Odd question but I am confident someone will know the answer.
I need a length of flat bar 6mm x 75mm . It has to be flat bar , angle / box whatever will not fit through the opening it has to be inserted into .
I want that flat bar to be strong and reasonably rigid .
We have demo’d the job using a length of 304SS, and its quite springy.
Would a cold forged steel give me any more stiffness? 214N cds comes to mind , but I only need 1 x 3mtr length so something exotic is out.

Imagine you were picking up a bag of sugar 3m away and moving it with the flat bar holding 1 end . The stiffer it is , and less bouncy the better.

Thanks

Unfortunately all steels have essentially the same stiffness.

+1

Chiefgrooveguru

Single wall carbon nano tube?

http://en.wikipedia.org/wiki/Young’s_modulus#Approximate_values

Unless some form of profile is used it will still bend/flex.
Only the ultimate breaking strength will vary by using different grades of steel.

Unfortunately all steels have essentially the same stiffness.

not sure that’s quite true! you can get all sorts of steel. the steel that you have is a very low carbon steel. this makes it flexible at the cost of some strength. A higher carbon steel would be much less bendy and would deflect less under an equal load. the disadvantage is that it could fail more suddenly and snap rather than bending or stretching. Ideally you want to increase the I value for the element. to do this you need to basically make it thicker in the same direction as the force is being applied.

There was a video about making bikes at Orange on here somewhere recently and that showed a wobbly bit of alloy getting seriously stiff with something like just a 2 degree bend in it. Don’t know if you could get a one off piece of steel done like that but it would help keep your very narrow profile. You gonna tell us what you’re up to??

A 3m length of steel with those properties will bend under its own weight let alone with any load.

How much load does it have to take and is here no other way of adding a web to the flat, to form an angle or a tee.

I can work backwards from the loads and maximum deflection and calculate what size you need but I fear it’s a re design rather than different materials. You don’t get much stiffness with 6mm.

A 3m length of steel with those properties will bend under its own weight

+1

Do they make a webbed T shaped extrusion or casting?
A pair might work .

Very hard to describe but its an interface or lockbar , like the bar on a medieval fortress door. slots through 6 points of contact in a row and provides a flat lifting point for a FLT

I know how much deviation a 3m 6mm goes through when picked up centrally with zero load . Just wondered if there was a way of incresing stiffness without folding.
Starting to think maybe rectangular box 1/2″ x 2″ , cut lengthways to make 6mm x 2″ channel might give a stiffer cross section.

Extra carbon gives you more strength not more stiffness. They are different properties.

Looking at the MetalShop Hexagon bar might be better suited for the job . We could run a pair in parallel to get the same results .
Tees and box all come up to big , even if cut down .
Trying to lift 300kgs quickly , easily and safely. Am fed up being crippled after manual handling about 10t a week. We now have a FLT just need to engineer a way to make it work for us.

can you strop it/ fix lifting chains?

PeaslakeDave – Member

“Unfortunately all steels have essentially the same stiffness.”

not sure that’s quite true!

it is.

Young’s modulus innit.

stored in my head as 207 GN/m^2

300kgs, or 3kN point load is not to be taken lightly.

I can’t see how you can lift this with just a piece of flat bar.

There must be another solution.

A higher carbon steel would be much less bendy and would deflect less under an equal load. the disadvantage is that it could fail more suddenly and snap rather than bending or stretching.

This is all failure and the onset of plastic deformation

not actually changing the stiffness

We have come up with different approach .
More structual but still utilising the flat bar.

Got a 1.6m ‘spine ‘ of 60mm x 40mm box , with 4 ‘Ribs’ 40mm x 40mm welded at 90′ onto the spine . Load will be on ribs mainly , but shared by the spine .

WHole assembly will resemble an over engineered TV ariel .

4 lengths of chain bolted to the 4 ribs and over the FLT forks,

The 6mm x 75mm flat bar is inserted into the slots and sits above the TV ariel . FLT lifts the ariel and the ‘ribs’ pick up the underside of the flat bar , and 6 full beer barrels are lifted evenly , without twisting, by the FLT and manoevered over a Euro pallet .

Once in position the forks are lowered till the chains go slack. The flat bar is withdrawn from the slots , and put ontop of the forks ,

FLT picks up ‘ariel’ and trundles off and lowers ‘ariel’ onto next 6 casks . Handles are aligned and flat bar inserted , then its up, up and away with another 300kgs. Repeat 3 times and thats 18 casks in a 2 x 3 x 3 high pattern @ 900kgs , 1.5m tall with zero lifting.

Repeat whole operation 4 times and thats 1 bulk tank of beer filled and stacked in about an hour, without me and oppo lifting 72 x 50kgs onto pallets 3 high. So I can hopefully ride my bike further and faster without being crippled.

There are so many different types of steel from austinitic, ferritic, duplex etc – Youngs modulus as mentioned earlier is a large part but this can vary depending on grain size, heat treatment regime, alloy composition etc…. 6mm by 75mm isnt that big – you could do the maths using beam theory!

You may find that the spine has to be exactly central between the barrels or it will rotate and the flat bar will slide off the ribs. So a double spine might be better.

But your biggest problem, sorry to say, is that you’re building a lifting appliance and there is a lot of legislation on that – principally, LOLER and the ‘Machinery Directive’. It has to be CE marked and certified, with significant chance of prosecution if it’s not.

There are so many different types of steel from austinitic, ferritic, duplex etc – Youngs modulus as mentioned earlier is a large part but this can vary depending on grain size, heat treatment regime, alloy composition etc

As has been mentioned by the obviously knowledgable types above, this just is not correct. Steel has the same youngs modulus (which is another word for stiffness) no matter what the grain size, heat treatment or alloy composition. Its approx 200GPa.

Greybeard is right, is it a fixed installation? If so the HSE may well want to see your CDM designers risk assessment as well.

If you are trying to demonstrate compliance with appropriate legislation/reg’s base it on some accepted applicable standards.

Depending on the type of lift we start assessing structural members using BS 2573 and 5950 and then maybe EN 13001 as it’s a “more current” standard…

As for appropriate steels draw material properties from BS EN 10025 as this will correspond to materials you can sensibly source and the stress allowable will all dovetail nicely with a 2573 code assessment start with S355 and go from there.

Are you after stiffness/minimal deflection? Or strength I.e. demonstrating a good margin to yield under SWL?

There are some really posh homogenized steels about heavily rolled to refine their grain structure but they are a bit specialist, can be expensive, and harder to source. Start with common structural steels.

And flat bar will always be the worst section to choose for just about any beam best avoided if you can…