The Rail Motor Society
 
42-FOOT CPH RAIL MOTOR
POWER UNIT

The 42-foot rail motor emerged from plans by the New South Wales Railways to design
a self-propelled passenger carrying vehicle for use throughout the state using the
experience gained from experimental Rail Motors No. 1 and No. 2. The 37 rail motors
of this series, would serve for a period of sixty years and be known as the CPH class.

The New South Wales Railway's design office prepared the plans for the car body using Rail Motor No. 2 as the basis for the layout and a new lighter underframe was developed. Construction of this new vehicle took place in the Eveleigh Carriage Works.

These Rail Motors were designed to run as independent vehicles, which meant that the underframe could be much lighter in design thereby reducing the overall weight. The lighter underframe was achieved by making the two main longitudinals from all welded Warren trusses and these gave good strength. This new underframe design was believed to be unique in railway vehicles, although some Sydney trams had similar frames dating back to 1908. Extensive use of timber such as cedar and pin e were used in the body design to ensure the overall weight of the vehicle was kept to a minimum.

Body Dimensions
overall length	44'   8"	over buffers
overall body length	42'   0"	outside
overall body width	9'   8"	outside
overall height	13'   6"	above rail

The body was divided into 3 sections, accommodating 52 passengers and 2 crew.
Two driving cabs were positioned at each end within the saloon areas.
The first area or first class section accommodated 21 passengers.
The middle area or guard's compartment accommodated 7 passengers (2nd class).
The third area or second class section accommodated 24 passengers.

Driving cabs were mounted in the passenger saloons located at each end of this vehicle. Entry to the cab was gained through a back door that opened into the passenger compartment. The driving controls were arranged to allow the vehicle to be driven from either end and this meant the vehicle did not have to be turned for the return journey.

The cab occupied the centre part of the car and single seats were mounted on either side for passenger use. These seats were in great demand by young and old alike because they had a forward aspect and overlooked the driver's controls providing an excellent opportunity for study of rail motor techniques.

The guard's compartment separated the first and second class sections and provided the necessary area for the goods traffic of parcels and mail. Wooden seats that folded away when not in use could accommodate an additional seven-second class passengers.

A compartment was located in the second class area housing the toilet and washbasin. This facility did not have running water so a tank was provided in the form of a large watering can that was filled by the guard.

The original seating was a fixed type and they were grouped in facing pairs. One side of the aisle had a two-seat arrangement while the opposite side had a three-seat arrangement. These seats were small and even with additional upholstery proved rather uncomfortable. From 1936, Hale and Kilburn turnover seating was progressively fitted to all CPH cars.

The roof was made from canvas and navy dressing laid on a wooden frame with ventilators.

Wheel & Wheelbase Dimensions
wheel diameter	0'   25"	3 axles
wheel diameter	0'   32"	drive axle
wheelbase	28'   0"

The first six vehicles were fitted with a 72 h.p. 6-cylinder Thornycroft Z6 marine petrol engine. This engine was mounted with its four speed attendant gearbox in the frame under the floor and all gears could be operated from either cab. It appears this engine did not perform as expected, as a further two engines were supplied free to replace the defective ones. This engine was considered unsuitable for hauling trailers.

The next batch of vehicles was powered by a 95.5 h.p. 6-cylinder (5.5" x 6.5") petrol engine manufactured by Leyland which became the standard for many years. These vehicles were geared for a road speed of 40 m.p.h. (@ 1200 r.p.m.).

The Leyland engine being more powerful allowed the rail motors to haul trailers when warranted by increased traffic demands.

Two independent systems of ignition were fitted :-
battery-fed ignition for starting
high-tension magneto for running

A gearbox was used to transfer power from the engine to the wheels and a clutch operated from a pedal in either cab was used to disengage the engine from the gearbox. Other auxiliaries belt driven from the engine were an air compressor and an electric generator.

The engine was cooled by radiators mounted under the floor and these were positioned along the outer side of the vehicle to obtain the best results. A fan was fitted to force air through the radiators and this system was arranged to obtain equal degrees of cooling for either direction of travel.

In the mid 1930's Rail Motor No. 3 (CPH 3) was fitted with a 150 h.p. Leyland engine and a Torcon torque converter, which proved so successful that vehicles No.'s 16, 21 and 30 were converted. This higher-powered engine combined with the torque converter led to the development of the more powerful rail motor, which was to become the 400 class.

