I Beam flex???

[Robert_in_NY]

We do a lot of work for a local machine shop and use their cranes quite often. They have 3 overhead motorized cranes in the main building with 2 hoist on each. The bridge is powered to go back and forth and the only thing that isn't is the hoist trolleys. The hoist themselves are powered and have the power cord and a chain that keep them from hitting each other if they are both in the middle. The plant also has a couple older lifts that are mounted off of a single vertical steel beam. The beam sticks out around 10' and has a hoist that can run that also. The beams in the plant are at least 12" but I think the heaviest crane might be on a 16". They are nice as you can lift and position what you are lifting anywhere in your shop but I also worry about hanging that much weight off of your trusses. If they were around 4' centers then it would be a little better but over 7' is a lot. Good luck with what you do though and have fun.

 

[RobS]

Thanks for that formula rlw. All I had here at work is my Machinery's Handbook. You'd think it would be a simplified version but the formula in there even accounts for the draft angle on the flanges. By the time I had half the numbers in Excel, you had already posted the answer! Again, good work /w3tcompact/icons/smile.gif

 

[Egon]

Dr. Dan:

If the longitudanal I beams are two feet from the wall an extra support for the trusses could be place right against the wall. It would not have to require drilling into the floor.

Just another thought. Have you consisidered a horizontal truss as the travelling beam. It would be lighter but deeper and the supplier would have all the engineering data on it. What I'm thinking of is the type of long span straight truss used for flat roofs.

Egon

 

[beenthere]

What is the column constructed of? and what is its size? Are you interested in hearing about the negatives (a lot of them are coming at you), or prefer to not hear them, and only want to know the I Beam flex in the bridge? I don't want to offer opinions where they are not requested.

 

[DrDan]

(3) 2" X 6" laminated with screws and glued. Treated soutern yellow pine I believe.

Yes input positive or negative is good. I am trying to put up a crane I can lift a ton with safely and move it all over the shop. Just as soon as I settle for less there will come the time when I want to hoist the Kubota and do something underneath it. Gotta trust what you have up!

DrDan

 

[rdln]

Sounds like a morton building DrDan, do you realize your warranty will be void if you attach a hoist to the structure?

Check out spanco.com for some ideas.

 

[rdln]

Also Doc, you were probably gonna do this anyway but fabricate a hangar to rest on the top chord of your truss and reinforce truss with plywood sheathing on both sides.


Looks like you ceiling is 9 or 10'? do a stack up of beams, gaps, trollies and hoist headroom to make sure you can lift the stump to the lathe bed height and drillpresses and such can clear as you are moving the load around.

You can extend the bridge beam beyond the 24' O.C. trolley beams to get hoist near wall, just weld a stop on the end.

have fun.

 

[Teash]

The formula for a deflection of a beam supported on the ends with a centered load is: (Force * length^3) / (48 * E * I)
E = modulus of elasticity
I = moment of inertia.

For structural steel, E = 29 Mpsi
I is calculated from the dimensions of the beam

I looked in a book for standard I beam data. There are 2 sizes listed for both the 4" and 6" I beam.
a) 4" beam with .193 thick web - I=6.08 in^4
b) 4" beam with .326 thick web - I=6.79 in^4
c) 6" beam with .232 thick web - I=22.1 in^4
d) 6" beam with .465 thick web - I=26.3 in^4

Putting the numbers into the formula:
(2000 * 360^3)/(48 * 29E6 * I)
This reduces to:
67/I
Therefore using the I values from above:
a) 11.02 in
b) 9.87 in
c) 3.0 in
d) 2.54 in

Clearly neither the 4" or 6" beam will meet your 3/8" max deflection requirement.

Using the reduced formula above, and 3/8", and solving for an I value: 67/I = .375, we get I=178.7

I went back to the beam tables and looked for the minimum sized beam that had an I value greater than 172. The minimum sized beam that will meet your requirements is a 12" beam. The book I have lists four different web sizes for a 12" beam (.350, .428, .462, .687). Any of these will work.
The dimensions for the .350 web beam are:
Flange width = 5.0 in
flange thickness = .491 in
I = 218
Its designation is S12 x 31.8.
This beam weights 31.8 #/ft, therefore 30 ft = 954 # beam.

If you really want to use the best 6" beam from above, we can put all the numbers into the equation and solve for max weight at 3/8" deflection. The answer: 294# is the max weight you could suspend at the center and have 3/8" deflection. -- Not a very useful crane.

You may need to look at the supporting 4" beams as well, to make sure they can take all the loads.

Hello, I am new to this and forums in general. I was trying to find some help with using two 3" I-beams 13' long sitting 22" on center parallel across the floor holding a 1050# gun safe centered between them that is 43" wide (the safe). The reason for this is because I am putting this safe over a basement and the room it is going in is 13' with the floor joist running perpendicular to the I-beams. Directly underneath, in the basement is a heavy beam supporting that area but it's not a load bearing wall. The idea is to spread the weight out all the way to the walls that are load bearing of concrete on either side and need to know how much flex to expect to make this work. The rest of the wall on either side of the safe will have cabinets which will cover up the I-beams. Any help is appreciated and sorry about not knowing how this stuff works.

 

[LouNY]

I don't know if you noticed how old this thread was,
the last post before yours was back in Nov of 2002.

I did not read all the previous posts but I will say this and your numbers and calculator will bear it out an I beam has to be considerable size to have a very minimal sag with any kind of load.
If the construction will allow it a simple truss under the I beam in tension will decrease the defection tremendously.
It is amazing how much rigidity and reduction of defection occurs with a tensioning addition to an I beam, simple flat stock with a spacer in the mid point.

 

[3Ts]

Why not just put some columns under the joists and beams in the basement directly under where the safe will go. No need to do the entire 13'. Or is there also an issue about getting it into the room?