Portable Gantry Crane Design – Patented Design Principles
This page explains some of the patented design principles behind all our portable gantry cranes. Learn why they are robust, enduring, and easy to assemble and disassemble. Learn why we have more gantries still in use than any other manufacturer.
Self-Centering Beam Support
A Wallace gantry crane is the embodiment of design elegance. The self-centering beam support design provides several advantages over more rigid beam suspension methods in mobile cranes. Wallace Tri-Adjustable, Hippolift, and 15-ton models all use this proprietary design.
Pinned Joint Construction
First and foremost, the “pinned at both ends” design minimizes stresses borne by the support member. From classical stress analysis theory, loads are transmitted along the leg structure. Torsional or off-angle loads are reduced because of the four-bar link design, as shown below. This linkage is the heart of the Wallace patented self-aligning beam.
The pinned joints make assembly easier. Parts rotate such that pin insertion can be done with a 16 oz hammer. The main legs are attached to the crane with a pinned joint going into the I-beam bracket at the top of the leg and a pinned joint on the lower leg going into the caster frame.
Assembly instructions only run only two pages, further demonstrating the simplicity and elegance of the design. You never have to try to bend metal to achieve the necessary fit.
No Welds In Tension
As you can see in the detailed CAD end-profile and free body diagram above, there are no welds in tension. The caster frame bracket welded to the leg is in pure compression. The internal weld is shielded from most impacts, again yielding a more reliable design.
The rendered image (below) shows how the caster frame pin at the base of the leg transmits the load across a single line.
The attachment of the leg to the beam support bracket is accomplished with one pin for each leg. Each support pin only carries 1/4 of the total crane load. According to the design for assembly techniques, this method provides a surer fit. The movable brackets and the single hole ease assembly and reassembly. The design allows for some misalignment allowing pins to go in easily, speeding up initial and subsequent reassembly.
The easy insertion of the load bearing pins further reduces the likelihood of assembly-induced pre-stresses. These stresses can reduce crane life and reliability.
The casters and frame flex so that the four wheels are always in contact with the floor. This allows the crane to handle uneven floors. The frame flex also ensures that the load is distributed among all the casters. Even if the load is entirely on one end of the crane, the load is evenly distributed between those two legs.
Robust, Enduring, Easy-To-Assemble Cranes
The net result of our patented portable gantry crane design is a product with a longer life because unnecessary stresses are reduced. Cranes are portable, adjustable, and easy to assemble and disassemble.
Our cranes are known for their longevity. Since having developed the original tri-adjustable patent in 1954, we have become the sought-after crane manufacturer for many of the world’s best-known brands including Coca-Cola, NASA, Goodyear, General Electric, Exxon Mobile, Lockheed Martin, and the United States Postal Service, to name a few.
“Sturdy yet moves with remarkable ease—quick and easy to assemble. We are certainly pleased with this unit and are still surprised at the quality for the cost involved.” WICHITA STATE UNIVERSITY
“Gantry is used mainly for changing the heavy steel molds on our 75-ton injection machine. It has cut our time in half and there is no risk of getting hurt in lifting. It’s been a dream…” ANDERSON MOLDS & DESIGN COMPANY
“Gantry used to dismantle and reassemble elevator motors (paid for itself in 2 jobs).” SCHNEIDER ELEVATOR COMPANY