Specifications

RailCorp Infrastructure Engineering Manual – Signalling

Maintenance Manual

Electric Point Machine Westinghouse Style M70 MKIII TMG E1583

4.2 Gear Train and Clutch Assembly

4.2.1 Description

The motor drives a spur gear train, which in turn drives a worm through a friction

clutch. The worm engages the main gear, which drives the lock and throw mechanism.

The clutch protects the mechanism from shock at the end of the movement and also

when the points are obstructed. The worm shaft is also engaged by a bevel gear

driven by a shaft, which engages the manual crank handle.

4.2.2 Adjustment of Friction Clutch

Before leaving the manufacturer, the friction clutch is adjusted for greater than average

point loads. This adjustment should adequately allow any high point loads, which may

be encountered during the machine's operation. However the clutch must be tested on

completion of installation.

Re-adjustment may be necessary during the maintenance visit and conducted in the

following manner.

To Test Clutch

1. Connect an ammeter in series with the motor circuit, and measure the normal

operating current.

2. Insert a block of wood or similar between the switch and the stock rail so as to

obstruct the operation of the switch.

3. Operate the switch machine, and measure the obstruction current. The clutch

should slip at approximately 150% of the normal operating current.

To Adjust Clutch

1. Remove supply from the motor by removing circuit fuses.

2. Remove split pin from clutch adjusting nut.

3. Tighten clutch adjusting nut, replace split pin and re-test. Repeat items 1-3 as

required until the correct adjustment is achieved.

NOTE: Clutch slippage may be caused by worn clutch discs or by fouling of the

clutch discs with lubricant from the gear train due to ineffective packing between the

clutch shaft and housing (see Section 4.2.3).

Issue Date: 1 December 2009 Uncontrolled when Printed