length and the brasses do not close together or are too loose in the
strap lengthwise of the rod.

103. Q. When should lost motion between engine and tender be taken up?

A. When the lost motion becomes so great as to endanger the breaking of
connections.

104. Q. How do you proceed to pack a driving box equipped with a grease
cellar?

A. Remove the filling plate on the inside of the cellar. Pull down the
indicators and follower plates, insert the grease between the follower
plate and perforated plate; when full, replace the filling plate on the
inside of the cellar and allow the spring and follower plate to force
the grease through the perforated plate to the journal.

105. Q. Please explain the principle on which an injector works.

A. With a lifting injector the steam valve is opened a small amount to
furnish steam for the priming or starting jet. This forces the air in
the body of the injector and top end of suction pipe out through the
overflow valve, producing a partial vacuum in the body of the injector.
Atmospheric pressure in the tank then forces the water into the injector
body. When it begins to come out through the overflow, a further
movement of the steam valve opens the forcing valve wide, so a full
supply of steam strikes the water at a high velocity and at the same
time condensing. This action of the steam gives the water sufficient
velocity to overcome the boiler pressure and pass into the boiler.