A. To act as a crusher of all cinders and prevent large cinders from passing out of the front end to the atmosphere.

38.  Q. What is the object of hollow staybolts?

A. To indicate when the staybolt is broken by the escape of steam through the small hole in the bolt.

39.  Q. What will cause the engine to tear holes in the fire?

A. Working hard or slipping when the dampers are open and the door closed, or too thin a fire.

40.  Q. Name the various adjustable appliances in the front end by which the draft may be regulated.

A. The exhaust nozzle, the diaphragm and the draft pipes or petticoat pipe.

41.  Q. What object is there in having the exhaust steam go through the stack?

A. To create a draft through the tubes and fire-box.

42.  Q. How does this affect the fire?

A. The exhaust steam escaping through the stack tends to empty the smoke-box of gases and produces a partial vacuum there, atmospheric pressure then forces air through the grates and tubes to refill the smoke-box, and in this way the draft through the fire is established and maintained.

43.  Q. Explain what adjustments can be made and the effect of each adjustment on the fire.

A. Larger or smaller nozzle tips cause less or greater draft on the fire; raising or lowering the draft pipes and diaphragm causes the engine to burn the fire more at the rear or front end of the fire-box; the size and position of the draft pipes increase the draft through the top or bottom flues; the latter adjustments should always be attempted before reducing the nozzle.

44.  Q. What does it indicate when the exhaust issues strongest from one side of the stack?

A. The stack, exhaust pipe or petticoat pipe are out of plumb.

45.  Q. What is the effect of leaky steam pipe joints inside the smoke-box?

A. The engine will not steam freely.

46.  Q. What causes “pull” on the fire-box door?

A. The partial vacuum in the front end; when excessive it indicates dampers closed, fire clinkered or insufficient opening for the admission of air under the fire.

47.  Q. If upon opening the fire-box door you discover there what is commonly called a red fire, what might be the cause?

A. The grates may have become clogged with ashes or clinkers so that sufficient air could not pass through them to the fire.

48.  Q. Is it not a waste of fuel to open the fire-box door to prevent pops from opening?  How can this be prevented more economically?

A. Yes.  This can usually be prevented by putting the heater into the tank, or putting on the injector, or by more careful firing.

49.  Q. Describe the principle upon which the injector works.