INTRODUCTION

ogies used on NSW railcars are one of two main types - fabricated or cast. Early bogies were of the fabricated type and as the metal industry casting techniques developed, cast bogie frames came into use. The first cast bogies to be deployed in NSW rail cars were the 2PA (PAA) type used on the Silver City Comet power cars. Cast bogies of the 2PE (PEA) and 2TE (NEA) types were introduced with the 900 Class in 1951, while the 2PG (PGA) and 2TG (NGA) types were introduced with the later members of the 620 Class and were built by A. E. Goodwin Limited. The 1100 Class of 1961 and the 1200 Class of 1972 also featured cast bogies from Bradford Kendall (Bradken). Fabricated bogies made a comeback with the Express Passenger Train (XPT) in 1983. Fabricated bogies have continued in use with the Endeavour/Xplorer and the Hunter Classes.

CONSTRUCTION

The fabricated type bogie has a frame that is constructed of various components (flat bar, plate, angle, channel, section, etc.) and are usually either welded or riveted (or a combination of both) while the cast type has a frame of steel that is cast as a single piece including both side frames, horn cheeks, and the main cross member or bolster. Bogies consist of a number of fixed and moving parts depending upon the construction type.

BOGIE COMPONENT DEFINITIONS

A Typical Cast Bogie Showing The Various Components
Drawing: Courtesy of the US Army

Air Bag - a rubber bag that is filled with pressurised air and acts like a spring. Air bag suspensions rely on an air supply from the train to maintain pressure.

Axle bearing - a bearing that is located in the axle box and supports one end of an axle. Axle bearings are either of the plain or roller type.

Axle Box - an enclosed box that supports the bearing for one end of an axle. The axle box is retained in the bogie horn cheeks and is sprung by either a coil spring or an equalising beam. In plain bearing applications, the box supports the bearing, the oil wick and the oil reservoir, while in roller bearing applications, the box supports the outer race of the bearing and is packed with grease.

Bolster - that portion of the suspension that supports the centre casting. The bolster is located transversely and is supported by the springs that are located between the bolster and the spring plank.

Brake block (or Brake shoe) - a consumable item consisting of either cast iron or composite material that is connected to the brake block mount and rubs on the wheel face to provide the braking force in the form of friction.

Brake block mount - a block that is attached to one end of the brake hanger and to which the brake block is fitted. The brake blocks are connected to the mount by pins to permit worn brake blocks to be changed easily.

Brake hanger - an arm that is fixed to the bogie frame at one end and to the brake block mount at the other. The brake rigging generally passes through about the centre of the brake hanger and enables the brakes applied to the wheels. A brake hanger is not used with disc brakes.

Brake rigging - a mechanical system of rods, arms and levers that enables the brakes on the bogie wheels to be applied from a brake piston and cylinder irrespective of the longitudinal orientation the bogie.

Centre casting - See King and Queen Casting.

Coil spring - a spring made by winding a section of spring steel rod in a helical pattern or shape around a circular core. A coil spring may be compressed or extended without permanent deformation.

Damping - a method of reducing excessive suspension movement. In bogies, this is usually achieved by an oil filled damper, a shock absorber or a stabiliser bar.

Equalised - a method of spreading the suspension movement across two or more axles.

Equalising beam - an elongated "U" shaped beam that joins the top of two adjacent axle boxes on the side of a bogie. The object of the beam is to equalise the forces caused by track irregularities nd suspension and vehicle movement.

Frame - the main part of the bogie that supports the moving parts. See also Sole bar.

Headstock - a transverse cross member located at each end of a bogie.

Horn cheek - an inverted "U" shaped component in which the axle box is able to move in a vertical plane. On fabricated bogies the horn cheek is a separate casting that is bolted or riveted to the frame. In cast bogies, the horn cheek forms an integral part of the cast frame.

Journal - the machined end of an axle. In plain bearing applications, the bearing is in contact with the top surface of the journal while an oil wick is in contact with the bottom surface to provide lubrication. In roller bearing applications, the inner race of the bearing is tightly fitted on the journal.

King and Queen Casting - a matched pair of "male" and "female" castings that connect the bogie to the carriage body and collectively known as the "Centre casting". These castings enable the bogie to rotate in a horizontal plane. The King Casting is mounted rigidly to carriage body while the Queen Casting is mounted on the transverse member (Bolster) in the centre of the bogie. A retaining pin is passed through the centre of both castings to stop the bogie from detaching from the carriage. Some later castings have a concave and convex shape that allows limited transverse movement as well.

Leaf spring - a simple form of spring built-up from a number of flat spring steel plates or various composite materials clamped together. Commonly used for the suspension in wheeled vehicles, it is also one of the oldest forms of springing, dating back to medieval times. Often called a "cart spring". See also Semi-elliptical spring.

