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Why always I beams for cranes?

Strostkovy

Stainless
Joined
Oct 29, 2017
I was thinking it would be far more convenient to use steel pipe versus and I beam. The exterior is smoother, and it isn't difficult to have four angled rollers. The deflection isn't bad, assembly is easy, (though I have plate cutting ability, so maybe that helps) and twist of the section in long lengths is no big deal.

A 20' simply supported length of 8" schedule 80 pipe will only deflect 1/8" under 1000 pounds of force midspan. This seems pretty reasonable to me. If my interpretation of standards is correct, that would actually be around a 4000 pound rated gantry but I'm not pushing it.

I started looking at cranes because I wanted a free standing bridge crane to cover a 16' x 16' area to easily move around press castings and large hydraulic components into their final assemblies. There are many for sale but they look fairly wimpy and I'm not convinced they roll well under load (other than very expensive ones).

I have no employees and buckling/side loading/etc are easily solved for and overbuilt, so actual fabrication methods aren't really an issue. Just curious why I've never seen a pipe crane.
 

Cole2534

Diamond
Joined
Sep 10, 2010
Location
Oklahoma City, OK
Because the I is the best section and easiest for a trolley.

Pipe/round tubing's best property is its uniform strength, it behaves the same any way you push it because it's the same section in all directions. I beams are best loaded normal to the flanges, where the web does most of the work. That's only 1 plane, but that's the only place a crane should operate.
 
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Strostkovy

Stainless
Joined
Oct 29, 2017
Because the I is the best section and easiest for a trolley.

Pipe/round tubing's best property is its uniform strength, it behaves the same any way you push it because it's the same section in all directions. I beams are best loaded normal to the flanges, where the web does most of the work. That's only 1 plane, but that's the only place a crane should operate.
A rectangular tube would have the same advantage, wouldn't it?
 
Joined
Apr 19, 2006
Location
Manchester, England
When I worked at “ Matterson” in the UK, who were a well known British crane maker, some of the smaller cranes they made used “ I “ beams. However on the bigger cranes the used welded rectangular box sections. In one of the bays, which was as big as a football pitch, they had a huge travelling “ submerged arc “ welding machine for welding the box sections together. It looked like a big travelling column planing machine but with four welding heads.
The sections were welded together with a slight camber or curve. They also had three overhead cranes that could be ganged together to handle the box sections.

Asset strippers closed the company in the 1980’s although a small spare parts operation is still in business I believe.

Regards Tyrone.
 

memphisjed

Stainless
Joined
Jan 21, 2019
Location
Memphis
round could be stronger.
Large cranes run on rails (train track) with a doubled top flange on the runway beam. Same with the bridge, unless made with box beams. This allows you to have straight and parallel critical part of the crane while the beam itself follows the wall contours.
Louden beams for cranes on simple hanging trolleys have tapered flange to self guide trolley.
Pipe is expensive, very expensive per foot, add in heavy wall to account for impact and uneven loads. Also need to have it rust proofed on the inside for structural part.
Round is hard to bolt to, ie, how are they attached to the columns? You can make box out saddles and weld them to the pipe, but you have to make sure everything is aligned - sounds easier than it is. Some outdoor train safety cable carriers are made like this. 3 inch xs is the biggest I have seen with these. Of course galvinized and drain holes left in for venting.

If you go thru the effort to make your own crane, add drives with remote control. The safety added is worth a lot, the convenience is major upgrade.
 

technocrat

Hot Rolled
Joined
Feb 9, 2009
Location
Oz
Round is too heavy, because there is strength in directions that are not needed for for a crane. I beam give you supreme strength in the vertical plane because of top strength in tension where elongation can strengthen the steel prior the yeild, plus compression strength in the lower plane. Buckling of the vertical member can be addressed with web stiffeners. Overall the strength to weight ratio is unbeatable without some form of pre-stressed box structures as Tyrone mentions, where an opposite curve is introduced into the structure. These pre-stressed structures are highly engineered and the engineering and insurance costs can outweigh the load advantage, though with heavy loads it is the only way to go. Add the simplicity of trolleys and the I beam wins hands down. This is confirmed with the use of I beams in building structures rather than rounds. Rounds excel in handling internal pressure as the load is equally distributed.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Ive got some crane runway that is a sort of oval tube slotted along the lower edge ,and edges folded back to form a beam of sorts .....basically lemon shaped in cross section............the monkey runs inside and has round wheels x4........about 1/2 to 1 ton capacity ,maybe.............Euro of some kind.
 

gbent

Diamond
Joined
Mar 14, 2005
Location
Kansas
A brief study into mechanics of materials and things like moment of inertia and deflection of sections will give you great insight into your I-beam vs pipe debate. For crane usage, even the beam is made of welded sections. Often there is a piece of C-channel on top and a piece of flat on the bottom.
 

Bill D

Diamond
Joined
Apr 1, 2004
Location
Modesto, CA USA
I believe the old riveted lattice crane beams are banned since there are too many joints to inspect. AFAIK They were all a form of I beam. Are the I beams with cut out holes in the main web still allowed? I would think so.
Bill D
 

memphisjed

Stainless
Joined
Jan 21, 2019
Location
Memphis
I believe the old riveted lattice crane beams are banned since there are too many joints to inspect. AFAIK They were all a form of I beam. Are the I beams with cut out holes in the main web still allowed? I would think so.
Bill D
Castle beams. Very rare, I understand they are not good for seismic codes- and being where I am all the cranes we have built need seismic loads engineered in.
The castle beam is a squiggly line split beam that gets welded back together as a wider beam than the original. Not exactly a beam with holes cut out.
 

gbent

Diamond
Joined
Mar 14, 2005
Location
Kansas
Castle beams used to be common on trailers. I haven't seen one for many years. Stiffness is greatly increased, but increased flexibility in y-y requires more bracing.
 

DanielG

Stainless
Joined
Oct 22, 2014
Location
Maine
8" Sch 80 weighs 43.4 lb/ft, I=100 in^4, S=23.1 in^3
S10x25.4 weighs 25.4 lb/ft, I=123 in^4, S=24.6 in^3

So to get equivalent strength and stiffness, The S beam only takes 60% of the material, and that material will be less expensive per pound. In my experience, rolled shapes are cheaper per pound than rolled and welded hollow sections.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
The sandblasters had two old lattice truss overhead cranes ,and bought a new Kone to fit the rails .....the thing was the size of a 4x4 winch but rated 5 ton the same as the old cranes ....and wouldnt lift 5.00001 ton..........the old cranes were also rated as 5 ton....and would lift 20.
 

scott-ak

Plastic
Joined
Oct 12, 2021
Of shapes that resist bending, round is the weakest of all. If you go down this patch at least build using A106b, structural seamless pipe. After pricing that I bet you find that I-beams are a better option.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Semi trailers have I beam chassis ,top and bottom plates are 3/4 or thicker ,the diaphragm is only 1/8"...........stiffeners are rarely used as they add to production cost........in any case the deck structure acts as. bracing.........if the frame does bend ,the trailer simply collapses..............back in the day ,trailers had a lower tension member ,similar to a railway wagon,except the railway wagon always had a turnbuckle that could be tightened to maintain the camber of the frame ........the trailer had a steel strap that could be tightened by cutting and rewelding.
 








 
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