THE ENGINE PROPER 



bore throughout; and the "tandem," having one cylinder 

 behind the other, with both pistons on the same rod. The 

 latter has proved to be the type best adapted for use on 

 farm and traction engines. 



The Woolf Compound. The cut Fig. 24 shows 

 a sectional view of the "Woolf "-tandem-compound cyl- 

 inder used on "Case" compound engines. Its operation is 

 as follows: The steam from the boiler enters the valve 

 (which is hollow), through the large opening at the crank 

 end, passes through the valve and out at the narrow open- 

 ing near the head end, which, as the valve moves, alter- 

 nately comes opposite the two ports leading to the ends 

 of the small or high pressure cylinder. The valve in 

 moving also alternately uncovers these ports, allowing the 

 high-pressure cylinder to exhaust into the steam chest. 

 The low-pres- 

 sure cylinder 

 receives the 

 steam from 

 the steam 

 chest, and ex- 

 h a u s t s 

 (through the 

 heater) into 



the stack, in exactly the same manner as a simple engine. 

 The valve is "balanced" because high-pressure steam is 

 under and tending to lift it, while the low-pressure steam 



r *! 



I 



J 



FIG. 25. FACE OF COMPOUNDED VALVE. 



