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GIRDER, BRIDGE - MESSENGER TRACK

GIRDER, BRIDGE - The principal horizontal beam(s) of the crane, which supports the trolley, is supported by the end trucks, and is perpendicular to the runway.

GIRDER, DRIVE (GIRDER "A"/”G1”) - The bridge girder to which the bridge motor and gearcase(s) are attached. For cranes having a drive on each girder, it is the girder to which the control panels and/or the cab are attached.

GIRDER, IDLER (GIRDER "B”/”G2”) - The bridge girder which does not have the bridge drive attached, but which usually carries the bridge conductors.

GIRDER, RUNWAY - A horizontal beam attached to the building columns GIRDER, Auxiliary (OUTRIGGER)- An additional girder, either solid or latticed, arranged parallel to the bridge girder(s) for supporting the footwalk, control panels, operator's cab, etc., to reduce the torsional forces such loads might otherwise impose.

HOIST, AUXILIARY - A supplemental hoisting unit, usually designed to handle lighter loads at a higher speed than the main hoist.

HOIST, MAIN - The primary hoist mechanism provided for lifting and lowering the rated load of the crane.

HOOK APPROACH, END - The minimum horizontal distance, parallel to the runway, between the centerline of the hook and the face of the wall (or columns) at the end of the building.

HOOK APPROACH, SIDE - The minimum horizontal distance, perpendicular to the runway, between the centerline of a hook (main or auxiliary) and the centerline of the runway rail.

INCH (INCHING) - See "jog". Often used incorrectly to refer to "creep speed" (which see).

JOG (INCH) - To move the hook, trolley, or bridge in a series of short, discontinuous, increments by momentary operation of a controller.

LEFTHAND END - A reference to parts or dimensions on the viewer's left of the centerline of span, established when facing the drive girder side of the crane.

LIFT (HOOK TRAVEL) - The maximum vertical distance through which the hook can move, as determined by the length of rope and/or the number of grooves on the drum.

LIMIT SWITCH - An electrical device which is operated by the bridge, trolley, or hoist motion to disconnect the circuit, to establish a new circuit, or to provide a warning.

LOAD, DEAD - The load(s) on a portion of the crane, which remain(s) in a fixed position relative to the member being considered.

LOAD, LIVE - A load which moves or varies relative to the member being considered. For the trolley, the live load consists of the rated load plus the weight of the block. For the bridge, the live load consists of the rated load plus the weight of the trolley.

LOAD, RATED - The maximum static vertical load for which a crane or an individual hoist is designed.

LOAD FLOAT - A control system which enables Stepless operation of a hoist in either the lifting or lowering direction for a range of about 04% of full rated speed, as well as permitting the load to be suspended stationary for a very short time with the holding brake(s) released.

MASTER SWITCH - A manually operated device which governs the operation of contactors and/or auxiliary devices of an electric control.

MESSENGER TRACK - A horizontal member, mounted along a handrail or girder, supporting movable carriers from which festooned wires are hung. The festooned wires may be used to transmit current from the bridge to the trolley or from the bridge to a pendant control unit.