STEAM LOCOMOTIVE ENGINEMAN’S. Manual - part 22

Chapter 11: - General Engine Questions and Answers

What natural factor will reduce the adhesion of the
wheels?

A wet or greasy rail, which lessens the friction between the
wheel and the rail.

How is slipping of the wheels overcome?

By the use of sand and judicious handling on the part of the
Driver.

What supports the weight of the boiler?

The frames support the weight of the boiler and also carry
the cylinders and valve gear. They absorb through the
springs many of the shocks incidental to running.

What is the general arrangement of the frames?

The PB15 locomotive and “Kilrie” are fitted with plate frames.
These consist of two main plates extending from the front
buffer beams or headstock to the rear buffer beam.

These plates are spaced and rigidly braced by means of the
smokebox saddle at the front end and the drag box at the
rear end, and also by means of the cross stays attached at
various points in between. Where necessary, the plates are
cut away to clear the axle boxes. Etc.

How is the boiler supported on the engine frames?

At the front end of the smokebox, which is riveted to the
boiler, is rightly bolted to the saddle casting, preventing any
movement of the boiler at this end.

The usual method of supporting the remainder of the boiler
is by means of expansion brackets or angles, attached to
either side of the outer firebox shell.

These brackets rest on other brackets riveted to the engine
frames, and the brackets are bolted together in a manner
which will permit the trailing end of the boiler to freely move
backwards or forwards as the boiler expands and contracts.

A clip over the top expansion bracket is attached to the
frame brackets, so as to prevent the boiler from lifting in the
case of derailments, etc.

Chapter 11: - General Engine Questions and Answers

How is the weight of the engine supported?

By means of bogies and wheel springing.

What class of springs is used on the engine?

The springs used on the Queensland locomotives are
laminated springs. They consist of a series of leaves or
plates of equal width, the length of each plate progressively
decreasing. The leaves are bound together at the centre by
means of a buckle.

The springs are either flat or cambered (i.e. slightly curved),
and are deeper or thicker at the middle than at the ends. As
the force is exerted on the springs they deflect or tend to
flatten out and absorb much of the shock that would
otherwise have to be borne by the engine.

How are the springs fitted, (a) in the case of under slung
or ordinary springing, (b) in the case of overhead
springing?

(a)

The springs are hung on T-hangers situated
under the engine axle boxes and the ends of
each spring are attached, by means of adjusting
screws, to pedestals fastened to the frame. The
adjusting screws permit each spring to be
adjusted to take the weight it is designed to
carry. This system of suspension is generally
referred to as non-compensated or independent
springing.

Where the springing is compensated, the springs
in each compensated group are inter connected
by means of pivoted compensating beams, the
pivots being attached to the frame between each
two adjacent springs. The outer ends of the
springs at either end of the group are attached to
pedestals fastened to the frame.

(b)

With overhead springing, the springs are situated
above the engine axle boxes, the load being
transmitted from the box to the spring (and vice
versa) by means of a strut or similar
arrangement.

The springs are compensated in a similar
manner to that described in (a).

Chapter 11: - General Engine Questions and Answers

What is the purpose of the compensating beams?

To connect the springs in such a way that, in the event of
any unevenness of the road that might cause a heavy shock
to the engine, the load will be distributed over more than one
spring and the whole of the load due to the shock will not be
thrown on to any one spring.

In some cases, the compensating beams are also designed
to redistribute the spring weight.

How are the cylinders attached to the engine?

One engines fitted with plate frames, each cylinder and its
steam chest from one unit, which is secured to the frame by
means of bolts.

What is the steam chest?

The steam chest is the upper chamber of the cylinder unit in
which the valve works, and in which are situated the
admission and exhaust ports to and from the cylinder.

What is the cylinder?

The cylinder is the chamber below the steam chest in which
the piston works to and fro, thus causing the wheels to
rotate.

What is the piston?

The piston consists of a circular head attached to the piston
rod and secured to it by means of a nut. It moves freely in
the cylinder, but is made steam tight by rings placed in
grooves around its periphery.

To what is the piston rod attached?

The piston rod is attached to the crosshead, to which it is
held secure by means of the crosshead cotter.

What is the purpose of the crosshead?

It forms the point of connection between the piston and the
connecting rod at which the reciprocating motion of the
piston transmits power through the connecting rod and
causes the rotation of the wheels.

Chapter 11: - General Engine Questions and Answers

What prevents the steam in the cylinder passing out
along the piston rod?

The provision of a bushing and stuffing box, which is packed
with a metallic packing kept in place by a spring and gland.
Studs to the back cylinder cover secure the gland.

What supports the crosshead as it moves to and fro?

The guide bars.

How are the guide bars fitted?

They are attached to the back cylinder cover at one end and
to the motion – or spectacle – plate at the other end, and are
held in position by means of studs and / or bolts.

What is the crosshead?

It is a block of metal, which provides the connection between
the piston rod and the connecting rod. At one end is a boss
into which the end of the piston rod is fitted, and the body of
the crosshead is hollowed out to receive the small end of the
connecting rod, which is secured to the crosshead by means
of the gudgeon pin. The crosshead is also fitted with shoes,
which bear on the guide bars.

Which guide bar is subject to the greatest string?

The top bar when running forward with steam applied, the
bottom bar when running in back gear with steam applied, or
when running forward without steam.

What is the purpose of the guide bars?

To support the crosshead and to keep both it and the piston
in line with the axis of the cylinder.

If the guide bars are not kept properly closed, what will
be the effect?

As the crosshead works to and fro it will not keep a true line;
thus it will cause wear on the piston gland and tend to wear
and packing, causing a steam blow from the cylinder. It will
also cause the shoes to slap the bars hard when the engine
is shut off and when the crank is passing the dead centres.

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