The position of the side crank engine upon the boiler allows of having
the Rear Gear traction attachment.
The Engine frame, guides for cross-head, cylinder, steam chest,
saddles, brackets and both pillow block bearings for crank shaft are
cast in one piece and bolted to the boiler.
The frame is cast oval, and cross-head guides are of the locomotive
style.
The Engine is furnished with a Friction Clutch, a specially designed
Reversing Gear, Governor, Marsh steam pump, Injector; and is mounted
upon an open bottom fire box locomotive boiler, with ash pan under fire
box and dome at rear end.
The boiler is mounted upon the traction wheels by brackets bolted to
the rear end, which contain the boxes for the main axle and cross shaft.
The traction wheels are of the cast iron rim type, with spokes cast in
both rim and hub.
The steering wheel and band wheel are on opposite sides of boiler, and
both engine and boiler are supplied with all necessary fittings.
[Illustration: A. W. Stevens Traction Engine.]
Q. How would you stop foaming?
A. Close the throttle long enough to show the true level of water. If
the level of the water is sufficiently high, feeding and blowing off
will usually correct the difficulty.
Q. What would you do if you discovered the water gone from sight in the
water glass?
A. Pull the fire or cover it over with dry ashes, and allow the boiler
to cool off as quickly as possible; and would not open or close any of
the steam outlets.
Q, What is a traction engine?
A. A traction engine is an engine the power of which is transmitted to
the driving or ground wheels by a combination of gearing.
Q. What is an exhaust pipe?
A. The pipe through which the exhaust steam escapes from cylinder to
smoke stack.
Q. What is the feed pipe?
A. The pipe through which the feed water passes from pump or injector
to the boiler.
Q. What is the steam pipe?
A. The pipe through which steam is taken from the dome to the steam
chest.
Q. What is a pet cock?
A. A small cock used in check valves, pipes and places where draining
off water is necessary to prevent freezing.
Q. What is clearance in a steam cylinder?
A. It is the space between the cylinder head and piston head when the
latter is at end of the stroke.
Q. What is “cushion” in a steam cylinder?
A. Cushion is the compression of steam let in through the lead of the
valve in the clearance of the cylinder, and is for the purpose of
catching the weight of the piston and rod, cross-head and connecting
rod when the engine reaches the end of each stroke. It also keeps the
engine from pounding.
Q. How much water would you blow off at any one time while running?
A. Never blow off more than one gauge.
Q. What are your general views regarding boiler explosions?
A. The greatest causes are from ignorance, carelessness and neglect.
Q. What precaution should you take if necessary to stop with a heavy
fire in the furnace?
A. Close the draught door, and put the injector or pump at work.
Q. What is the proper height to carry water in the boiler?
A. About 2½ inches above top row of flues.
Q. At what pressure should you blow off a boiler?
A. At a pressure not to exceed ten pounds.
Q. If you wished to increase the power of an engine what would you do?
A. Increase its speed or get higher steam pressure.
Q. How do you find the horse-power of an engine?
A. Multiply the speed of piston travel in feet per minute by the total
effective pressure upon the piston in pounds, and divide the product by
33,000.
Q. What is meant by “brass bound”?
A. Brass bound means that the half brasses touch each other and cannot
be driven up any closer by the key.
Q. How would you remedy a brass bound box on crank-pin or wrist-pin?
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?
A. An imperfect fitting one.
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.
Q. How is a steam engine rated?
A. By amount of horse-power developed.
Q. What is a foot-pound?
A. One pound of force exerted through one foot of space.
Q. How many foot-pounds are required to lift 100 pounds one foot?
A. One hundred.
Q. How many foot-pounds required to lift one pound 100 feet?
A. One hundred.
Q. To lift 110 pounds through 300 feet how many foot-pounds required?
A. 300 × 110 = 33,000 foot-pounds.
Q. Would that equal one horse-power?
A. Yes, if done in one minute.
Q. Suppose it took two minutes?
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.
Q. What is a single acting engine?
A. An engine in which the steam acts on one side of the piston only.
Q. How do you find the “piston’s speed”?
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. Why do you divide by 12?
A. To reduce the inches to feet.
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.
Q. What is the horse-power developed by an engine, say 12 × 24 inch,
running 125 revolutions per minute, with 40 pounds mean effective
pressure?
A. Area = 12 × 12 × .7854 = 113.0976 sq. ins.
Piston speed = 24 × 2 × 125 ÷ 12 = 500 feet per minute.