Gantry beam SWL???

[zzr1200]

The "I" beam on my gantry is a 178 x 102 x 19 section beam, 2700mm (9ft-ish long), I've tried looking for single point loading capacity chart for this beam length/section, I can't make head or tail what i can find online.

Does anybody have a chart I can understand/read or do you have the knowledge to edgeumkate me...............

Kos, I ain't got a scooby, I reckon it should be good for 750Kgs at least, just asking out of interest for the recommended max structural loading before I really test it........

 

[Erie Fred]

Have you tried the any of the inline calc programs like beamboy ?

 

[zzr1200]

Have you tried the any of the inline calc programs like beamboy ?

Yep, I've tried, but I can't get my head around them as per the inputs required, it asks me for the loading applied to it, I want to know what it will take.....ie:- swl.

 

[Erie Fred]

Yep, I've tried, but I can't get my head around them as per the inputs required, it asks me for the loading applied to it, I want to know what it will take.....ie:- swl.

Loading should be single point loading.
Post up a screen shot, and I think myself or someone else can walk you thru it.

 

[sako243]

My understanding is you will have to determine what is the amount of deflection that is acceptable. There is a point where the steel goes inelastic and permanently deforms (failure in this instance) but the beam will deflect with even a small amount (might be unmeasurable but it will deflect).

Your worst case will be in the middle if it's equally supported. If it takes say 10t to permanently deforms the beam then 1t is almost certainly fine. However if it's 2t to deform it then 750kg is probably cutting it a bit fine as it'll bend quite a lot. I also though there was a factor of 5 somewhere in lifting charts (i.e. Your maximum rating of what it will actually handle but a 5th of it to have some safety margin would be your SWL).

In terms of your exact instance if you wanted 750kg suspended (note kg is mass not force) then multiply that by gravity (9.81m/s²) to get Newtons (kgm/s²). So 750kg in the centre point of the beam will be roughly 7.5kN. Feed those into the calculators and it should tell you how much it will bend.

 

[DaveB]

The load the beam can take and the load you can sensibly apply to it are unlikely to be the same.
And you need to consider the supports as well.

Since you say the beam is on your gantry, can we safely assume it holds nothing else up ?
The maximun load should not cause permanent movement in the beam, and ideally there should be a safety factor on that.

Is it a gantry with 'A' frame ends, does it have castors at the corners. How is any form of hoist attached to the beam ?

 

[Agroshield]

See sako's post above. It does not have an inherent SWL.

You design things to codes/rules/standards. They tell you what is permitted under the rules they contain. There are many possible modes of failure of a beam. The codes list all the ones you need to check and the section capacity is whichever gives the lowest number.

The one about which you ask is simple bending. Just as a for instance, a long beam can fail in a different way called lateral torsional buckling, where it twists sideways as well as bending downwards. That mode of failure is governed by the slenderness (length/height ratio) of the beam. On a short beam with a mega load, another mode of failure is possible: the web can buckle (that is why your steel beams have web stiffeners on them if a new column starts part way along the beam).

In a domestic house, the thing that limits the span of a certain size of floor joist is the deflection that joist gives under standard loading. The same criteria apply to the steelwork shown in your profile picture. 95% of the time, it is allowable deflection that determines what section is chosen rather than ultimate structural capacity.

For your gantry, you could calculate the load the beam will take before it permanently deforms (called its elastic limit) and assess how much smaller your desired load is than that value. You then decide if the two values are far enough apart for comfort. Note that you can still increase the load after the elastic limit before the beam completely fails (called its ultimate load) but when you remove the load you no longer have a beam but a banana.

The calculators will only tell you what happens to the beam under a load you specify. They will not say if what happens is OK or not. Try this one:

Free Online Beam Calculator | Reactions, Shear Force, etc

Reactions of Support · Shear Force Diagrams · Bending Moment Diagrams · Deflection and Span Ratios · Cantilever & Simply Supported Beam

skyciv.com

Beam length 2.7m
Support: pin joint one end, roller joint the other end
Section moment of inertia 13600000 (ref: https://www.steelforlifebluebook.co.uk/ub/ec3-ukna/section-properties-dimensions-properties/)
Young's modulus 210000 (Dr Google - every form of steel is close to 200 000)
Point load midspan of 10kN (approx. 1tonne)
Midspan deflection (this is what it calculates) 1.4mm or span/1880

With a point load, deflection is proportional to load, so 3t midspan gives 4.3mm deflection or span/660 deflection.

