There was a question in a thread that is now closed but there was no solution to the Rigging question that was asked. Itwas what is the tension on a sling with the load and angle known. I have made this simple spread sheet to calc it. You can input the Weight and angles and it will calculate the tensions.
On another note I am trying to figure out the equation to adjust the vertical slings on a 4 point pick with 3 spreader bars. I have been using a CG calculation that adjusts the Y part of the upper spreader bars to move the crane hook over the center of gravity. What I am trying to figure out is how to make it so I adjust the 4 lower vertical sligs by adding shackles to come up with the CG adjustment.
The center of gravity is a known factor. This is for hoisting equipment where the load on each sling is calculated from the vendor which in turn gives an accurate center of Gravity. I have been using excel to generate lift plans for 6 years and I would like help for this equation. If possible can we leave out the beta's and alpha lingo since all it requires is simple math equations. The idea is so people actually doing the work can understand how to figure the new sling length.
So to get started here is the idea. If the CG was perfect between 4 pick points then all slings would be the same length (lets say 20'). If it moved to one side horizontally then the 2 slings on the heavy side would have to stay the nominal length while the 2 on the light side would have to get longer (20' + 1ea 25ton shackle). The idea is to lengthen the slings with the use of a shackle or 2 on one or 2 slings while the other ones stay the original length. This can be compounded if the CG moves in both horizontal directions.
If you have a solution please advise and I will try to implement and share the file as I generate it. Appreciate the help.
http://files.engineering.com/getfile.aspx?folder=44326e70-0598-4e75-a171-519a8108ea9d&file=Simple_Sling_tension.xlsx