, 
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PUMPS 511 
Detailed illustrations of a compensating cylinder and its ram are 
sown in Fig. 819. 
The compensating cylinders contain water, which is in free communi- 
with an accumulator under air pressure. During the first half of 
a stroke of the pistons the excess work done by the steam is used to push 
rams into the compensating cylinders, thereby compressing the air in 
e accumulator, and during the second half of the stroke the work done 
the first half in compressing the air is restored, the rams being 
_ forced out, and, as they now slope the other way, they assist in driving 
forward the cross-head. 
The action of these compensating cylinders presents an interesting 
problem which is worthy of careful study by the student. Dimensions 
and further particulars relating to the engine just described * will now 
be given, so that the problem may be fully worked out. 
The dimensions are as fcllows. Diameters of steam cylinders, 14, 
22, and 38 inches. Diameter of water cylinder, 104 inches, Stroke of 
all pistons, 24 inches. Diameter of rams of compensating cylinders, 
5 inches. Distance between axes of trunnions, 29} inches. Distance 
between axes of gudgeons, 13 inches. The pressure in the compensating 
cylinders is 515 Ibs. per square inch. 
The indicator diagrams taken from the steam cylinders are given in 
Fig. 820, while Fig. 821 shows these diagrams corrected to show effective 
144 
\ Twp | HP, 
- —t— 120 
\ : oe ie \ 
Fa \ 
; 22 
ster Te 48 x 
re apa 24 a 
T+ +-- 
BSenanemachanesese FS FS F 8 § 
8 
Fig. 820. Fig. 821. 
es per square inch on the several pistons for one stroke. The 
dotted lines on the intermediate and low pressure diagrams in Fig. 821 
represent the pressures on the intermediate and low pressure pistons per 
* Kindly supplied by the Worthington Pump Co., London. 
