Need direction

[Grabber70Mach]

This is a smoker that I have been working on but realize I started building it without doing the needed research. I now realize that the Firebox is too small, the stack isn't the proper height to draw correctly. I have thought about trying to modify it into a RF or tuning plate setup. Also would replace the firebox with a correct size one, probably move the smoke stack and make it a bigger diameter. Here is what I am working with...

[Grabber70Mach]

I am using this calculator to try and figure things out. http://www.feldoncentral.com/bbqcalculator.html
It's a old 275G oil drum. The drum is 67"L x 28 3/8"T x 42 3/8"D. Bottom of cook chamber to ground is 20", top of it to ground is 46 1/4". The trailer frame rail to ground is 10". On the inside of the cooker to the bottom of the frame that holds the grate is 12 1/4" to the top of the grates is 14".
I would remove the existing FB and if my calculations are correct build a FB that is 21"H x 36.75"W x 28"L. The reason for these dimensions is I would install the FB between the two existing trailer frame rails. The Chimney would be schedule 40 pipe, 6" diameter it would be 38 1/4" and would be relocated to the FB side on the back if I do the RF, not sure where it should be located for a tuning plate setup. This one kinda puzzles me on the FB intake if I use a 8" round it says I need 1.29, would 1 be enough or should I go with a rectangle setup. FB to cook chamber opening would be 30 x 6. Thanks for any advise on correcting my mistakes.

[Frank_Cox]

Without running the numbers myself and just guessing, it sounds like you're on the right track. I would go a size smaller on the air intake and use 2 of them. otherwise sounds perty close.

[Gizmo]

Any way to get the firebox below the cook chamber? That pipe that comes out of the FB and goes down just looks counter-intuitive to me. Maybe with enough draft it would be fine but if the FB was lower it's heat would more naturally rise up into the cook chamber - that's just me...

[Gizmo]

Maybe I'm looking at a warming cabinet...? Picture 1 has me thinking I might be...

[Tom_Heath]

Lets see if I got it right.....just guessing here.

I am thinking that the firebox is on the back since its not a RF and the stack is at the opposite end. Then the box at the front with the piano hinge is a storage box.

If thats right, heres my take on things.

First off, I would check and see just how close the numbers are for the firebox you have.
If there close at all, I would stay with that firebox.
Turning it 90 degrees and dropping it down so that the bottom was about 8 inchs off the ground.
I would cut the rear cross member and brace it back to the second cross member. If the firebox is heavy wall then I would weld the frame right to it. If its cast then I would cut a section, drop it and make a support for the box to sit on. Like a cradle.

I would go with a full reverse flow to take full advantage of the radiant heat values.

Tuning plates could possibly work for this rig but I would want to go with a full size firebox. Keep in mind that most of the calcs I have seen are set up for Reverse Flow.



I am with Franks thinking on the specs that you are close but with out running the numbers myself its had to make a good guess on the stack end of things.

As said I would go full RF, meaning that the stack has to move to the firebox end.


On the air intake, I'm not sure which way I would go without seeing the available space. Either 2 smaller round vents or 1 thats around 10 inchs.

When you ran the numbers for the air intake, did you calculate the full circle? I'm thinking, Yes. Only because thats how most calcs do it.

When it says you need say 1 round vent thats 8 inchs, then you need to look at the square inchs and then do the math for the butterfly shape that will actually be the openings. Been there done that, is the only reason I know.

My 16"x42" rf with a 20" long firebox needed 1 butterfly vent that was almost 8 inchs. Since you won't get the full area for air flow.
You could maybe use rectangle sliding vents and make it work tho.

[Grabber70Mach]

Maybe I'm looking at a warming cabinet...? Picture 1 has me thinking I might be...

The SS box on the front is supposed to be a warming box, the old wood stove on the back is the FB.

[Grabber70Mach]

Lets see if I got it right.....just guessing here.

I am thinking that the firebox is on the back since its not a RF and the stack is at the opposite end. Then the box at the front with the piano hinge is a storage box.

Yes that is correct

If thats right, heres my take on things.

First off, I would check and see just how close the numbers are for the firebox you have. FB size recommended 21175.0 c/in
FB size at this time 10766.25 c/in
50.8% too small
If there close at all, I would stay with that firebox.
Turning it 90 degrees and dropping it down so that the bottom was about 8 inchs off the ground.
I would cut the rear cross member and brace it back to the second cross member. If the firebox is heavy wall then I would weld the frame right to it. If its cast then I would cut a section, drop it and make a support for the box to sit on. Like a cradle. It's thin metal with fire brick inside

I would go with a full reverse flow to take full advantage of the radiant heat values.

