Gravity feed build pron

I'm new around here (first post!), but I like what I see so I thought I would start by posting about my smoker I've been building. I should be finished by this weekend and hope to have my first smoke on Saturday after a break-in on Friday.

I've got a bunch of pics lined up to post which I'll post in the order they were taken (for the most part). I'll try to be moderately descriptive for those of you who are interested in the glory details but if you have more specific questions please feel free to ask. If you just want to see what the final product looks like you'll have to wait an extra day because I haven't taken them yet!


So without further ado, I present to you my first pic...of a metal box! Well, it is a metal box - but more specifically this will be the ash box. On top of the ash box will be the fire box. The 3 sided metal lip around the fire box opening is to support a lining of fire bricks (to keep them in place - more pics on that later). You can also see the ends of the supports for the fire grate. The hole in the side is for a 1.5" intake pipe which will be fed by a guru fan mounted underneath the cook chamber (protected from the elements). The box is made out of 1/4" steel except for the top which is 3/8" (which will be the bottom of the firebox).



FWIW, this was my first welding project (using a Lincoln 220v MIG with 75/25 gas)...so go easy on the weld critiques!

So here's the next piece of the puzzle - the sides for the fire box. This was made out of pre-cut 10x10 pieces of 1/2" steel. Because of the dimensions I needed and the size of the stock I couldn't do normal corner welds. So I oriented the pieces such that an end butted up against the flat of the other side. I then beveled both connecting edges and 2-pass welded them together from the outside along with an inside corner weld (I'm sure there's a better/more professional explanation for what this method is called).

The cutout is for the transfer tube which will feed the hot air and smoke into the cook chamber. I used my angle grinder with a cutoff wheel and a sawzall to cut it out.

Charcoal Chute

So the next piece of this puzzle is the charcoal chute. For simplicities sake I opted for straight (as opposed to tapered) walls made out of 1/4" steel.

The bottom of the chute drops right through the top of the firebox by about 3/4" or so and acts as a retainer for the fire brick in the fire box (pictures of that shortly).

Cutting that hole in a big plate of 1/2" steel was no fun. In hindsight it would have been easier to assemble 4 pieces of 1/2" flat stock together to make it. Live and learn...

Firebrick

So here's the "secret sauce" that make's this smoker different from almost all other gravity feed smokers out there - a firebrick lined fire box that will never burn through. I had read enough threads out there about fire boxes that burned through after a few years and I wanted to prevent that. Using stainless was out of the question because I don't have a TIG welder. So I went with firebrick which has been used at least once before in smoker's of this type.

I designed this fire box in such away that the firebrick can be replaced without dis-assembly by lifting up on the firebricks (through the bottom opening to the ash box) to release them from their retaining lip on the bottom. Some Lego building experience required though...lol.




Here's a shot through the transfer tube opening showing the fire brick sitting behind and on top of the retaining ring - leaving a smooth wall for charcoal to fall onto the grate below (not shown in this pic).




Here's a profile pic of the firebrick showing the cutout for the retaining lip and a back bevel so you can lift and slide them out easily (I verified this!!!).




And here's a shot of the grate that helps keep charcoal from getting into the transfer tube:

A couple hundred pounds of steel...

So if you weld all those parts together as well as the transfer tube ( 3 x 5 x 3/8 )you end up with a toe crushing hunk of steel something like this:

And people wonder why gravity feed smokers weight a lot! The frame and sheet metal themselves don't weigh much (relatively speaking). But a gravity feed smoker is essentially a miniature furnace and you have to build appropriately to contain that hot fire.

The Frame

I unfortunately didn't take any pictures while assembling the early stages of the frame, so here she is in all her glory - complete with drain pan, 1 inside side wall, and some wheels.

The drain pan is sloped right to left and back to front - its kind of hard to see in this pic unless you are looking for it. The lowest part of the pan drains into a 3/4" drain.

I don't have a metal brake nor did I want to pay someone to bend metal for me so I cut all the sides separately and welded them into place (from the outside).

This view is from the "back":



This shot is from the front:




And here's a shot from the side where the fire box goes. Note the top side support hasn't been installed yet (to make it easier to lift the fire box assembly into place).

Putting the pieces together

So here's a slightly out of order shot of the fire box assembly being trial fit into the frame (so I could measure for the transfer tube hole):



And a frontal shot showing the transfer tube extension into the cook chamber:

Details, Details, Details

If we fast forward in time a bit we end up with the following picture. The exhaust has been put on, the shelves and shelf supports are in, and the front skin is on. You can also see my "control center" box I added for the temp/fan controller. There is a pipe in there that leads to the cook chamber for temp probes and another pipe going out the bottom for power and the fan. I'll get more pics of these later to better explain. You can also see the fire grate which for some reason is sitting in the drip pan.




Here's a shot of the right side skins including 2 supports for a handle that are through welded onto the frame. All of the holes are plug welded. The hole to the left of the ash box is for a recessed catch for the door latch.

If I had to do it over again I would pay someone to bend a large piece of sheet metal for all 4 sides at once to minimize welds and probably just rivet the skin on.

Oh yeah, the charcoal and ash from the last pic was from a test firing to check for leaks before putting on the outside skin.

More skin in the game

Here's the last 2 sides being finished up (not all of the plug welds have been ground down).




And here' s a couple of the top before assembly showing the insulation:

More secret sauce...

Here is my as yet un-tuned (but tunable) heat diffuser and drip tray. I can independently adjust the angle of the diffuser for better heat distribution left-to-right. The drip tray also has a bend in it that you can't see from this angle to direct the grease down into a channel along the middle. The threaded rod and nuts are stainless steel. I went with this design because I didn't want any supports touching the bottom drip pan for ease of cleaning it.




Here's a shot straight on showing the spacing between the two as well as the transfer tube (the heat diffuser is actually about 1/4" above the transfer tube in this shot):

Exhaust damper

Here's the exhaust damper I fabbed up out of some scrap 1/4" steel. This is the view from the back.

Optimus Primer

If you take all that junk and slap a couple coats of epoxy primer on it then some body filler and sand it all down you end up with this:

All good things start with a design

So that's all I have until I take some more photos of it tonight or tomorrow.

Until then, I leave you with some shots of the SketchUp design I developed to help me out.