Specifications

RailCorp Infrastructure Engineering Manual – Signalling

Maintenance Manual

Electric Point Machine Westinghouse Style M70 MKIII TMG E1583

2.2 Operation

The components of the main operating mechanism are shown in Figure 2.1.

The operation of the mechanism when power is applied to the main crank is shown in

Figure 2.2 and is described below:

1. Normal position (Figure 2.2-1)

A reverse movement is commenced by a clockwise rotation of the main crank.

Unlocking of the lock slide is achieved through the action of the lug on the upper side

of the main crank against the rollers on the slide bar. This causes the slide bar to

move thereby unlocking the lock box from the lock slide. Simultaneously, the roller on

the underside of the crank moves through an arc of 40 degrees in the radial section of

the escapement of the throw bar, thus freeing the throw bar for the reverse stroke.

During the next 140 degrees of revolution of the main crank, the roller engages the

straight section of the escapement of the throw bar, which moves the throw bar into

the reverse position.

2. Intermediate Position (Figure 2.2-2)

At the intermediate position the crank is still rotating but is not transmitting motion to

the slide bar as the lug on the crank has become disengaged from the rollers.

Movement of the slide is prevented by the action of the ends of the crank on surfaces

X and Y of the slide bar, which are now radial to the centre of the shaft. Motion of the

throw bar is occurring by action of the roller on the escapement of the throw bar.

3. Reverse Position (Figure 2.2-3)

The roller on the underside of the main crank has thrown the throw bar into the reverse

position and secured it by entering radial section of the throw bar escapement. The

opposite lug at the top of the crank has engaged the rollers on the slide bar and

moved the slide bar and the lock box into the reverse position. The lock box has

engaged the notch in the lock slide, which has also been moved into the reverse

position by the action of the points.

4. Locking

The locking of the lock slides in the lock box is achieved by means of two lock dogs in

opposite ends of the lock box, one at the top and one at the bottom. The lock slides

have corresponding notches cut in the top and bottom of the slides. Positive locking in

both normal and reverse positions is achieved by engagement of the dog in the notch.

Issue Date: 1 December 2009 Uncontrolled when Printed