Articulating Crane Terminology
Here's some words you should know and understand when getting into owning, operating and maintaining an articulating crane.
Load Moment
Outriggers
Outrigger Extension Span
Outrigger Pads
Crane Base
Mast
Inner Boom
Outer Boom
Power Links
Adjustable Side Wear Pads
Boom Sequencing
Hook Approach
Center of Gravity
Jib
Crane Storage Height
Rotational Torque
Crane Attachments
Rotation
Resistance to Bending Moment (RBM)
Capacity Chart
Load moment: = Distance x load weight
Outriggers: Mechanical extensions to the crane or truck which expand the foot print of the truck thereby increasing stability. The extensions may be manual or hydraulic powered and the vertical elements which make contact with the ground are typically hydraulically actuated.
Outrigger extension span: This is the overall outrigger reach from left to right measured from center of pad to center of pad. This is also referred to as the “footprint” of the crane.
Outrigger pads: The vertical outriggers typically have a foot of small diameter onto which can be slid/attached either metal or plywood pads of larger area to reduce ground pressure. The pads may also be loose in nature and placed under the foot of the outrigger.
Crane base: Most articulating cranes are designed for truck installation and the crane base is typically comprised of slide tubes for the outriggers upon which is mounted the slewing gear for rotation of the crane which might be actuated by a hydraulic motor and reduction gear or hydraulic cylinders. The crane base may also contain the hydraulic oil reservoir and may be of cast steel or fabricated steel construction. All IMT cranes have fabricated crane bases which are lighter, stronger and less prone to leakage or failure.
Mast: The articulating crane mast is a vertical element attached to the slewing gear which gives the articulating crane the ability to articulate. It contains a fabricated vertical structure to the base of which is attached a gear which meshes with the slewing gear in the crane base. It also incorporates a hydraulic cylinder known as the inner boom cylinder which raise and lowers the inner boom which pivots off the top of the mast.
Inner boom: The inner boom, which is a fabricated steel structure, attaches to the top of the mast and is raised and lowered by the inner boom cylinder. It incorporates the outer boom cylinder which raises and lowers the outer boom which is attached to the tip of the inner boom.
Outer boom: The outer boom which is a fabricated steel structure, attaches to the tip of the inner boom and contains one or more extension booms each of which can be extended, depending on the make and model, hydraulically or manually.
Power links: Different manufacturers refer to them differently but are additional linkages which can be installed between the mast and inner boom and/or the inner boom and the outer boom.
- These are designed to allow for closer hook approach and constant load moment.
- They also provide consistent speed and power through entire movement reach.
- They provide better fold geometry. Jib can be held in a complete stretch position which is especially important for long reach loaders
Hexagonal boom sections: Compared with earlier rectangular boom sections the hexagonal boom section provides a higher lift-to-weight ratio and is self aligning to minimize lateral movement.
Adjustable Side Wear Pads: These are replaceable wear pads made of either a polymer or bronze type material which maintain vertical boom alignment for consistent loading on extension boom assemblies. These can typically be replaced without boom disassembly.
Boom sequencing: Is a design feature which allows the various boom extensions to be extended or retracted in a given order. This is achieved through optimization of cylinder sizing and grouping.
Hook approach: Hook approach determines how close the crane hook can get to the crane base thereby determining how close to the crane a load may be picked up. There is a vertical and horizontal element referred to HAv and Hah.
When the crane inner boom is elevated to the vertical and the outer boom is collapsed as far as possible the HAv is the distance between the bottom of the crane base and the bottom corner of the last boom extension with the outer boom fully retracted. The HAh is the distance between the centerline of the crane and the bottom corner of the last boom extension with the outer boom fully retracted.
Center of gravity- Stored: This indicates the cranes center of gravity CoG when the crane is in the stowed position
This is important when doing weight distribution and stability analysis.
Jib: The jib relating to the articulating crane is an additional articulating arm that raises, lowers, extends and retracts. It enables the crane to reach up and over walls and obstructions and is frequently utilized in construction applications such as poured wall construction and air conditioner placement. A crane that uses a jib to achieve maximum reach compared to a non jib boom has a much reduced capacity at maximum reach because of the higher comparative weight of the jib assembly compared with the straight boom.
Crane storage height: Needs to be considered in some applications to ensure truck + crane will fit in a garage or under an obstruction.
Rotational torque: How much torque it takes to rotate the loaded crane:
- Is measured in foot-pounds or ton-meters in the metric system.
- Also used to rate the crane rotation system capacity. This rating is very important when the crane is rotating up a grade under full load.
- Must be considered when the crane is used with an auger drive
Crane attachments: There are a range of various attachments designed to be mounted at the boom tip. These include grapples of various types, clam shell buckets, auger drives and even hydraulically powered chain saws. Cranes can be provided with additional hydraulic controls and hoses to provide hydraulic power to the boom tip to supply the attachment. Like other crane functions they can be manually or remote controlled via tether or radio.
Rotation: Indicates the extent of crane mast rotation. This is accomplished using a motor/gear drive or hydraulic cylinders. Motor drives typically allow continuous rotation and cylinder rotation offers typically up to 410 degrees. With cylinder rotation it is sometimes important to “time” the rotation to ensure the continuous 360 degree rotation occurs in the correct sector relative to the truck. Most applications allow continuous rotation around the rear of the truck.
RBM: Resistance to bending moment. Refers to the relative strength and resistance to bending of the truck frame rails.
Capacity chart: Normally affixed to the crane to advise the operator of the maximum capacity at a given boom extension.