Structural engineers assemble! Steel sheet to hold 200kg...

Russinating · 2 Jun 2020 at 14:59

dl8860 said:
Two of those 127x76x13s are giving you 35kNm of bending resistance when you've got 1kNm, so it's certainly huge overkill in terms of capacity, but the key thing to think about is how you fix it all together.

In your sketchup you've got a vertical propping up under the oven, is your 2200mm span ignoring that?

Yeah I was thinking two for, purely as you say, fixing it all together, so the two RSJs run along the front and back of the 'table top'. If there was just one running in the middle then the sheet might get a bit wobbly over time or have more deflection front or back.

If the vertical isn't essential then I'd rather leave it out which gives us more flexibility over what we store under there, or what/how/where we build shelves and what made from.

dl8860 · 2 Jun 2020 at 15:07

What would you have your RSJs bearing onto? Is that concrete either side? Does seem a little bit nuts using steel beams for a little setup like this, whatever your beams transfer the load of the oven into are also going to need to be pretty strong too so why not just put the oven on whatever that is? Putting a big heavy block in the middle of a span like that is a bit nutty, unless you basically want to try your hand at installing some structural steelwork for fun or design aesthetic.

Bug One · 2 Jun 2020 at 15:10

RSJs? Wow - talk about overkill. Why not just get some box section and weld a frame together for it. You could make it so the steel sheet never has to span any sizeable gaps.

builder22 · 2 Jun 2020 at 15:15

...and could get the sheet folded to cover the box section frame...would look similar to the table in the link on the last page then too

Gav_r26 · 2 Jun 2020 at 16:08

Exactly, box steel frame and a sheet top with a fold on the front to hang down over the frame and hide it.

Russinating · 2 Jun 2020 at 16:17

When you guys say 'box steel frame', is that literally just a wireframe cube made of this kind of stuff https://www.metals4u.co.uk/materials/mild-steel/mild-steel-box-section ? Same question as the OP applies to those as well; what sizes would I need? How easy would a ~1.5mm steel sheet be to bend over and under the edge (u-shape)?

And bricks either side.

Cyber-Mav · 2 Jun 2020 at 16:20

1mm sheet steel can easily hold 200kg on it if its placed like a table top. Get a decent frame on its backside and it will probably hold 500kg.
Thats if your 200kg weight is got the surface area of a cement bag. If its got the surface area of a nails point then its gonna poke straight through

Gav_r26 · 2 Jun 2020 at 17:37

Russinating said:
When you guys say 'box steel frame', is that literally just a wireframe cube made of this kind of stuff https://www.metals4u.co.uk/materials/mild-steel/mild-steel-box-section ? Same question as the OP applies to those as well; what sizes would I need? How easy would a ~1.5mm steel sheet be to bend over and under the edge (u-shape)?

And bricks either side.

Yes lengths of Box section like that across. Probably 4 or 5 and then a steel top with just the end bent over like an L to hang down the front to cover the box. Would probably need a fabricator to bend it or some metal suppliers have benders that would fold it.

As fr thicknesses, without modeling it up (I'm too lazy for calcs

) I wouldn't know but as a guess 4mm and probably 5 off.

JBuk · 2 Jun 2020 at 17:52

dl8860 said:
40mm is serious steel! If the OP is using the word 'sheet', if you looked at a piece of 40mm steel plate then the word sheet wouldn't be springing to mind, trust me.

it would cost a fortune for his dimensions @40mm

30mm box section about 3mm wall thickness Tack welded under a few mm of steel plate should do it to support the weight with out much sag and probably cheapest option , would also look better than Rsj

sigma · 2 Jun 2020 at 17:52

Make it out of 40mm thicc box section, just to be sure

It’d be a beast! Might even support your whole house!

PlacidCasual · 2 Jun 2020 at 18:41

When I looked at your sketchup with the leg under the weight my first thought was cast concrete for everything, with care you can get a loverly smooth surface, you could even resin seal it. It would have a nice heft to it and none of the expansion or flexibility concerns of box section and steel sheet.

Russinating · 2 Jun 2020 at 19:13

PlacidCasual said:
When I looked at your sketchup with the leg under the weight my first thought was cast concrete for everything, with care you can get a loverly smooth surface, you could even resin seal it. It would have a nice heft to it and none of the expansion or flexibility concerns of box section and steel sheet.

It was on my radar but would 2400x800x50mm of concrete not weigh a silly amount? It wouldn't be able to be cast in place (I don't think) so would need lifting on.

And yeah it'd need sealing since we want the part to the side to effectively be for food prep/serving.

famas · 2 Jun 2020 at 19:53

Would corrosion be some thing to consider using box section and sheet steel? How would you prevent it?
Also thermal movement maybe an issue in very hot weather.

If I was going down this route I would consider using stainless steel, especially if you intend to use the surface for food but it will be a lot more expensive.

Personally I would look into building it in brick and cast a concrete counter top which can be done in situ, though maybe a bit more work.

Any reason you have chosen that particular oven? For that sort of money you could build a very nice Pompeii oven which would be a lot more versatile than the Morso.

The Morso being cast iron with no insulation means it will be fine for pizza and the odd grilling but it will not be able to hold any heat for retained cooking.

The beauty of a Pompeii oven is you can fire it to pizza temperatures on the first day and it will still be hot enough to roast or bake bread on the 2nd and 3rd day without the need to re-fire.

If you're going to all the trouble and expense of this outside area it's worth investigating if you're into out door cooking.

PlacidCasual · 2 Jun 2020 at 19:56

Yeah 200kg unless you go for a lightweight concrete, a pumice based concrete might come down to a quarter of that at a guess.

Dirk Diggler · 3 Jun 2020 at 07:32

Couldn't you pile a few concrete flagstones and sit it on them? Or, get a Brickie to create a raised area for you to sit it on?

It's 96kg so it's not the behemoth that you're planning for.

Bug One · 3 Jun 2020 at 08:44

Do yo own a welder? If not, you'll have to factor that into the cost of building a box section frame.

Bug One · 3 Jun 2020 at 08:48

Just going back to your original inspiration for building this.

https://morsoe.com/en/product/outdoor/accessories/outdoor-tables/morso-garden-outdoor-table

To me, that looks like it's steel box section with a steel shell - all powder coated. No way that'd be solid steel at that thickness.

Russinating · 3 Jun 2020 at 08:53

famas said:
Any reason you have chosen that particular oven? For that sort of money you could build a very nice Pompeii oven which would be a lot more versatile than the Morso.

The Morso being cast iron with no insulation means it will be fine for pizza and the odd grilling but it will not be able to hold any heat for retained cooking.

The beauty of a Pompeii oven is you can fire it to pizza temperatures on the first day and it will still be hot enough to roast or bake bread on the 2nd and 3rd day without the need to re-fire.

If you're going to all the trouble and expense of this outside area it's worth investigating if you're into out door cooking.

We've had the Morso Forno for 3 years and none of that is correct, other than not needing to re-fire it.

Russinating · 3 Jun 2020 at 09:56

Bug One said:
Do yo own a welder? If not, you'll have to factor that into the cost of building a box section frame.

And no, which is the trouble with that idea! Impossible to get tradesmen as it is, let alone for small jobs.

Gav_r26 · 3 Jun 2020 at 11:26

Just use straight lengths bridging between the 2 walls. No need for a welder.