2nd Build - Tank Offset Trailer Build

[dacolson]

After lots of consideration and some help from you all - thanks Big T - I’ve decided on building a standard offset with the 3 tanks and trailer I picked up. The plan is to shorten the 80 gallon tank to 44” by cutting one end off to use as the firebox. That leaves me with about a 60 gallon tank and a 20 gallon firebox, rough and tough.

The 2nd tank I have is a 30 gallon tank which will become a vertical smoker/warming chamber on top of the firebox. It will have baffles between the FB and the WC as well as a baffle between theFB and the CC. I haven’t decided I will also have a baffle between the CC and the WC, adding tuning plates to allow it to convert it into a reverse flow. TBD. A little mystery for me till I get that far.

The 3rd tank is 20 gallons and will become a charcoal grill sitting behind the smoker on the trailer.

Here are the tanks and trailer:

80 gallon tank


30 gallon tank


20 gallon tank


Trailer on the way home.

Tonight, I made the first cuts and mocked up the overlap on the CC/FB. Gonna have to research the calculators to get the right overlap.


First cut - about 18” off the end.


Mock up of the rough overlap


Saw someone else on this forum used castors under the tank to allow for easy positioning. Works awesome.

I’ve got some 1/4” plate to cap off the ends. Will work on that this weekend.

Once it’s done, I might have to get the whole thing sandblasted. ntjones just painted their smoker w clear coat high temp. Love that look.

I’ll try and post a drawing of the plans soon.

More to come.


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[Big T]

It sounds like you've got it all figured out... well sort of figured out Good luck!! I'm sure you'll end up with a nice rig when you get it finished.

[dacolson]

If I don’t like it, it’s alright. I have a weld eraser ...

[Dirtytires]

Nice....lol

[dacolson]

Question on the CC/FB throat calculation. The calculator for overlapping tanks shows an option for sizing with a dam between the CC and the FB but the calculator does not differentiate or show what adding a dam adds to the size of the overall throat. For example, based on my calculations, I need a throat that is 13" wide and 4.8" tall. If I add a dam - say 2" high at the bottom, do I just add 2" to the 4.8" height? New specs would be 13" wide by 6.8" tall including the 2" dam at the bottom? Here are the outputs of the calculators:

Pit Calculator output

Throat Calculator output for overlapping tanks

Also, I've read there is a maximum FB size somewhere. Mine is currently 125% of the minimum. Should I cut it back a couple inches to get closer to the calculator? I'd like the extra length for room to attach vertical warming chamber.

[Dirtytires]

I believe you are using the wrong throat calculator. The proper one is entitled ‘throat calculator for overlapping cylindrical tanks.’ If you enter the 20 inch dia for both the cook chamber and firebox diameter, the 42.73 cubic inch throat and the requested 2 inch dam the results are as follows: height=5.976inch, width=14.25 inch.

And yes, I would decrease your firebox size. If you want to keep the length, consider putting a false bottom in the firebox.

[dacolson]

I believe you are using the wrong throat calculator. The proper one is entitled ‘throat calculator for overlapping cylindrical tanks.’ If you enter the 20 inch dia for both the cook chamber and firebox diameter, the 42.73 cubic inch throat and the requested 2 inch dam the results are as follows: height=5.976inch, width=14.25 inch.

And yes, I would decrease your firebox size. If you want to keep the length, consider putting a false bottom in the firebox.

Thank you Dirtytires. I totally missed the dam height field. I had the right calculator, I'm just blind and left it blank. I get the same outputs now.

The false bottom is a good call also. Great idea. Might be a good way to integrate a removable ash pan. Good stuff sir.

[dacolson]

I can maths! Minor adjustment to the throat calc using ID measurement of 19.625” yielding a height of 6” and width of 14.125”

Better yet, both ends can come out of one sheet. It’s a good day.




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[dacolson]

A little more work before I shut it down tonight. I wanted to see how the end cap lined up w the CC as I suspected it sprung when I cut it. Sure enough, egg shaped. Went to work with the jack and chain and tacked around the edges till it all line up. Didn’t make for the smoothest welds with so many tacks but she held and everything is straight.











The last shot is just a mock up of the cap for the end of the firebox. Feeling good about the start.


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[Big T]

You're definitely off to a great start!! I know that you mentioned a grease dam in an earlier post but I can't tell from the picture if there's a lip left.

[dacolson]

Ya. I kind of forgot about it in my excitement of fitting both end caps onto my one piece of 1/4”. That will be an add on I’m afraid. Would have been cleaner to leave it part of the cut. I just have to remember to do it before I attach the firebox.

[Dirtytires]

No one will ever know once the two get joined......and we won’t tell!

[dacolson]

Haha. Thx DT. Another reminder to slow down, measure twice and cut 3 times. I think I read that somewhere.

[dacolson]

Got an early jump today and mounted the fire box to the CC. Came out decent. Thought I’d spray arc the joint on the top. Didn’t turn out that great on the up hill. Thought I could get away with a slight incline but no dice. Started grinding it out to lay a normal bead but I’m out of discs. Have to run to the HW store. Maybe I’ll change my mind between now and then.


Capped the FB and added the grease dam back in.


Shot of the spray arc. Started grinding it even but I may just grind it out and start over.


Side shot. I’ll use the plug on top of the FB as part of the baffle for the WC.


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[hogaboomer]

You should have run it downhill.

[dacolson]

Thanks hogaboomer. The tank is on a roller. If I grind it out, I’ll reposition the tank and give that a shot.

[ntjones]

I like that it says sears. That looks pretty cool.


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[dacolson]

I like that it says sears. That looks pretty cool.


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Me too. Trying to keep that and the specs label intact. I think Sears will burn off when I fire it up though.

[hogaboomer]

Thanks hogaboomer. The tank is on a roller. If I grind it out, I’ll reposition the tank and give that a shot.

Pretty sure you will like the outcome. What gas are you running for the spray?

[dacolson]

Cheating. 80/20. Should be 95/5. Spatters some but I can usually run ok.

[hogaboomer]

I've run pulse spray before on a job with 90/10, but I haven't done it with my new machine at the house. All's I have at the moment is 75/25. Been itching to spray some on my new build, but I may just have to do it all short arc.

I did this 3 inch(may have been 4) rolled out going downhill.

[dacolson]

Looks awesome. I’m a hack. No way would mine look anything like that.

[dacolson]

Cheating. 80/20. Should be 95/5. Spatters some but I can usually run ok.

Sorry - 75/25. Not 80/20.

[hogaboomer]

How hot did you run? I might have to give it a try.

[dacolson]

24 at 400. On 1/4”