Question relating to sizing of pins and what calculation to use

[ajmac1973]

Hi there, firstly thanks for taking time out to look at and hopefully answering my question.
I am currently designing a stacking skid system the three will be connected together by means of four pins.
Please have a look at the attached PDF for a clearer idea of what I plan to do. I am just not sure of what calculation I should use to determine the pin size.
The outer cylinder diameter is 80mm and the inner cylinder that goes into it is 40mm in diameter. The resulting sling load on each pin is 23303Newtons.

Again many thanks.....Tony

 

[MikeHalloran]

Your sketch is neat, but is not a model of clarity or sufficiency.
e.g.:
You talk about pins, but the only identifiable objects in the sketch appear to be socket head capscrews.
You talk about a sling, but don't show it.
Please add some detail.





Mike Halloran
Pembroke Pines, FL, USA

 

[TVP]

I agree with Mike. You might need to show more than 1 view to adequately describe the situation.

 

[ajmac1973]

Thank you both for your interest.
I have attached two files one called problem. In this I have tried to detail the drawing a bit better. However you will probably get a better idea in the attached pdf called problem3d. In this you will see two skids. The top one will sit on the bottom one. Then all four courners will be "pinned" the top skid will then be lifted (by a sling not shown) which in turn will lift the bottom one due to the four pins. As mentioned the load on each pin will be 23303N or 2375KG which ever you prefer. So to recap I cant figure out how to work out the pin sizing.

Tony

 

[ajmac1973]

Just realised you can only attach one file at a time so here is the second one....

 

[MikeHalloran]

In the 'problem' document, you have not made it clear whether you are depicting a side view or a section view. The 'problem3d' document suggests that you intend the views in the 'problem' document to be sections, and all features of the subject details to be cylindrical.

If the 40mm tenon is indeed cylindrical, a reasonably sized crosspin will leave essentially no net area with which to lift anything.

Machining a 40mm tenon from an 80mm round is fairly expensive, as is efficiently terminating the other end of the round to a skid.

It appears that you plan to have two interchangeable skids, and to use the upper ends of the posts of whichever one is uppermost as padeyes for lifting. Lifting applies bending loads, for which you have perhaps not accounted. That's why you need to show the sling to be used.

I mean no offense by this, but you appear to need local help with both drafting and engineering. By local, I mean an experienced person, right there, looking over your shoulder and pointing out mistakes as you make them.

We cannot do that from here.

Please rent an engineer.


Mike Halloran
Pembroke Pines, FL, USA

 

[KENAT]

What regulations apply in your situation? Some 'below the hook' regulations require significant safety factors/margins of safety - way more than 1.5.

For a first pass, look at simple shear.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[hydtools]

You must evaluate the double shear of the pins, the tear out capacity and the tensile capacity of the remaining cylinder material accounting for the hole through which the pin passes.

Ted

 

[MikeHalloran]

And the bending stress on the pin at its root, and on the post at its root, and all the stresses in whatever the hell fixes the post to the skid, with the skids hanging from a sling hanging from a hook, and the bending of the skid frame, and....



Mike Halloran
Pembroke Pines, FL, USA

 

[chicopee]

Doesn't anybody know how to scketch anymore?

 

[desertfox]

Hi ajmac1973

The pin will be in double shear as stated by others, have a look at the bolt in double shear at this site, the same formula apply to your situation:-

http://www.roymech.co.uk/Useful_Tables/Screws/Bolted_Joint.html

 

[chicopee]

Also don't forget to include in the analysis the stresses(tensile,bearing,and tear) at the pin holes.