Want to build first coal forge

[Pat Masterson]

So I got this bbq for free and thought I had a pretty good plan (drill a hole in the bottom, some black pipe fittings and a cheap hair dryer, bricks and dirt to build it up maybe a brake disc in the middle, coal over the top and get going to see if I like it to start) until I put it together and saw all these holes already in the bottom and it kind of threw me. I can still get about a 2.5” hole in the bottom without breaking through to the oblong ones. Should I just try to patch them (with what?) and go with original plan? Leave them covered with the piece that comes with the grill and go in the from the side with the air supply? But don’t I need some kind of hole in the bottom for an ash dump anyway? I don’t have a bunch of money to pour into this but I really want to have the option of coal along with the propane since my gas forge is pretty small. I’d love to hear what you guys would do with a small budget in the same situation. Thanks. 

[Daswulf]

Looks a bit deep but could still work. 

I'd go with a brake rotor. A good style to use is a rear rotor that had the drum style E brake. Inner pot size should be between 8-9" inner "pot" diameter and 2-3" deep. Use the grill more as a table of sorts. You'll want to cut the hole for the T pipe to pass through the bottom of the grill and attach it to the bottom of the rotor. You'll also want to cut sections out of the sides of the grill to act as a pass through for stock to be able to get it into the sweet spot of the fire. 

Depending on what coal you use, a hair dryer might not be powerful enough, but if you have one at hand you could give it a try first. 

[Frazer]

My first forge was a BBQ just like that. Like Das said, one of the problems with it is it's depth. Remember, whatever you're heating should lay horizontally across the fire and those high walls will get in the way. There are ways around that, but it is something to consider. 

I actually had a lot more success with v2, where I used the lid rather than the BBQ to make a size blast. That turned out to be much more convenient to not only build, but also to use in general. Plus there aren't any big holes going through the center.

A break rotor set in a table -- v3 -- ended up being even better still. So you have some options.

[Pat Masterson]

hoping to finally get around to this over the weekend. Frazer did you end up using any kind of refractory cement as a base below the coal? If so what kind? My head is spinning looking for something to use as some range from 20-100$ for the same amount. Hoping someone can throw out a name of something that’s worked for them so I can stop the guessing game. Thanks. 

Edited June 1, 2021 by Mod30
Remove excessive quote.

[BIGGUNDOCTOR]

I would just fill it with dirt, and run a side blast.  Think JABOD.  I have an old cast iron bottom blast, and clinkers can be a drag, With a side blast they are not as much of an issue when using coal.

[Daswulf]

Depending where you live you could dig up some clay and that would be pretty much free. Worst case cheap cat litter is pretty much just clay. You would ofcourse have to soak it and rehydrate it, mixing it up to get it to a moldable consistency. There are some threads on the subject here on ifi that could explain it better then I could atm.

[BIGGUNDOCTOR]

Have you looked at the JABODs on here?

 

[Glenn]

Spend the little bit of extra money and get NEW kitty litter when making the JABOD.  (grin)

[Charles R. Stevens]

Yep, get a piece of 3/4” schedule 40 black pipe, run in about 5” from the rim (bottom of the pipe) stop 2” short of the middle or offset it to one side if you want more room in front of the fire. 

fill the kettle with mineral soil (what ever you find below the topsoil) or an Adobe mix of about 1/3 clay and at least 1/2 sand (silt and gravel can make up the rest) a bit of coal or wood ash are helpful to the mix but not necessary as Glenn hints cheap caroused or dry sweep works well as clay, but so dose clay soil from the ground or discarded clay from a potter. 
So ideally you want to form a trench extending from the bight of the rim to an inch below the tuyere and 4” wide tapering to about 12” long with mounds added to each side about 4-6” high if you plan to use charcoal. If you plan to use coal only you can form a round or rectangular bowl 6” across and stop filling the kettle an inch below the rim. Fire spread thru coal isn’t as much an issue as it is charcoal. Some folks might make the top of the hearth 2” lower and form a 1” high rim around the bowl. This lets you hold more reserve fuel on the table. 

Air control and blast can be provided buy a cheap bed inflator pump from Walmart with a harbor freight foot switch (if your using a 12v pump use an old starter switch). Turning of the blast with charcoal between heats really saves fuel. Use a ball valve to control the blast. Outing the pump in a wooden box will reduce the noise: 
 

[Frazer]

Pat, Are you referring to v2 or v3?

I'm guessing you are talking about the grill lid. Either way, I don't have much to add to what has been said above. The idea behind v2 was essentially a JABOD. However, rather than building a box you use a vessel you have on hand for dirt. Unfortunately a VYHOHFWD doesn't have the same ring to it.. I had some fire bricks laying around so I put a layer of those down and covered them in a sand/clay mix. I found clay soil to work a little better than clay kitty litter, but that may have just been a bad clay/sand/water ratio on my part.

If you're talking about the brake rotor, I did form a bowl in that using kastolite 30. Let it be known that this is overkill and arguably unnecessary. Therefore, while it worked quite well, I don't mean to imply that is what you should/need to use. Using some form of clay/sand mix lets you reshape the fire pot as needed for next to nothing, which is a good thing. Once you start using something that sets hard your only option is to break it up and start over. 

Das doesn't even line his rotor IIRC, he just lets the ash do it's thing and that seems to work well for him. 

[Daswulf]

True Frazer, I haven't lined my rotor and it still has another 6 or more years left in it. They are easy enough to change out if you build them right anyway. The only thing I did do was to weld up the lug bolt holes. Clay could work for that as well. 

I'm not really sure which style Pat means to be building at this point either. 

Either proven design will work if done right. And you can always build something and improve on it as you try it, or build another one with a better plan. 

