MLMartin Posted June 9, 2011 Share Posted June 9, 2011 Hello everyone I am hoping to build a rolling gantry crane for my shop soon. I plan to make the crane 10 feet wide and 10 feet tall. I need a 3000 lb capacity for the crane. The legs are no problem but I don't know how to calculate the size of I beam to use. And what dose mass distribution do for this application? Example a beam that has a web of .5" by 4" and flanges that are .5 by 3" has the same mass per foot of a beam that has a web .25" by 8" and flanges that are .25" by 6". Because the crane will roll I understand that torsion will be exerted on the bream so its not just about the strength in one direction. And obviously it needs to be build over the breaking point so I guess I would actually need a bream that could handle 4000 even though I would only use it for 3000 So how do I calculate what size beam to use, or what size beams have you used that has worked for you? Thank you for any help Quote Link to comment Share on other sites More sharing options...
David Einhorn Posted June 10, 2011 Share Posted June 10, 2011 I looked around and found this discussion. ... http://www.craftkb.com/Uwe/Forum.aspx/metalworking/10040/designs-for-a-better-shop-crane They even point to a set of plans at: http://www.plansandprojects.com/portable.htm Quote Link to comment Share on other sites More sharing options...
monstermetal Posted June 10, 2011 Share Posted June 10, 2011 The simple thing is to go to the Spanco website. They list all the beam sizes for span and capacify of all there gantries Quote Link to comment Share on other sites More sharing options...
Fosterob Posted June 10, 2011 Share Posted June 10, 2011 Do not try to re invent the wheel here, copy something that has been properly engineered. I use the dearborne crane site. It lists all sizes and spans with other info as well. Link: http://www.dearborncrane.com/pdf/gantry/gantrybro.pdf Rob Quote Link to comment Share on other sites More sharing options...
Glenn Posted June 10, 2011 Share Posted June 10, 2011 copy something that has been properly engineered. How do you determine *Properly engineered*? Are they not engineered to the minimum standards for the application so as not to waste materials? Quote Link to comment Share on other sites More sharing options...
MLMartin Posted June 10, 2011 Author Share Posted June 10, 2011 Thanks guys, not trying to reinvent anything. I looked for some type of length to strength ratio or chart on line and could not fine one. When I passed across the gantry cranes on the internet I did not see any sites that listed the sizes of beams used. But I will gladly look up both sites suggested, just what I wanted! Thank you Quote Link to comment Share on other sites More sharing options...
Fosterob Posted June 10, 2011 Share Posted June 10, 2011 How do you determine *Properly engineered*? Are they not engineered to the minimum standards for the application so as not to waste materials? I think that these large corporations that make overhead lifting equipment know what they are doing and have large amounts of safety built in to their products. One reason is they have DEEP pockets and any injury from failure would likely mean a cash payment and legal fees. These companies use a certain size beam for a certain span and load, I would not even think twice about using the same size members for my shop. Rob Quote Link to comment Share on other sites More sharing options...
Bentiron1946 Posted June 10, 2011 Share Posted June 10, 2011 I remember when way back when I spent a week working in structural engineering office doing some drafting, talking with one of the engineers asking him how big was big enough? He said that he could always engineer any piece of steel to hold exactly the load it was supposed to hold but given what human nature was he always add in his fudge factor. I asked him what that was and his reply was that he wasn't going to tell or some idiot would try to see how close to that he could get and not get killed. It's that way with cranes, they put that load limit on there for a reason, yeah, that right so you can run right up to the "do not exceed" limit and think how clever you are all the time and still be under the true load limit by fifty percent and still come to work the next day, alive. :blink: Quote Link to comment Share on other sites More sharing options...
monstermetal Posted June 10, 2011 Share Posted June 10, 2011 Well for cranes its no secret... There is a standard that says in order to pass a load test the system must pick 125% of its rated capacity.. There are deflection allowances for diffrent types of cranes but in all cases a measurement is taken from the bridge to the floor and the bridge must return to its unloaded state after the 125% pick.. if it doesn't it fails.. Standard for any overhead lifting apparatus is it must be able to withstand 5 times the rated load before failing... That doesnt mean its safe to 5 times it rating.. that means it shouldn't come crashing to the floor until 5 times rated capacity.... It will only bend or give until that point... And your right... cranes are not something that is engennered to "just enough" I worked as a sub for Kona Cranes for some time, my brother still does... They are the largest crane company in the world... there single largest consideration and expense is liability... They dont cut anything close... Its always way overbuilt... its the cheapest thing to do... Quote Link to comment Share on other sites More sharing options...
SmoothBore Posted September 12, 2011 Share Posted September 12, 2011 I use a rolling Gantry nearly every day, and find it to be a valuable asset. One bit of advice : Make it as high as possible. I often wish for "just a few more inches" under the hook. . Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted September 12, 2011 Share Posted September 12, 2011 I use a rolling Gantry nearly every day, and find it to be a valuable asset. One bit of advice : Make it as high as possible. I often wish for "just a few more inches" under the hook. . Yep! There's never enough head room! :rolleyes: Quote Link to comment Share on other sites More sharing options...
MLMartin Posted September 13, 2011 Author Share Posted September 13, 2011 I have built the gantry now, and I did build my gantry only 6" shorter than my main door. Quote Link to comment Share on other sites More sharing options...
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