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Messrs. H. T. Tizard and D. R. Pye on the 



castor oil. The duct BC in the bracket which carries the 

 indicator is based on the slope to prevent the possibility of 

 any oil getting back along it and into the combustion space 

 at C, This arrangement was very satisfactory, for, besides 

 forming a perfect seal, it served to keep the piston well 

 lubricated ; it was found, moreover, that only a very small 

 quantity of oil was forced down past the piston, even after 

 continued exposure to high pressure. 



The arrangement of fan and fan-spindle is shown in 

 fig. 4. Here the plug A, shown in section, was made to 

 screw vertically* downwards in the centre of the cylinder 



LEA THEH 



head, its lower end finishing flush with the top of the com- 

 pression space. At the highest compression ratios this space 

 is \ inch deep, so that the piston head under these conditions 

 is close up to the under side of the fan. The fan was driven 

 at varying speed by an electric motor through the usual 

 form of flexible drive used for speedometers. 



To prevent leakage up round the fan-spindle, this was 

 made long and thin, and was also provided with a cup-leather 

 of which the tightness could be adjusted by the screw B in 

 fig. 4. By using a motor with ample reserve of power for 

 driving the fan, it was possible to keep the cup-leather so 

 tight as to reduce the leakage to a negligible amount. 



