Need review of side-blown charcoal forge design

[kierkkadon]

I have designed the refractory lining for a forge I'd like to build - I happen to work at an industrial refractory specialist, so I can have it cast out of the finest, strongest, most heat resistant refractory material available for essentially no cost. This is the current stage of my design, and before I push it to be cast I'd like a review - criticisms, dangers, warnings, praises, whatever. I'm especially unsure about the design of the trough - does it need to be deeper, less deep, wider, and so on.

This is just the refractory lining; it would be surrounded and held by a steel plate construction. I'm building a box bellows to go along with it.

 

All dimensions are in inches.

refractory.pdf

[L Smith]

Don't over think your lining. I have an old forge I bought from an old lady who told me her husband got it from sears. it is lined with something cement like and has lasted for decades. I have owned it for probably 34 years. I have no idea how old the lining really is -- it just holds up!  The drawing you furnished looks good just don't make it too deep. Mine is fairly flat except for the nest. That part is about 3--4 inches deep just enough to hold a good fire.

[Everything Mac]

I think it looks good. I envy your position.


I've only ever used home made side blast forges but the fire tends to be a bit short and fat, almost square in front of the tue rather than a long rectangle. You might want to shorten and widen your trough. As you will likely find working from the side of the forge better than working facing the tue.

The only major change I'd make to that is to make sure you raise the tue off the floor of the forge so that you have space for your clinker to collect.

All the best
Andy

[Frosty]

Welcome aboard, glad to have you. If you put your general location in the header you might be surprised how many of the IFI gang live within visiting distance.

 

As already said, don't over think your forge. Nothing is perfect, you can waste a lot of time chasing something that doesn't exist. I've never seen a solid fuel forge made with proper refractories and I doubt it's necessary. Plain old river clay can last hundreds of years. Of course if it's free why not, I'd go for it.

 

What you've drawn looks pretty good to me but I'm a propane forge guy for the most part. I'm looking forward to seeing the finished forge fired up.

 

Frosty The Lucky.

[SJS]

Are you going to use coke? Cause unless your companies refractory is pretty shock resistant, watering the green coal could be a spalling experience. Be a shame to engineer this lovely forge and crack it up first time you use it or worse have it explode. But this isn't my area of expertise, and clayed forges hold up so maybe I'm all wett? ;-) and the other comments about wider and deep with the tueyer coming in higher so the clinker doesn't clog you air all sound right, on my phone so can't look at the drawing directly;-)

[Frosty]

Are you going to use coke? Cause unless your companies refractory is pretty shock resistant, watering the green coal could be a spalling experience. Be a shame to engineer this lovely forge and crack it up first time you use it or worse have it explode. But this isn't my area of expertise, and clayed forges hold up so maybe I'm all wett? ;-) and the other comments about wider and deep with the tueyer coming in higher so the clinker doesn't clog you air all sound right, on my phone so can't look at the drawing directly;-)

 

These are good points to consider SJ but can be dealt with up front. A couple things may make water and spalling non-issues:

 

First if you're using river clay, mix it with sand in a ratio of 1pt. clay to 2pt. sand and if it doesn't clump tightly when rammed add 1/2pt. Portland cement. Don't automatically add the cement the theory more is better is often a good way to paint yourself in a corner without an exit. Even that small a proportion of cement can make the clay mix VERY sticky and it can very well make it almost unworkable. Lastly only add just enough water so it sticks together when hammered. If you make it like potters clay it's going to shrink check badly as it dries, visualize a dried mud puddle.

 

The important part of that recipe is the sand it does two major important things, it lets steam exit the liner without building pressure and secondly it makes the liner a little flexible. Preventing pressure building up puts paid to the spalling issue and even a little flexibility prevents thermal cycle checking. Once fired it's not going to care about a LITTLE water on it.

 

Using commercial refractory is a different animal. Most commercial refractories are concretes you prepare the form, mix the proper amount of water, apply it, let it set/cure properly and fire it. commercial refractories are usually designed not to spall, even when liberally wetted at heat. I don't recommend dumping buckets of water on a HOT liner but that's not what sprinkling coal is.

 

When wetting the coal around a fire you're not supposed to wet the forge pan, it's just supposed to slow combustion of the coal for a couple reasons: steam pyrolizes coal more efficiently than a dry flame front. Almost all the undesirable volatiles you're driving out of coal are at least partly water soluble so steam leaches it out faster than dry heat. It helps prevent the carbon from burning while it's pyrolizing (coking) so  more of the desirable CARBON (breeze/forge coke) remains. Then it helps the coal stick together and dome up for you.

 

As I recall those are the high points of why you wet a green coal fire but I'm a propane guy so I could have a lot wrong, miss important things or . . .  Heck if I knew I'd tell ya. <grin>

 

Anyway, the short stories are: Execution. Use the liner material correctly, use the fire correctly and use the water correctly and the liner should last for years.

 

Frosty The Lucky.