STEAM LOCOMOTIVE ENGINEMAN’S. Manual - part 21

Chapter 11: - General Engine Questions and Answers

Defective joints can sometimes be observed by noting the
absence of soot and dull sheen caused by a steam blow
from the defective joint. To test for blast pipe defects, the
joints should be examined while the engine is being moved
slowly under steam with the brakes applied.

What should be done if a tube bursts?

Both injectors should be put on, to maintain the water high
enough to the boiler and reduce the steam pressure. Every
effort should be made to get the train to Box Flat. The fire
should be withdrawn and the engine stabled until repairs are
arranged.

What should be done if a lead pug fuses?

If the water is registering correctly in the gauge glasses, both
injectors should be put on to maintain high water leve l,
steam pressure should be reduced, the fire should be
withdrawn, assistance arranged if necessary and the engine
prepared for towing to Box Flat.

If the plugs fuse due to a shortage of water, i.e. it is not
registering in the gauge glass, the fire should immediately be
smothered by covering the top of the funnel, the smokebox
ash ejector steam cock should be turned on, and dampers
closed and the fire withdrawn as quickly as possible.

On no account should the injectors be put on to raise the
water leve l as this will damage the boiler, assistance should
be arranged and the engine prepared for towing.

In each case the fire door must be locked at the first
available opportunity.

What precautions should be taken to avoid the tubes
leaking?

A bight fire and an even firebox temperature should always
be maintained, the use of the blower should be avoided as
much as possible, and the ash pan slides should never be
open, or allowed to remain open except when dumping
ashes.

What attention to the tubes and smokebox, etc by
drivers and shed staff is necessary?

To get the best work out of the engine it is necessary to
frequently attend to the cleaning of the firebox, brick arches,
tubes, smokebox screen, and the blast pipe.

Chapter 11: - General Engine Questions and Answers

Many drivers and firemen do not realize the value of regular
attention to these parts.

Owing to this work being neglected it often happens that the
engine is condemned as being unsuitable, when such would
not be the case if the blast pipe, etc were properly looked
after.

The most suitable time to do this work is when the engine is
without fire and steam. The firebox should be examined by
going inside it.

All cinders and clinkers should be removed from the back
corners of the box, tube ends, and brick arch, the firebars
should be examined and, before coming out, the top half of
the tubes should be swept through and the lead plugs
inspected.

At the smokebox end, the lower tubes, spark arrester, and
blast pipe should be thoroughly cleaned; it is also very
important that the bottom of the smokebox should be kept
airtight by occasionally putting either a mixture of tar and
sand, or cement, around the steam and blast pipes.

If all these parts are regularly cleaned, the boilers will steam
well with a full sized nozzle, run faster, pull better on account
of the freer exhaust, and throw fewer sparks or cinders out of
the chimney.

All smokebox joints should be made thoroughly airtight. If
this portion o the work is ‘slummed’ the smokebox will
always draw air, with the result that the boiler will not steam
with a full sized nozzle, and ashes will take fire in the
smokebox and be thorn out of the chimney with the blast, the
partial vacuum in the smokebox will be destroyed and the
boiler hindered from steaming.

What are the relative positions of the crank pins on each
side of the engine?

The cranks on one side are set to 90º ahead of those on the
other side. Where the left hand crank is set ahead of the
right hand crank, it is described as being a left leading
engine.

Why are the cranks set as right angles?

The cranks are set at right angles so that when one piston is
at the end of its stroke full power is being exerted on the
other.

Chapter 11: - General Engine Questions and Answers

When the piston is at the end of its stroke, what is the
position of the valve?

The valve is in a position such that it allows a small opening
of the steam port that permits steam to pass from the steam
chest to the cylinder. This opening of the steam port is
called the lead of the valve.

What is the purpose of the lead?

The lead allows a flow of steam to enter the cylinder just as
the piston is finished its stroke, and acts as a cushion to the
advancing piston and also assists the piston when changing
its direction.

Is the amount of lead the same for all travels of the
valve?

On engines fitted with Walschaert’s valve gear the lead is
constant, but in the case of engines fitted with Stephenson’s
valve gear the lead increases as the valve travel is
shortened.

When the piston is at the end of its stroke, what is the
position of the crank?

The crank is on dead center. It will then be in a straight line
with the crosshead pin and driving wheel centre.

When one crank is dead centre, what will be the position
of the crank on the opposite side?

The crank on the opposite side is either on the top or bottom
quarter, according to whether the engine is left leading or
right leading.

With the left hand crank on the back dead centre, what
will be the position of the valve on both sides?

Assuming a left leading engine, the valve on the left side will
open the left back port to lead, irrespective of the position of
the reversing lever.

The valve on the right side will allow full opening of the front
port if the lever is placed in fore gear, full opening of he back
port if the lever is placed in back gear, and will close both
ports if the lever is placed out of gear, i.e. in the central
position.

Chapter 11: - General Engine Questions and Answers

What is the relationship between the piston and the
crank?

The piston is attached to the crank by means of the
crosshead and connecting rod. The motion of the piston is
imparted to the crank such that, whilst the piston moves
backwards and forwards in the cylinder in a horizontal path,
the crank rotates or moves in a circular path.

What is a slide valve?

The slide valve is a device that travels over a seat containing
ports and controls the admission of steam from the chest to
the cylinder and from cylinder to the exhaust.

What are the functions of a slide valve?

To admit live steam into each end of the cylinder in turn, to
cut off the supply of this steam to either end of the cylinder at
a certain point of the piston’s stroke, and to allow the used
steam at one end of the cylinder to commence passing to
the exhaust before live steam is admitted at the other end.

What is the purpose of the knuckle joints?

They provide flexibility to the rods, so that when running over
uneven portions of the road the rods are enabled to
accommodate them in this unevenness, thus avoiding a
breaking strain being thrown on to the rods.

Why are the wheels coupled together?

To enable the use of more than one pair of wheels in the
propulsion of the engine, and to distribute the weight
required for the adhesion of the engine in such a manner
that permissible axle loads will not exceeded.

What is meant by the adhesion of the engine?

The adhesion of the engine is the frictional grip of the
coupled wheels on the rails, and is governed by the weight
on these wheels and the nature of the surface of the wheel
tread and rail.

If an engine had insufficient adhesion, what would be
the result?

The engine wheels would slip when power was applied, as
the power used to rotate the wheels would exceed the
frictional resistance of the adhesion weight.

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