The Wallace Tri-Adjustable 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 the 15 -Ton models all use this proprietary design. Shown below is a false color detail of a square tube Tri-Adjustable crane.

First and foremost, the "pinned at both ends" design minimizes the 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 seen below. This linkage is the heart of the Wallace patented self-aligning beam.

As you can see in the detailed image above (a blow-up of the "before" four bar design), there are no welds in tension. The cast caster frame bracket welded to the leg is in pure compression. Too, the internal weld is shielded from most impacts, again yielding a more reliable design.

Finally, the attachment of the leg to the beam support brackets is accomplished with one pin for each leg. Each support pin only carries 1/4 of the total Crane load. And according to design for assembly techniques, this method provides a surer fit. The movable brackets and the single hole ease assembly and reassembly. In fact, assembly instructions only run two pages, further demonstrating the simplicity and elegance of the design.

The net result for users is a product with a longer life because unnecessary stresses are reduced. And because the design allows for some mis-alignment, pins go in easily, speeding initial and subsequent reassembly. Too, the easy insertion of the load bearing pins further reduces the likelihood of assembly-induced pre-stresses. These stresses can also reduce crane life and reliability.

Revised 5/6/05