Parts Load Descriptions
The effects of two different types of loads are of
concern regarding the structure known as the Suspendulum®. Dead
loads verses live loads. Dead loads (static loads) are considered
permanent loads and vary only with regard to the weight of the individual
aerialist or swing vehicle occupant. Live loads such as dynamic weight
changes from performing “drops” change the value of forces
applied to the structure.
The Suspendulum® is a tetrahedron. The loads bearing down on each
of the legs is in direct proportion to the weight applied to the leg
closest to the weight being applied; i.e. when the load is aligned
with any of the legs that leg bears the load. When the load is aligned
halfway between the supporting legs both legs share bearing the load.
Each leg is composed of steel tubing that has a compression rate failure
above 40,000 lbs. In order to swage the ends of the tubing 40,000 lbs.
of pressure must be applied in order to squeeze the tubing into a swaged
form in order to make one end of the tube fit into any other non-swaged
end. The four inch swage insures against bending of the tubing. Leg
tubing are inserted into 4 inch swage with spring-button to assure
depth of fit into adjoining tubing.
The quarter inch thick mounting plate holding the legs in place at
the apex (top) is rated at 36,000 psi made from hold rolled A36 Carbon
steel. Swing bolts attaching the steel tubing to the mounting plate
are made from hot-forged steel.
The u-bolt with which the user attaches various vehicles to is made
from forged metal bases meeting or exceeding all requirements of ASME
B30.26 including identification, ductility, design factor, proof load
and temperature requirements. Importantly, the u-bolt used for the
apex of the Suspendulum® meets other critical performance requirements
including fatigue life, impact properties and material traceability,
not addressed by ASME B30.26 and meets the performance requirements
of Federal Specification FF-C-450 TYPE 1 CLASS 1
The O-ring attached to the u-bolt at the apex has the
following criteria:
Uses for Military/Parachute 1298-1 11-1-599 Cargo/Fall Arrest/Safety
1298-1S Hot Forged Alloy Steel Thermal Treated
Cadmium, Zinc Plated 100% Proof Load Tested @ 15.3 KN (3,600 lbs) Meets
or exceeds PIA-H-7195 Meets or exceeds ANSI Z-359.2
The cables used to keep the legs from splaying outward
and hold the tetrahedron shape in place have a 3/16” x 7/19
strand format normally used for aircraft cabling and has a breaking
strength of 1920 lbs. The quick-link holding the cable to each foot
assembly has a working load limit of 1900 lbs.
