Tensile     Elong.              Fractured    Broke    Fall
Tons.      in. 5”     Bend.      Blows.      Blows.     In. 
G =  30.9     271/2  p. c.    Good       59         66       12
H =  29.3     30   p. c.    Good       66         90       12
I =  28.9     28.9 p. c.    Good       53         68       12

I think all of the above tests show that this material, when carefully made and treated with sufficient mechanical work on forging down from the ingot, is suitable up to 34 tons for crank shafts; how much higher it would be desirable to go is a question of superior excellence in material and manufacture resting with the makers.  I would, however, remark that no allowance has been made by the Board of Trade or Lloyds for the excellence of this material above that of iron.  I was interested to know how the material in the best iron shafts would stand this fatigue test compared with steel, and had some specimens of same dimensions cut out of iron shafts.  The following are the results:  Best iron, three good qualities, rolled into flat bars, cut and made into 41/2 cwt. blooms.

  J = 18.6 24.3 p. c.  Good 17 18 12

Made of best double rolled scrap, 41/2 cwt. blooms.

  K = 22 321/2 p. c.  Good 21 32 12

You will see from these results that steel stood this fatigue test, Vickers’ 73 per cent. and Steel Co.’s 68 per cent., better than iron of the best quality for crank shafts; and I am of opinion that so long as we use such material as these for crank shafts, along with the present rules, and give ample bearing surface, there will be few broken shafts to record.

I omitted to mention that built shafts, both of steel and iron, of large diameter, are now in general use, and with the excellent machines, and under special mechanics, are built up of five separate pieces in such a rigid manner that they possess all the solidity necessary for a crank shaft.  The forgings of iron and steel being much smaller are capable of more careful treatment in the process of manufacture.  These shafts, for large mail steamers, when coupled up, are 35 feet long, and weigh 45 tons.  They require to be carefully coupled, some makers finishing the bearings in the lathe, others depend on the excellence of their work in each piece, and finish each complete.  To insure the correct centering of these large shafts, I have had 6 in. dia. recesses 3/4 inch deep turned out of each coupling to one gauge and made to fit one disk.  Duplicate disks are then fitted in each coupling, and the centering is preserved, and should a spare piece be ever required, there is no trouble to couple correctly on board the steamer.