Need a book? Engineering books recommendations...
Return to index: [Subject] [Thread] [Date] [Author]
RE: Center of Gravity & Sling Loadings
[Subject Prev][Subject Next][Thread Prev][Thread Next]- To: seaint(--nospam--at)seaint.org
- Subject: RE: Center of Gravity & Sling Loadings
- From: "Lutz, James" <JLUTZ(--nospam--at)earthtech.com>
- Date: Mon, 12 Aug 2002 10:53:20 -0700
I don't have a good feel for what you mean by "trolley." Assuming you are trying to pick up a fairly rigid object at four points, and the center of gravity is within the polygon defined by the four pick points, then the load should be stable. If you don't mind being conservative, you could successively analyze the system four times with a different sling assumed slack each time. It's not all that much math. A few of the models will fall out as unstable unless the center of gravity lines up exactly with the intersection of the diagonals between the corners of the polygon. It won't be an accurate solution, but it will give you a load envelope that should cover you. I suspect that one of the cables will carry very little load in any case, so the results may not be that far off. -----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 ! ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ******** ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
- Prev by Subject: Re: Center of Gravity & Sling Loadings
- Next by Subject: RE: Center of Gravity & Sling Loadings
- Previous by thread: Re: Center of Gravity & Sling Loadings
- Next by thread: RE: Center of Gravity & Sling Loadings
- About this archive
- Messages sorted by: [Subject][Thread][Author][Date]