Question on beam

[ricksm]

I'm a hydraulic engineer by trade, so I'm a little rusty on structural problems. I have a shop behind my house that I am looking to install a beam with a pulley to lift +/- 1500 lbs straight up and down. The span is 14' with posts supporting both ends. I prefer not to use an ibeam due to the costs. How many separate 6" or 8" square channel will it take to support this load?

Thanks.

[PinkertonD]

Welcome to the forum.

I have a hydraulic pump that has a label saying 3000 psi. What size pump do I need?

All too often we get question and nowhere near enough detail to even make an educated guess. "Straight down," is that a technical term for weight x distance?

OK, sarcasm all put aside now, where is the load? In the middle, distributed evenly all across the 14'? Is the "pulley" on a trolley that can be moved along the beam? Can the load swing? How are the posts supported against tipping over? Are they steel? Bolted to the floor?

Finally, steel is steel, is steel and welding chunks of channel together to arrive at the same strength as a lump of I-Beam has it's limitations. And, it will probably cost more. The I-Beams are designed to use the minimum amount of metal to achieve a certain level of stiffness. The beam's own weight is an important factor and four lengths of channels welded would have more weight than an equivalent I-beam.

[ricksm]

Thanks for the reply and point taken. The posts are 6x6 wood buried 2-3 feet down and poured in concrete. The beam will be sitting on top of the posts and bolted down. The weight will be on a pulley system that can move from end to end. Anything else?

[PinkertonD]

The weight will be on a pulley system that can move from end to end. Anything else?

You might consider something like this. For the bucks, the steel may cost about as much for just your beam. This thing is sometimes on special for under 500-bucks.

http://www.harborfreight.com/1-ton-t...ane-41188.html

[zeke]

Dave,
He needs a span of 14 feet.

I think he can do it with a 6x2 channel
8.2lb/foot, section modulus=0.5; I=0.5
Correct me if I'm mistaken

I calculate a max tensile stress of 10,500 psi, max deflection of 0.7 inches, when the 1500 lb load is centered. on the beam.

A 5x1-3/4 , 5.4 lb/ft might also handle it with reduced safety factor.

[zeke]

correction

should read

I think he can do it with a 6x2 channel
8.2lb/foot, section modulus=0.7; I=0.5

[PinkertonD]

Zeke, I understood the 14', but with wheels and an 8' span it will go anywhere in the shop. A 14' length of probably 10-by, beam will cost 50% more than the gantry.

Also, a channel does not make a good runner for the trolly. So he would have to have two back to back to give him a track. $$$$

[zeke]

Dave,


You're right.Guess I missed the wheels.

[RWOLFEJR]

Without doing the math...
The channel... if it does indeed calculate to .7" deflection with the load centered... is going to twist a good bit also if not paired up with another. Then you need to figure the load slipping a link or two and free falling an inch or so giving it a big tug.

Buy a beam that's triple what you require. Mount the beam (6 x 6 timbers wouldn't be my first choice... I'm a big fan of steel... it doesn't dry up and split.) Then if money is tight skip buying the nice C&M two speed hoist or the like and toss a $50.oo chain fall or a come-a-long up there until some cash comes along.

If you check around you'll easily find a used I-beam that short for a little over scrap $$. You'll just need to clean off the rust...

[zeke]

I did some checking and found a standard 20' I beam cut to length will cost $109 delivered to my door in ct.

The I beam is 3x2-1/2
5.7lb/ft
s=1.7
I=2.5
The stress will be well below 5000 psi
The max deflection about 2"

[vipin mittal]

please help me to provide data for selection of complete column mounted jib cranes from 500 kg to 5000 kg and upto the span of 6 mtrs. with 180 / 270 / 360 Degree manual rotation

[RWOLFEJR]

I did some checking and found a standard 20' I beam cut to length will cost $109 delivered to my door in ct.

The I beam is 3x2-1/2
5.7lb/ft
s=1.7
I=2.5
The stress will be well below 5000 psi
The max deflection about 2"

??
Might want to have another look at that stress figure. I come up with way higher. Too much deflection for a 14 foot span also.

If it's lagged to a couple of wooden posts. All that twang (technical term for deflection) will also pull at the posts. Less twang means less pull and a more vertical load at posts. You want to keep the deflection down to no more than .01 per foot. Less if you like big safety factor like me. Our overhead cranes at the shop have a 3x's plus factor of safety in them throughout. (but don't tell anyone here cause they might get the idea to put up heftier hoists and defeat my design intention...)

If the load of 1,500 is it... and hopefully with some bounce or safety factor included... I wouldn't go with anything less than a beam with a moment of 35 or more. That'd put you at a W6 x 20 (I=41.4) or a S7 x 15.3 (I=36.7). Butt... for another 14 lbs. of material over the W6 beam you could go W8 x 21 and get a nice hefty 75.3 moment and have that warm and fuzzy feeling of knowing the beam will handle double your estimated load. Or if headroom isn't a huge concern then go W10 x 17 and save weight / dollars and get a nice 81.9 moment.

I haven't purchased any structural steel in a good while but I can't imagine it'd be over a buck a pound for wide flange beams? (about 20 years ago I recall about 35 cents / lb.?) Regardless of per pound cost... adding a few pounds of beam for a nice gain in moment and further reducing the deflection is a win since only adding the cost of an additional few pounds of material.

