Hello.

I am working on a assembly which is to be simulated to mimic the action of crane lifting it. Just like one shown in image. If anybody did similar kind in solidworks simulation kindly help.

Hello.

I am working on a assembly which is to be simulated to mimic the action of crane lifting it. Just like one shown in image. If anybody did similar kind in solidworks simulation kindly help.

Hi Ryan,

Thank you for the prompt reply. And I am interested in analysinig the four hooks which are used for lifting the assembly. My main concern is that if hook breaks while lifting the assembly. Also I am interested to define what should be the height ofpivot point of the chain which lifts the assembly I am attaching the model as well as the sim. setup. It would be great if help me out in setting up study. Thanks in advance.

Hi Gaurav,

The slings and hooks used in rigging are a bit of a science in themselves. The hooks (in Australia) have to be latch-lock which means that they are fully self enclosing. These hooks are/should always be set so that the opening is facing towards the outside perimeter of any load.

Any sling, whether it be fibre or chain loses a percentage of it's Safe Working Load (S.W.L.) the more aggressive it's angle is from the main crane hook. To give you a basic example, in the photo you show, the sling angle looks very appropriate whereas in your own image above the purple chains have far too much angle on them and therefore would probably need to be rated at a much higher S.W.L. than should reasonably be needed. Furthermore, any form of pinch-point in any form of sling decreases it's S.W.L. by a much more dramatic amount.

I could go on about this for hours but it really depends on how much you really need to know to affect your simulation. Google can explain to you most of this stuff also.........

Dave.

It is not proper design technique to guestimate or use percentages to adjust for angle of the rigging sling in selecting the tensile strength of the sling material. This angle directly influences the tension that the sling (rope/strap/chain) undergoes. You can lift a 1 ton block and the rope will experience a roughly a 10 ton tension if it is connected at a very steep angle. This cannot be accounted for with "percentages". This tension must be accurately calculated before selecting a rope or other components of the rigging. A person should be very proficient at statics and mechanics of materials before attempting to design anything that can put lives at risk. A giant TV tower collapsed because the rigging was not selected by an educated engineer. google "TV tower collapse 1982 U-bolts" for more info.

This doesn't seem to answer the OP's question.

By the OP's problem description the analysis is not of the sling, but rather the hooks.

For the purpose of the analysis the slings can be set far beyond yield. (

**Edit:**Let me rephrase that so that there is no confusion - that is, the slings can be selected with material and diameter far greater than needed to lift the given load - they will not be the failure point for the purpose of the stated analysis.)For the purpose of analysis the slings can be set to rigid links.

Successive approximation in 3D analysis environment (guestimation) can be very efficient technique for honing in on answer to question.

Can you post hand calcs and 3D model verification?

I'm not addressing the OP I am addressing Dave Bear's comment. While it is good that he is discussing practical implications of design I wanted to clarify that the angle can severely effect tension and therefore tensile strength requirements and must be accurately calculated by a knowledgeable engineer. This also effects the hooks. They may experience a 10 Ton load instead of a 1 Ton load based on the angle used.

What I think the OP should do is calculate the tension (which is the force the hook will experience) then apply that tension in simulation at the angle it was calculated for to the hook. Use an iterative process of changing the "pivot height" and calculate the resultant tensions until you find something that works.

Google "static Equilibrium" for examples on how to calculate tension.

Marcus Dimarco wrote:

Google "static Equilibrium" for examples on how to calculate tension.

Given that I teach a class were we solve this very analysis (but in a different MCAD software) I think I will pass on the Google research, unless you convince me that my understanding is faulty - I am always open to constructive critique, I would hate to be passing invalid information on to my students.

Hmmm, I really would like to tackle this problem in SolidWorks, particularly in showing how a parametric model can be set up to very quickly analyze successive configurations. Once we have validated our digital prototype we can run far more scenarios. Maybe I will find the time in the next couple of weeks.

I think that is a great thought to set up a model for this type of situation in Solidworks and I figured from your last post you were gathering data to do this. That's why I said google "static equilibrium" because you asked me for hand calc's. But ya that would be great if this sort of modeling could be done in Solidworks without first having to calculate tensions by hand.

Hi Marcus,

Marcus Dimarco wrote:

It is not proper design technique to guestimate or use percentages to adjust for angle of the rigging sling in selecting the tensile strength of the sling material. This angle directly influences the tension that the sling (rope/strap/chain) undergoes. You can lift a 1 ton block and the rope will experience a roughly a 10 ton tension if it is connected at a very steep angle. This cannot be accounted for with "percentages". This tension must be accurately calculated before selecting a rope or other components of the rigging. A person should be very proficient at statics and mechanics of materials before attempting to design anything that can put lives at risk. A giant TV tower collapsed because the rigging was not selected by an educated engineer. google "TV tower collapse 1982 U-bolts" for more info.

The engineering part comes into play within the manufacturing, design and testing fields of rigging equipment.

Within the field of practical rigging, you CAN actually use calculations of percentages for the S.W.L. of slings with regards of angles. You CANNOT however exceed by any measure the S.W.L.

Slings, as standard are engineered and manufactured to withstand nominal loads within the guidelines of normal rigging procedures. The sling capacity decreases dependent on it's application, as I stated. You did not need to clarify that.

