XL on feet??

Cobra · July 2010

Does anyone know if it is safe to have the XL on the feet? I had posted a picture of my table thats in process, and someone asked about the feet. They commented that they had heard the XL bottom needed to be fully supported?(I dont doubt you, just wanted to verify) Does anyone know if that is correct, I dont really want to lose the bottom of my egg. Anyone else have an XL on feet?

WessB · July 2010

The XL does NOT come with the feet from Big green egg, so I would take that to mean they don't want them used with the XL..

Weekend Warrior · July 2010

That is correct. The XL should not be placed on the 3 little green "feet". Too much weight supported by to little surface area could lead to cracking of the base.

Mark

fishlessman · July 2010

bobbyq from bge posted not to use the feet with an xl

Unknown · July 2010

Didn't have a close-up pic, best I could do this morning. I put my XL on feet, mainly because it's sitting on a cedar riser. Cooks great, no problems.

http://img.photobucket.com/albums/v663/JBC77/House/DSC03535Large.jpg

Frank from Houma · July 2010

I would replace the cedar riser with a paver

Unknown · July 2010

Thanks. That's what I will do, as I didn't realize it was a weight issue.

Frank from Houma · July 2010

Had my XL on the feet for a couple years without a problem. Since seeing the recommendation not to use the feet it now sits on some large bricks - the kind like you see in flower bed borders.

Frank from Houma · July 2010

OS77 - The weight issue is certainly a concern. The cedar riser is more of a fire hazard issue.

There are a few folks who have had some major scorching underneath an Egg simply supported by the feet on top of wood.

Cobra · July 2010

I have my XL on 4 feet on firebrick. I guess I will be taking the feet out and go with just the firebrick.

Humphrey Chimpden Earwicker · July 2010

sorta...
but maybe for a different reason than any crushing or compression.

the feet (and base) won't crush under the weight. ceramic can take quite a bit of compression.

my guess is it is the span from foot to foot. in a large BGE (or smaller) egg, the span is probably within the typical limits for ceramic. i don't think the BGE ceramic is reinforced (like, with glass fiber), so as far as an engineer would be concerned, it is technically ('technically') unable to span anything beyond it's own thickness times a factor of four, maybe 6, or even eight.

add the ridiculous temps that the bottom is exposed to, and the ceramic is LESS likely to span. heat something, and it expands and loses a little strength (in general).

ceramic can't really deflect and then bounce back, it's not really elastic. it would just crack and break. especially if there's a void or inconsistency in the ceramic.

better to sit that thing on a flat surface and take all tension out of the equation...

hard to crush a concrete block, but breaking one with your hand is no real trick at all. concrete blocks have virtually no tensile strength, and as long as you make it span, and then try to get it to bend, it'll crack. Hi-YAH! ka-ra-te chop.

now, i'm off to 'wax off, daniel-san'.

...as an aside, when you look up and see those concrete beams spanning the highway, it may surprise you to realize that the concrete is there to do nothing more than take up the space between the rebar. it is virtually (though not literally) doing nothing structural, since the steel is running the show. sure, if it is an arch, or prestressed, yeah, it's structural...

just saying, in a simplified way, the concrete is there to hold the steel in such a way (in the dimensions required) that the steel takes all the stress anyway. heck, you have to size the steel to carry the dead weight of the concrete itself.

blew my mind the first time i heard that... :laugh:

ChokeOnSmoke · July 2010

Just purchased an XL this past Friday!!! It did NOT come with feet.

ChokeOnSmoke · July 2010

Just purchased an XL this past Friday!!! It did NOT come with feet.

Weekend Warrior · July 2010

Just fyi, hitting the "Back" button on your browser after submitting a post is what causes a double post. Welcome to the forum.

Mark

ChokeOnSmoke · July 2010

Thanks, that was bugging the "you know what" out of me.

FlaPoolman · July 2010

But Mark, I think he bought 2 of them :laugh:

Matt · July 2010

st!ke --

Actually, the concrete also carries the compressive load and prevents the steel from buckling. In any simply supported beam, there will be tensile forces on one side and compressive forces on the other (the transition from one to the other is the neutral axis). The rebar is placed in the portion of the beam being subjected to the tensile forces, but the concrete carries the compressive load on the other side of the neutral axis. If loading conditions change (e.g., earthquake) such that the steel is forced into compression, it would buckle without the lateral support of the concrete (the loads on the unsupported rebar itself would lie outside of the Euler buckling hyperbola).

Sorry, I'm a geek.

Matt

Humphrey Chimpden Earwicker · July 2010

guess what i'm saying is that if the compressive load developed, the concrete would be there to carry it, but (especially in pretensioned beams) the steel at the bottom of the beam is designed to initially taking all the tension. and by taking all the load at the bottom, the compression at the top of the cross section is greatly minimized

if you keep loading and loading it, the top of the beam will see the compression, but usually the tension at the bottom is what is critical, and the steel takes that load.

i understand that the compression at the top is pretty much the opposite value (in tension) at the bottom. but by prestressing, you make the steel do the bulk of the work. yeah, of course the concrete will see compression, but not in the same way that a wood beam does, where it is neutral until loaded. then the upper half is compressed to the same extent the lower half is in tension.

i was generalizing... unfortunately, that means you can always drill deeper.

the simplest thing to say is that the concrete at the bottom half of the beam is doing very very little when in place and the system is loaded.

few beams fail because the top half of the beam fails under compression. it's almost always bending or tension at the bottom.

not trying to be mr. theory. nor do i mean to make it sound too simple. my structural engineering profs were all hard core math guys, but principle and concept were always first. and that always requires a little generalization/simplifying.

being a nerd is fine with me. you got me thinking... i have a few very costly buildings to my credit, and hope that i didn't design them incorrectly. :laugh:

concrete design is a pretty fascinating thing, much more complicated than wood or steel. the beam is sized, then the steel reinforcing, then the weight of the steel and concrete is fed back in, the beam resized to carry that... etc.

XL on feet??

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