l go through this opening and oil
the piston rod and cylinder packing. If not possible to block the valve
properly, cover the ports and oil the cylinder through the indicator
plug openings or relief plug holes. If not possible to do this, slack
off the bolts on the front cylinder head, wedge the head open so oil can
be introduced. In some cases it may be necessary to take the head off;
that however, allows dust and grit to enter the cylinder.

67. Q. What is the by-pass valve, and what is its duty?

A. By-pass valves are connected to the steam port leading to the
cylinder. Its duty is to open when the engine is drifting with steam
shut off, and close when working steam, to allow air to pass back and
forth from opposite sides of the moving piston.

68. Q. What is a vacuum relief valve? What a cylinder relief valve?

A. A vacuum relief valve is usually located on the steam chest or the
live steam passage to the chest and opens when steam is shut off and
engine drifting, allowing atmospheric pressure to pass into the steam
chest, closing when working steam. A cylinder relief valve is a pop
valve screwed into the cylinder head and set at high enough pressure so
it does not open in ordinary service, but will open to allow water to
pass out when the exhaust port is closed by valves; or on compound
engines when the pressure in the low-pressure cylinder gets too high.

69. Q. What would be considered a bad engine or tender truck wheel?

A. One loose on axle; having bad flat spots; very sharp flanges; bad
sand spots; cracks shelled out; or other defect that would make the
wheel unsafe.

70. Q. What should be done if a tender truck wheel or axle should break?

A. Would place a piece of timber or rail across the tender, jack up the
corner of the truck that is disabled chain it to the timber and fasten
the timber at the other end to hold it so it would carry the disabled
truck. If it is possible to slide the wheel or truck, place a tie across
the rail and keep the wheel from turning, then slide it to a siding.

71. Q. What should be done if an engine truck wheel or axle should
break?

A. Would block between the engine frame and truck frame over the good
wheel on disabled side, swing the disabled corner of the truck to the
engine frame with a chain. Look out when crossing frogs that disabled
truck does not leave the track. With a broken flange, would block the
wheel to prevent its turning and skid it to a siding.

72. Q.