Bridge Crane designs and ideas...38' span

[LD1]

LD, maybe I missed something but you said "It will have 12' of run, the a push-trolley on the 38' span" Why don't you turn the design and make the 12' span the bridge and put your posts in the other direction so that you can use smaller material all the way around??


Also, your deflection calculation is most likely going to control your beam design as long as their isn't a localized failure in the flanges of the beam due to the high point loading from the very small trolley wheels. Also, don't forget that if you have to much deflection center span, that the beam could potential rotate off the running gear at the ends or at the least bind it up. Also, don't forget to look at lateral torsional buckling when you get tall slender sections.

Not sure what you mean by turn the design.

Picture this....I need a crane that will travel 38' north and south, and 12' east and west.

My current plans are to have 4 posts set making a 12'x38' rectangle. Going to set an I-beam with 40# rail track on top of the posts spanning the 12' direction, then a large beam to make the 40' span with the push trolley.

Swapping the design and going with TWO beams to span the 38' is going to require MORE material, as both beams would have to be fully rated for whatever load, and almost 80' of rail track which I dont have, I only have 30'. And I would have TWO permanent beams that could get in the way if backing the backhoe in. With a single beam spanning over top of my work area that is movable, I can always push it all the way to the back if needed.

As far as the calculations, Deflection is a NON-issue with any of the beams I listed in the first post. With the 5:1 safety allowing no more than 7200psi stress, deflection on any of them is under 1/2". It takes dropping all the way down to a 14" beam with only a 3:1 safety factor before I even get to 1" deflection.

So I guess by design, the 5:1 safety factor does limit the deflection right there. Example: a light W12x26 beam under static conditions, failure point of 36ksi is 10,500#. But 3.4" deflection. So yes, deflection is a factor, but not using a 5:1SF.

The torsional buckling is why I dont like S-type beams. Especially with a load dangling from a chain.

 

[RedNeckRacin]

Well the layout makes more sense to me now. I was just think of additional support posts around your doors to try and get all the structural members as small as possible.

I only did a quick calc on the first beam listed and not every single one. It was just one of the things we always checked for in steel class that was often over looked when doing alot of calculations. Have you sourced trolleys for the end points of the beam yet? I def think the W shape would be a goo guard around the lateral torsional buckling.

I take it your trolley is very width adjustable for the different flange widths you are looking at?

 

[Rustyiron]

Man, you're building the crane that I want to build! I got 4 beams from a bridge replacement on I-70, 37' long, about 30" tall. I bought them to build a bridge, then sh.. canned that idea, well actually moved from that property. Now I want to build your same crane. If I understand you, you want a crane that will cover every sq inch of one bay (12x40). I have a nice electric hoist, footers under the slab to carry the (4) posts, 4 - 6X6X.25 steel posts & bases, and rollers for the small "cross carriage" that the hoist will mount to. All I need to do is get them 650 miles north to my place!
I will have 2 extra beams…. in MD. You might be closer to them than I am:laughing:

 

[LD1]

Trolley is a 5t trolley. Not sure how wide of a beam it will handle. But was planning on just using the wheels and making one that spaces the rollers about 3' apart, as to not overload the bottom flange since whatever beam I get will likely be 10 or 12" wide.

Havent sourced the wheels yet. But considering making them myself. Double flange type, two on each end, so 4 in total. Havent decided yet if I would go with a pair of tapered rollers or needle bearings in the wheels. Just gonna depend on what parts I have on the shelf once I start going though stuff.

 

[otlski]

This is from Gorbel's sales lit.
https://www.gorbel.com/docs/default-source/brochures-and-fliers/gantrybro.pdf?sfvrsn=5
See page 5 for the 5 ton steel cranes. They use a 27 inch deep I beam for a 30 foot span. Somewhere on their site is another pdf that specs out what the 27 deep I beam call-out exactly is. I don't find Gorbel cranes to be overbuilt so I would go to the high side of the choices when scaling up to the 38 foot span.

 

[RedNeckRacin]

This is from Gorbel's sales lit.
https://www.gorbel.com/docs/default-source/brochures-and-fliers/gantrybro.pdf?sfvrsn=5
See page 5 for the 5 ton steel cranes. They use a 27 inch deep I beam for a 30 foot span. Somewhere on their site is another pdf that specs out what the 27 deep I beam call-out exactly is. I don't find Gorbel cranes to be overbuilt so I would go to the high side of the choices when scaling up to the 38 foot span.

A w27X114 is a massive beam. I don't think LD needs something that massive. His beam calc already come out with less than 1" of deflection with a 5:1 safety factor.

 

[4570Man]

Here is my shop crane. It is actually a 1 ton and not a 1/2 ton like I said earlier. Its primary purpose is lifting engine blocks into the parts washer and honing machine. The parts washer is more like an industrial duty "dish washer" and not the type most of you probably have. The hoist can also reach the milling machine if such a need arises. We used it once to lift a large dozer head up to the mill to drill out broken exhaust manifold bolts.

 

[Shield Arc]

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.

 

[LD1]

I don't find Gorbel cranes to be overbuilt

I do.

W27x114 for a 30' clear span and 10k hanging from it..................

That amounts to 3ksi stress and 0.079" deflection. So ~12:1 safety factor.

They even use that same beam on the 25' spans, which is over 14:1 safety, and 0.04" deflection.

Would have no issues at all pushing 15t on "their" 5 ton rated beam. Would only just slightly exceed a 5:1 safety. (like 4.8:1), and deflection just slightly more than 1/8" over 25'.

If YOU dint think that to be overbuilt, I'd hate to see the size of the floor joists in your house.:laughing: Are they made of 8x24 lumber, spanning no more than 12', and no more than 16" OC spacing.....

 

[4570Man]

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.