Grapple (tool)

Grapple (tool)

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A grapple is a hook or claw used to catch or hold something. A ship's anchor
Anchor
An anchor is a device, normally made of metal, that is used to connect a vessel to the bed of a body of water to prevent the vessel from drifting due to wind or current. The word derives from Latin ancora, which itself comes from the Greek ἄγκυρα .Anchors can either be temporary or permanent...

 is a type of grapple, especially the "grapnel" anchor.


A throwing grapple (or "grappling hook
Grappling hook
A grappling hook is an anchor with multiple hooks , attached to a rope; it is thrown, dropped, sunk, projected, or fastened directly by hand to where at least one hook may catch and hold. Generally, grappling hooks are used to temporarily secure one end of a rope. They may also be used to dredge...

") is a multi-pronged hook that is tied to a rope and thrown to catch a grip, as on a parapet or branch of a tree. It may also be used in a boat to "drag" the bottom of a waterway to hook debris or to find missing objects.


In logging
Logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...

 and other engineering vehicle
Engineering vehicle
Heavy equipment refers to heavy-duty vehicles, specially designed for executing construction tasks, most frequently ones involving earthwork operations. They are also known as, construction equipment, construction plant, earth movers, engineering vehicles, or simply equipment...

s, a grapple is a hydraulically
Hydraulic machinery
Hydraulic machines are machinery and tools that use liquid fluid power to do simple work. Heavy equipment is a common example.In this type of machine, hydraulic fluid is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders and which becomes pressurised according to...

 powered claw with two or more opposing lever
Lever
In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...

s that pinch
Pinch (action)
A pinch is a grip of a flexible object in which a portion is taken between two fingers, until it hurts, or something of resemblance and squeezed so the gripped portion of the object is lifted from its normal level...

 a log or other materials, usually to lift
Forwarder
A forwarder is a forestry vehicle that carries felled logs from the stump to a roadside landing. Unlike a skidder, a forwarder carries logs clear of the ground, which can reduce soil impacts but tends to limit the size of the logs it can move...

 or drag them.

The logging grapple used in swing yarding is not moved by hydraulics but by cables. To open and close the tongs of the grapple, two cables are used. One is tensioned and the other is slacked off to move the tongs. A third cable goes back to the tail hold then to the yarder. This third cable is used to pull the grapple out into the setting and to create tension for lifting the grapple in the air.

A grapple can be mounted to a tractor
Tractor
A tractor is a vehicle specifically designed to deliver a high tractive effort at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction...

 or excavator
Excavator
Excavators are heavy construction equipment consisting of a boom, stick, bucket and cab on a rotating platform . The house sits atop an undercarriage with tracks or wheels. A cable-operated excavator uses winches and steel ropes to accomplish the movements. They are a natural progression from the...

 with a movable arm that may lift, extend/retract, and move side-to-side (pivot or rotate). Some machines also have a separate control for rotating the grapple.

Simpler grapple machines consist of a hydraulically liftable fork, rake ("grapple rake"), or bucket and a movable, opposing "thumb" (one or more hooks or levers) that enclose and grip materials for lifting or dragging. A "demolition bucket" or "multi-purpose bucket" on a loader may also operate as a grapple whereby the bottom and rear side of the bucket are hinged and can be forced apart or together with hydraulic
Hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...

 cylinders.

A lifting grapple is a type of hardware
Hardware
Hardware is a general term for equipment such as keys, locks, hinges, latches, handles, wire, chains, plumbing supplies, tools, utensils, cutlery and machine parts. Household hardware is typically sold in hardware stores....

 that can be attached to most large, heavy or bulky object to provide a feature on the item to which material handling equipment can attach. Lifting grapples sometimes double as tie downs, allowing heavy items to be held firmly in place by providing a point to which ropes or chains can be attached to the item to hold it in place.

See also

  • Robot end effector
    Robot end effector
    In robotics, an end effector is the device at the end of a robotic arm, designed to interact with the environment. The exact nature of this device depends on the application of the robot....

  • Skidder
    Skidder
    A skidder is any type of heavy vehicle used in a logging operation for pulling cut trees out of a forest in a process called "skidding", in which the logs are transported from the cutting site to a landing. Here they are loaded onto trucks , and sent to the mill...

    , especially with a grapple claw