Tuning plates could possibly work for this rig but I would want to go with a full size firebox. Keep in mind that most of the calcs I have seen are set up for Reverse Flow.



I am with Franks thinking on the specs that you are close but with out running the numbers myself its had to make a good guess on the stack end of things.

As said I would go full RF, meaning that the stack has to move to the firebox end.


On the air intake, I'm not sure which way I would go without seeing the available space. Either 2 smaller round vents or 1 thats around 10 inchs.

When you ran the numbers for the air intake, did you calculate the full circle? I'm thinking, Yes. Only because thats how most calcs do it. Yes full circle

When it says you need say 1 round vent thats 8 inchs, then you need to look at the square inchs and then do the math for the butterfly shape that will actually be the openings. Been there done that, is the only reason I know. My thought was a full circle with a plate on the end of it that with a center screw could move in and out.

My 16"x42" rf with a 20" long firebox needed 1 butterfly vent that was almost 8 inchs. Since you won't get the full area for air flow.
You could maybe use rectangle sliding vents and make it work tho.

Thanks for the help

[Tom_Heath]

OK..

Looks like a new FB is in order.

If your going with a new firebox then you could actually go with a set of rectangle vents....I will try and find a pic of a build way back where the guy made his vents operate with a remote rod.

It was way cool having the vents on the sides and the adjuster out where it was handy.

You have an awesome looking cook surface. Lots of room.

[Grabber70Mach]

Thanks I appreciate it.

[Grabber70Mach]

Finally started on a new FB for the smoker.






It will end up being 36.5" x 30" x 20"

[TrailerBuilder]

A new firebox is a great idea. I would add 2 maybe 3 more cross members to your trailer, cut the end of the trailer off and drop the firebox down. I would brace the firebox to the trailer with gussetts of some kind and make sure its solid. I would also slide the whole cooker set up farther to the rear of the trailer. Your going to have some serious tongue weight issues with how its sitting now. Id get my firebox welded to the chamber and then slide the cooker/firebox set up back until you get a desireable tongue weight. Keep in mind that you will have your box on the front to adjust for too. Id get everything sit at a good balanced postion and then weld everything in place and add cross members as needed.

JM2CW

[Grabber70Mach]

Thanks appreciate the advise.

[Grabber70Mach]

Did some more calculating for the FB tonight, does it look like I'm on the right track?




Looking at having 5 air inlets on each side of the FB with a slider similar on the King Cooker project. The ten inlets will be a little over the calculations but I don't think it will
hurt anything.

Smoke stack will be from 6" SCH 40 pipe. Thought of using two, one on each end with a tuning plate setup. Just not sure how wide the first plate should be and the size of the rest of the plates to move around to get it dialed in correctly.

[Gizmo]

I'd love to help but this is the part I hire done....

[The Czar]

The only problem is its a guideline.....but should work but not entirely accurate....

[Grabber70Mach]

Is there anything I should do different than what's there? I just want to get it as close to correct as I can this time.
Thanks

[The Czar]

If that is your goal then you are on the right path...but some of us *cough cough* (RIck)....are very anal...(can I type that?)....and want very precise numbers.....with that calculator does not do.....but it is close....make sense?

[Grabber70Mach]

Yes it makes since, but are you saying there is a more precise calculator out there for peculiar (anal) people.

[Smokeone]

We call him Frank Cox! I'm Sure he will be along to help you out!

[The Czar]

That is right....He is the one to call....but he won't be back till Sunday....

[Gizmo]

Yeah you can type that DC - I've been called worse!

And grabber, I always look at the few bucks to get it calced dead-on as insurance against the big bucks to get her built.

After 15 weeks of nights, weekends, and dollars building Edgar, the first time I lit him it was 28 degrees outside and freezing rain. In about an hour he was holding 238 degrees.

A lot of the other addicts on this site will confirm - THAT is a great feeling!

And now I will get off my soapbox... sorry

[Grabber70Mach]

Yeah you can type that DC - I've been called worse!

And grabber, I always look at the few bucks to get it calced dead-on as insurance against the big bucks to get her built.

After 15 weeks of nights, weekends, and dollars building Edgar, the first time I lit him it was 28 degrees outside and freezing rain. In about an hour he was holding 238 degrees.

A lot of the other addicts on this site will confirm - THAT is a great feeling!

And now I will get off my soapbox... sorry

No problem get on the soapbox anytime if you see me going in the wrong direction. I've already made mistakes as you can see and would not like to repeat things again.

[Frank_Cox]

sounds like you will be fine grabber. The good ol pit calc works fine. like I say, it gets you in the ball park. Lookin great so far!

[Grabber70Mach]

Thank does the FB to cook chamber dimensions seem to be proportioned correctly.