Nowhere in my post is the word 'guestimate' used as I for one now what virtual perils there are with getting this sort of thing wrong. You state

*"You can lift a 1 ton block and the rope will experience a roughly a 10 ton tension if it is connected at a very steep angle",*now that's a guestimate and I would venture that you have little idea as to what angle or diameter that rope would have to be, let alone the fact that rope was a bad choice to start with..........This cannot be accounted for with "percentages". So, So, very incorrect my friend.......... A rigging sling loses a percentage of it's S.W.L. at each increase in angle from the crane hook and it is often calculated in this manner!

I was merely giving the OP some 'basic' insight into what they might need to consider should they want to venture into adding rigging formula's into there simulation. As I stated to the OP, if they use the correct rated S.W.L. hook and sling at the correct angle from the crane hook nothing will exceed it's limits.

Dave.

Oh, BTW, I've held an Advanced Riggers qualification in Australia, which is the highest practical field qualification you can hold, and I have had this since 1988.

This cannot be accounted for with "percentages". So, So, very incorrect my friend.......... A rigging sling loses a percentage of it's S.W.L. at each increase in angle from the crane hook and it is often calculated in this manner!

So can you tell me what percentage S.W.L it looses per degree? Unfortunately the way tension is calculated it will not change in a linear manner per degree! I don't have a camera to photograph my hand calculation but if you are holding a 10kg weight (98 Newtons) with two ropes and the angle of the ropes with the load is 3 degrees (a very "steep" angle), the Tension on

*each*rope (and therefore on each hook) is 936 Newtons! All combined (both ropes) that is a roughly*20X higher*load then if it was held with 1 rope that was vertical.I think I would want my rigging engineer to actually calculate the tension and select a rope rated for that tension... But maybe that's just me.

Marcus Dimarco wrote:

...So can you tell me what percentage S.W.L it looses per degree?

Do you know how to use a calculator? I will assume you can.(if not see link below).

I have attached 2 PDF files that will explain in great detail how to calculate sling loads.

One of the files have lots of pictures.

Use your calculator to calculate as many angles as you desire, to your hearts content.

If a calculator eludes you, here is a link to a handy dandy online calculator. Just type the angles and read the tresult.

Lifting Sling Capacity Equations, Calculator and Considerations - Engineers Edge

Marcus Dimarco wrote:

This cannot be accounted for with "percentages". So, So, very incorrect my friend.......... A rigging sling loses a percentage of it's S.W.L. at each increase in angle from the crane hook and it is often calculated in this manner!

So can you tell me what percentage S.W.L it looses per degree? Unfortunately the way tension is calculated it will not change in a linear manner per degree! I don't have a camera to photograph my hand calculation but if you are holding a 10kg weight (98 Newtons) with two ropes and the angle of the ropes with the load is 3 degrees (a very "steep" angle), the Tension on

*each*rope (and therefore on each hook) is 936 Newtons! All combined (both ropes) that is a roughly*20X higher*load then if it was held with 1 rope that was vertical.I think I would want my rigging engineer to actually calculate the tension and select a rope rated for that tension... But maybe that's just me.

Google "Bullivants V2 Rigging Handbook"

When you've read it and think you are fully conversant with it, then, and only then, come back and talk to me about rigging!

Dave.

While I haven't read all the posts in detail, I would caution that using the remote load rigid connection or displacement rigid connection could very easily provide hazardously misleading results. If the slave nodes are single nodes on solid elements it will work fine as no moments will be generated by the rigid connection. If multiple nodes exist at the slave locations - say one picks a surface patch then the connection will support moments and this may cause unintended load paths. I would recommend that one puts at the "hook" location a vertex made from solid elements and vertices where the slings connect to the load. This would involve splitting the surfaces of the hoisting clevis and ensuring the hoisting clevis is oriented correctly. Then use the link connectors between these vertices and the hook vertex. Then the compressive loads induced by the slings will be generated correctly. The structure above has slender "longerons" that may buckle due to these compressive loads and you want an analysis that will capture that as just a stress analysis may produce stresses that are far below a level of concern but buckling may still occur. I have done this exact analysis for steel structures (pallets really) for supporting military air and ground transportable equipment. The restraints on the model must ensure the removal of all rigid body modes without adding any over constraints. The link connector is perfectly stiff as it is a geometric constraint, however, deformations in the rest of the structure may require a large displacement analysis but maybe not. The above mentioned equipment underwent test without any issues.

Rigging Engineering is difficult and takes lots of training even if you have a ME degree. So be careful out there everyone!

Marcus Dimarco wrote:

Rigging Engineering is difficult and takes lots of training...

Which proves that Dave Bear knows what he is talking about from both an engineering point of view and practical hands-on point of view.

Marcus, what degrees and real world experience do you have?

1-AG4JLT wrote:

...Marcus, what degrees and real world experience do you have?

Comment from John Stoltzfus...

*Let me guess Rick…….**Greater “Annoyance” Degree - GAD**Sir Marcus Dimarco, GAD*

Hi Gaurav,

The same sort of setup is applied to the model in this thread: Simulation: Load Applied on Lifting Lugs

The model in that thread uses "Use Reference Geometry" fixtures to restrain the lifting lugs as though they are being held by tension cables attached to a crane. If what you are looking to analyze the palette and not the crane then this is probably what you are also looking to do.