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Re: Center of Gravity & Sling Loadings

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Mr Kausik,

        Respectfully, this is an excellent equation but in reality it's essentially a variation on the well known equation

            f = P/A + M*c/I.

If your slings have differing E*A/L stiffness you will have to factor this in to EACH sling.  This will make the equation a little messier than you
have presented but it will certainly be valid.

        Good thinking to use this equation.

Regards,

H. Daryl Richardson

Kausik wrote:

> 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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