Fig. 21.—Diagram of Atkinson Mechanism.
Fig. 22.—Section of Charon Motor.
Charon motor (Fig. 23).—M. Charon has attempted to obtain a prolonged combustion without the complicated devices resorted to by Atkinson. He has obtained the same result by means of a regulator controlling a double cam, one half of which actuates the admission valve and the other half an auxiliary valve, which opens into a tube forming a sort of reservoir, into which part of the explosive mixture passes during the compression. After the explosion this stored-up mixture is gradually allowed to re-enter the cylinder and prolong the combustion. By this means a considerable gain in economy is obtained, so that engines of this type only use about 500 litres of coal gas per horse-power hour. In appearance the motor much resembles the Otto motor, the crank-shaft and valve-shaft and valves being placed in the same relative positions. Although these motors are rather more expensive than others working with the Otto cycle, they are nevertheless widely used. This is due to the fact that if cost of coal gas in a particular district is high it is cheaper in the end to pay a higher price for an efficient engine than to buy a less expensive and at the same time less economical machine.
Fig. 23.—Charon Motor (latest type).
Roger motor.—This excellent little engine (Fig. 24) was especially designed for small workshops. The extreme simplicity of the working parts in no way lessens the efficiency, for the two horse-power only burns 700 litres of gas per horse-power hour. The simple design also keeps the cost of construction low, and the price averages about £30 per horse-power.
Fig. 24.—Roger Vertical Gas Engine.