Build has begun

I posted my intro in Cattle Call last week. Figured I'd fill it in with some info on the offset I am building. Pics will follow when I get some taken. Here are the specs:

Cook chamber: black steel, unpainted, untreated 55gal drum. Second drum cut into a panel to double wall. Panel door approximately 24x18. So far, I have all the cuts done.

Firebox: 18"x24"x18" custom fab. 1/8" plate. Top load with a sliding plate for a door (the pics will show this better than I can explain it). the sliding design will allow me to open it a little to add fuel if needed, and also slide the door out and an expanded grate in if I want to use the box as a grill. Intake will be controlled by a single 4" blast gate (woodworking dust collection item). charcoal basket made of expanded steel. with a cookie pan ash collector. So far, the box is bolted together. I need to make the frame for the door from angle.

Duct System and exhaust: two 3" carbon steel car exhaust pipes ducted from the top of the firebox into the bottom of the cook chamber side by side. Initially I intend to run these to about 4 inches from the far end of the cook chamber to facilitate reverse flow. Depending on heat distribution, I may slot or drill the duct to introduce smoke/heat in the middle of the cook chamber. Exhaust is a 3" 90deg ss elbow at the grate level. Blast gate after the bend attached to the stack to control exhaust. I need to do some homework to figure out the optimal height of the stack (any suggestions are welcome)

Misc: two NPT attached thermos at grate level (haven't picked these up yet. might raid the metrology shop at work) Cook grate will be segmented expanded steel. Might install a ball valve at the low point of the cook chamber for washout. Building the support/cart from angle that I had as scrap. Should be sturdy. High heat primer and high heat flat black paint (I've done a test patch on a drum surface, it takes really well to the smooth wall.)

Concerns I have so far: Door I cut out of the drum seems a little flimsy. I might bolster it with bar stock. I need to pick up some gasket for the door. I am unsure of the duct design. I hope it works, or I am going to have to pull the thing apart and rebuild. I am going to minimize the duct between the two chambers to the minimum needed for clearance. It should be no longer than the blast gate transitions, maybe 4". I might wrap it with auto exhaust/header wrap to minimize heat loss.

Does anything stick out to you guys as a bad (or good) idea? I certainly welcome any and all suggestions?

I promise to post pics soon.

Greg

Thanks Marty!

I will be hitting your site for handles when ready. One less thing I have to make, and yours look fantastic. Jealous of the shop. I sold off most of my woodworking gear when I started my holster company and kept only what crossed over to cut/grind plastic. I miss working with wood, and the endless supply of hardwood blocks for the fire.

landarc said:

I am not so sure about a top loader being the most efficient setup for feeding fuel, heat retention or draft control. I think feeding fuel from the end works really well, doesn't let all of the heat out and drafts straighter.

Click to expand...

landarc,

Thanks for the suggestions!

Draft was always designed as a low to high cross draft. Intake blast gate low on the firebox side, outlet ducts high on the smoke chamber side.

I am second guessing having only the top opening for loading though. You make a really good point on heat loss. The top sliding door will be sealed well with gasket, but I am liking the addition of a side door for in-cook loading more and more. Easy as cutting one in. the top will only be opened for the initial add, and to get the fire basket in and out.

I also considered segmenting the top door. 16" on the smoke chamber side and then a smaller 8" piece on the firebox side. That way, I could slide the small piece out a little to add and then slide it back. It would still be a high opening, but I could keep it behind the fire, to minimize somewhat the heat loss. My thinking is that that opening won't be much worse than a large enough side opening on the same side which will still have open air above the fire level where heat can escape. Thoughts?

That brings up another question: How high to make the firebasket? The firebox is 18" deck to top. If I go side load, I will need room to get over the side to add a split or chunks or coal, thoughts?

Greg

Now with pics

Ok, some pics of the smoker so far:

First the fire basket. I picked this up today, and already need to take it back. It was dimensioned to fit inside the lid of the firebox (see below). I modded the specs on the lid, and forgot to send them new dimensions for the fire basket. It will need to be one inch narrower. As it is, it is 16"x20". It will have to go to 15".



Now the firebox. It is 18"x24" and 18" deep. I picked up the lid today. It is designed so that the plates (1/4") slide into the angle which will be gasketed to seal the plate in when in place. The large plate is 16" and the small plate with the handle is 8". The small one will be fitted with a lip on the side that it meets the large to seal that joint when in place. I will slide the small out to add fuel. I should be able to keep the fire in a 16"x15" portion of the basket covered by the large piece for the short time the small plate is open.







More pics to follow as progress is made!

More Pictures - Drum is taking shape

A full day of welding and cutting and welding and the cook chamber is taking shape. Here are a few more pictures:

Here is a view showing the duct welded to to the outside of the drum:



It penetrates approximately four inches into the drum as shown here:



As you can see, the duct is continued for the length of the cooker on the sides only. I will cover the duct with plates that can be moved to create gaps anywhere along the duct to tune the smoke and heat. Here is a large plate in place. I won't have any that large, but it is all I had to show the design today:




Here is a neat view looking down the open end of the cooker at duct level towards the penetration:



Here is a view of the whole thing:



You can see the door opening, the angle welded in to hold the cooking grates (I have a half sheet of expanded carbon steel to play with), and the duct with one of the covers.

It is coming together pretty much how I want it to. The double walled drum is stout. I'd much rather have 1/4" rolled steel, but maybe the second one!

Greg

Thanks for the tip Eric! We are certainly not expert welders!