Rigging Paper Project Help

[choircamper]

Hey, so for the rigging class I am in I have to figure out the prefered way to rig this, so far I have an answer, but I think that there are better ways to do it. Mainly I'm looking for where the bridles should be placed and if there should be a dead hang at center. Any thoughts or ideas would be very helpful. So here's the scenario:

Givens:
- 12 x 12 Truss (5.5 lb/ft) - 50ft long
- 1020 lbs evenly distributed load
- 500 lb point load at center
- Trim height to the bottom of the truss needs to be 40ft
- There are 3 I-Beams on 29' centers. One is located at center at 80ft from the deck and the two outer I-Beams are 70ft from the deck.
- BHEL=1.7ft w/5ft Baskets
- Only can use 1/2 ton chain motors w/50ft chains.

So there it is, mainly if there are some experienced riggers who could give me advice, where should I place the points on the truss?? Thanks

 

[gafftapegreenia]

I'm not saying we aren't going to help, but:

I would assume that your instructor has taught you the principles and methods needed to figure out this problem. I would be very surprised if this question has been thrown at you out of left field. Why don't you tell us what you have come up with first? That way we can nudge you along in the right direction, and help you learn in the process, instead of doing to work for you. Who knows, maybe you've already got it.

 

[MPowers]

Ditto what gafftapegreenia has said. Tell us your solution and how you reached it and we'll be glad to comment and guide. BTW, Different grades/models/brands of truss have different load capabilities, are you given a particular grade or brand or model # of 12x12 truss?

 

[choircamper]

Alright, so for the purpose of the problem they only specified 12x12 truss, mainly for the purpose of the dimensions, not the forces involved, so for this we're going to ignore the actual forces on the truss, what he cares about is the proper placement of the bridles/deadhangs assuming the truss can hold it. Alright, so what I have right now is:

Right now I have the pick points on the truss 4' in from each end and at Center.

I came up with those answers using the givens and then after some struggling, to find "nice" numbers to be used when figuring out what arrangement of hardware to use, I went and put the parameters into LD Calculator Lite just to adjust the bridle legs to something that worked nicely. From these numbers, once I'm happy with them I will be figuring out the tensions and forces put on the bridle legs and the I-Beams. Actually I have already done a lot of the work on scratch paper, I'm just worried that the initial setup is not ideal so those numbers become worthless anyways. Anyways, please take a look. Thanks