Metalworking advice

[Pete Verdon]

Hi,

I'm planning to build a "moderately epic" barbecue this spring. The main structure will probably be of brick, but there will also be some steel involved. You can't cook a turkey on an open grill, so I will have to incorporate a lid, which seems to be feasible only in metal.

I've not done much metalwork before, but I'm not too worried about most of it. However, there are a few points I'd welcome advice on.

Firstly, fixings. I'm not planning anything very complicated, and if necessary reckon I can do it all with rivets, folds, etc, rather than any hot work. I don't have access to welding gear, but I might be able to braze or solder the joints with a blowtorch. However, I wonder if this is suitable for a barbecue lid that will be over a hot fire.

Also, coating. Presumably if I were to just use mild steel it would rust away in short order (especially with the heat) so I need something. I suppose one option is to buy stainless, though it might be a) expensive and b) hard to work and especially to braze. Is galvanised steel likely to be suitable? Or what paints/coatings are available for steel in hot environments? I'm aware of "manifold paint" for car engines, for example.

Material. Essentially, I'll be making an open-bottomed box, perhaps

800x450x300mm (random guess, I haven't come up with a design yet). Assuming cutting a cross-shape and bending down the legs, that would be cut from a sheet 1400x1050mm. I've pulled the figure of 2mm thickness from nowhere - is that likely to be unacceptably floppy once formed into a box? Any idea of a ballpark figure for price of such a sheet?

Finally, I've posted on our internal newsgroups at work for suggestions of local suppliers, but any general suggestions from here are welcome as well. I'm in Southampton if you happen to know somewhere specific.

Answers to any of the above appreciated, as well as any other advice. However, to forestall a certain class of comment, yes I'm aware I can probably buy a big barbecue cheaper, but I'd rather build one.

Thanks,

Pete

ps: Since writing the above, I've found a cheap and cheerful "arc welder" at Screwfix. I realise this is a rock-bottom budget tool, but is it likely to be capable of bodging up my big steel box, do you think?

[Harry Bloomfield]

Pete Verdon used his keyboard to write :

Solder would quickly melt. Braze or weld.

Not if you make it thick enough.

Small oil drum, cut in half with an angle grinder then weld hinges on, a handle and a base/frame. When it has rusted away, build another.

[Andy Dingley]

Nightschool class. It'll give you cheap access to MIG, hopefully plasma cutting too.

You could do it with stick, but I'd much prefer MIG.

[Doki]

"Pete Verdon" wrote in message news: [e-mail]...

is *not* suitable IIRC. I can't remember the exact reasons, but recall someone trying to make a grille from a bit of shopping trolley, until someone said "aaaaaang on a minute".

[cerberus]

> Galvanised is *not* suitable IIRC. I can't remember the exact

The zinc would melt in no time + it gives off arsenic fumes.

Don.

[Pete Verdon]

Sounds worth avoiding :-) I asked the question because I couldn't remember seeing anything galvanised and meant to be used with heat - I guess that's why.

Mind you, speaking of trolleys, I have used supermarket baskets once before:

[Pete Verdon]

Yup, done it before, works well. But as a permanent feature of the patio aesthetics are important with the new one, and a rusty drum doesn't really do it for me.

Cheers,

Pete

[Doki]

Clean the drum up and use VHT paint then.

[Dan Smithers]

It would probably be useful up to around 3mm steel. MachineMart do Clarkes around the same price too.

> Galvanised is *not* suitable IIRC. I can't remember the exact

Actually, the zinc would burn off. Zinc fumes are poisonous. I got the full story on a welding group when I asked about welding it.

it's outside, you would probably get away with it, but you wouldn't get any benefit from the coating.

If you can get an oil drum, it's excellent. I've got one cut in half with a stand made from angle iron so it's portable. I used bolts so I can take it apart if I need to.

Bricks can cause problems when the water gets trapped.

dan

[1501]

Poisonous yes - arsenic no.

[<me9]

You can't transmute one element into another (except nuclear processes,) so there's no way arsenic could be produced if none was already there.

Hot dip galvanising involves dipping the steel in (IIRC -- Sulphuric) acid, and then immersing in molten zinc, so heat involved.

[<me9]

A gas bottle cut in half can make a good barbicue. JUst ensure it is free of gas whilst cutting.

[Andy Dingley]

Noxious, but not toxic in these levels. Hot-dip galvanised sheet welds very badly, as there's enough zinc around to make for a significant impurity in the resulting weld. If you gas weld then it's hot for long enough to allow the zinc to boil off, if you electrically weld it it's too quick and you get a weak weld. For car repair work it's common to use "Zintec" sheet which is a thinner electroplated zinc coating. This stuff welds straight through without a problem. It's also useful rustproofing under paint, but not enough to leave bare out in the garden.

Chromium, now that's a different matter. "Chrome flu" is much more horrible.

If you want arsenic fumes, try making the Japanese decorative white copper alloy, kuromi-do (another new word for Huge!). This is 99:1 copper:arsenic. Easy to make in principle, pretty nasty to actually do it.

[Owain]

So hide it behind a nice brick or stone wall

Owain

[Pete Verdon]

Yup, I've put together in the past exactly the same thing, right down to the angle-iron and bolts. Mine was made to be carried in the back of a car - all the pieces fitted inside the half-drum, with a wooden board that fitted exactly in the top and made a table when removed.

However, this project is not to make an oil-drum barbecue. I'm actually taking a certain amount of design inspiration from here:

mine will be charcoal rather than gas, and won't be quite so ragingly, Americanly, over-the-top. Will probably be a little rougher round the edges too since I'm building it :-).

Oh? Sounds like something I should take care to avoid - what do you mean exactly?

Cheers,

Pete

[Dan Smithers]

I've had issues where water gets into the surroundings (either bricks, mortared joints or concrete). When it gets hot, the water vaporises and if it can't escape it pops bits of the surroundings off. Mainly this has been using the bricks to contain the fire directly.

Some materials are worse for it than others.

[Pete Verdon]

Makes sense. I would have the coals on a grid, but the sides would be straight brick. On the other hand, it is going to have the famous lid over it so perhaps less likely to have water soak into the internal faces of the brick in the first place? I was intending to look for the densest brick I could reasonably find, but I'm not going to pay for something exotic.

Pete