AMERICAN STEAM ENGINEERING 285 



should in no case exceed 150 pounds per square inch. As 

 regards crank pins and crosshead pins, American practice 

 might with much advantage be altered, and the pressure 

 per square inch of projected area decreased. The standard 

 Enghsh mill engine practice perhaps goes to extremes, but 

 it is preferable to the American practice. As an example 

 we will consider a cross compound vertical engine designed 

 to w^ork at a steam pressure of 150 pounds per square inch 

 running 80 revolutions per minute. The crosshead pin 

 in British practice would be 7 by 10 inches and the crank 

 pin 9 by 11 inches. The corresponding dimensions of an 

 Allis engine to do the same work and with same dimensions 

 as regards cylinders, stroke, speed and steam pressure would 

 be : — crosshead pin 6^| by 6 J inches; crank pin 6^ by 6^ inches. 

 That this is large enough to avoid heating is undoubted, 

 but if knocking is to be prevented the liners of these smaller 

 pins will require taking up much of tener than would be the case 

 with the British engine. Taking another example, say an 

 engine designed to develop 800 indicated horsepower and 

 able to develop 1,000 horsepower continuously at a pressure of 

 150 pounds steam at 90 revolutions per minute; this would 

 have cylinders 22 by 44 inches and 42 inch stroke, crosshead 

 pins of 6i inches diameter by 7 inches long, and crank pins 

 of 7 inches diameter by 7 inches length would give com- 

 plete satisfaction. The standard American practice for such 

 an engine would be crank and crosshead pins both 6 by 6 

 inches. Or, in other words, and in round figures, the pro- 

 jected area of the crosshead pin should be 20 per cent greater 

 and that of the crank pin nearly 30 per cent greater than 

 standard American practice. 



The outside finish of continental engines, particularly, 

 is much better than is usual with Americans. Nearly all 

 bright parts are polished. The rim of the fly wheel is polished. 

 Burnished or Russian steel sheathing is used, and all the 

 hand rails are bright. In connection with German engines 

 it is interesting to notice that, owing probably to the prevailing 

 depression in Germany which forces them to sell at any price, 

 they have secured orders for steam engines in the heart of 

 Lancashire at prices lower than either British or American 



