Installation manual

Community S-Series - Operation and Installation Manual - Page 43
4. Load Angles
This is an area that is often misunderstood, so let’s clear it up. Whenever an object is
suspended from one point, it has no choice but to hang directly below that point of
suspension; in other words at a zero degree angle to the suspension point. When an object
is suspended from more than one point, the points may or may not be at zero degrees to
the suspension point. When the suspension points are not at zero degrees to the object,
they form a bridle. As the angle of the bridle increases, the force through each leg of the
bridle also increases (see Figure 12 below). A high angle bridle can produce forces in the
suspension legs that are many times the weight of the suspended object. This is
counterintuitive, as most people’s understanding of physics would suggest that the object
cannot produce a greater load than that of its own weight. Not true. For example, a 100
lb. object can produce 300 lbs. of force at a bridle angle that may not appear dangerous to
the untrained observer. At very steep angles, the load can far exceed the rating of even
the most robust rigging components, in addition to placing an enormous compression or
expansion force on the object itself (depending on the direction of the bridle). Therefore,
steep bridle angles are to be avoided under all circumstances.
Figure 12: Load Angles
Even more dangerous, is the practice of reeving a suspension cable or sling through two
shackles or eyebolts, forming a type of basket hitch (see Figure 13). This again increases
the force through each leg, as well as significantly increasing the loading on the shackles.
It also allows the load to easily tip or shift its weight in the hitch. It should always be
avoided.
Figure 13: Never Reeve Cables!