[RWOLFEJR]

please help me to provide data for selection of complete column mounted jib cranes from 500 kg to 5000 kg and upto the span of 6 mtrs. with 180 / 270 / 360 Degree manual rotation

If I'm understanding you correctly.... ?
Type jib crane in your google bar and you'll get a lot of jib crane manufacturers to choose from.

[PinkertonD]

Or if headroom isn't a huge concern then go W10 x 17 and save weight / dollars and get a nice 81.9 moment.

Have to go with you on that one Bob, that's why I said "a 10-by" in my earlier post. I didn't do any calcs. as I was suggesting the rolling gantry as a better alternative. At 14' span I would be reluctant to go below an 8" just as an experience-based guess. Hoists are invariably overloaded at some point.

If it were my shop, then a 10" would be it for me. I actually have a 2T cherry picker that I modified the leg-wheels to rollers and prefer it as I can move stuff around with it. I unloaded my 14" x 40" lathe (1900-lbs) off the trailer and into position by myself and didn't raise a sweat.

It would hands down beat a fixed beam. IMHO.

[zeke]

??
Might want to have another look at that stress figure. I come up with way higher. Too much deflection for a 14 foot span also.
If the load of 1,500 is it... and hopefully with some bounce or safety factor included... I wouldn't go with anything less than a beam with a moment of 35 or more. That'd put you at a W6 x 20 (I=41.4) or a S7 x 15.3 (I=36.7). Butt... for another 14 lbs. of material over the W6 beam you could go W8 x 21 and get a nice hefty 75.3 moment and have that warm and fuzzy feeling of knowing the beam will handle double your estimated load. Or if headroom isn't a huge concern then go W10 x 17 and save weight / dollars and get a nice 81.9 moment.

I haven't purchased any structural steel in a good while but I can't imagine it'd be over a buck a pound for wide flange beams? (about 20 years ago I recall about 35 cents / lb.?) Regardless of per pound cost... adding a few pounds of beam for a nice gain in moment and further reducing the deflection is a win since only adding the cost of an additional few pounds of material.

I disagree,
The section modulus of the beam was 1.7 in^3 and the max bending moment is 5250lbin, making the stress<4000psi
Now the deflection I got was 2" for simple support but goes down to 0.5" if you use the clamped edge., closer to the actual situation
I personally don't see a big problem with .5" but if you want to spend this guy's money on a somewhat sturdier beam then why not the
4W13 which will increase the I by factor of 6 bringing the deflection under .1" which should be warm and fuzzy enough IMO.
The cost if I extrapolate would be $219. I don't know if the guy is inclined to go for that much.

[ricksm]

??
Might want to have another look at that stress figure. I come up with way higher. Too much deflection for a 14 foot span also.

If it's lagged to a couple of wooden posts. All that twang (technical term for deflection) will also pull at the posts. Less twang means less pull and a more vertical load at posts. You want to keep the deflection down to no more than .01 per foot. Less if you like big safety factor like me. Our overhead cranes at the shop have a 3x's plus factor of safety in them throughout. (but don't tell anyone here cause they might get the idea to put up heftier hoists and defeat my design intention...)

If the load of 1,500 is it... and hopefully with some bounce or safety factor included... I wouldn't go with anything less than a beam with a moment of 35 or more. That'd put you at a W6 x 20 (I=41.4) or a S7 x 15.3 (I=36.7). Butt... for another 14 lbs. of material over the W6 beam you could go W8 x 21 and get a nice hefty 75.3 moment and have that warm and fuzzy feeling of knowing the beam will handle double your estimated load. Or if headroom isn't a huge concern then go W10 x 17 and save weight / dollars and get a nice 81.9 moment.

I haven't purchased any structural steel in a good while but I can't imagine it'd be over a buck a pound for wide flange beams? (about 20 years ago I recall about 35 cents / lb.?) Regardless of per pound cost... adding a few pounds of beam for a nice gain in moment and further reducing the deflection is a win since only adding the cost of an additional few pounds of material.

Thanks for all the input guys. How are you arriving at the moments and max stress of the beams? I'd like to check the calcs myself, if I can. What is the acceptable limits for deflection & stress?

Thanks again.

[PinkertonD]

Thanks for all the input guys. How are you arriving at the moments and max stress of the beams? I'd like to check the calcs myself, if I can. What is the acceptable limits for deflection & stress?

Read Bob's post above, it covers most of that. Deflection is a somewhat personal thing, it is what you feel comfortable dealing with.
http://www.engineersedge.com/enginee...ull=1#post2065

For a beam with a hoist, I would opt for more safety than less safety. Things like a chain slipping a a kinked-link as your 1500-lb load is being lowered and instantly injecting 5+ times the load with the bounce. Suddenly a Safe Working Load (SWL) start point of 2.5 = 3750-lbs (my personal minimum) looks a little short.

Also wooden sticks to hold it up will not afford much help in preventing deflection as the posts will bow freely. With sticks, (derision intentional ) the beam cannot be considered fixed at both ends.

I stand with Bob and the W10. It's our way or the wrong way !!