Crane Types, Components, and Terminology
What the exam tests
This domain checks whether you can identify crane families and use component names precisely, because every capacity calculation depends on them. Mobile cranes include rough-terrain, truck-mounted, all-terrain, and crawler types; tower, overhead bridge, and gantry cranes appear mainly as comparison items. The load-bearing chain on a mobile crane is boom, boom pivot, boom hoist, boom stop, load hoist, wire rope, sheaves, hook block, and lower works: carrier, outriggers, swing bearing, and counterweight.
Terms that change the answer
Radius is the horizontal distance from the center of rotation to the vertical hoist line, not boom length and not distance along the boom. Boom length, boom angle, and radius are linked by geometry; a jib changes both geometry and which chart applies. Rated capacity is not one number: it depends on boom length, radius, quadrant, outrigger extension, counterweight, and whether the crane is on rubber or outriggers. The load moment indicator or rated capacity limiter shows percent of capacity, but the manufacturer's chart is the authority. Anti-two-block devices prevent the hook block from contacting the boom tip and are safety devices, not conveniences.
Worked example
A 12,000 lb load is reeved with four parts of line. Ignoring friction, line pull is 12,000 ÷ 4 = 3,000 lb. With sheave friction, allow roughly 3–5% per sheave; three sheaves can push hoist line pull toward 3,450 lb. That is why the hoist's line-pull rating, not just rope strength, can limit a pick.
Traps
Do not confuse boom length with radius. Do not read a jib capacity from the main boom chart. Do not treat the LMI as a substitute for the chart. Do not assume a crane has a single fixed capacity.