Firebox Material thickness

[firmwood]

About to copy and paste before sending to a cnc laser.

I was going to use 16g 304 and lots of cross tubes for water.

Set that mess inside another 304 16g box with liner supports.

Stainless couplers. Done. Fab up a water cooled stainless door, done.

Yes, it's all planned to be stainless.

Any concerns for ash/creosote build up? Fire snuff issues? Stainless getting soft maybe, seems unlikely with low water Temps/no pressure and liner support.

I planned to span the edges and across top overall with 80 1.5" 48" long tubes..

I plan to copy the old school CB design somewhat. , smoke draft. Rest assured, legalities are already addressed.

Some rough math shows a tremendous amount of Sq area for water to touch firebox.

Thanks.

 

[firmwood]

No one? The sheet iron is free.

The 80 pieces of tubing 48" long isn't... Lol

Before I weld them in my box I'd rather get a 2nd opinion on firebox thickness....

 

[H-Ranch]

Mine is not stainless but I used 1/4". going on 10 years and still counting.

More welds just seems like more areas to fail.

Good luck. By far the most satisfying project I've built.

 

[firmwood]

Laser cut, tight edges, and leak check dye. I'm not worried. The size of the stove, cost of materials, the fact I can burn it on my paid break,
If it pukes out in 10 years, so be it. It'll be heating both houses, dhw, garage, radiant floor, and a jacuzzi.

Being able to have pieces cut within a few thousandths of an inch will make it super easy to burn and fuse with a nice tig stinger.

I build attitude testing chambers. Those cannot leak, and are stoutly built. This should be manageable.

And yeH, I'm considering 10gauge with stiffeners on the bottom sheet for firebox bottom , along with liner supports.

 

[homemade]

I’d go 10 gauge to .25in for the fire box myself. 16 gauge just seams too thin for my liking.

 

[H-Ranch]

Laser cut, tight edges, and leak check dye. I'm not worried. The size of the stove, cost of materials, the fact I can burn it on my paid break,
If it pukes out in 10 years, so be it. It'll be heating both houses, dhw, garage, radiant floor, and a jacuzzi.

Being able to have pieces cut within a few thousandths of an inch will make it super easy to burn and fuse with a nice tig stinger.

I build attitude testing chambers. Those cannot leak, and are stoutly built. This should be manageable.

And yeH, I'm considering 10gauge with stiffeners on the bottom sheet for firebox bottom , along with liner supports.

You are a far better fabricator than I. Mine was 100% arc welded and looked like it. Actually, by the end of the project I didn't think I did too bad. You may never have to worry about a joint going bad. I chose not to plumb the door for water just for complexity and another source of leaks.

Maybe compare what some of the commercial OWB companies use for thickness. If they are all heavier there might be a reason.

Another thing to consider is loading it - I toss in splits without any concern about damaging the firebox.

Whatever you decide, document and post it. We like pictures.

 

[firmwood]

No used 1/4 inch stainless partial sheets . If new material it gets expensive.

Could cut a bunch of holes in one sheet and plug weld two sheets of 12g together for the bottom of firebox.

/me shrugs.

Cad is endless. Machine cuts fast.

 

[dave_dj1]

If I were to build one I would look at how the heatmor 200 css is built, very sturdy and very simple. No tubes with water and no water under the fire or on the two sides either. Keep it basic. If you build the firebox with 16 ga you could maybe add a layer of fire brick on the bottom and the sides.
I am running a Heatmor 200 css and I burn good dry wood, I have very little smoke and a very efficient fire. I load it twice a day, 7 am and 7 pm, I do not stuff it full, just put in 6-8 normal splits 24" long. YMMV

 

[firmwood]

I see there's flues in there. Same idea, except blower to clean up smoke and pushing flue Temps over the water tubes.

I think im gonna go 12g, and brake stainless 12g angle pieces for floor stiffeners, ontop of liner supports.

It'll be involved, but I have unlimited electricity and a nice Miller water cooled torch, with a wireless pedal. Seriously, it's nice killing a trip hazard.

Everything is pointy in this shop.

 

[Whitbread]

My 304ss empyre 200 boiler only lasted 4 years. The Firebox was 16ga and 14ga. I repaired the first cracked weld in the second year. Granted it was mig welded and not tigg'ed like I would've done it, but I'm not sure I'd ever risk the amount of cost and time to build a 304ss boiler. 409ss has a wayyyyy lower coefficient of thermal expansion and will likely still outlast your wood burning years corrosion wise.

If you're dead set on the project, I'd go no thinner than 1/4" for door frame, 3/16" - 1/4" for firebox, and 10ga for the outer shell. The firebox takes a crap ton of abuse, I wouldn't skimp on it. Nothing worse than a water leak in the middle of winter.

 

[firmwood]

My 304ss empyre 200 boiler only lasted 4 years. The Firebox was 16ga and 14ga. I repaired the first cracked weld in the second year. Granted it was mig welded and not tigg'ed like I would've done it, but I'm not sure I'd ever risk the amount of cost and time to build a 304ss boiler. 409ss has a wayyyyy lower coefficient of thermal expansion and will likely still outlast your wood burning years corrosion wise.

If you're dead set on the project, I'd go no thinner than 1/4" for door frame, 3/16" - 1/4" for firebox, and 10ga for the outer shell. The firebox takes a crap ton of abuse, I wouldn't skimp on it. Nothing worse than a water leak in the middle of winter.

Ran a partial of 12g through cnc for slug holes and cutouts for tubes.

Then burned the sheets together with slugs

The bottom.

Later this week let's see what falls in the recycle bin.

Need 24ft of 12g to make 2 breaks. 4x1 inch sides? 2nd layer of stiffeners.

Unfortunately not a camera friendly place.

 

[firmwood]

Yeah, firebox is 12g all ariund. I'm breaking the edges so there's two seams incase one fails.


It's identical to a chamber liner we built for Boeing for testing @ high altitude.

We pushed that box from - 170*f to 350*F under 210,000ft of vacuum.... Lots of stiffeners on the liner. So im copying it. It was also 20ft deep, 12ft high, and 8ft wide.

304 held up.

Im also breaking some stainless and running all around inside of firebox corners for strength.

I decided to ditch the cross tubes. Ill build a smaller one for burning chips. I have an ideal on that one, another project...