inches.

Q. What do you mean by average pressure?
A. If the pressure on boiler is 60 pounds, and the engine is
cutting off at 1/2 stroke, the pressure for the full stroke would
be 50 pounds.

Q. Why do you say less 5 pounds?
A. To allow for friction and condensation.

Q. What is the power of a 7 x 10 engine, running 200
revolutions, cutting off at 1/2 stroke with 60 pounds steam?
A. 7 x 7 = 49 x .7854 = 38.4846. The average pressure of
60 pounds would be 50 pounds less 5 = 45 pounds; 38-4846 x
45 = 1731.8070 x .333 1/3, (the number of feet the piston
travels per minute) 577,269.0000 by 33,000=17 1/2 horse
power.

Q. What is a high pressure engine?
A. It is an engine using steam at a high pressure and
exhausting into the open air.

Q. What is a low pressure engine?
A. It is one using steam at a low pressure and exhausting
into a condenser, producing a vacuum, the piston being under
steam pressure on one side and vacuum on the other.

Q. What class of engines are farm engines?
A. They are high pressure.

Q. Why?
A. They are less complicated and less expensive.

Q. What is the most economical pressure to carry on high
pressure engine?
A. From 90 to 110 pounds.

Q. Why is high pressure more economical than low
pressure?
A. Because the loss is greater in low pressure owing to the
atmospheric pressure. With 45 pounds steam the pressure
from the atmosphere is 15 pounds, or 1/3, leaving only 30
pounds of effective power; while with 90 pounds the
atmospheric pressure is only 1-6 of the boiler pressure.

Q. Does it require any more fuel to carry I00 pounds than it
does to carry 60 pounds?
A. It don't require quite as much.

Q. If that is the case why not increase the pressure beyond
this and save more fuel?
A. Because we would soon pass the point of safety in a
boiler, and the result would be the loss of life and property.

Q. What do you consider a safe working pressure on a
boiler?
A. That depends entirely on its diameter. While a boiler of
30 inches in diameter 3/8 inch iron would carry I40 pounds, a
boiler of the same thickness 80 inches in diameter would have
a safe working pressure of only 50 pounds, which shows that
the safe working pressure decreases very rapidly as we increase
the diameter of boiler. This is the safe working pressure for
single riveted boilers of this diameter. To find the safe
working pressure of a double riveted boiler of same diameter
multiply th