178 AUTOBIOGRjiPHY OF JOHN FRITZ
better than one of wrought iron as they used to be forged. In the first place, by the use of good iron, intelUgently melted, in an air furnace, you can get a tensile strength of 32,000 pounds per square inch, and with a proper sink-head you can get a practicaUy soUd casting, and I nflght add, homogeneous and close in the grain; while, as I have already stated, the forged shaft of that day would in aU probabiUty be unsound in the center and coarse-grained, and its tensfle strength Uttle greater, if any, than cast iron.
I shaU now refer to a single experience I had, beUeving that a brief description givuig the reasons why I used wrought-iron and steel shafts in place of cast iron, which had for over forty years served me weU, wiU be both in¬ teresting and instructive.
The reason for using wrought iron and steel in place of cast iron was that I wanted a three-throw crank for a three-cyUnder engine, and I had to use a built-up crank, as at that time I could not get any other in this country. As the stroke of the engine was rather short, it reduced the distance from center of shaft to center of crank pin, so that the shafts had to be kept down to the smaUest possible size, in order to get sufficient metal between the holes to give the cranks the required strength between the shaft and the crank pin.
As steel at that time was more expensive than wrought iron, I concluded to make the main shaft and first crank pin out of steel, and the others out of wrought iron. Not having at that time any overflow of confidence in either forged-iron or steel shafts, and being anxious to get the best that could possibly be gotten, I consulted a friend, who was using steel shafts, and asked him where was the best place in this country to get them. He kindly advised me where to go for the steel shaft and crank pin, and I took his advice and ordered them. The iron shafts and pins were ordered