Credits:
I am not the original designer of this firebox, I am told that it is 
fairly standard. I first saw it in Nova Scotia and merely sketched it  on 
my pad with the intention of building one in the distant future.
More credit should go to members of this group who provided me with much 
needed dimensions and hints so, let's call it a community effort.

Comments
Now that it is built and I have had the occasion of doing a couple of 
quickie welds (if there is such a thing!) I find that it works quite well 
and the clinker breaker saves a lot of time in cleaning the fire though 
it also drops a lot of coal down the tuyere. Perhaps I am not using it at 
the right time? Any suggestions out there?
The steep sides keep the pot very clean and the molten slag tends to drip 
into the ash trap without even having to use the clinker breaker. The 
result is almost no clinkers at the bottom.
An additional benefit of the steep sides is that the cavity caused by 
spent fuel almost refills itself by gravity so I always have a bottom!

Welding heat is reached a lot faster with a slower blast and the fire 
stays quite clean so I am very happy!
For instances where a shallower fire might be desirable (this is 7" deep) 
you may want to consider making a removable false bottom or a basket with 
the 1/4" plate. This way your fire can be adjusted to your needs and, for 
smaller jobs,m you will not use up as much fuel.

Construction
As you can see from the enclosed Jpeg file the box is very simple. It 
consists of an inverted pyramid, 13" x14" x 7" deep made of 1/4" iron or 
very mild steel. If You have thicker stock it would be a bonus but not a 
necessity.

The tuyere should have been made with a 4" pipe but, since I could not 
find any I used 18 gauge cold rolled plate instead. Making a square cross 
section was simpler than making a round one so this is what I did!

The clinker breaker is made of 1/2" square stock and 1/2" round shaft 
then fitted into the two slots at the top of the tuyere. Then the whole 
contraption is welded to the bottom of the firepot.

The trapdoor at the bottom must be carefully fitted so as to ensure a 
fairly airtight joint so as not to loose any pressure. 

Installation

I have a 4' x 4' loose brick table with a wooden frame, I merely welded a 
4" lip around the top and dropped it into an opening in the brick 
surface. I don't suggest mortaring it in place as you may want to remove 
it for maintenance reasons.
The orientation of the air intake, clinker breaker shaft and the bottom 
gate handle depends on the placement of your forge, so is the height of 
the tuyere.

If  you have any questions feel free to write me. I haven't worked with 
it for very long burt the results so far are extremely satisfactory and 
way better than my old conventional firepot.

If you have problems with the file (I am a Mac user) I can send it to you 
in other formats including Photoshop.

Good luck
PS
I welcome any suggestions and comments from old timers who have used this 
contraption before

Bill


Bill Franchini
Argyle And BroadStreet