﻿Ignition of Gases by Sudden Compression. 



83 



Of these, the first two were completely eliminated and the 

 third reduced to something quite negligible. Figures of 

 the actual leakage are given below. 



The method of eliminating piston leak will be understood 

 from fig. 2. The piston is made in two parts. Below the 



F/a 2 



cast-iron top, which carries a single piston ring of the usual 

 type, there is an aluminium body which for some distance is 

 of smaller diameter than the cylinder. Round this waist 

 are two cup-leathers, C and D, each with the periphery 

 turned upwards, which are separated by a cast-iron ring of 

 square section (E, fig. 2). The whole space above and 

 between the cup-leathers was filled with castor oil so that 

 no air could leak down past the piston head until it had first 

 made a space for itself by forcing castor oil down past the 

 two cup-leathers in series. 



¥3r 



g 





.JP2 



i A 



na 3 



To eliminate le k past the indicator piston, the plan was 

 hit upon of turning the whole indicator upside down and 

 then pouring in a little castor oil into the space above the 

 piston, as illustrated in fig. 3. Here A represents the piston 

 of the inverted indicator with the sp;ice above it filled with 



G2 



