Help with bending an I-beam (math)

[jtb51b]

Ok so I need to make a flat trailer into a dovetail trailer. I will be cutting and plating the existing I-beams under the deck to do this. The welding and cutting I can handle but the math has me boggled. I know I have been taught how to do this equation but I can't even get started. So, here it is. I have a 6" I-beam (just imagine it in 2d as a 6" rectangle) that is 20' (240" long) I will be bending it at the 188" line and lowering the remaining 52" by 12" (this 12" drop will be at the TOP of the rectangle) .. Now, what I need to know is how much of the bottom of the I-beam I need to plasma out? The top will just be have about a 1/16 gap cut in it but the bottom of the removed "pie piece" will be much larger. I do not want to remove too much but don't want to be cutting a 1/4" at a time till I get there either. Someone save me here, I can't even seem to get there with CAD.. My brain is fried..

Thanks,

Jason

 

[Dune]

I would figure out the angle you are going to end up with, divide it in half, lay it out at the 188" mark, cut the beam right off at that angle, flip the short section over, and weld it back together, but I am kind of simple.

 

[jtb51b]

Problem is i am not removing the beam. It is staying under the trailer.. The top is steel plate and is will be stitch cut and re-welded.. It would be a TON of work to remove the beams.

Jason

 

[jtb51b]

Now. if I could figure out the angle then I would already be somewhere. Ugh..

Jason

 

[semipro]

Ok so I need to make a flat trailer into a dovetail trailer. I will be cutting and plating the existing I-beams under the deck to do this. The welding and cutting I can handle but the math has me boggled. I know I have been taught how to do this equation but I can't even get started. So, here it is. I have a 6" I-beam (just imagine it in 2d as a 6" rectangle) that is 20' (240" long) I will be bending it at the 188" line and lowering the remaining 52" by 12" (this 12" drop will be at the TOP of the rectangle) .. Now, what I need to know is how much of the bottom of the I-beam I need to plasma out? The top will just be have about a 1/16 gap cut in it but the bottom of the removed "pie piece" will be much larger. I do not want to remove too much but don't want to be cutting a 1/4" at a time till I get there either. Someone save me here, I can't even seem to get there with CAD.. My brain is fried..

Thanks,

Jason

If I understand you correctly it should be a simple ratio of 52/12=6/x or 12/52=x/6 (doesn't matter) where "x" is how much you need to cut out.

Then cross multiply so 72=52x so x=72/52 or 1.4 in.

Its basically the ratio of radius to chord length where the radii are 52 and 6 and the chords are 12 and "x".

 

[jtb51b]

Semipro, you are correct.. I actually got out some graph paper and figured it out but you are correct. I actually quoted the numbers wrong, it was 50" past the cut not 52" which makes the bottom of the cut 1.44" (I will cut it on 1.5").. I could not for the life of me remember how to do this, man I feel dumb.. I will get it cut on the next dry day.. Thanks again.. Oh and BTW I love the avatar, I have a black lab lying on my feet as I type..

Jason

 

[semipro]

Semipro, you are correct.. I actually got out some graph paper and figured it out but you are correct. I actually quoted the numbers wrong, it was 50" past the cut not 52" which makes the bottom of the cut 1.44" (I will cut it on 1.5").. I could not for the life of me remember how to do this, man I feel dumb.. I will get it cut on the next dry day.. Thanks again.. Oh and BTW I love the avatar, I have a black lab lying on my feet as I type..

Jason

Thanks. Though I love black labs, believe it or not he's a shelter mutt that's a cross between a border collie and golden retriever. The photo makes him look a lot bigger and tall than he is.

Good luck with the trailer conversion.