Trolley

The trolley is the travelling carriage of the jib. Driven along the bottom chords, it sets the working radius — the distance from the slewing centre to the hook.

Construction

Welded steel frame with four flanged rollers riding the bottom chords of the jib, a rope guide sheave set, and a luffing winch or rope drive that pulls the carriage in and out. On a flat-top crane the two bottom chords also form the running track, so no separate rail is needed.

Role on the machine

All lifting loads pass through the trolley frame into the jib, and all hoist rope passes through its sheaves. The sheave geometry determines the verticality of the rope at short radii, which is why the trolley is the first place to look when the hook drifts off plumb.

Inspection and maintenance

• Check roller wear and the clearance between the rollers and the chords.
• Inspect sheave grooves for rope wear and confirm the rope guard is intact.
• Test the trolley limit switches and the luffing brake before each shift.