es the wide fire-box type of boiler differ from the
ordinary boiler, and what are its advantages?

A. The wide fire-box type of boiler is built so the fire-box is above
the frame and extends out over the driving wheels. The advantages of
this are to obtain a larger grate area in the same length of fire-box
and to give a slower rate of combustion per square foot of grate
surface. The deep fire-box is limited in width to the distance between
the frames, while the shallow fire-box sets on top of the frames and
between the driving wheels.

17. Q. Why have two fire-box doors been placed in the large type of
locomotive boilers?

A. For convenience of the fireman on account of the greater width of the
fire-box, so that coal can easily be distributed to all parts of the
fire-box.

18. Q. Describe a locomotive fire-box.

A. The modern form is a rectangular shaped structure located at the back
end of the boiler. It has a door and is composed of two side sheets, a
crown sheet, a back sheet and a flue sheet from which the flues extend
to the smoke-box at the other end of the boiler.

19. Q. To what strains is a fire-box subjected?

A. To crushing strains and to those of unequal contraction and
expansion.

20. Q. How are the sheets of a fire-box supported?

A. They are supported by staybolts screwed through the inside and
outside sheets with their ends riveted over.

21. Q. In what manner is a crown sheet supported?

A. By crown bars or radial staybolts.

22. Q. What are the bad features about crown bars?

A. They are hard to keep clean and frequently cause crown sheets to
become mud burned.

23. Q. What are the advantages of radial stayed crown sheets?

A. They are easier to keep clean and cheaper to repair.

24. Q. How are the inside and outside sheets of a fire-box secured at
the bottom?

A. They are riveted to a wrought iron ring called a mud-ring.

25. Q. Describe the ash-pan and its use.

A. It is a receptacle secured to the fire-box and usually provided with
dampers to regulate the flow of air to the fire. It collects the ashes
that drop from the fire-box and prevents them from setting fire to
bridges or other property along the track. Engine-men must know that
ash-pan slide and hopper bottoms are closed before leaving enginehouse.

26. Q. What is a "wagon-top" boiler?

A. It is a boiler that has the fire-box end made larger than the
cylindrical part to provide more steam space.

27. Q. Why are bo