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Re: Center of Gravity & Sling Loadings

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I work on erection methods and frequently work on designing trollies or platforms. Hence I follow the procedure below to calculate load on slings:
1. Take moments; once Mx & then Mz. P/n+Pe/e^2 x emax

2. Now you have got the result

Kausik 

----- Original Message ----- 
From: "Robert M. Hanson" <Bob(--nospam--at)KappaEngineers.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, August 13, 2002 3:37 AM
Subject: RE: Center of Gravity & Sling Loadings


> Determine the center of gravity of the lug pattern relative to the cg of
> your load. Distribute the loads as one would for foundations with many
> piles. As long as the cg of the lug reactions match your load cg its a
> go.
> 
> Robert M. Hanson,S.E.
> Kappa Engineers
> Carson, CA.
> (310) 233-3800
> 
> 
> -----Original Message-----
> From: Jeremy Kuhn [mailto:jkuhn(--nospam--at)americancrane.com] 
> Sent: Monday, August 12, 2002 5:18 AM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: Center of Gravity & Sling Loadings
> 
> I have a trolley which I need to lift which has 4 lifting lugs on it...I
> have determined the C.G. of the load and now I am in the process of
> determining the different vertical load which each lug sees due to its
> proximity to the C.G. and then I will determine the tension in the
> slings by
> trigonometry.
> 
> Here is the question...I have come up with 2 different methods of
> determining the vertical loads on each lug - both seem to be
> logical...but
> results are very different ! Is there a correct way to determine
> vertical
> loads at 4 different locations which are at unequal distances from the
> C.G.
> ? I looked through all the Riggers Handbooks in the office and came up
> empty.
> 
> The first method I used (working in an XZ plane) was to divide the
> problem
> into 2...two lugs had a distance of 30% of the length to the C.G. in the
> X
> direction - so I assumed those two lugs saw 70% of the load - then one
> of
> the lugs which saw 70% of the load had a distance of 40% of the length
> to
> the C.G. in the Z direction so it got 60% of the 70% (42% of entire
> load)...and so on for each of the other lugs..
> 
> The second method which I used was to take a straight line distance from
> each lug to the C.G. and then determine the vertical load seen by
> assuming
> that each vertical load would be inversely proportional to the distance
> from
> the C.G. - little tough to explain the exact process.
> 
> Anyhow...any insight into an approved method would be appreciated !
> Thanks !
> 
> 
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