Modifying my rim forge

[Gustav]

Hey guys!

It's time to upgrade my forge. The first picture is what it looks like ATM and the secound is what I want it to (sort of) look like:

 

The plan is to weld sheet metal to make this a "table" and then cut out a round opening to make room for the rim forge.

 

That way the forge I have now acts as a firepot. It will probably look like something like this:

 

The things I am uncertain about are:

1. How large should the "table" be?

2. Should I weld some plates (like these: ) inside the rim to make it look more like the firepot from the picture I pasted?

3. How thick does the sheet metal have to be? Both for the table and the eventual plates for the firepot in question number 2 above.

4. Should I ditch the rim and make an entirely new firepot? This could be difficult since I'll have a hard time finding extremely thick sheetmetal.

 

Just realized that this got picture heavy.

Very thankful for all answers.

// Eophex

[JHCC]

1. Depends on how much room you have in your forge, but I’d recommend no less than 24”/60cm square. 

2. If you’re going to go to that much trouble, you might as well weld up a new firepot. 

3. The tabletop doesn’t have to be super-thick, so 1/16”-1/8” (1.5mm - 3mm) is probably sufficient, so long as the table frame is sufficiently rigid. The firepot needs to be  about four times as thick, say 1/4” - 1/2” (6mm - 12mm).

4. If you can’t source the heavier plate for the firepot right now, don’t let that hold you back from improving your rim forge. You can always add the new firepot later. 

Quick tip: all the heavy plate that I’ve used in my own welding projects has been scrap from building sites. The contractors were more than happy to give it to me to save themselves the trouble of hauling it away. Keep your eyes open: you might be surprised by what you can find at little to no cost.

[Gustav]

Thanks for the quick reply! I'll try to find some thicker plate. I suppose it doesn't matter what type of steel it is? As long as it's not galvanized or something like that.

Mod note: don’t use the quote feature if you’re replying to the immediately preceding comment. It’s a waste of space and bandwidth. 

[Frosty]

If you're going to weld up a fire pot what use is the wheel rim? Lose the useless thing, all a wheel rim does is take up space and make the forge heavier unless you're using the rim as a fire pot, then it wastes fuel extravagantly. 

Weld up your fire pot from 6 mm or thicker and put a rim around the edge that lays flat on the forge table so you don't have to weld, bolt, rivet, etc. it to the table it'll stay there just fine. attach your ash dump air blast and you're done. The air grate can just lay on the bottom of the pot there's not reason to attach it, it'll be easy to replace when you think of something different or that one burns out.

Frosty The Lucky.

[Glenn]

Wheel rims have been used in a variety of different configurations and they can work and get the metal hot. Adding clay mud to reduce the amount of interior space and fuel needed, or to reconfigure the fire to try if a different style fire, was both a learning experience. It showed that there is a good reason to go another forge design. 

Keep the wheel rim until you get a better forge design built.

[Gustav]

If I find some 10 mm sheet metal, what kind of welder is required? I have a "Micro-Mig" atm (with specs I don't have in my head). Will that do?

[JHCC]

Impossible to say without knowing the specs. Check that out and get back to us. 

[Frosty]

If it's too thick for your welder, (It's YOUR welder read the specs) make a bolt together fire pot. Make two sides 25 mm longer or wider, so it over laps then drill holes and bolt it together. A little clay to shield the bolt heads and you're good to go.

Frosty The Lucky.

[Gustav]

2 hours ago, Glenn said:

Adding clay mud to reduce the amount of interior space and fuel needed, or to reconfigure the fire to try if a different style fire, was both a learning experience.

What kind of clay would that be?

[Frosty]

Any garden variety works. Don't over-complicate things. 

Frosty The Lucky.

[Glenn]

Eophex, dirt will do as fill material. We have clay available so it was used. 

As to building without a welder, design the project so you can use rivets, bolts, screws, etc as fasteners. Folded or metal bent to a matching angle will serve to reinforce the joint when using fasteners. Angle iron will do in some cases. Straps across the gap will work if you then have a small gap or go back and fill the gap with clay or something.  Be creative.

[Gustav]

Well, turns out we have 2 welders!

[JHCC]

I don't read Swedish, but I think that says you can weld up to 3.15 mm? If that's the case, you should be able to weld up 6-8 mm plate if you bevel the joint deeply and weld multiple passes. 

(Caveat: do NOT take my word for it. I am very much a novice welder, and I readily defer to the pronouncements of those with greater experience and skill.)

[Frosty]

It looks like 3.15 mm max to me too. Don't quote me but I think that's at a 80% duty cycle or about 48 seconds out of a minute with adequate cooling time. From my long ago memory equal cooling to running time. I can't say though.

This is just a fire pot, not structural elements, it doesn't even need to be leak proof just held together enough to support maybe 5 kg.

Rather than deep bevels and fillet welds, leave a gap between the parts, use a piece of wire or say a 4 penny nail for spacers and weld into the space. This gives a good space for a fillet but the low power welder isn't trying to make a puddle in the center of an area. It's melting the edge of an outside corner. The base metal will melt more deeply because of the reduced heat sink and the filler wire will fill the gap.

I HATE doing fillet welds with low power mig welders, they're designed for sheet metal , body and fender work, not structural. Still, you can cheat a decent weld by filling the gap between two outside corners and get decent strength on stock too thick for the welder's rated capacity.

I will happily bow to currently practicing welders, I haven't maintained a cert since the mid '70s.

Frosty The Lucky.

[Charles R. Stevens]

I used to push my 20% duty cycle miller to weld heavier stock. You start buy tackingevery thing up, pre heat and then fill in the gaps. With a fire pot, square edges or fine, as they leve ready made filets on the outside of the pot. 

Now the fire pot is the only thing that thick stock is needed for, 2.5 mm is plenty thick for the hearth, infact 1mm will do just fine. 

[Dale Russell]

Gentlemen , that 3.15 mm is the rod size with the unit set at 115 amps  , so welding 6mm / 1/4" plate shouldn't be a problem as long as he don't exceed the duty cycle

 

Dale Russell  

[rockstar.esq]

Eophex,

Have you considered a side-draft forge?  I believe the JABOD forge is a significant upgrade to a brake drum forge.  Side drafts offer many advantages in use, not the least of which is that they are easily adapted to different fuels and forging needs. I think they're a better solution for coke forges because a bottom blast coke forge needs a very heavy firepot to hold up to the heat.

However, if you'd prefer a bottom blast, I second JHCC's comment about construction sites.