Plain bearing - This type consists of a brass casting that mounts in the top of the axle box and features a curved surface on the bottom. This surface is lined with white metal as the bearing material. The white metal bearing surface rests on a journal machined on the end of the axle. Lubrication is obtained by a woollen wick that is partially submerged in an oil bath in the lower part of the axle box and is in contact with the underside of the journal. Oil is applied to the lower surface of the journal through the wick by capillary action and is distributed to the bearing surface by the rotation of the axle.

Primary suspension - the suspension component that provides the main stability for the bogie's moving parts.

Roller bearing - This type of bearing consists of two circular races. Between these two races is located a series of cylindrical rollers that permits the outer race to rotate effortlessly about the inner race. In rail applications the outer race is fixed in the axle box while the inner race is tightly fitted to a journal machined on the end of the axle. These bearings are packed with grease for lubrication. Roller bearings are either of the parallel or tapered type and provide reduced rolling friction and require less maintenance that plain bearings.

Secondary suspension - the suspension component that provides additional stability for the primary suspension.

Semi-elliptical spring - a spring made up of multiple leaf springs. This type of spring usually consists of three rows of leaf springs with each row consisting of two leaf springs, one facing upwards and one facing downwards, six in all, joined together. The ends of each pair of springs are joined by a single shaft making a single composite spring unit. From a side-on view the spring forms a semi-elliptical shape. A semi-elliptical spring is used in compression.

Sole bar - The side frames of the bogie.

Side bearer or radial bearer - a block located on either side of the bolster that is used to limit the transverse body roll of the vehicle. When the vehicle is stationary and level, the side bearers are clear of the vehicle body on either side (side bearer or radial clearance).

Spring - A component of the suspension system that cushions and absorbs shocks and bumps and to keep the vehicle level on turns and through track undulations. After the stress or pressure exerted by the flexing of the spring has been removed, the spring returns to its original state. The spring does this by first absorbing and then releasing a certain amount of energy.

Spring plank - a transverse plate that is suspended on either side of the bogie and is used to support the suspension springs.

Swing links - link that are attached to the bogie main centre cross member and to the spring plank. These links enable the spring plank to move in a transverse plane, that is, at right angles to the direction of travel.

Transom - a transverse cross member that is fitted across the ends of some fabricated bogies. Because of the nature of their construction, transoms are generally not used in cast bogies.

BOGIES CODES

Prior to the 1930's NSWGR bogies were described by a title that either related to the car under which they were found, e.g. Ashbury, Mann etc. or to the type of construction. This system was cumbersome as there were over 50 separate types, each with a number of sub-categories. In 1933 a new system was devised for locomotive hauled coaching stock. It involved one number and two letters, the number designating the number of axles, the first letter denoting the bearing size and the last letter distinguishing the bogie from other bogies with the same journal size. For example, the six-wheel bogies on the 72' 6" mainline cars introduced in 1913 were coded 3AD, 3AE, 3AF and 3AG to distinguish them from the earlier six-wheel types. The cast bogies under the Southern Aurora cars were coded 2BS. This same system was later applied to both goods rolling stock and railcar bogies. Concurrent with this coding the bogie types were allocated blocks of numbers. The bearing codes used for coaching stock bogies were, A, B, C and S and they related to the journal size as shown in the following table.

Rail motor bogies followed a similar scheme except that the first letter was either "P" for a power bogie or "T" for a trailer bogie. The second letter distinguishing the bogie from others of the same type. This applied to bogies used on the Silver City Comet vehicles and later classes. There was no coding to indicate variations in the journal bearing size. The earlier CPH Class and No.38 bogies being coded 2QG, 2QO, 2QR and 2SG.

A three-letter coding system was adopted in the early 1980's for new bogies. The first letter indicated the bearing size, the second letter indicated the bogie type while the third letter distinguished the bogie type within the group. With this scheme, the first letter on rail motor bogies was "P" for a power bogie and "N" for trailer bogies. Old bogies of the "2P" and "2T" types were retrospectively given codes in the new scheme, however, the bogie number plates were not changed. The following table shows both the old and new codes along with other details of all rail motor bogies.

NOTES

With the introduction of the Silver City Comet in 1937, power and trailer bogies were distinguished by different codes. However, the 2QG type bogies used on the CPH Class rail motors and No.38 did not distinguish between the two applications.

BOGIE TYPES

RAIL MOTOR BOGIE CROSS REFERENCE TABLE

REFERENCES

• "Rail Motors and XPTs" by David Cooke (Australian Railway Historical Society - 1984)
• "NSW Passenger Bogies" by David Cooke (Unpublished paper - 2001)
• Drawing by U.S. Army and Bruce Agland
• Photographs by Bruce Agland
• Wikipedia Bogie Article