|
 |
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 above is a detail of a 2-Ton nominal capacity
round 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 (shown left, and in the I-Beam bracket detail
below) is the heart of the Wallace
patented
self-aligning beam.
|
As you can see in the
detailed images above (CAD end profile and free body diagram),
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. The rendered
image (right) shows how the caster frame pin at the base of leg
transmits the load across a single line. Please note that bolting
hardware was removed from the CAD image to draw attention to the load
bearing pin.
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.
|
|
CAD images created
at Wallace Cranes with SolidWorks, Dassault
Systèmes, SolidWorks Corp.
© Wallace
Cranes, 2009.
Revised 4/11/09, 7/24/09,
9/30/09
|
