Bridge Crane designs and ideas...38' span

[Tractor Seabee]

Trying to plan out and decide how I want to build my bridge crane in the shop.

Thoughts, Opinions, Am I crazy?

Quote from your OP.

You asked for it; here it is.

Thoughts: you have many posts with exactly that.

Opinion: After all this dialog you have created you are still trying to figure this out. That should convince you that you are out of your league and need a proper engineered design as several of us have stated.

Are you crazy: No, just not in the world of reality.

No response is necessary, I answered your questions.

Ron

 

[LD1]

Double would be placing them side by side I think.

IE: two identical beams rated to carry 2k. Side by side you would be good for 4k. But stacking has a different effect.

Doing as you suggest,

2x2 solid chunk of solid steel has an i4 of 1.33 in both directions

2x4 solid chunk of solid steel has an i4 of 10.66 and 2.66 in the 2" direction.

So they double if width is doubled. but go up by a factor of 8 if stacked. Since in the equation, the height gets cubed.

My issue though is trying to use different sizes.

IE: a W12x65 beam with a 533 i4 stacked on top of a W6x12 beam with an i4 of 22.1.

I know stacking them will have a greater effect than side x side (just adding the moments), but how much greater is what I am trying to figure. So in other words, lets say you have a pair of 2x2 square tubes. And weld them together. If laid flat where its only 2" high, you will be twice as strong as a single. simply additive. But place them so they are 4" in the vertical it is going to be alot more than double the strength.

 

[LD1]

Quote from your OP.

You asked for it; here it is.

Thoughts: you have many posts with exactly that.

Opinion: After all this dialog you have created you are still trying to figure this out. That should convince you that you are out of your league and need a proper engineered design as several of us have stated.

Are you crazy: No, just not in the world of reality.

No response is necessary, I answered your questions.

Ron

Appreciate your input and concern. But 2 things are certain

1. I AM going to build this
2. I AM NOT hiring an engineer to crunch numbers and formulas that I am more than capable of. Just seeking assistance in finding the appropriate formula for stacking beams.

In a perfect world, I would just buy a new beam to suit my specs. (which would likely be cheaper than an engineer). But when shopping the used market, that perfect beam isnt always available.

The W12x65 I mentioned will safely carry 5500# with a comfortable 5:1 SF. Why would I want to hire someone just to tell me that?

Concern is the W12x65 is a 12" wide beam. (good for resisting top flange buckling). But would like to add a smaller beam under it better suited for a trolley to ride on. I would like to know how much additional capacity this "may" give the beam. Worst case scenario I just call it 5500# max capacity. And thats fine. But I think we all "know" adding that beam under adds strength. Just trying to solve for = how much.

 

[Streetcar]

Ld
How would the two beam attach to each other? Bolted , continuous weld, intermittent weld
This would affect the strength

 

[LD1]

Ld
How would the two beam attach to each other? Bolted , continuous weld, intermittent weld
This would affect the strength

I have the ability to do any. But I have yet to find any programs or calculations, let alone worry about connection type.

 

[Streetcar]

Search moment of inertia.
This is what gives the beam its strength
width increases strength in linear function . Increase in height is squared assuming the beams are rigidly connected
If I knew where my steel Manuel was located to get base numbers ,the calculation is relatively easy

 

[CNC Dan]

Double would be placing them side by side I think.

IE: two identical beams rated to carry 2k. Side by side you would be good for 4k. But stacking has a different effect.

Doing as you suggest,

2x2 solid chunk of solid steel has an i4 of 1.33 in both directions

2x4 solid chunk of solid steel has an i4 of 10.66 and 2.66 in the 2" direction.

So they double if width is doubled. but go up by a factor of 8 if stacked. Since in the equation, the height gets cubed.

My issue though is trying to use different sizes.

IE: a W12x65 beam with a 533 i4 stacked on top of a W6x12 beam with an i4 of 22.1.

I know stacking them will have a greater effect than side x side (just adding the moments), but how much greater is what I am trying to figure. So in other words, lets say you have a pair of 2x2 square tubes. And weld them together. If laid flat where its only 2" high, you will be twice as strong as a single. simply additive. But place them so they are 4" in the vertical it is going to be alot more than double the strength.

OK. Now we're getting somewhere.
If you look at The Machinery's handbook, you can find out how to figure out the I^4 of any shape, by breaking it down into smaler parts. And figure out the neutral axis too.

I think that's the key, knowing how far away the steel is from the neutral axis so you can calculate how much it contributes to the overall moment of inertia.

You could do that with your beams.
But I can't help thinking that there must be someplace online that can give you the I^4 of any shape you give it.

 

[Streetcar]

Ld
Is there an 18 deep beam in your table with similar flange to the small beam. If yes the two beams welded together would be a slightly stronger beam

 

[CNC Dan]

There was this program called "beam boy" that would calculate all sorts of data related to beams and deflection and loading. I can't remember if you could give it custom shapes. You might try looking into that.

For Android smartphones there is an app called epic FEM, but doesn't allow custom shapes far as I know.

 

[LD1]

Ld
Is there an 18 deep beam in your table with similar flange to the small beam. If yes the two beams welded together would be a slightly stronger beam

I wish. The 6x12 has a 4" flange that is 0.280" thick. The lightest 18" beam 6" x 0.425" flange. And that light 18" beam has a smaller moment than teh w12x65 I would be starting with. So that dont work out.

There was this program called "beam boy" that would calculate all sorts of data related to beams and deflection and loading. I can't remember if you could give it custom shapes. You might try looking into that.

For Android smartphones there is an app called epic FEM, but doesn't allow custom shapes far as I know.

Beam boy dont allow custom shapes. (I use beam boy alot). Also tried a couple more beam tools I downloaded, but dont allow custom shapes.

I'm even drawing a blank on the moment calculations by breaking down into individual shapes.