Man's physical universe

xanabras

310 FORMS OF ENERGY

He was impressed with the very large amount of steam required to

operate it. Greater efficiency required that the cyHnder be kept as hot

as the steam, and yet the cyHnder must be cooled as much as possible

to obtain a good vacuum. While taking a walk by himself one Sunday,

the solution suddenly occurred to him. He rushed to his workshop and

constructed a steam engine with the condenser separate from the

cylinder. The piston was forced up by introducing air into the cylinder

and was forced down again by removing the air by pumping the air out

of the cylinder by means of the steam-condenser. After ten years of

work on the development of his steam engine, James Watt said, "Today,

I entered the thirty-fifth year of my life, and I think I have hardly

yet done thirty-five pence worth of good in the world; but I cannot

help it." Finally Watt found a wealthy backer, Matthew Boulton;

but manufacturing difficulties seemed to be almost insurmountable.

There were no machine-builders and tools. Finally, the great ironfounder

Wilkinson created a sensation by producing a cylinder that

was accurate to a quarter of an inch.

Watt's steam engine became a commercial success only after it was

Fig. 104. Francis runner for a hy

draulic turbine. (Courtesy of the Allis

Chalmers Manufacturing Company.)

applied to pump water from the deep coal .mines of Cornwall.

The next advance in steam engines

was to use the expansive

force of the steam on one side of

the piston and the partial vacuum

produced by the steam in the

condenser, on the other side of

the piston. By thus avoiding the

back pressure of the atmosphere,

more power is developed. In

reciprocating steam engines the

steam acts alternately on either

side of the piston. In some expansion

engines the steam is

allowed

to expand into a second,

third, or fourth cylinder, each

larger than the preceding. The

piston is fastened by means of

a connecting-rod to a wheel or

shaft, which is thus caused to

rotate as the piston moves back

and forth in the cylinder. Attached to the wheel or shaft is an eccentric,

which cuts off the steam at the proper time. The large flywheel gives

enough inertia to the system to maintain a uniform motion when

steam is not pushing on the piston.

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