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Weight Distribution

07/11/2017 5:47 PM

This is not a homework assignment. We have a 14,000 pound machine to be delivered next month. The machine rest on 4 pads that are 5' diameter. Assuming the center of gravity is in the middle of the machine, there will be 3,500 pounds on each foot. The machine sets on a .138" thick drip pan. I need to know how much the drip pan spreads the weight. If the drip pan has no effect of spreading the weight I will need 2' square plates to keep from exceeding the limit of the concrete floor. I thank you for any help you can give me.

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#1

Re: Weight Distribution

07/11/2017 6:51 PM

That's about a 10 gage(3.5mm) galvanized steel sheet.... what is the measurement of the machine HXWXD? The weight is already spread out nicely with 4 ea 5' round pads....what is the floor limit you speak of?

http://www.engineersedge.com/calculators/flat-plate-deflection.htm

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#2
In reply to #1

Re: Weight Distribution

07/11/2017 7:02 PM

Solar Eagle,

The machine is 7.5"x7.75'x7.0'. The floor is 5" concrete rating 5500 psi. It has double row rebar with good packed soil under.

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#3
In reply to #2

Re: Weight Distribution

07/11/2017 7:21 PM

So it's a steel slab...?

....sorta like this? that's about 2,827 sq inches per 5' pad...

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#9
In reply to #3

Re: Weight Distribution

07/12/2017 4:35 AM

That would make it, on those dimensions and weights, a density of 6634kg/m3.

The ground pressure of an object that footprint and weight is lower than the rating of the concrete below it, therefore any support pads are not needed; the thing is its own support pad.

Either that, or something is wrong.

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#4

Re: Weight Distribution

07/11/2017 8:07 PM

It's not my field, but my math says that the loading is about 178 lb/sqft. I would think that a 5-inch thick concrete slab could easily handle that.

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#5
In reply to #4

Re: Weight Distribution

07/11/2017 8:37 PM

For a very few dollars you're also on 2' square steel plates. Seems like cheap insurance.

What size are the feet that sit on the drip tray?

Vibration?

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#8
In reply to #4

Re: Weight Distribution

07/12/2017 4:05 AM

Damp topsoil will handle that!

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#15
In reply to #4

Re: Weight Distribution

07/12/2017 10:23 AM

I think that's 178 lbs per sq inch....still should be no problemo...

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#16
In reply to #4

Re: Weight Distribution

07/12/2017 12:05 PM

If the pads are 5 feet in diameter, area is about 19.6 sqft for each pad, 3500/19.6 is about 178 lb/sqft.

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#17
In reply to #16

Re: Weight Distribution

07/12/2017 2:13 PM

5 inches in diameter....

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#6

Re: Weight Distribution

07/11/2017 10:41 PM

Not knowing what the function is of this said machine is. You said, "The machine rest on 4 pads that are 5' diameter." The .138 thick drip pan will not have enough strength to really help to distribute the weight.

As JE asked, what size are the feet? Also as JE stated, forget the bean counting and go for the insurance of the 2' square plates, so that the weight will be distributed evenly.

One more question, how thick are these 2' squares?

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#7

Re: Weight Distribution

07/12/2017 1:13 AM

Did you mean to write 5' or 5" for the diameter of the feet? I suspect you made a typo and intended 5"....otherwise, the 2' squares don't make much sense...and the load would already be widely distributed.

No. The drip pan will not help meaningfully.

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#10
In reply to #7

Re: Weight Distribution

07/12/2017 9:41 AM

Not so nimble fingers, the pads are 5 inches diameter. I planned on the 2 foot square plates to be 1 inch thick.

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#13
In reply to #10

Re: Weight Distribution

07/12/2017 9:56 AM

If the shape is as in 3⇑ then with the weight stated it is already inside the concrete pressure rating without any intervening pad or plate. In which case, is the current level of worry justified?

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#18
In reply to #10

Re: Weight Distribution

07/12/2017 2:55 PM

So you're loading 5500 psi concrete with 178 psi.

I don't think you have a problem.

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#11

Re: Weight Distribution

07/12/2017 9:47 AM

That drip pan is a drip pan, not a machine support. You really need to go back and think this over from the start. Are you stating that the drip pan extends the entire length and depth of the machine? No pads heavier that 0.138" for weight support and distribution? I suspect you need to get the OEM manual and read carefully the machine set-up section for the first time.

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#12
In reply to #11

Re: Weight Distribution

07/12/2017 9:51 AM

James,

I read the manual from cover to cover and talked to the builder. No help. The only information I got was the foundation is to have a load capacity of 2,000 kg/m sq.

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#14
In reply to #12

Re: Weight Distribution

07/12/2017 10:03 AM

If the shape in 3⇑ and the weight are correctly described, then the item is inside that rating at 63% of it without any intervening plate or even concrete.

Either that, or something is wrong.

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#19

Re: Weight Distribution

07/12/2017 6:09 PM

What we have here,, is a failure to communicate....

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#20
In reply to #19

Re: Weight Distribution

07/13/2017 3:08 AM

Really? It looks like an obese vehicle on stilts and an idiot from here; "the camera never lies" - Anon.

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#21
In reply to #20

Re: Weight Distribution

07/13/2017 9:18 AM

Shhh....those kind of trucks are essential to business and ranching and farming in Texas. Not so much in Merry Old.

Not sure I go along with having that type of truck lift, although it is probably safer than a single hydraulic pedestal.

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#23
In reply to #21

Re: Weight Distribution

07/13/2017 10:12 AM

Presumably the stilt assembly comes with it so the prospective owner can cope with expected repeated breakdowns?

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#25
In reply to #23

Re: Weight Distribution

07/13/2017 1:33 PM

That must be why there are so many old Dodge trucks seen on Texas highways.

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#22
In reply to #20

Re: Weight Distribution

07/13/2017 9:33 AM

Yes oddly enough it weighs 14,000 lbs....

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#24

Re: Weight Distribution

07/13/2017 10:29 AM

The sheet metal will provide negligible load spreading.

Borrow a copy of Roark's formulas for stress and strain to size the thickness of the plates. Use deflection calculations to determine the thickness as deflection will be much more limiting than stress for your application.

WAG figure on a 3/4" plate with a flexible machinery mount pad underneath.

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