Bridge Crane designs and ideas...38' span

[LD1]

This is lateral torsional buckling that I was talking about. If you put bracing along the yardstick it wouldn't do that.


LD, you checked your posts and side carry beams that support the bridge right?

Yep. Posts will be 4x6x1/4 tube, carry beams will be S7x20. Posts will be 12' apart, with the side beams overhanging each by a foot and a half. They are 15' and a knee brace both directions by 1.5'. Effectivly limiting span to ~9'. And with the load distributed along a 4 or 6' "truck", there is no worries there.

 

[LD1]

With the span beam placed right at a post, and the chain fall in the center of the span beam I could pick 2-tons, with 3/1 safety factor.

I think it is more than that. At 5 ton I figured a 6:1 SF.

Stress = (1/2 beam depth x W x l)/(4 x i)

A 2-ton load would be 2470psi stress and 0.08" deflection.

Your side beams with a 3500# load (I added 1500 for 1/2 the weight of the bridge beam and hoist), 5780psi stress. Jumping to 2-ton would be 9000psi, still a 3:1 SF, and probably the stress would be less with it not being a point load, rather two loads at whatever spacing your rollers are at.

 

[Shield Arc]

Over the years Mike told several of my co-workers when he had to run the numbers for me. He upped the safety factor, because he felt I never told him the whole story.

 

[FarmWrench]

I don't know how your end trucks are set up. Why not use two beams and put the hoist between on a top running carriage. For the right price two s beams could become as box just for rigidity.

Other than you already have an underhung hoist, and you have no desire to save headroom.

 

[LD1]

I don't know how your end trucks are set up. Why not use two beams and put the hoist between on a top running carriage. For the right price two s beams could become as box just for rigidity.

Other than you already have an underhung hoist, and you have no desire to save headroom.

Im lost. Not sure what you are trying to say.

A bridge crane requires THREE beams.

Two side beams, and the bridge beam that the hoist goes on.

I have a 38' span and a 12' span. The 38' direction is the width of the shop. The 12' span is along the outer walls.

Rather than span 38' TWICE, I would like to only span it once. On this beam, there will be a 5-on trolley and 5-ton chain-fall. The two beams that comprise the 12' run will be along the outer walls, and have 40#/yd rail on top, in which "trucks" will ride that carry the 38' bridge beam.

Not sure why some are suggesting to reverse the design, That would require TWO 38' beams instead of just ONE. And TWO beams spaning accrpss the width of the shop that are NOT movable. How does that help with anything. I would rather have a single 38' span beam, which would cost half as much as 2 beams, and have the ability to push it all the way to the back if needed for clearance reasons.

 

[LD1]

Over the years Mike told several of my co-workers when he had to run the numbers for me. He upped the safety factor, because he felt I never told him the whole story.

So...how much have you lifted on this "1-ton" crane??

 

[Shield Arc]

So...how much have you lifted on this "1-ton" crane??

I don't really know. A buddy brought me a load of steel one time. I knew it was heavier than 1-ton. So I used the 3-ton manual chain fall.

One of the best things I did to my crane was to install a winch on top of the span beam for power travel. :cool2:

 

[otlski]

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.....

My opinion comes from my experience operating several of these cranes. Positioning 3000 to 8000 lb test masses and fixtures to within 0.010". Also being the guy working 20 feet in the air making the fine adjustments while the bouncing is occurring. The cranes are bouncy at much less than their rated load. When the load stops moving, the whole thing bounces 10 seconds before damping out. I ran the numbers, I agree with your safety factors. I have to guess that not just Gorbel but other crane manufacturers treat unintended off axis forces less casually. Must be a reason they are overbuilt because they would never sell any if the extra costs associated were frivolous. Anyway I was just a guy offering the OP (you?) a different perspective. I'll go back to my normally built house which I indeed built normally and enjoy the thread.

 

[farmer2009]

I'm just subscribing to this. One day I'll be building one so I'm making notes.

Shield Arc. What is supporting the ends of your side beams? From the picture they're just hanging in the air. I'm sure it's the picture angle.

 

[Shield Arc]

Shield Arc. What is supporting the ends of your side beams? From the picture they're just hanging in the air. I'm sure it's the picture angle.

At the ends of the rails, (40-feet long) I have 4-inch schedule 80 pipe. In the center of the rails I have 6" x 6" x 1/2" wall square tubbing. I got the majority of the iron to build the crane for free.

 

[countrybumpkin]

I've been really tossing the idea around to build or buy one for one bay in my new shop , would be 15' wide and 30' long. I don't need one near as heavy as most of the ones here a 2000 lbs would be way more than enough.

