A derrick crane is a stationary lifting device built around a central vertical mast and an angled boom, used primarily for heavy lifts in construction, shipbuilding, and steel erection. Unlike mobile cranes that drive to a job site on wheels or tracks, derrick cranes are assembled in place and anchored to the ground or bolted directly to a building’s structure. They’ve been a fixture on major construction projects since the early 19th century, and modern versions can lift 60 tons or more at impressive reach distances.
How a Derrick Crane Is Built
Every derrick crane shares a few core components. The mast is the vertical column at the center. It carries the weight of the crane and its load down to the foundation. The boom extends outward from near the top of the mast at an adjustable angle, and the load hangs from the boom’s tip on a cable system. By changing the boom’s angle (called “luffing”), the operator controls how far the load reaches from the mast and how much weight the crane can safely handle. A steeper boom angle keeps the load closer to the mast and allows heavier lifts, while a shallower angle extends the reach but reduces capacity.
The boom and mast are made from built-up steel members, meaning they’re assembled from plates and angles rather than cast as a single piece. This makes them both strong and relatively light. A bull wheel, a large rotating mechanism at the mast’s base, allows the boom to swing horizontally. Depending on the type of derrick, the bull wheel is turned by hand cranks, wire rope powered from a hoist drum, or both. The actual lifting is done by a separate hoist engine connected through a rope-and-pulley (reeving) system.
Guy Derricks vs. Stiffleg Derricks
The two most common types of derrick cranes are the guy derrick and the stiffleg derrick, and the difference comes down to how the mast stays upright.
A guy derrick uses a set of angled wire ropes, called guys, that radiate outward from near the top of the mast and anchor into the ground or a solid structure at various points around the base. These guys hold the mast vertical the way tent ropes hold up a pole. The mast base itself is also anchored. Because the boom can rotate freely within the circle of guys, a guy derrick offers nearly 360 degrees of swing. That rotation is slow, though. The boom is swung by workers operating a bull wheel or crank by hand, and no powered slewing mechanism is used. Wind forces on the boom are considered negligible in engineering calculations precisely because the boom rotates so freely.
A stiffleg derrick replaces the flexible guy wires with two rigid inclined legs (also called tie-rods) that connect the top of the mast to a fixed base on either side. These stiff legs are anchored at their far ends and braced to resist both horizontal and vertical forces. The tradeoff for that rigid support is limited swing: the boom can only rotate within the arc between the two stifflegs, typically around 270 degrees or less. Stiffleg derricks use a powered bull wheel, with wire rope pennants driven by auxiliary drums on the main hoist, so swinging is faster and more controlled than on a guy derrick. Because the boom doesn’t swing freely, engineers must account for small dynamic forces during rotation, and when used in bridge erection, wind loads on the lifted object factor into the design.
The Chicago Boom
A third variation worth knowing is the Chicago boom, which is purpose-built for work on tall buildings. Instead of standing on the ground with its own mast, a Chicago boom clamps directly to a vertical structural member of the building itself, using that column or beam as its mast. The boom is stepped into a fixed socket attached to the building’s framework, and it operates with load lines, boom lines, and swing lines just like other derricks. This setup is common during high-rise steel erection, where the crane climbs the building as new floors go up. It’s a compact solution for sites where there’s no room for a freestanding crane at ground level.
Lifting Capacity and Reach
Derrick cranes are designed for heavy lifts at long reach distances. A large modern derrick might have an 80-meter (roughly 260-foot) boom and handle payloads of 40 to 60 tons depending on the boom’s angle. At steeper inclinations, between about 30 and 85 degrees from horizontal, the crane in that configuration can handle 60 tons. Flatten the boom below 30 degrees to extend the reach, and the rated capacity drops to 40 tons. Every derrick has a load chart that maps these relationships, and operators must stay within the chart at all times.
This capacity-versus-reach relationship is fundamental. The farther a load hangs from the mast, the greater the tipping force on the crane. Load charts account for this physics, and exceeding them risks structural failure of the boom or overturning the entire machine.
Anchoring and Ground Requirements
Because derrick cranes don’t have the ballast or outriggers of mobile cranes, their stability depends entirely on how they’re anchored. Federal construction safety regulations spell this out clearly. For guy derricks, the mast base must be anchored and every guy wire must be secured to the ground or another firm anchorage point. The anchoring system must be engineered to handle the maximum horizontal and vertical forces the crane will encounter when lifting at rated capacity, given the specific guy slope and spacing for that job.
Stiffleg derricks require anchoring at both the mast base and at the foot of each stiffleg. The ground itself must be firm, drained, and graded so it can support the equipment. On softer ground, timber blocking or cribbing is placed under support points to spread the load across a wider area. Before any assembly begins, a qualified director must evaluate the site’s bearing capacity and confirm the blocking material is sufficient in size, condition, and stacking method to keep the crane stable throughout the lift.
How Derrick Cranes Evolved
The earliest derrick cranes appeared in the early 1800s for shipbuilding and heavy construction. Those first versions relied entirely on manpower and simple pulley systems, making them slow and labor-intensive. The arrival of steam power, and later electric motors, transformed the design. Powered hoists dramatically increased both lifting speed and capacity while cutting the number of workers needed on the ground.
By the mid-20th century, derrick cranes had become sophisticated machines with engineered steel components, precision load charts, and powered rotation systems. Advances in materials science pushed the evolution further, producing lighter but stronger structural members that increased lifting capacity without sacrificing stability. Today’s derrick cranes remain a go-to choice for steel erection on high-rise buildings and bridges, jobs where extreme lifting capacity in a fixed position matters more than the mobility of a wheeled crane.
Where Derrick Cranes Are Used Today
Derrick cranes fill a specific niche. They excel in situations that demand high capacity, long reach, and a fixed working position. Steel erection on skyscrapers is the classic application: a guy derrick or Chicago boom sits atop the rising structure and lifts steel columns and beams into place, then gets jacked or reassembled one floor higher as construction progresses. Bridge erection is another common use, particularly for stiffleg derricks that can handle wind loads on large structural pieces being swung into position over open water or roadways.
They’re also used in shipyards, oil refineries, and industrial plants where heavy components need to be placed precisely and the crane can remain in one location for an extended period. Their simplicity is an advantage in remote or congested sites: a derrick can be assembled from individual steel members carried to the location, while a large mobile crane might not fit on the site or reach the working height required.