[ThomasPowers]

My most used coal forge has the firepot made from an axle cover from a 1930's banjo rear end---they were often repurposed as jack stands and I found a pair at the fleamarket for US$3.  Been using the first one for around 35 years now.  Beginning to look like I won't need the second one as I retire this year and the first is going strong!

[Pat Masterson]

Thanks guys. All super helpful. I was worried about just going with dirt/clay but now that I know others have used it that’s what I’ll try. And being able to easily redo anything that doesn’t work as opposed to breaking up some kind of refractory is a huge plus and a great point. 

[Frazer]

I use roughly 3 parts sand 1 part clay (dirt). Add water slowly so you don't add too much. Clinker tends to fuse to clay so that's why I go heavier on the sand.

You're just making mud pies so it's not an exact science 

Let us know how it turns out!

[pnut]

I use a kettle grill just like that for my MARKIII style jabod. I have a piece of round plywood that I put in the bottom so I didn't have to use as much dry kitty litter and I use bricks for the firepot. Simple to set up and disassemble. I will definitely get pictures next time I set it up. 

Pnut

[ThomasPowers]

I wonder if a round steel or Al pizza pan would fit in it?

[Charles R. Stevens]

Dirt and fly ash and cinder have been used for centuries, no reason to fear them. Sand can melt and form slag, but clay seems to moderate that. Ash added to the mix (either wood or coal) helps keep slag from sticking to richer clay mixes. 
If weight is an issue small bag of perlite can replace the sand in much of the mix, then skim coat with sand/clay/ash for a more durable face. This is not for insulation just weight savings. As to saving materials, anything heat resistant works, to fill the container to with in a couple of inches of the fire bowl. 

[Pat Masterson]

So this is where I got this weekend. I was really liking it until I went to move it haha. Not that it’s too heavy to move but I think it’s just too heavy for the legs of this cheap grill. So...I’m thinking about doing it the same way but using the lid instead of the bottom like Frazer suggested. Cut the same hole in the lid as I did the bottom and just slip the lid on to the pipe so the lid would be resting on the edge of the bottom and there would be a gap between the top of the lid and the bottom (where most of the dirt is with the current setup) I hope that’s making sense. If it does, does anyone see an issue with that? In my head it would basically be exactly what I have here except half the weight of the dirt?

OR I leave it the way it is and move it to a mostly permanent spot but that would be outside. My plan was to bring it in the garage once the fire is out after each use.   
What do you guys think?

 

 

[ThomasPowers]

I would have filled it with vermiculite and just topped it with a couple of inches of dirt.

[Pat Masterson]

That’s not a bad idea. Easy enough to change it to that. Would definitely take a lot of the weight out. 

[Frazer]

Looks good. Normally, I would say use the lid, but TP's suggestion about the vermiculite might make the grill a better option as it will not only reduce the weight, but it will insulate the grill body quite well. That'll be nice if you have to wrap up quickly for whatever reason.. Weather, obligations, etc.. One less hot thing to worry about. Plus you can keep the legs on there and the lid can still be a lid, which is convenient.

I would probably continue adding dirt until the surface is even with the disc, but that's just me. I feel like that little step would get in the way. I would also cut 2 slots on opposing sides so I could lay long stock across the fire horizontally.

Once you get it up and running, use it for a few sessions and take a some notes on the things you like and the things that need improvement. Make the change(s) and repeat until you have something that works for you.  

 

[Charles R. Stevens]

Ah, another aspiring smith falls victim to the brake drum forge...

for what the 2” pipe fittings cost you I could have outfitted my basic smithy.

that said it looks great and should burn up plenty of steel wile you polish your skills. 

[Pat Masterson]

Yeah I like the idea of still having the lid. The level of the dirt and the rotor were the last questions I had. I left the dirt level lower than the rotor thinking it would be some extra space to have fresh coal. The rotor is about 2 inches lower than the rim of the grill right now. So the way it sits I would definitely need to cut those slots for long stock or I bring the rotor up flush with the edge of the grill. 
Once again though I spent way too much time worrying/thinking about the right way to do something instead of just trying it. I could have had this going weeks ago and gotten it to my liking by now lol. 

Oh and I forgot to order the coal...might need that. 
Thanks for all the help though guys. Much appreciated. 

[BillyBones]

You can use the lid for a cover rather than moving after it cools down. 

I would also make the dirt level with the rotor. I have about a 1/2" step on mine and it does get in the way at times.

After figuring out location and setup i would work on strengthing those legs though. It is most likely not the legs them selves that are weak but the sockets connecting them to the body of the grill. Get that thing good and sturdy. You definately do not want it falling over while in use. 

 

[Frazer]

I don't know Charles, I had reasonable success with my rotor firepot. I modified it to suit my setup, but all things considered I (in my limited wisdom) consider them to be a perfectly viable starting point. I think you know as well as anyone that forge builds 1, 2, 3, etc. tend to be refined, tweaked, scrapped, etc. over time as you get some experience and figure out for yourself what works and what doesn't. I think IFI is pretty good at getting people on the right track from the start, but a lot of people (myself included) need to feel things out and get the ball rolling to have that "OHHHHHH, I get it" moment.

1 hour ago, Pat Masterson said:

Once again though I spent way too much time worrying/thinking about the right way to do something instead of just trying it

You're not alone, I find myself doing that sometimes too. Of course there is a balance, but IMHO sometimes "good enough" is just that. You'll learn more from 1 hour of the forge running than you will from 10 hours of imagining how it's going to run. The nice thing about a setup like you're putting together (or a JABOD) is nothing has to be permanent. If you can't find coal, pick up a bag of lump charcoal while you're getting vermiculite (they are often sold in the same stores) and try to sneak an hour or two of hammer-time in!