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).
Engine valve sizes and a comparison of Roots and Powerplus type blowers for the Bensport engine.
| Identifier | ExFiles\Box 3\4\ 04-page031 | |
| Date | 14th May 1932 | |
| - 2 - We are particularly interested in the question of the valve sizes as we shall be worse off in this respect than the Alfa, the Alfa being a short stroke large bore engine with hemispherical head. With regard to the question of blowers for the Bensport, the position still remains as it appeared some months ago, and that is, it is necessary to add oil to the petrol for the Roots type, and it is, therefore, no better off in this respect than the Powerplus. This, therefore, makes it possible to use the Powerplus, and we thought it would be desirable to arrange the design so that either type of blower could be tried. The Powerplus has an additionally small oil pump for metering a small quantity of oil to parts requiring lubrication in the blower, but if this fails to operate it does not result in the blower breaking down. This oil pump could be connected to the low pressure oil system on the engine, and should preferably have a cock coupled to the throttle which would shut off the oil supply when the throttle is closed. The difficulty at the present moment with regard to using this blower is that it is much too long to go in the space available, but as a portion of this length is due to subsidiary features which can be modified by design we are looking into this matter to see how the blower could be re-arranged. The Powerplus blower that we bought for our original compression ignition supercharging experiments had two gear trains for the drive between the vane cage and the rotor shaft. In the latest design this gearing has been ingeniously replaced by an Oldham coupling form of drive which should be much more silent. The advantages claimed for the Powerplus over the Roots type are:- (1) Greater pneumatic silence. (2) Greater mechanical silence. | ||