Specifications

RailCorp Infrastructure Engineering Manual – Signalling

Maintenance Manual

Electric Point Machine Westinghouse Style M70 MKIII TMG E1583

2.1 General Description

The Westinghouse Brake & Signal Co. "M70" Mk Ill point machine is similar in design

to the McKenzie and Holland Style 'M' machines. It comprises a throw and lock

mechanism driven by an electric motor, both of which are housed in a single cast iron

casing. The casing also houses a motor protection unit, a circuit controller, points

detection mechanism and a point contactor.

The motor drives the throw and lock mechanism through a spur gear train which

incorporates a friction clutch and a worm gear drive to engage the main crank. The

main crank drives the throw bar and the slide bar to which the lock box is attached.

The lock slides engage the lock box to positively lock the mechanism.

The locking mechanism is of the 'straight through' type, with the lock slides having one

notch on the top and one notch on the bottom, which engage corresponding lock dogs

on each end of the lock box, ensuring that the machine cannot complete its travel

unless the lock slides correspond to the position of the points.

The circuit controller incorporates motor and detection contacts, which check that the

points are closed and locked in their correct position.

The motor protection unit is located near the motor and the point controller. For

protection of the motor, the motor circuit is switched off automatically by the motor

protection unit when operation takes abnormally long. The point contactor determines

the switching direction of the motor.

A heavy gauge sheet steel cover with a moulded neoprene gasket provides ample

protection and a granulated cork coating on the inside crank inhibits condensation.

The cover, which is hinged at one end, can be removed completely and has a hasp

and staple for padlocking.

Emergency manual operation is achieved by inserting a hand crank through a

separately covered hole in the main cover.

Issue Date: 1 December 2009 Uncontrolled when Printed