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RE: Center of Gravity & Sling Loadings

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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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