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: Load calculation
: Load calculation -- Nigel Thomas	Post Reply	Top of thread	Engineering Forum

Posted by: zekeman ® 11/01/2009, 10:08:12 Author Profile eMail author Edit

Need a picture of design, since your description isn't clear to me.

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: : Load calculation
: : Load calculation -- zekeman	Post Reply	Top of thread	Engineering Forum

Posted by: Nigel Thomas ® 11/02/2009, 05:02:09 Author Profile eMail author Edit

Hi Zekeman, I've been trying to download a pic, but can't get it to happen. I'll try explaining more clearly. The lifting strap is square section EN8 mild steel bar. It sits on top of the tool and is bolted down with M16 bolts to the tool. The distance between these two bolts is 400mm. Mid way along its length is a tapped M16 hole, ready to take an M16 eyebolt. We have straps of this design on our smaller tools but I need to calculate the height and width of the square section of the bar, so that I can make one for lifting the 1 ton tool. The lifting strap could be thought of as a small spreader bar. Hope this is more understandable, thanks again.

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: : : Load calculation
: : : Load calculation -- Nigel Thomas	Post Reply	Top of thread	Engineering Forum

Posted by: Nigel Thomas ® 11/02/2009, 06:47:29 Author Profile eMail author Edit

Hi Zekeman, managed to get a picture

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: : : : Load calculation
: : : : Load calculation -- Nigel Thomas	Post Reply	Top of thread	Engineering Forum

Posted by: zekeman ® 11/02/2009, 11:39:25 Author Profile eMail author Edit

I hesitate to comment on this design, since any failure can result in human injury. I will say this however, that the bolts holding the strap must be better secured than just a blind threaded hole and the eye bolt, similarly must be locked better to the strap. The actual stresses must be dependent on a dynamic load, say 3 times the one ton static load; and safety precautions must be present during any lift operations so that a failure won't result in injury. The basic problem is fairly simple and I suggest you involve a professional engineer to rule on the adequacy. Sorry that I couldn't offer you more assistance and assurance.

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: : : : : Load calculation
: : : : : Load calculation -- zekeman	Post Reply	Top of thread	Engineering Forum

Posted by: jboggs ® 11/02/2009, 13:43:19 Author Profile eMail author Edit

There are beam calculators on this site that can give you the mathematical results. Looks like a simply supported beam with a single point load to me. My comment would be that you should consider the microscopic motions that occur at the bolted joints as the lifting beam deflects. Do not say "It won't deflect" because it will. In fact, I would caution you against tightening the bolts all the way down on the lifting beam. That would leave room for natural deflection. You should carefully consider all the possibilities when you assign safety factors in your calculations.

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: : : : : : Load calculation
: : : : : : Load calculation -- jboggs	Post Reply	Top of thread	Engineering Forum

Posted by: blacksmith1956 ® 11/07/2009, 16:44:06 Author Profile eMail author Edit

If you have the hoist and head room why not use two shoulder eye bolts and a two leg chain sling to lift the tool. Make sure each leg of the chain is long enough to maintain an angle that will not exceed the WLL rating of the chain.

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