would be about 52
inches. This allows sufficient work to be put on the couplings, as
well as the shaft. To make solid crank shafts of this material, say of
19 inches diameter, the ingot would weigh 42 tons, the forging, when
completed, 17 tons, and the finished shaft 113/4 tons; so that you see
there is 25 tons wasted before any machining is done, and 51/4 tons
between the forging and finished shaft. This makes it very expensive
for solid shafts of large size, and it is found better to make what is
termed a _built shaft_; the cranks are a little heavier, and engine
framings necessarily a little wider, a matter comparatively of little
moment. I give you a rough drawing of the hydraulic hammer, or
strictly speaking a _press_, used by Messrs. Vickers in forging down
the ingots in shafts, guns, or other large work. This hammer can give
a squeeze of 3,000 tons. The steel seems to yield under it like tough
putty, and, unlike the steam hammer, there is no _jarring_ on the
material, and it is manipulated with the same ease as a small hammer
by hydraulics.

The tensile strength of steel used for shafts having increased from 24
to 30 tons, and in some cases 31 tons, considering that this was 2
tons above that specified, and that we were approaching what may be
termed _hard steel_, I proposed to the makers to test this material
beyond the usual tests, viz., tensile, extension, and cold bending
test. The latter, I considered, was much too easy for this fine
material, as a piece of fair iron will bend cold to a radius of 11/2
times its diameter or thickness, without fracture; and I proposed a
test more resembling the fatigue that a crank shaft has sometimes to
stand, and more worthy of this material; and in the event of its
standing this successfully, I would pass the material of 30 or 31 tons
tensile strength. Specimens of steel used in the shafts were cut off
different parts--crank pins and main bearings--(the shafts being built
shafts) and roughly planed to 11/2 inches square, and about 12 inches
long. They were laid on the block as shown, and a cast iron block,
fitted with a hammer head 1/2 ton weight, let suddenly fall 12 inches,
the block striking the bar with a blow of about 4 tons. The steel bar
was then turned upside down, and the blow repeated, reversing the
piece every time until fracture was observed, and the bar ultimately
broken. The results were that this steel stood 58 blows before showing
signs of fracture, and wa