Why aren’t the rotation motion and traverse motion powered usually?

rotateIt’s common to see the hoist motion powered on a jib crane. However, it is rare to find the traverse(trolley) and rotation motions powered. Many times the jib crane is purchased as a cost-effective tool to cover a small workstation. IN that workstation, parts are lifted by the jib crane and mounted into machines and also bolted on to larger assemblies. The finished piece is then transported to the next workstation by the overhead crane in the same building. In other words, for movements of more than five to ten feet, the overhead crane is used. Many times buyers do not feel the jib crane also needs to be motorized, that the operator can gently push the load to nearby machines and workbenches. For buyers that do want a motorized jib crane, both rotation and traverse(trolley) motions are available as powered motions at extra cost.

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What Rotation options are available on a Jib Crane?

numb1The idea of a jib crane is to cover an area by rotating instead of travelling. Most customers prefer to have as much area covered by the rotation of one jib as is possible. However, some customers may prefer to limit the rotation of a jib crane. For a small additional sum, rotation stops can be installed on most floor-mounted jib cranes. For example, the customer in a machine shop with a million dollar computerized machining center next to a jib crane does not want his jib crane to be able to rotate into the neighboring CNC machine. Also, some customers will require different electrification options such as a “top entry collector” or “bottom entry collector” depending on the rotation types. This decision will be made by the crane engineer because each option has a more appropriate application. Collectors of this nature help make jibs more flexible because these collectors allow unlimited rotation in one direction. Simple tag electrification is like a dog’s leash – eventually if the dog walks around a post enough, the leash will become wrapped around the post and the dog will not be able to move any more in that direction. Finally, the boom can be motorized itself. This option is expensive and is usually used in heavy duty or high-capacity applications. Pipe pit-casting applications typically see powered rotation jibs – in fact, the first overhead crane in the world was a motorized pit-cast jib crane in Birmingham, Alabama.

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What dimensions are important when purchasing a jib crane?

What dimensions are important when purchasing a jib crane?

The most important dimension is the weight of the heaviest load to be carried. Starting from there, measure how far the load must be moved from the wall or base. That will be the reach of the jib crane. How high does the load have to be lifted? That is the lift height. While this sounds simple, there’s also a need for some margins on the design to allow machinery of the crane to fit in the space as well. Most jib cranes will have a hoist of approximately 24” height as well as a beam of approximately 12” height. In other words, the lowest obstructions above the required load height are 42” including hoist, beam, and required 6” safety margin. Further, because the load cannot be traversed along the beam all the way to the edge, a 3” must be left at the moving end of the beam and minimum 12” must be left at the stationary end of the beam to accommodate the post, bearing, hinge, wall, and any other obstructions.

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What Holds a Jib Crane to the Floor?

What Holds a Jib Crane to the Floor?

A jib crane is anchored to the foundation or wall with anchors that can be ordered with the jib crane or purchased by the customer at a local bolt or supply house. It is important that the jib crane be anchored to a proper concrete footing or properly engineered wall or building column. Bolts alone cannot anchor most jib cranes into industry standard 6” reinforced concrete floor. The floor will buckle, the crane will collapse, loads and/or people will be hurt. If you have any questions, please call our office first or reference your owners’ manual supplied with every jib crane. A jib crane is easy to install provided the directions are followed carefully. Most customers prefer to install their own jib cranes but installation is available through Jib Crane Outlet installation field crews.

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How Big Can a Jib Crane Be?

How Big Can a Jib Crane Be?

In theory, one could order an enormous jib crane of any capacity or reach. In fact, the principles of the jib crane are employed on oil rigs and in harbors on what is commonly known as a “whirly crane” (pictured), a crane that rotates as a jib crane but travels as a bridge or gantry crane would.

But there is a practical limit to the industrial jib crane. After all, most factories and warehouses where jib cranes are installed do not have the same space configurations as a harbor. A harbor has little land to mount a bridge or gantry crane on, but lots of air space to let the top of a jib crane swing around. A factory has little air space because of the roof, but the entire factory has a floor underneath it to mount a crane.

