CATALOG OF THE MECHANICAL COLLECTIONS Igl 



inch thick. The pistons are 5 inches in diameter and 4 inches long. 

 They are slightly tapered from the middle, where they are 0.005 inch 

 smaller than the cylinder bore toward the outer end, where they were 

 0.0075 inch smaller than the bore. The outer piston ring was 0.0035 

 inch narrower than its groove, the second one 0.003 inch, the third 

 0.0025 inch, and the inner one 0.002 inch narrower than its groove. 

 The rings were bored one-sixteenth inch off center with the exterior 

 surface and had one-eighth inch diameter of spring. They were of 

 the lap joint type, with the sides of the laps carefully fitted and only 

 one sixty-fourth inch clearance at the ends of the laps to allow for 

 thermal expansion. As no grinding facilities were available in 

 Washington, the cylinders were carefully bored smooth and free 

 from taper, and the pistons were worn in to a perfect fit by running 

 them in by a belt for 24 hours with a copious oil supply. 



The main connecting rod was seven-eighths inch in diameter and 

 solid, while the other four were of the same diameter but with a %- 

 inch hole in them. The gudgeon pins in the pistons were hollow 

 steel tubes, seven-eighths inch in diameter and case hardened, and 

 were oiled entirely by oil thrown off by centrifugal force from the 

 crankpin bearing, the oil running along the connecting rods and 

 through suitable holes in the heads into oil grooves in the bronze 

 bushings in these heads. 



The arrangement of connecting rods consists of a main connect- 

 ing rod formed of a steel forging terminating in a sleeve that 

 encircles the crankpin and is provided with a bronze bushing for 

 giving a proper bearing surface between the connecting rod and the 

 crankpin, both the steel sleeve and the bronze liner being split, 

 at right angles to each other, to permit assembling them on the 

 crankpin. This steel sleeve, the upper half of which is formed in- 

 tegral with the main connecting rod, is rounded off to a true circle 

 on its exterior circumference except at the point where the rod 

 joins it. The other four connecting rods terminating in bronze 

 shoes are then made to bear on the exterior of this sleeve, being 

 held in contact therew^ith, and permitted to have a sliding motion 

 thereon sufficient to take care of the variation in angidarity of the 

 connecting rods, by means of cone nuts, which are screw-threaded 

 to the sleeve and locked thereto by means of jam nuts. The main 

 connecting rod acts in the same way as in the ordinary case where 

 each cylinder has its separate crankpin. The other four connecting 

 rods deliver their effort to the crankpin through the sleeve in which 

 the first connecting rod terminates, and they, therefore, do not receive 

 any of the rubbing effect due to the rotation of the crankpin except 

 that of slipping a very short distance over the circumference of the 

 sleeve during each revolution, the amount of slipping depending on 

 the angularity of the connecting rod. 



