Building a small coal forge

[verndahl]

I've been happy with my two gas forges but there are times it would be handy to be able to heat spots that won't pass through either of them, so a small coal forge would be just the ticket. I'm trying to spend as little as possible (as always) and i don't have a welder. So..... what i've been thinking about is a brake drum forge. So far as my research says that a draw back of that is it doesn't have a "box", that is a tapered recess where the air comes up and burns the coal. This wastes a lot of fuel and probably is harder to control. I was thinking of a way to modify a brake drum so that it would work better.
If i were to make some sort of cone or box (probably the wrong terms) to fasten to the bottom of the drum, how big and deep should it be?
Any other ideas are welcome too.

 

[Shawn]

If it's only for occasional use, would one of those dirt box forges be sufficient for what you need? Wouldn't require a welder or much money, and you can experiment with what size firepot would work best for you and adjust as needed.

 

[verndahl]

Hmmmm. I'd never seen one of those. I guess i was thinking of something a little bit smaller (like a rivet forge) and more portable. my space is limited.

 

[Shawn]

They don't have to be real big. A 2'x2' box with some dirt in it, a pipe stuck through the side and into the firepot hole in the middle for air and you are set.
Another option could be a square box just full of dirt for your insulated bottom, two hard firebrick stood on their side, an air pipe coming through them, and stack your coke/charcoal against that for a side blast forge.

I have a little rivet forge. It works but there isn't really any firepot to it so it takes a bit more attention to keep the hot coals pulled into the middle and not let it spread across the entire forge.

Just trying to think of low cost options for you that don't need a welder.

 

[Mike Blue]

If you had some access to bentonite clay (as in digging some up from the local geology) you can make and bake a nice tuyere (the word you were looking for was tuyere) that will last a bit longer than baked dirt. But dirt will work fine too if you shape it right.

As Shawn mentions, a side blast forge can be built using stout brick (firebrick is best).

Blacksmiths were known for building all sorts of fires to heat work in just the right spot on odd shaped pieces. One forge does not fit all.

 

[Bruno]

I built my first charcoal forges from ashes, kitty litter and cement. The lasted a long time

 

[verndahl]

Hey, thanks guys. Now you've got me thinking in a different direction. Bruno what's the mix ratio of your ashes, kitty litter and cement? If i were to find some sort of suitable container and pack it full of a clay mix is there a more desirable shape/depth for the tuyere? Or am i over thinking it (probably) I just like to get things right the first try.
Also, where would one find a cheap fan for the blower?

 

[Shawn]

I've seen an old hair dryer used a lot.

 

[Mike Blue]

Or build a small box bellows, ala Japanese style and use charcoal as fuel...

A hair dryer doesn't need to heat anything. All you need is the blower.

 

[32t]

I have played a little bit with a hand crank forge looks more like a grill. enough to be dangerous!

Air more seems a volume thing but does the coal/charcoal create enough back pressure to think of pressure from the blower?

 

[Bruno]

Hey, thanks guys. Now you've got me thinking in a different direction. Bruno what's the mix ratio of your ashes, kitty litter and cement? If i were to find some sort of suitable container and pack it full of a clay mix is there a more desirable shape/depth for the tuyere? Or am i over thinking it (probably) I just like to get things right the first try.
Also, where would one find a cheap fan for the blower?

Honestly didn't overthink it. I think about a third each in volume. Maybe a little bit more of kitty litter.

Also you want to mix it first and only then add water because the litter will draw water and it will be difficult to mix.

Anybold hairdryer is what i used

 

[Mike Blue]

My first forge was a portable railroad forge. It all fit into an iron box (legs tuyere and blower and tools). I had to rebuild the clay liner once or twice.

 

[verndahl]

My first forge was a portable railroad forge. It all fit into an iron box (legs tuyere and blower and tools). I had to rebuild the clay liner once or twice.

Cool! i saw a Calvary forge that was built like that. I'm looking for a old metal bathroom medicine cabinet now( of course there's never one around when you need one), maybe screw on some metal legs etc.

 

[verndahl]

So I know it's been a few years since i posted this question and i finally got it built! Kind of a hybrid of many ideas. Basically a dirt box forge with a metal fire box and a bottom blower. I tried it out for the first time today. I can see it would be nice if it were bigger but it should work. Made a couple experimental pieces (shown on top of the forge) Now to figure out how to forge weld. (I can get it to burn the steel really well, just not stick together) Any suggestions?

 

[32t]

Did you paint your grass? I don't think that you are to far south from me........ LOL

 

[Bruno]

Setups like these are great when you look at how cheap they are vs the added value you have.
I will never surrender my propane forge but I do agree that the ability to work large pieces is priceless.
I rarely need that but like when I was making that D guard, I always have to keep in mind that I do enough work in 1 heat in a way that makes everything fit back in the forge.

How does it rate in terms of fuel efficiency? I assume it's cheaper to run than propane?

 

[verndahl]

Right now the fuel is free! My friend has four bags in his barn he doesn't need so he said i could have it. Propane is $12 for a grill size tank which lasts me about a month. Haven't price coal yet.

 

[32t]

If I could buy a 20/16 lb propane refill for $12 I wouldn't even consider using coal. Unless it was free!

 

[Bruno]

I'm paying 47 Euro for an 18 liter tank at full pressure. It's not cheap but it lasts for a while. Depends on the work I'm doing. A couple of full afternoons and it's gone.

 

[32t]

I checked prices today and a so called 20 lb cylinder that is filled to 18 lbs is $22.60 USD at one of the cheapest places around that I know of. Many fill to less than 18.....

Roughly less than half that you are paying Bruno and more than Vern states.