Lifting Shackle Stresses
Lifting Shackle Stresses
(OP)
Hello All,
I'm currently designing a lifting shackle to aid the recovery of a ROV, my problem is that I'd like to do some hand calculations to find the stresses in the shackle but I'm really not sure as to where to start.
I know how to calculate the stresses in the fixing holes but it's the point where either a hook or another shackle will be used.
I've looked all over the net and in Roark's but to no evail.
Please see the attached image.
Regards
Will
I'm currently designing a lifting shackle to aid the recovery of a ROV, my problem is that I'd like to do some hand calculations to find the stresses in the shackle but I'm really not sure as to where to start.
I know how to calculate the stresses in the fixing holes but it's the point where either a hook or another shackle will be used.
I've looked all over the net and in Roark's but to no evail.
Please see the attached image.
Regards
Will





RE: Lifting Shackle Stresses
Strength of materials textbooks always have one of those problems.
Moment Maximum will be P/2 * 1/2 distance between the bolts. Limit stresses to at leasat 1/4th the elastic yield point so you don't get something that looks like your sketch, and watch stress concentrations in the threaded sections.
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.liv
RE: Lifting Shackle Stresses
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.liv
RE: Lifting Shackle Stresses
You say that the max bending moment will be the force applied/2*1/2 distance between the bolts. What is meant by 1/2 distance between the bolts?
Cheers Again
RE: Lifting Shackle Stresses
That could probably be reduced a tiny bit, because you might get some end moment resistance from bolt and nut fixity, thereby reducing the centerline moment, but I'd not count on it and just use PL/4 * c/I to get the bending stress. Tension load is P/2 to each bolt end, with maybe PL/10 as a fixed end moment.
"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
http://www.youtube.com/watch?v=hpiIWMWWVco
"Being GREEN isn't easy." Kermit
http://virtualpipeline.spaces.liv
RE: Lifting Shackle Stresses
RE: Lifting Shackle Stresses
I did have a look around briefly before.
RE: Lifting Shackle Stresses
Or you could hire one of the many experienced unemployed engineers to do the calculation for you.
To do this analysis. You need to figure out how much Load is going to be lifted. The center of gravity will play an important part in deciding how the weight is divided.
Also, you need to read the American Petroleum Institute Recomended Practices on crane lifts and wire rope.
Hint: Two of the four wire ropes must be able to carry the whole load.
While the weaklest link of the whole system could be the pin, it is often to over-engineer the padeye, so be careful.
The shackles are selected based on the weight.
Weight-> Shackle -> Wire Rope -> Master Link -> Block -> Crane -> Padeye -> Shackle -> Wire Rope
It's an iterative process.
Try not to kill or injur anyone.
RE: Lifting Shackle Stresses
If you "heard" it on the internet, it's guilty until proven innocent. - DCS
http://www.eng-tips.com/supportus.cfm
RE: Lifting Shackle Stresses
You can also calculate as a fixed end DEEP beam , Roark "Beams of relatively great depth", section, assuming a pinned ends.
Don't forget to check the Bolt end for tearout.
Finally you can check for contact stress using Roark section "pressure between elastic bodies", cylinder on cylinder, Allowable=2xRe.