16. Q. How does 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.