Other engines trialed with torque converters were the :-
150 h.p. AEC engine first tested in No. 35 and later in No. 6.
160 h.p. Winton engines  later tested in  No. 25 and No. 30.

The Winton engines were greater in height than the underframe's clearance and protruded above floor level, requiring a false floor to be fitted which was a hazard to passengers.

In April, 1945, No. 14 tested the 165 h.p. (@ 1800 r.p.m.) 6-cylinder (4-1/4" x 5") diesel engine model 6/71 manufactured by General Motors. A Twin Disc torque converter was fitted and this drove the inside axle on the bogie (second class end) via a cardan shaft and final drive.

The transmission has three positions
First position	Acts as the torque converter is used for starting and accelerating the load.
Second position	Above 30 m.p.h. the driver can select a direct drive position that bypasses the converter and connects the engine directly to the drive shaft.
Third position	Neutral is used when no power has to be transmitted. ie. when standing in stations, etc..

No.'s 3 and 19 did not have direct drive or neutral provided as the General Motors torque converters were permanently coupled to the engine. This meant that before the vehicle could change direction the engines had to be stopped to avoid damage to the final drives. The engines also had to be stopped and when the vehicle became stationary for lengthy periods to prevent over-heating of the converter.

As the only cooling medium is natural air circulation, the radiators were relocated to the roof to provide greater cooling for the more powerful engine. Water lost from the radiators was replenished by a hand-operated pump supplying make up water by a from a tank in the guard's compartment.

Main auxiliaries, the air compressor and generator were coupled to the engine via a shaft drive. The air compressor supplied air for the brakes, horn, sanding gear and other controls. The generator supplied power for battery charging, lighting, etc..

Multiple unit working was possible when General Motors engines and their electro-pneumatic controls were fitted. Electrical control jumpers and air hoses were fitted and this started the rostered Multiple Unit working of of up to five units. No.'s. 3 and 19 were excluded from this multiple unit working and were confined to pulling trailers only, due to their unusual converters.

Before multiple unit working was available and two rail motors were required to run coupled together, a driver was required in each of the units. To synchronise the driving controls a system of bells was set up to allow communication between the drivers. Trailers could not be fitted with controls and this meant that when trailers were used the rail motor had to run round its trailer at each terminus. Rail motors rarely coupled to other vehicles because of their light draw-gear.

September, 1956, saw the complete fleet converted to diesel power.

The original Rail Motors weighed 14 tons 14 cwt., but this has risen to 18 tons with the fitting of different engines and bogies. Rail Motors No.'s 33 to 37 have a tare weight of only 16 tons because of the lighter bogies. The fuel tank with a 96-gallon capacity is mounted under the guard's compartment and allows a normal working range of 600 miles.

Light hook-type drawgear, small buffers, cowcatchers and headlights were mounted at each end of the vehicle. Electric marker lights were fitted during the life of these vehicles.

A safety feature to protect the train was a dead-man's pedal and if the driver becomes incapacitated and releases the pedal, the engine is returned to the idle position and a warning buzzer is sounded in the guard's compartment.

The Rail Motors provided the postal service for lineside communities on branch lines. The postal boxes were hung on brackets mounted outside the vehicle at each end and within easy reach of the platforms.

These vehicles were nicknamed 'Tin Hares' as their introduction occurred at a time when tin hare dog coursing was becoming popular, yet they are better known by their classification code of CPH allotted in 1937.

CPH's lasted well into the mid 1980's giving sixty years of reliable service and even though retired from active service, some of these units are still in operation with railway museums. The Rail Motor Society is currently restoring and operating CPH type rail motors to ensure people can still experience these remarkable machines which were the backbone of country branchline passenger services.

Two types of Trailers were designed for use with the 42-foot CPH Rail Motor :-
Bogie Trailers of the CTH class to cater for increased patronage and
4-Wheel Parcels Trailers of the GT class to cater for the increased parcels traffic.

The next major development in Rail Motors was the 55-foot CHP (twin engine) Rail Motor

Ron Preston has kindly given permission for this extract from his work on 42-foot Rail Motors to be used in the TRMS Web Site.