GAS HELMET 



3439 



GAS HELMET 



blast-furnace gas 

 per brake horse- 

 power hour. The 

 calorific values of 

 the three gases are 

 roughly 550, 140, 

 and 105 B. Th. U. 

 per cubic ft. re- 

 spectively. 



Owing to the 

 verv high tem- 



employcd, and in the rejected hot 

 gases, much heat is thrown away ; 

 the percentage actually utilised 

 in developing useful power rang- 

 ing from 15 p.c. to 30 p.c. It 

 has, therefore, been proposed in 

 the Still and other engines to 

 utilise this waste heat by raising 

 steam with it and using the steam 

 to drive a supplementary engine. 



A. Williams 



able feature of the ordinary type 

 of gas engine, the heavy fly-wheels 

 employed. This excessive weight 

 is necessary in order to equalise 

 as far as possible the turning move- 

 ment of the engine crank, and to 

 damp the effect of the explosion. 

 It will be easily understood that 

 if an engine could be designed in 

 which an explosion would take 

 place every revolution, double 

 the power might be obtained from 

 an engine of a given size, and a 

 more equal turning movement 

 would result. 



This end was obtained by Mr. 

 (now Sir) Dugald Clerk in 1886 by 

 his invention of a two-cycle engine, 

 in which he introduced an extra 

 cylinder, the purpose of which was 

 to draw in and compress the 

 charge and to sweep out the burnt 

 gases from the power cylinder by 

 a blast of air. The principle of the 

 Clerk cycle has been embodied in 

 the large gas engines of to-day, 

 some of which have an individual 

 rating of 5,000 h.p., a capacity 

 which it would be difficult to reach 

 in engines of four-cycle type. 



Many varieties of gas engines 

 are now available, but practically 

 all follow one or other of the 

 cycles which have been indicated ; 

 while the charge of gas and air is 

 ignited in all, either by a small gas 

 flame which is made to enter for 

 an instant into the cylinder, or by 

 an electric spark from a magneto 

 or battery. Various methods of 

 " governing " the engine are 

 adopted ; in some the weight and 

 density of the charge is varied, 

 and in others the duration of the 

 period during which the charge is 

 admitted to the cylinder, the 

 duration being extended and more 

 gas admitted as the power re- 

 quired increases. 



The consumption of coal gas in 

 small engines has been reduced to 

 as little as 24 cubic ft. per brake 

 horse-power hour; on Mond gas, 

 experiments have given a consump- 

 tion of 66 cubic ft. per brake 

 horse-power hour in an engine de- 

 veloping 750 h.p. ; while a full 

 load of 1,200 brake horse -power 

 has been developed with a con- 

 sumption of 102 cubic ft. of waste 



Gas Engine. 1,500 B.H.P. gas engine with rope-drive fly-wheel. Above, 

 seven 600 B.H.F. Cockerill-Westgarth gas-driven blowing engines 



peratures reached by the exploded Gas Helmet. Device for pro- 

 mixture in the engine cylinder of tecting troops against the effects 

 a gas engine it is necessary to cool of lethal or irritant gases dis- 

 the walls of the cylinder, and also charged at them by the enemy, 

 in large engines the piston, by cir- The gas helmet was developed by 

 culating water around or through the Allies during 1915, after the 

 them. In the coolinc water thus German use of clouds of chlorine 



4 ! 

 it 



Gas Helmet. 1. Box respirator used in the British army. The wearer inhales 

 through the tube from the box respirator and exhales through the little soft 

 rubber valve shown behind the tube in 2, as no gas can enter through the 

 valve. 3. Tin box containing the chemicals which absorb the gas as the air is 

 inhaled. 4. German, and 5, French gas masks 



