-; TWO MARINE INSTALLATIONS OF PRODUCER GAS. 223 



The engines, as stated, are two-cycle. The explosive charge after 

 xpansion is completely blown out by a charge of air before the gas is 

 admitted to the cylinder. The admission of the latter is so timed that none 

 of the gas is lost through the exhaust ports. This gives a clean charge of 

 great power and efficiency, and without any possibility of back-firing. 

 Producer gas is particularly susceptible to back-firing, due to its slow burn- 

 ing, and in eliminating all back-firing in the type of engine described a 

 decided forward step has been made. The saving in heat losses and in 

 friction due to an explosion every revolution in each cylinder compensates 

 in large part for the loss in the air and gas compressors. The working 

 cylinders are of the ordinary construction but with exhaust ports extending 

 around the entire circumference of the cylinder. The exhaust gases pass 

 with the utmost freedom from the cylinders to a large water-jacketed 

 exhaust manifold. Differential pistons and cylinders are used as gas pumps. 

 The downward stroke of the piston induces direct suction on the producer 

 compressing same into a receiver on the upward stroke. This receiver 

 communicates with the cylinder heads and the air and gas valves controlling 

 their admission. Air only is drawn into and compressed in the base and 

 of a volume of about fifty per cent, in excess of both the working piston 

 displacement and the clearance in the combustion chamber. Both air and 

 gas are admitted to the cylinder through mechanically operated valves 

 and are so timed that such a proportion of the air as is intended for scaveng- 

 ing is first admitted, blowing out the burnt gases. The gas valve is 

 then opened, admitting gas direct to the cylinder and mixing with the 

 balance of the air from the base. 



The trials of the Mary A. Sharp were quite exhaustive and some interest- 

 ing data were secured. Tests for horse-power were made on June 23 and 

 24, each run being about eight hours. Indicator cards were taken every 

 half hour. 



The card reproduced as follows was taken at practically full power: — 



