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wilco612  
#1 Posted : 07 March 2019 15:10:39(UTC)
Rank: Forum user
wilco612

Hi All

I am trying to calculate the tipping point of a pack of steel sheets and wondered if anyone could provide any help.  We have a rectangular pack of steel sheets but are trying to find out at what height we would run the risk of the pack becoming unstable and potentially falling over. I realise it will be to do with the centre of gravity.

Is there a simple calculation?

Hsquared14  
#2 Posted : 07 March 2019 15:46:35(UTC)
Rank: Super forum user
Hsquared14

If you are talking about the centre of gravity of a single sheet of equal thickness then it is simply half the length of the sheet.  If the sheet is heavier at one end than the other then there is a calculation based on moments of inertia - oh heck my mind has gone blank and I can't remember it but will look it up and post again.  If you are talking about the stability of a stack of metal sheets then its not so much about centre of gravity alone but about how the material is stacked, friction between the sheets, weight etc.  Can you clarify what you mean a bit more?

wilco612  
#3 Posted : 07 March 2019 15:58:49(UTC)
Rank: Forum user
wilco612

To clarify, we have been asked to supply a stack of metal sheets which are rectangular in shape. Roughly 200mm wide x 600mm long x 1mm thick.  From a health and safety perspective we are concerned that the stack has the potential of being unstable and toppling over due to the height we have been asked to stack them.  We have suggested smaller packs which does make it more expensive.

Ian Bell2  
#4 Posted : 07 March 2019 21:33:36(UTC)
Rank: Super forum user
Ian Bell2

So you have a stack of thin plates. If they aren't banded together, then they are probably more likely to slide across one another. Given the width/length ratios, they are quite slender, so are probably more likely to slide and tipple over along the shorter side. The Cof G would not be my main concern,

Think a pack of cards

Put them in a container or band/strap them together. As they are only 1mm thick, if they fall any height, it will be like dropping a knife.

wilco612  
#5 Posted : 08 March 2019 08:16:36(UTC)
Rank: Forum user
wilco612

The sheets are banded together but we are concerned that there is a greater risk that the sheets could topple over under certain circumstances.

AcornsConsult  
#6 Posted : 08 March 2019 08:23:59(UTC)
Rank: Forum user
AcornsConsult

We could probably , with care stack 1mm sheets quite high, probably 1-2 metres. However, as soon as an attempt is made to move them or something / someone comes in contact with them, then we can expect the stack to become unstable and a cascade of slivers falling off. As well as stack height and tipping point, consider how they are going to be handled or managed. Lots of website to help with the baseline calcs. You could try practical progressive tests, and see at what point the slide and then tip. Far easier and safer to bind, secure or make smaller stacks. What height are you talking about? 50 leaves @ 50mm or 2500 leaves at 2.5m / 8 foot?

Edited by user 08 March 2019 08:25:43(UTC)  | Reason: Not specified

wilco612  
#7 Posted : 08 March 2019 09:27:06(UTC)
Rank: Forum user
wilco612

We are not really talking about the stack being that tall.  Somewhere in the region of 600mm which would equate to 600 sheets.

There must be a calculation somewhere that would help or some way of working it out.

fairlieg  
#8 Posted : 08 March 2019 09:39:37(UTC)
Rank: Forum user
fairlieg

would it be possible to lay them side by side rather than stack them

Blackburn31728  
#9 Posted : 08 March 2019 09:42:04(UTC)
Rank: Forum user
Blackburn31728

if stacking these on your premisis why now make or buy a stacking rack for them make life easy or if for transport I would strap and box

chris42  
#10 Posted : 08 March 2019 10:12:50(UTC)
Rank: Super forum user
chris42

So, you want to imagine the stack of plates is a solid block (i.e. the sheets cannot slide on one another – I think they will, but). So, then you just need to work out the centre of gravity simply for a stack of these plates say 1m high it will be 500mm up from the base (or down from top) 100mm in from the long side and 300mm in from the short side. However, the “Block” will likely fall over onto its long side (ie the 600mm long side) so you should consider the end of this block in the calc’s.

This would be 200mm by 1000mm high so as said CoG would be 500 up and 100 in from edge so you just use good old SOHCAHTOA to work out the angle.

So, the angle the edge of the stack will be at would be Tan of the angle =Opposite / Adjacent

Which is Tan Angle = 100/500 = 0.2 and the arcTan of that is 11.31 degrees

That is in theory the point it would be at balance, so if a fat butterfly landed on one side or the other that is the side it would fall ( ie back to upright or fall over).

If the stack is 2m high (so the CoG is now 1000mm up) then that angle is 5.71 degrees, so it would need less tipping for it to go over.

But I agree with the others the plates will slide over one another and so this goes out the window. Also, the moment you try and move such a stack on a pallet and Fork truck with all the bouncing / vibrations, not being level and momentum, you just throw your calcs in the bin.

Hope the above helps in some small way and it was more fun than actually doing my work at the moment.

hilary  
#11 Posted : 08 March 2019 11:13:18(UTC)
Rank: Super forum user
hilary

Have you seen those lorries for transporting logs - the just have uprights on both sides to prevent the logs from rolling out.  I think I would be inclined to use some structure of this nature to absolutely ensure that these razor sharp sheets of steel cannot slide off each other.

Ian Bell2  
#12 Posted : 08 March 2019 14:35:08(UTC)
Rank: Super forum user
Ian Bell2

So you have a stack with a volume of 0.6x0.6x0.2 = 0.072m^3

Steel has a density of in the region of 8050kg/m^3  ;- 8 tonnes

So your stack will have a mass of circa 579.6kg

Band the stack together, to include the provision of a lifting point, use a crane/hoist.

Lay them down on their biggest side.

Basic H&S - safe handling & storage etc.

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