Question on Shackles

It seems to me that both types work just fine. Don't over analyze something that has worked in a million applications. _{(And that's no exaggeration)} I prefer screw pin shackles myself. Only two parts to keep track of.

Screw Pin Anchor Shackles

I been here before, I do not have the direct hyperlink but I did a quick google you should find it on this site for stresses, but you'll have to search for it on the site. I'm sure its there.

I also did a lifting lug program in MS-Excel, and all the stress calculations I did, I used the cross sectional area of the pin through the lug itself, and there is of course play there, initially a line of contact between the pin itself and the thickness of the lug.

My experience is I notice every new or green engineer will over analysis everything until its unrecognizable only to fail anyways

these calculation were as per ASME requirements, if your interested in it, PM me with your email address and I'll email it to you.

p911

I know the typical standard for the oilfield is pad eye hole to be 1/16" larger than the pin and no narrower than 75% of the shackle opening, using cheek plates (not preferred) or a thru welded tube (preferred), but this is sometimes problematic due to the thickness of the paint coatings that are often used. after all the paint and primer, the hole is often so tight that you have to hammer the pin in.

screw type shackles are not used because it is too easy for them to back out, it also puts the root diameter notch of the thread in the load bearing area. the shackle type with the nut and the cotter pin are usually specified.

The issue of line contact is explained fairly simply. With line contact you usually get both elastic and plastic deformation (brinelling) of the pad eye which if the hole size is close to the diameter of the pin, results in a fairly large contact area while under load.

I would also add the two primary types of shackles are anchor and chain and both are available with a tapped leg for a threaded bolt, pin and cotter as well as BNC (bolt, nut, cotter). In that case, a threaded bolt is used but the thread length is such that when the associated jam nut is run to the end of the thread, it will not contact the shackle. A hole is provided in the bolt end, about 5/16" from the end for typically a humpback cotter.

The difference between anchor and chain shackles is a chain shackle has straight legs with the radius of the closed end 1/2 the opening whereas the radius of the closed end of an anchor shackle is greater than half the opening width.

A chain shackle is typically stronger than an anchor shackle in tension because the typical failure mode is pin or bolt bending which tends to spread the shackle opening.

as per standard given by DNV 2.7-1, shows that manufacturing tolerance will be -0%/+3% from actual value tabulated in the table. and also as per EN13889 shows f bolt manufacturing tolerance. Therfore, I usually design the pin diameter for the shackle to 5% larger than the tabulated values of shackle pin diameter. where 2% to take account for the painting thickness. It seems works well

See Crospy_Shackles, (round pin type & screw pin type), and see how to select the required size as illustrated in example at page 4 of 13:

Example: For lifting lug with thickness 50 mm (dimension A), the selected shackle nominal size is 1-1/4" with working load limit 12 Ton per shackle.