the
eccentric rod would not effect it, but would widen the port opening at
one end of the travel and reduce it at the other. It should be equal at
both ends. Lead is controlled by the position of the eccentric on the
axle and it must be equal at both ends. Changing the length of the
eccentric rod from the proper one does not really affect the lead,
because no proper measurement can be made until lead is equal at both
ends. Therefore improper length of eccentric rods varies the port
opening at the beginning of the stroke of the piston at both ends.

42. Q. Why are eccentric rods made adjustable?

A. In order to change their length to make adjustment of the valve gear
not as easily made in other ways.

43. Q. Why is it necessary to keep the cylinders free from water?

A. In order to avoid damaging valves and cylinders, to insure perfect
lubrication and obtain the most efficient service from the locomotive.

44. Q. Where is the piston rod packing located? Where cylinder packing?

A. Piston rod packing is usually soft metallic rings located inside of a
gland at the back end of cylinder and around the rod. Cylinder packing
rings are usually cast iron, placed around the piston head and bearing
against the walls of the cylinder.

45. Q. How are metallic packing rings on piston rods and valve stems
held in place? What provisions are made for the uneven movements of the
rod?

A. The packing rings fit into a vibrating cup or cone located inside the
gland, being held therein by means of a spring as well as by the steam
pressure. Provision is made for uneven movement of the rod by making the
inside of the gland larger than the vibrating cup and using a ball-joint
ring between the vibrating cup and gland.

46. Q. While running under steam and there is a failure of part of the
locomotive which does not seem to prevent running at full speed, how
would you proceed?

A. Keep the locomotive running if in your judgment it is safe. Try to
ascertain what the injury is and be prepared at the next stop to do such
work as the case demands, being careful to make the stop at such a place
that the work can be done without interfering with the movements of main
line trains.

47. Q. If one side of a locomotive is disabled, what would you do in a
general way to make it possible to use steam on the other side?

A. Disconnect enough parts to allow for the turning of the wheels and
for reversing of the opposite side without moving the val