Bridge Crane designs and ideas...38' span

[LD1]

I ran into the same situation when I built my bridge crane. I designed it, but a PE friend of mine picked the sizes of the shapes.
With only a 24-feet span, an S-Shape was going to be too tall. The PE had me use a Wide Flange, rip an S-shape, and skip weld it to the bottom flange of the Wide Flange. I used a 12" x 87# Wide Flange. For 1-ton capacity.

IS that the beam the PE requested? Seems overkill for 24' span and 1-ton.

1220psi shear load, and deflection of .04......seems you could lift a bit more if wanted.

Unless I am missing something...W12x87, 24' span, even with a 5t load would still be a 6:1 SF for stress, and only .224" deflection. Which is still under L/1000 which is what seems pretty common for cranes an trolley beams.

Fortunately I dont need a PE to sign off. Wonder what beam he would have spec'd for you if you wanted 5T and 40' span?

 

[Shield Arc]

Have any of you guys seen the duel 300 ton cranes inside of Hoover dam? They probably span 200 feet and run the length of the 600 foot long room.

Oh those are toys. I worked with this derrick a lot. 1000-tons. The heel of the boom is 40-feet wide. The boom weighs 100-Tons.

 

[Shield Arc]

IS that the beam the PE requested? Seems overkill for 24' span and 1-ton.

Well not really. I got on the telephone, and called my buddies who were still working and asked what they had on their jobs, that I could have. Then I called the PE with the list. He said go get the 12" x 87# wide flange.

 

[4570Man]

Oh those are toys. I worked with this derrick a lot. 1000-tons. The heel of the boom is 40-feet wide. The boom weighs 100-Tons.

If those are toys what are the couple ton jobs that most home shop guys have?

 

[Shield Arc]

If those are toys what are the couple ton jobs that most home shop guys have?

Smaller toys!

 

[bigdeano]

Just for fun, here's the 2000 ton crane at the third power house at Grand Coulee dam.

 

[Leejohn]

LD how tall is your shop?

 

[LD1]

Well not really. I got on the telephone, and called my buddies who were still working and asked what they had on their jobs, that I could have. Then I called the PE with the list. He said go get the 12" x 87# wide flange.

Makes a little more sense. Dont know about the bridge rails or anything else, but with that beam, you may have well over a 1-ton crane.

What are your thoughts on using 3 beams like I pictured in the first post? Ever seen anything like that?

LD how tall is your shop?

14' to the ceiling, But will have to limit the height of the top of the bridge beam to ~12' or 12'6" to clear the lights and door tracks. So even with a 24" beam, will still have 10'+ clearance under it.

 

[Shield Arc]

Makes a little more sense. Dont know about the bridge rails or anything else, but with that beam, you may have well over a 1-ton crane.

What are your thoughts on using 3 beams like I pictured in the first post? Ever seen anything like that?

Mike (PE) was head of the engineering department of the construction company I worked for.
I had a 12" x 31.8# S-Shape from another bridge crane. I used it, and bought more for the rails for this bridge crane. The posts are 20-feet apart. Mike said those beams are the weak link. With the electric chain fall all the way to one end of the span beam, and with the span beam in the center of the posts I could only pick 1-Ton, with a 3/1 safety factor. With the span beam placed right at a post, and the chain fall in the center of the span beam I could pick 2-tons, with 3/1 safety factor.

No I never seen that done before. I don't see why it wouldnt work. All the big bridge cranes I've seen over the years had a horizontal truss for the span beam.
Remember when a beam fails, its the flange that buckles first. Thats why a Wide Flange is stronger than an S-shape.
Example: Push down on a yard stick, it bows to one side before buckling. Larger the flange less likely this will happen. You could always double up on the flanges of a beam to help it. Done this thousands of times.

 

[RedNeckRacin]

Example: Push down on a yard stick, it bows to one side before buckling. Larger the flange less likely this will happen. You could always double up on the flanges of a beam to help it. Done this thousands of times.

This is lateral torsional buckling that I was talking about. If you put bracing along the yardstick it wouldn't do that.


LD, you checked your posts and side carry beams that support the bridge right?