New Offset Build_Design Phase

[Back9Q]

Hey all. Just introduced myself in welcome board. I am avid bbq'r and been competing for a few years with many awards. I have mainly used pellet cooker and cabinet smokers (pitmaker vault) for competition but want to get into the offset game. I just heavily modified an OKJ Longhorn RF for a whole hog cook but that was temporary until I built the new Rig. Any advice/design changes/etc would be greatly appreciated

Basis of design: 24" x 52-54" CC with Jambo/Outlaw FB/CC opening. Front load insulated FB with damper underneath like Outlaw. Will be mounted on golf cart wheels and the steering will be tie rod style not wagon wheel

CC - I have a piece of 24" sch 40 pipe at work but it has .68" side walls. I see three issues with this. 1. I only get roughly 22.5" of interior space. 2 it weighs 800 lbs for just pipe. 3 the door will be 150ish pounds and I am not the Rock and I dont like counter weights. Other option is 120 gallon propane tank with the ends cut off (I dont like the look of the propane style smokers. Would prefer flat ends). This would likely be 3/16" shell which should be sufficient for what I need

FB - Internal dimensions 20.5" all the way around made out of 3/8" steel. Air damper will likely be 2.5"x16" and underneath the FB. door will be insulated and recessed in with slam latches like the pitmaker vault. Will be a front loader as that is best for where it will sit on the patio. Outer shell will be 1/8" or 3/16" depending on price of steel

Exhaust - I found a 6" ID sch 40 pipe from work roughly 3' long I plan to use. The bottom will be flanged and bolted to the collector for removal if needed. For the collector which is better and why? the Jambo/outlaw style or the Franklin style that covers entire width.

Unknown's - Design of frame. I like the look of the outlaw with the tapered ends. I dont want it to look like a big box. Shelf height is another which I am leaning towards 36"-38". Rear wheel placement either under the end of CC with free hang FB or under center of rear FB (outlaw patio style)

Again any help would be greatly appreciated. Thanks

[Dirtytires]

I am not a fan of the front loader type firebox as I feel it dumps a lot more hot air when opened as compared to an end load design. Also, a single air vent on just one side could be problematic. A damper on both sides can promote better airflow, cleaner burns and are more versatile in case one side needs to be shut down in windy conditions.

Your outer skin is only to hold the insulation in. Something in the 18-22 gauge would be fine. I like to go just thick enough to prevent dings---going thicker will work Burt adds weight and expense.

[hogaboomer]

Don't use that 24 inch pipe, you don't want to be struggling to move this thing around, and it will take forever to heat up.

[Back9Q]

Yeah I have decided against that pipe. Nice that it is free but too much of a pain. I have to use front loader based on location of pit. There is not enough room to have side loading FB. Based on pit building calculators I should be able to get 120% the size indicated for air damper into FB from underneath. Cant do multiple sides do to front loading and I dont want one on the front door.

is 3/16" sufficient for tank thickness? I have been asking around at pipe shops but no one has drops in the length I am looking for in 1/4" thick.

Forgot to mention I picked up 3/8" steel pieces off FB marketplace that has some laser cutout in them for a project company was using. I will be filling in with 3/8" flat bar and piecing together to get the inner FB shell needed. Since it is inside I am wondering if I should take the time to grind everything smooth to make it look like one piece. its one of those no one will ever see it but I will know its there sort of thing.

[hogaboomer]

3/16 will be fine, IMO. There is a place in Houston called Texas Iron and Metal, they take in all kinds of surplus and unwanted steel. I got some really nice 24 inch 1/4 wall for I think it was $35 a foot, basically 35 cents a pound. You might look around for a place like that in Jacksonville. Pipe is a lot less hassle than tanks.

[Back9Q]

I have called a few places and they would be willing to sell but not big enough drops

Called trailer company and they are willing hook me up with tube and 1/8” plate. Would 1/8” or 3/16” side wall on 2” tube be fine for supporting a propane tank and insulated FB?


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[dacolson]

Side loader shouldn't be a problem. Heat drops in the FB recover quickly. I do think having vents on either side of the pit are a good option to avoid winds messing w/ your temps.

I built a 120 gallon propane tank pit that was 1/4" wall. I'm sure there is deviation between tanks but that was my experience. Do you have any way of confirming it's 3/16" thickness? I also have a pit built out of 3/8" pipe that is 130 gallons. My 23" doors are very heavy w/out counterweights. Can't imagine what 5/8" would weigh.

On the collector, there are literally thousands of both options out there. Doubt you'll be disappointed either way. Personally, I like the collector style which conceptually moves the hot spot back from the grate into the collector, extending the cook surface. I've had good luck with mine. Pick the look you like and I'm sure it will work out fine. I like the bolt on stack. Never done one myself but I like the look and think being able to remove it for storage may be nice if it's taller than your garage door.

1/8" or 3/16" wall square tubing is fine. You're not trailering right? Golf cart wheels around the yard will be just fine.

On the smoothing on the inside of your FB, that's 100% your call. No reason to unless it bothers you. I'm sure you'll have this forever. If it will bug you forever, maybe do it now. lol ...

