328 BENTLEY 50 THERMOSTAT AND FAN DRIVE ETC. Referring to sheeme PD.64, no thermostat is shown on thedrawing, but one will be required since B.50 will have a fixed grille and not thermostatic shutters. We have carefully gone into the question of cost of various thermostat schemes with a view to using the cheapest satisfactory one for B.50 and have decided that it is most economical to use a scheme with thermostatic "cut-off" of the bypass (which should be approx. 5/8" - 3/4" dia. ) especially as the water pump on the project engine is so close to the front water outlet. For the project engine, therefore, the thermostat scheme to be used should either be that used on B.III or that shown on print attached herewith, according to which can be made most suitable for the bypass to the water pump inlet. For the B.III engine to be used initially for B.50 the scheme drawn for B.III will presumably be used provided no serious objections are found during test. We are, however, looking into whether a complete casing unit such as the Vauxhall or Standard would show any saving over the present scheme and will advise you of the result. With regard to the fan drive shown on PD.64, the speed ratio as drawn is too high, being 1/1, we wish to start with the ratio which we are using on B.III and Wraith i.e. .85/1. This can only be achieved (without having an extremely large fan pulley) by reducing the size of the driving pulley somewhat and increasing that of the driven pulley. This will necessitate the fan driving pulley being made a separate pressing from the dynamo water pump driving pulley. In view of the fact that difficulty in making the combined pulley on PD.64 will probably be experienced, this alteration seems desirable and should not materially affect the cost. Will you therefore, please make this alteration when schemeing the B.50 project engine, the adjustment should | ||