The jib crane then is available up to fifteen tons rated capacity and twenty feet reach. Many times we find the jib crane is really only practical up to five tons rated capacity and twenty feet reach, but that is a game-time decision. If your project manager notices the design of a crane is approaching the threshold for design effectiveness, he or she will mention such an issue and make suggestions.

Wall mounted jib cranes are available to twenty feet reach in the cantilever format, and thirty feet reach in the tie-rod format. Again, it’s important to ask your project manager what solution is best when approaching the limits of the design.

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How Does a Jib Crane Work?

How Does a Jib Crane Work?

Whether wall-mounted or floor-mounted, all jib cranes have two important characteristics. A jib crane will always rotate and a jib crane will always lift or support a load. Most jib cranes will also have a third motion, that of traverse: The load will be able to traverse the beam from the center of the circle to the edge of the circle created by the jib as the jib rotates. Jib cranes typically have a hand-powered rotation and traverse motion, while it is common to see either electric-powered or hand-powered lift motion. The hand-powered rotation and traverse motion are accomplished by push/pull, while the hand-powered lifting is accomplished by a chain similar to a non-powered garage door. Options for electric rotation and traverse are available on almost all jib cranes for those wishing to purchase such a crane.

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Footing Design for Jib Cranes

Footing Design for Jib Cranes

Floor mounted jib cranes need to be mounted properly or the crane will collapse, resulting in damage to the load as well as human injury or death. A small selection of jib cranes can be mounted straight to a 6” reinforced concrete floor, the industrial building standard. The rest of the floor-mounted jib crane range must have a square of factory floor torn up and a specially-designed concrete footing installed.

How do I determine if my jib crane needs a foundation? Plan on needing a foundation unless your crane engineer tells you specifically otherwise. How do I know how big to make that foundation? Dearborn will supply you with a drawing showing the length, depth, and width of the foundation required, as well as any reinforcement required and the anchor bolt placement. Dearborn also offers a kit consisting of anchor bolts, anchor bolt template, and early kit shipment so the customer can set the foundation including anchor bolts before the actual jib crane arrives.

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Jib Crane Standard Configurations

Jib Crane Standard Configurations

The jib crane is a ubiquitous tool for any factory, and almost all jib cranes come in one of three configurations. The main three configurations can be adapted to almost any situation with a little thought, saving the customer money and time over specialty products. Jib Crane Outlet sells hundreds of jib cranes every year and very few are outside the main group. The three main configurations have two sub-groups: Floor-Mounted and Wall-Mounted jib cranes.

Floor Mounted Jib Cranes. Although there are about five types of floor-mounted jib crane, only the free-standing floor-mounted jib crane is truly important. This is a jib crane with an upright mast, a running beam or boom (interchangeable terms), and a concrete foundation (supplied by others) to allow the jib crane to stand upright on a factory floor without any other support. In fact, if a concrete foundation were properly applied, a jib crane could work on the top of a mountain or the bottom of a sea floor without any other support. The free-standing floor-mounted jib crane typically has a design range up to 25’ reach and five ton rated capacity. Most dimensional needs over fifteen foot reach are better served by a gantry crane or bridge crane.

Wall Mounted Jib Cranes. Most wall-mounted jib cranes are actually mounted to a steel building column that would be behind the wall if an industrial building were really a living room or office. The wall-mounted jib crane can be a tie-rod jib crane, where a tie-rod mounted to the wall above the boom and tied off to the far end of the boom supports the weight, or the wall-mounted jib-crane can be a wall-cantilever jib crane, where a beam is cantilevered out without a tie-rod to support the load. As a rule of thumb, the tie-rod jib crane is chosen when maximum lifting height is not as important as economy or price. A wall-cantilever jib crane is more expensive but can also allow the load to be lifted fifteen percent higher because the tie-rod does not need to be mounted above the crane.