[Back9Q]

Due to location of cooker the vent must come from underneath. Wind wont affect it at all as it will be under a covered patio in an area that gets very little if any breeze. Will look very similar to the Outlaw patio but bigger opening

The two tanks I am looking at both have tags on them indicating 3/16" wall thickness. Just waiting on the owner to reply to me with pricing so I can pick up. With collector the flange for 6" sch 40 pipe is 11" in diameter so the collector will take up atleast half of the CC diameter. I will probably make it 13" wide or there abouts. This will not be on a trailer just on back patio for 99% of time. Other time is wheeling it off to pressure wash patio or clean out smoker. I am pretty OCD about appearance of things so I will start out grinding filler pieces smooth to look like one piece. I am sure after 3 or 4 hours of grinding I will say F it and not worry about it.

Hoping to start on frame and FB this week. Still unsure of where to locate the 2nd wheel either under far edge of CC or under the FB. under CC allows me to get the smoker off the ground and mobile from the start and easy to level both anchoring points. Under FB delays this. I will probably go under CC with FB free hanging.

[dacolson]

I'd make the collector the full width of the cook chamber. The idea is to get smoke to be drawn into the stack across the whole grate and to move the constriction point of heat past the end of the grates before it heads up the stack. Better smoke coverage on your meat and more usable cooking area.

[Back9Q]

Thanks. Looks like I will make it whole width. Ill have to come up with something so it isnt round along edge. Appearance wise I dont think I could take that. May do multiple triangular panels similar to what is done on stealth aircraft to make it look a little "cooler"

One thing I found looking through threads is the propane tanks happen to go out of "round" when cutting off end bells. Better to cut door first then reach in and tack rods supporting walls and keeping round structure?

IS there a way to prevent springing by cutting doors in sections and applying straps for support before final cur is made? What is best thickness for the straps 1/8' or 3/16"?

[dacolson]

$1m question there. And there’s 1 million answers. You can always massage a tank or door back to round. It just takes some effort and time. All you need is a jack and chain.

People say they’ve tried this and that - myself included - and it worked. My bet at this point is to minimize heat input when you cut. I’ve had luck splitting the tank lengthwise to release the spring and welding in a flat bar to fill the gap but that’s no guarantee either. And it was a ton of work. Maybe more than just straightening the door if it sprung.

[Back9Q]

Thought about splitting tank but didnt want deal with it.

Ill be starting fab process this week and will post photos


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[hogaboomer]

Last one I did was a tank, I split it and it barely moved. I did one with pipe and it sprung out 3-1/2 inches.

[Back9Q]

Local steel shop was out of 3/8” flat bar so had to pick up 1/4” still good for firebox and only be about 20sq” worth. Rest will be 3/8”

4’x3’ sheets of 1/8” galvanized metal came up for sale today on marketplace for $25 each. Im tempted to get this for outer shell and remove coating by grinding and vinegar. Regular sheet of 1/8” is $300. I can get 4’x9’ for $75


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[Back9Q]

I have a whole new respect for fabricators. After welding and grinding for half a day I cant feel hands and arms and back wont straighten

Here is what I am working with. They are 14.5”x14.5” 3/8” thick. Filling in all holes and trying to grind smooth.



I am by no means a welder and it showed on first few with some issues after grinding



Finally got decent and smoothed out to where cant really notice if looking in FB. I completed 5 of 14 and will leave welds as is on remainder since will be side walls and roof of FB. Wont need to be smooth to slide basket around




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[dacolson]

That's a lot of work. And yes, grinding all day leaves my hands numb. I've been using wrist braces and have upgraded my grinder to a model with less vibration which helps a lot.

[Back9Q]

Found this tank about hour away from house. Its 120 gallon but no name plate. Others I have seen owners wont answer back. Based on age do you think atleast 3/16”?




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[hogaboomer]

That thing looks pretty rough.

[Back9Q]

Rough as in not worth it? I have few other options but this one is free

Are these prone to rust out if sitting for a while. Only concern is if I start tapping on it and hand goes thru


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[hogaboomer]

They rust on the bottom where the base is. That's where the majority of the pitting I've found has been. Hard to beat free, though. Might clean up OK when you get all that paint off. You could always make fire rings out of it as a last resort, if it's too far gone.

[dacolson]

I’d take it. It’ll be 3/16 or better. A good burn out after you open it up and I bet it cleans up nice. I love the 120 gallon size. Can go on a trailer or a backyard cart.


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[Back9Q]

This is going on some 12-14” blacked out golf cart wheels. Sent you PM regarding throat design. Can def use some help there


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[Devin&Bobbi]

The 120 my wife and I are currently working on is in close to the same shape. I'd use it, hard to beat free... Both 120 tanks we cut into are 3/16 I think that's the standard thickness for a 120 but I could be wrong.

[Back9Q]

Thats what I am thinking. Just wish guy who is selling one 20min from my house would answer messages. I mag him from marketplace, his FB profile, and even sent him $1 thru fb pay in hopes he would reply. Nothing


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[Devin&Bobbi]

Thats what I am thinking. Just wish guy who is selling one 20min from my house would answer messages. I mag him from marketplace, his FB profile, and even sent him $1 thru fb pay in hopes he would reply. Nothing


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Have you tried calling around to propane companies in your area? Don't be discouraged if one or two say no. My wife spent an entire day calling around and she found a guy a few hours away that sold us 4 tanks (2 250's and 2 120's) and delivered them to our house! He was going to scrap them and we offered him more than the scrap yard which wasn't much... Now he's a contact of ours and is actually holding a couple more tanks for us right now. We have found a couple other places to, we'll be picking up another 120 tank soon to build a maple syrup evaporator. We haven't had much luck outside of dealing with propane companies. Your luck may vary but that's the route I would go if you haven't already tried.