This was actually a subject that I was really interested in back a few months ago, and I spoke to a number of rigging professionals to try to figure out how one would actually calculate the loads and forces involved. Interestingly, the responses I received from some of the most respected riggers in our industry varied widely, from "it's identical to a
truss parallel to the floor" all the way to "it requires all these calculations with center of gravity" and so on and so on. All the responses, however, stated that they just calculated the full load of the
truss on each individual
point whenever hanging angled
truss in order to prevent against possible overloading. So it seems like, at least
in one faction of the industry, this isn't an important calculation.
As I understand it (with the help of an old physics professor), the change in loads is caused by the changing of the positioning of the
truss itself in relation to the points. As you lift one of the points of the
truss, the center of gravity of the
truss starts to
shift, causing it to move horizontally. Assuming the points were originally directly above their attachment points on the
truss, each pick
point would no longer be completely vertical, thus adding a horizontal force component and changing the weight distribution on each
point. As it was explained to me, if the supports were something rigid (steel beams or
ground supported
truss) the forces would remain the same, but since the aircraft cable/chain holding up the
truss has the ability to move off vertical, this changes the equation. Again, I don't know if any of this is right, but it's what seemed the most logical to me when I was trying to figure this out, and perhaps it will provoke new discussion.
Out of curiosity - does anyone actually know the answer to this (and how exactly to get it), or is everyone actually stumped. You don't need to step in and answer it just yet, I'm just wondering because it's been open to all responses for almost two weeks, but no one's given the answer.