A. Take off the boxes and file off the top and bottom edges, being careful not to take off too much.
Q. Does a perfect fitting or an imperfect fitting valve have the most friction?
Q. How would you refit an imperfect fitting or leaky valve?
A. It should be re-faced on a planer or filed and scraped until it fits seat perfectly tight.
A. One pound of force exerted through one foot of space.
Q. How many foot-pounds are required to lift 100 pounds one foot?
Q. How many foot-pounds required to lift one pound 100 feet?
Q. To lift 110 pounds through 300 feet how many foot-pounds required?
A. Then there would be only half a horse-power, or 33,000 ÷ 2 = 16,500 foot-pounds per minute.
Q. Is it correct to say “horse-power per minute” or “horse-power per hour”?
A. No. When an engine is working at the rate of 10 horse-power, it is doing 10 horse-power all the time. It is an error to assume that such an engine is doing 10 horse-power per minute, and 10 × 60 equals 600 horse-power per hour. When it is said that an engine uses 20 pounds of steam per horse-power per hour, it is meant that this amount of steam is used per hour for each horse-power developed.
Q. How is the foot-pounds of work done by a steam engine, found?
A. Multiply the average pressure per square inch during the stroke by the number of square inches in the piston, and by the number of feet through which the piston has moved.
Q. What do you understand by the “mean effective pressure”?
A. The mean pressure is the average pressure pushing the piston through the stroke, which is about one-third the pressure in the boiler. There is generally some back pressure working against it, therefore the “effective” pressure is only the difference between the two. It can only be determined accurately by measurements from an indicator diagram.
A. An engine in which the steam acts on one side of the piston only.
A. On double acting engines, multiply the stroke in inches by two and by the number of revolutions per minute and divide by 12.
Q. Why multiply the stroke in inches by 2?
A. Because in double acting engines there are two working strokes to each revolution.
Q. How is the “piston’s speed” of a single acting engine found?
A. Multiply the stroke in inches by the revolutions per minute and divide by 12.