A second pointer, colored red-, indicates the Safe Working Load for the actual radius at which the crane is
working. This red pointer is driven by a cam in the Control Box operated by a flexible drive from the boom hinge pin. The
gear train which drives the red pointer also rotates electrical contacts which light a warning light at 90% S.W.L. and
sounds a warning bell should the Safe Working Load be exceeded.
The Bell and Light Unit is a separate item, mounted in the crane cab so that it is clearly audible to the Operator-
VISUAL INDICATION. The safety margin is clearly indicated by the gap between the black pointer, indicating the
load on the crane hook, and the red pointer, indicating the Safe Working Load. An amber light is illuminated at 90%
S.W.L. A Red Light goes on at 100% S.W.L.
AUDIBLE WARNING. The Warning Bell sounds when the lifted load meets or exceeds the Safe Working Load.
It follows, therefore, that as soon as the black pointer reaches the red pointer the load should be reduced or the
boom derricked in. On no account should the crane be operated with the bell continuously ringing.
In addition to the dial indicating the load on the crane hook, the Control Box is fitted with a further scale indicating
the actual working radius of the crane. This is positioned in the lower half of the Control Box.
Certain adjustments are necessary to cater for the various duties of the crane and these have been made as
simple as possible, In most cases, three adjustments only are necessary and are as follows:-
1. Cam Change.
2. Reeving Change
3. Black Pointer Zero.
Describing these adjustments in detail:-
1. CAM CHANGE. The cam is a brown fibre plate which is mounted within the Control Box, secured by one wing nut
on its boss. Access to this cam is obtained by opening the front door of the Control Box. All the