 

[Arc weld]

I think you'd have to have some kind of welding credentials and it would need to be inspected. Shield Arc built his bridge crane but he had the assistance of an experienced engineer and he's been welding for a few weeks. A 10,000lb overhead lifting device isn't something to experiment with and hope for the best. Can some people design and build their own, sure but there's usually an engineer involved to check things over.

 

[LD1]

Relax safety police.

This is my own personal shop and no one for hire will be using the crane. No need for inspections or eng. stamp

Whatever beam I go with, I will run the calculations and assign a SWL. Dont need a freakin engineer to do some simple math for me.

 

[Shield Arc]

he's been welding for a few weeks.

Yeah but I'm a quick learner.
The beams I used for my span beam, were a spreader bar for setting pre-cast concrete utility vaults for the Pier D aircraft carrier pier in the local Navy ship yard. I told Mike I would have to splice the two beams right in the center. I ask if he was going to have a problem with that. He replied "if you can't handle that, we're going to have a long talk"!

 

[Streetcar]

Relax safety police.

This is my own personal shop and no one for hire will be using the crane. No need for inspections or eng. stamp

Whatever beam I go with, I will run the calculations and assign a SWL. Dont need a freakin engineer to do some simple math for me.

An engineer will tell you the safe working loads . Using your simplified calculation you need a large factor of safety.

 

[Streetcar]

Relax safety police.

This is my own personal shop and no one for hire will be using the crane. No need for inspections or eng. stamp

Whatever beam I go with, I will run the calculations and assign a SWL. Dont need a freakin engineer to do some simple math for me.

An engineer will tell you the safe working loads . Using your simplified calculation you need a large factor of safety.

 

[LD1]

An engineer will tell you the safe working loads . Using your simplified calculation you need a large factor of safety.

5:1 safety factor. What Im going off of.

Its not a simplified calculation. Its THE calculation for beam stresses and defletion. What else is there to calculate? ITs impossible to calculate an unknown amount of dynamic forces. THUS the safety factor.

Using my "simplified" calculations as you call them, my numbers match up very well with:

http://www.harringtonhoists.com/tech_support/edocs/EDOC 0367 rev02.pdf
https://www.cmworks.com/Public/11822/Crane Bridge Kits thru 5 Ton- 113535-27.pdf

So I dont see what the problem is. Whatever beam I use, I can calculate a SWL based on 5:1 SF. Or I can just use the sizing charts I listed.

IE:
W14x34 for 1-ton cap @ 40' span
W18x60 for 2-ton
W18x71 for 3-ton
Etc, etc

Problem is the charts list a single beam for each weight cap. Those specific sizes are not always available in the used market. All I am doing is recalculating for maybe a shorter but heavier beam, or taller and lighter. Since those "charts" dont list every possible beam that will work. One would be foolish to think that ONLY the beam listed can meet the rated capacity.

 

[FarmWrench]

Im lost. Not sure what you are trying to say.

A bridge crane requires THREE beams.

Two side beams, and the bridge beam that the hoist goes on.

I have a 38' span and a 12' span. The 38' direction is the width of the shop. The 12' span is along the outer walls.

Rather than span 38' TWICE, I would like to only span it once. On this beam, there will be a 5-on trolley and 5-ton chain-fall. The two beams that comprise the 12' run will be along the outer walls, and have 40#/yd rail on top, in which "trucks" will ride that carry the 38' bridge beam.

Not sure why some are suggesting to reverse the design, That would require TWO 38' beams instead of just ONE. And TWO beams spaning accrpss the width of the shop that are NOT movable. How does that help with anything. I would rather have a single 38' span beam, which would cost half as much as 2 beams, and have the ability to push it all the way to the back if needed for clearance reasons.

Wow. My idea was to keep your current design of non moving 12' rails with the matching trucks you have, but instead of an underhung hoist (load on the bottom flange of the beam) on one big beam, use a top running design (hoist rides on top of and between two smaller beams).
The two beams do not move in relation to each other. Think IOI instead of a big I with an O hanging under it.


This design also leaves the bottom flanges of both beams available for smaller hoists for greater manipulation of a load. You can hang multiple hoists on a single beam but they are unable to bypass one another. With a main hoist on top and one on the bottom that can bypass the top, turning loads over becomes easier and safer.


This will help you by having smaller beams to lift into place. Two beams can have better torsional rigidity. Top running provides more room under the hook. A larger area of each beam is loaded.

 

[Shield Arc]

Shield Arc. What is supporting the ends of your side beams? From the picture they're just hanging in the air. I'm sure it's the picture angle.

farmer2009 I gave you bad information! The center posts are 8" x 8" x 1/2" wall square tubing. You know how many times a day I walk right by those posts? And forgot what size they are.