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Thrust and Pull – Wall Jib Loadings

Thrust and Pull – Wall Jib Loadings

Thrust and pull are the forces exerted by a wall-mounted jib crane on the wall. Most of the time the phrase “wall-mounted” actually means the jib crane is mounted to a steel building column as if that building column were a wall. A standard steel building column is engineered to support the weight of the building roof as well as anything that hangs from that roof: lights, ducts, fans. Typically these extra items are light weight and inconsequential to the building design. However, when one mounts a heavy jib crane capable of lifting 4,000 pound loads, the building column must be specifically designed or adapted to support the jib crane.

Jib Crane Thrust and Pull

Jib Crane Thrust and Pull

Who can design or adapt a building column to support a wall-mounted jib crane? Typically this person is an architect, engineer, or general contractor with engineers on staff. A safe rule of thumb is to have a Professional Engineer or “PE” stamp the drawing showing the modification or design.

So what exactly is thrust and pull? All wall-mounted jib cranes have a beam and a beam support device, usually either a tie-rod or vertical-mounted mast. There will be two hinges to allow the jib to swivel 180 degrees. One hinge is always at the place the beam meets the wall. The beam is the running beam for the hoist/trolley. The other hinge is always where the support device meets the wall: either the end of the tie-rod or vertical mast. The tie rod is above the beam, while the vertical support member hangs below the beam, like an inverted “L”. Because the load is hanging off the beam, the beam is like a lever being pulled by the load.

If one envisions the beam as a lever being pulled down, it’s not hard to imagine the top hinge is effectively fighting to pull out of the wall, while the bottom hinge is effectively fighting to go thru the wall. Pull and Thrust. See the drawing. The wall or column must be engineered to withstand the pull on the top hinge and thrust on the bottom hinge.

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Jib Cranes – From Start to Finish

Jib Cranes – From Start to Finish

Jib Crane Outlet gets a lot of questions about the interaction between jib crane supplier, jib crane buyer, general contractor, and other subcontractors such as concrete subcontractors. How do they interact? Which parties contract with which parties, and who directs others in the design of their products? Over the next few weeks, I’ll cover about ten topics involved in the design and engineering phase of a jib crane project. The first and most important topic is the design flow process and the contract flow process.

The Architect will typically design the building in concert with the wishes of the owner and the capabilities of the general contractor. If the architect or general contractor does not request loading data from the jib crane supplier at this point in the design phase, the range of cranes that can be installed in the building is limited to whatever cranes happen to have compatible loadings with the building capabilities. Mitigating factors may exist if the architect already has a working understanding of crane loadings or the building already exists and a re-engineering or rebuilding is not feasible.

Introduction to Jib Cranes - An Overview

Introduction to Jib Cranes - An Overview

Once the building has been designed, the general contractor or the owner will request a proposal from the jib crane supplier. The jib crane supplier will send a price, specification, and drawings. From the specifications and drawings, the buyer must specify electrical, structural, and concrete requirements to the subcontractors responsible for those phases of the project. The jib crane supplier does not supply concrete footings or power to the crane, and can supply structural steel in certain circumstances. Look for blog posts on all three topics: concrete, electrical, structural.

Once the other subcontractors have the power, concrete footings, and structural steel ready, the jib crane supplier will ship the jib crane and hoist. On contracts where the crane supplier is required to install the jib crane, the crane supplier will visually inspect the site to ensure the other subcontractors are compliant but the crane supplier cannot reverse engineer the project on site. If the owner, architect, or general contractor know the site is not ready, they shall notify the crane supplier not to ship or travel to the site as no work can be performed.

When the jib crane is installed, the jib crane should be tested for all motions to ensure it works properly. It shall also be inspected in accordance with OSHA’s initial inspection requirements and load tested to 125% of rated capacity. Dearborn’s installation crew will do all of this provided the weights are supplied by others.

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