Q. What is "lap?" A. It is the distance the valve overlaps the steam ports when in mid position.
Q. What is lap for?
A. In order that the steam may be worked expansively.
Q. When does expansion occur in a cylinder? A. During the time between which the port closes and the point at which the exhaust opens.
Q. What would be the effect on an engine if the exhaust
opened too soon?
A. It would greatly lessen the power of the engine.
Q. What effect would too much lead have. A. It would also weaken the engine, as the steam would enter before the piston had reached the end of the stroke, and would tend to prevent it passing the center.
Q. What is the stroke of an engine?
A. It is the distance the piston travels in the cylinder.
Q. How do you find the speed of a piston per minute? A. Double the stroke and multiply it by the number of revolutions a minuet. Thus an engine with a 12 inch stroke would travel 24 inches, or 2 feet, at a revolution. If it made 200 revolutions a minute, the travel of piston would be 400 feet a minute.
Q. What is considered a horse power as applied to an
engine?
A. It is power sufficient to lift 33,000 pounds one foot high
in one minute.
Q. What is the indicated horse power of an engine? A. It is the actual work done by the steam in the cylinder as shown by an indicator.
Q. What is the actual horse power? A. It is the power actually given off by the driving belt and pulley.