As a comparison, the domestic joist deflection limit is roughly span/360 so even at 3t point load you are roughly half that.

You will overload the axles on the castors before you worry the beam at the top.

 

[zzr1200]

The load the beam can take and the load you can sensibly apply to it are unlikely to be the same.
And you need to consider the supports as well.

Since you say the beam is on your gantry, can we safely assume it holds nothing else up ?
The maximun load should not cause permanent movement in the beam, and ideally there should be a safety factor on that.

Is it a gantry with 'A' frame ends, does it have castors at the corners. How is any form of hoist attached to the beam ?

The gantry will have castors for moving it around the castors have a swl of 1400Kgs in total, but there will be 4 of 30mm screw down HT studding support legs to by-pass any heavy loads away from the castors also to level the gantry if required. The chain block will be electrical operated with a manual push trolley, so an imposed shock loading could be viable.... depending on the hoist fitted.

Gantry here:-

Lifting Gantry Height Adjustable Project.

Ordered some material a while ago. I spent the day checking my layout/measurements on the scrap paper design, against the material and started cutting to final size, this will be an as and when, I get time build. Today I was laying out and confirming the height control holes. I will add photos...

www.mig-welding.co.uk

 

[DaveB]

Well, you can play it safe and assume that the gantry is massively stiff and strong so will not flex and it will never be truely straight and on level ground.
Then the worst case is as it rocks backwards and forwards only 2 of four castors are carrying the weight.
Your screw down studding legs are a problem to do calcs on, they have to carry the load through the thread, they will likely be more of a problem in buckling than compression, and because the fit between nut and stud has to be loose enough to turn them they will never be loaded centrally.
And if the nuts are just standard M30 nuts welded to somewhere the heat treatment will be gone and they will not last long as the thread form and tolerencing is not intended for repeated use.
Much better to use a buttress thread.

Safer to have castors to carry the full load so any off axis issues are already dealt with, if you don't want it moving while loaded get castors with brakes on the wheel and swivel.

Remember to add all the material in the gantry to the load the castors see.

Having looked through the ganrty thread - you should have welded on the spacer washers then milled them.

 

[zzr1200]

Having looked through the ganrty thread - you should have welded on the spacer washers then milled them.

Easier said than done in the workshop atm.

When I worked in the forklift industry, we had a gantry in the workshop with a 3 ton swl on the castors and 5 ton on the 4 thread support legs, I agree metric studding is not the best answer, but it will by-pass the loading on the castor axles/wheels at a sensible cost especially when barrel nuts are used.

 

[Erie Fred]

Have you looked here at the designs ?
some good info.

Thrifty Portable Steel Fixed-Height 1 to 7.5-Ton Gantry Crane

Strong, fixed-height gantry crane with exceptional clear span. Easy to assemble, disassemble, move, steer, and store. Made in the USA.

www.wallacecranes.com

 

[gaz1]

as explained above

you see it more with light guage steel beams but the tests are the same

this shows you at failure

 

[Misterg]

The point is that if this is to be used as a crane within a commercial setting, it'll need to comply with a standard somewhere that relates the SWL (if that's still the correct term) the maximum deflection for particular types of crane and some safety factor on mechanical strength (maybe BS EN 15011:2020).

This is worth a read to get a description of the process. It relates to European standards, but until recently, we would have been 'harmonised'.

 

[DaveB]

Easier said than done in the workshop atm.

I can appreciate that.

I did type should - should is guidance or advice, shall is compulsion.

I presume 'barrel' nuts have an engagement length of 2 or 3 times the thread diameter. Google was not helpful on the subject.

It's a personal thing, I just don't like the studding as legs if they are of any height. If you cranked the base rails so the stud only projects 25mm from the nut I'd give it more change of success.

 

[8ob]

Kos, I ain't got a scooby, I reckon it should be good for 750Kgs at least, just asking out of interest for the recommended max structural loading before I really test it........

I would happily stand under that, the beam on the A frame in the yard isn't much bigger than that and that is ok for 1.5 tons.

Bob