shade tree mech

[pablo]

OK here is a question for all you back yard engineers.

First let me lay the ground work. i am almost done with my shop, 30 by 50 with 12 foot ceiling. I am at the stage where i would like to buiild a bridge crane before I move every thing inside.

the question

How much weight will a 4 inch tall, 3/8 inch think 29 foot long piece of Jr I beam hold, at its weakest point ( the middle ) before it will fail?

I am trying to determine what kind of steel i would need to build a bridge crane. I have looked on line for specs on steel, but i guess I am not pputting inthe right search criteria.

do any of you guys know? or know where I can find this info?

your helpp is appreciated.

Pablo

 

[Tripper]

Pablo,
I'd ask the steel place... they should know!

BoB

 

[Bonehead]

This one looks harder than it is to figure out.
http://www.engineersedge.com/beam_bending/beam_bending2.htm

 

[Bonehead]

Here was my search...
http://www.google.com/search?hl=en&q=beam+deflection+formula&aq=0&oq=Beam+deflection

 

[Bonehead]

Without doing the math, I can tell you a truss top for that beam will bump it up quite alot if you can add one to it.

 

[pablo]

???

cool....um.....ya....can you find me a web page that will explain that web page?



that web page reminds me of a joke

do you know what engineers use for birth control?


their personality

i figure if i cnat figure out what they will do i will just be childish and make fun of them LOL

Pablo

 

[wrecker55]

if all else fails put a post under it

 

[Bonehead]

I'll work on it, but I am having trouble finding the specs on 4x4 Jr I beam, other than it weighs 6lbs per foot. You need to know the specifics of the material so you can input the info to the formula. They make handy pocket books with that info, but I don't have one. Seems to me that doubling the height increases the load by 8 X. So an 8 inch high by 4 inch wide beam would be 8 times as strong than a 4x4 beam, of the same wall thickness. That is why I say, add a truss if you have room.

 

[59imp]

hey Pablo, i work in the paper industry and we use lots of different sizes of overhead cranes, a 30' span is pretty big, i think you'd be shocked at the size of the beam you'll need to make it safe. probably best to ask a structural engineer to do it right. i've seen a couple of hoist's fail at work and things happen real fast and the risk of getting hurt isn't worth that fact that you may have a piece of i-beam laying around that you could use. sorry i don't have a better answer, but if you build it right, you'll never have to worry. oh and by the way, even though every crane/hoist at our site is Gov. inspected annually and has a daily use log, it's a real no-no to work under any suspended load, and in 30 years on the job, even though i've seen several failures, we've never had a suspended load related injury.........

good luck....mo

 

[Bonehead]

hey Pablo, i work in the paper industry and we use lots of different sizes of overhead cranes, a 30' span is pretty big, i think you'd be shocked at the size of the beam you'll need to make it safe. probably best to ask a structural engineer to do it right. i've seen a couple of hoist's fail at work and things happen real fast and the risk of getting hurt isn't worth that fact that you may have a piece of i-beam laying around that you could use. sorry i don't have a better answer, but if you build it right, you'll never have to worry. oh and by the way, even though every crane/hoist at our site is Gov. inspected annually and has a daily use log, it's a real no-no to work under any suspended load, and in 30 years on the job, even though i've seen several failures, we've never had a suspended load related injury.........

good luck....mo

I Agree, I am guessing, less than 500lbs will bow the beam several inches, which makes the span shorter. Could be a wreck.

 

[CR55]

Pablo, please check with a structural engineer or a competent steel supplier. You wouldn't believe how fast a steel beam that is undersized will collapse! You will need a lolly column in the middle at the very least. That's a lot of weight to dodge when it fails and comes down. I had a steel beam come down inside a basement once. 4 of us were like rats scurrying, trying to get out of the way! Please be careful.....CR

 

[Sam_Fear]

If your looking for some ballpark figures for a 'feasibility study', either try posting on an engineering board or maybe get a hold of RRR member Moronthethrottle - he seems to have some clue as to what would be needed. Be sure to mention it is just to get an idea if it is practical and you would have it certified - most engineers, electricians, etc. don't like to give definitive answers for safety reasons.

 

[moronthethrottle]

beams

Pablo, don't use a Jr beam. They are intended for vertical column use. You need an S beam or maybe a W beam for your hoist.
View attachment BEAMS.pdf
The M beam on the left is the strongest 12" M beam produced. The S beam on the right is the smallest/weakest 12" S beam produced.
I'm giving my structural engineer in Birmingham AL a call. I probably won't have a solid answer for a week. Are you planning on a 2 ton or e ton hoist? Check with your hoist manf for beam recommendations. Any idea what your heaviest loads will be?
If this is a commercial application you will need a PE to sign off on it. It will probably cost at least $1000.
Paul

 

[Bonehead]

They are intended for vertical column use.

Explains why I couldn't find the specs on them.

 

[moronthethrottle]

S12x31.8#

Hey Pablo, I saw your shop in your art thread. Looks nice! You should use a S12 x 31.8#. That's the lightest recommended beam member.

The formula is 29 (feet of span) divided by 25 equals 1.16' or 14"...this is an engineering rule of thumb for simple span member sizing. That size member will hold up to 5000 lbs, which is probably a lot more than what you need, but engineering is not always about what you need, it's more about being over-cautious. With this member size your supporting columns to your shop will likely be the weak spot, which is ok provided they have been checked.

I'm guessing you won't want to spend as much as what that beam is worth, but I just wanted to give you an answer from an engineering standpoint

Be sure to have good lateral reinforcement to keep the beam from tipping!

Oh yeah, you can thank Namboo for the engineering calculations.

 

[59imp]

hey Pablo, just talked to the head P Eng here at our site, with a few quick calculations he said that a 4" I-beam would prolly hold about 350 lbs, but he would not reccomend using it. he said a Standard 10" I-beam X 30' span would be good for 1 ton, a Wide flange I-beam 8" X 6 1/2" X 30' would also be good for 1 ton..... so you have to get a bigger beam or he reccomended shortening the span........

 

[59imp]

Pablo, i had a similar problem in my shop, the ceiling was too high, and a lifting device was gonna be a problem. i bought a portable engine hoist instead of a stationary beam and i really like it. being portable i can pull an engine and roll it outside to pressure wash etc. and i've used it all over the shop to lift tool boxes into pickups and to even move/setup my lathe and drill press, i've even used it to move my welding table and fab bench, all by myself. it's one of the handiest pieces of shop equipment i have. i don't think i could have done half of those things with an overhead beam lift. my only reccomendation is to but the best quality one you can, mine is heavy duty and i have pulled a big block with a turbo 400 attached out of my chevy, no problem. i have seen/used cheaper, lighter built ones and they're always a bit scetchy to use. like any tool, buy a good one, it'll last you forever, and the more you use it, the more uses you will find for it....


mo

 

[Bonehead]

I built and used this A frame in two different shops, and finally gave it to a buddy when I moved again. But I used it a bunch. It was on solid steel wheels. Really handy.