Cheap offset converted into a reverse flow...

PetesMeat · Post by **PetesMeat** » October 15th, 2013, 11:25 am

Hi Everyone,

I got a cheap offset smoker (new brunfels somethingorrather) and I have been modding it quite a bit. I installed some big cam latches to pull the doors shut, and I put a fibreglass seal around the doors so its sealed properly.

I also put a seal inside the main door on the end of the firebox, and a really solid cam locking latch to hold it shut.

I made a baffle and a reverse flow floor, and I have installed a new chimney on the firebox end of the cooking chamber to turn the smoker into reverse flow.

The question is, where do I go from here. I just lit a chimney of briqquets and put them in, and its struggling to get above 40-60C. I havnt got much charcoal in there so im not too surprised, but im looking at this and thinking how the hell can this ever work?! It just seems the smoke and heat has such a maze to go round, from the firebox into the chamber, then down the ramp the baffle creates, along the bottom then through the food and out the chimney. I have got a good draw and a strong flow of smoke so all is OK on that front.

What should I do, build a charcoal basket? I have found before that when I pile coals up (similar to how they are in a basket) after an hour or so they are so gummed up with ash, they dont burn that well anymore....

Any advice? Whats the golden rules to getting the smoker up to temp and keeping it there... I can metal work and weld so I can make pretty much anything, I just need some reassurance that this smoker will get up to temp and stay there!

Pete.

Rev.Mike · Post by **Rev.Mike** » October 15th, 2013, 11:47 am

run the dimensions through the pit calc, i think youll find that your firebox may be to small JM2C

Grabber70Mach · Post by **Grabber70Mach** » October 15th, 2013, 11:51 am

Have you ran your CC, firebox, baffle plate opening, FB to CC and smokestack length/diameter through the calculator to make sure your proportions are correct?

Gizmo · Post by **Gizmo** » October 15th, 2013, 12:06 pm

It acts like it can't breath too well either. Not saying it isn't drawing ok but breathing has more to do with heat transfer than just drafting enough oxygen to support the fire - throat and/or BP gap might be too small.

I agree - looks like the FB is too small for that CC.

Definitely run your dimensions through the pit calc. to see where it's at.
If you post the numbers here then we can all help.

Post by **Rodcrafter** » October 15th, 2013, 2:06 pm

I agree the calc will help all of us see where you are in the process.

PetesMeat · Post by **PetesMeat** » October 15th, 2013, 4:08 pm

Hi Everyone,

Done the calculator, looks like my firebox is actually bigger than it needs to be. It says my chimney should be 24inches long, currently its not. This is rather annoying as I welded the new chimney in the other week, and its gonna be an absolute pain in the arse to extend it, since it has that curved over top. Gonna have to cut and shut and weld a bit more in. Very annoying.

The air intake is triangular, and i didnt know if it wanted me to put in the fully open position? I put 4x3 inches in which feels like it would square out to about the same sized hole.

Thanks for your help,

Pete.

Miketheforester · Post by **Miketheforester** » October 15th, 2013, 5:29 pm

I fire basket or grate is a must to get oxygen all around your fire. If everything else checks out in the calculator it all comes down to fire management. Too wet of wood, too little in coming oxygen, poor fuel arrangement, or smoke flow is being trapped in the firebox and impeding the fire.

Gizmo · Post by **Gizmo** » October 15th, 2013, 5:54 pm

What size is your throat opening right now?

PetesMeat · Post by **PetesMeat** » October 15th, 2013, 6:01 pm

What's a throat opening? lol

PetesMeat · Post by **PetesMeat** » October 15th, 2013, 6:21 pm

I just googled 'Smoker Throat Opening' and now wish I hadn't. Eeeww, im glad Im not a cigarette smoker.

Do i gather correctly that the throat opening is the hole from the firebox into the cooking chamber?

Il have to measure tomorrow but from memory its quite large, takes up almost all the space in the intersect between the two barrels. It is made smaller though by the baffle which blocks the first two inches or so. Im wondering if I might change that, it cant help - as heat rises etc.

Pete.

Smokeone · Post by **Smokeone** » October 15th, 2013, 6:37 pm

You are correct, fire box to cook chamber opening.

Clover Ridge Smokers · Post by **Clover Ridge Smokers** » October 15th, 2013, 9:36 pm

Looks like you are getting some sound advise.

PetesMeat · Post by **PetesMeat** » October 16th, 2013, 5:01 am

Hi Everyone,

Im going to post some photos of the smoker then, and if anyone could tell me if theres any blindingly obvious mistakes ive missed... maybe ive done something wrong and ive not realised what yet....

The silver chimney is the reverse flow one. The original one is blocked up for now.

The baffle

The reverse flow floor

Just to note, I have not ever tried this smoker with a charcoal basket, so it could be that it works fine. Ive tried it with briquettes in the firebox and had problems getting up to temp unless using very large ammounts of charcoal.

The smoker is sealed, the firebox into the cooking chamber is airtight and the seals round the doors (both on the firebox and the cooking chamber) together with the cam latches seal the thing absolutely airtight. I have also laser cut and welded a seal onto the inside of the main door on the firebox as there was a huge gap all the way round. The only place air can get in is the damper hole by the fire, and the only place it can get out is the chimney.

Thanks for your advice, you have been great.

Pete.

Gizmo · Post by **Gizmo** » October 16th, 2013, 6:42 am

Where is the bottom of your CC door opening in relation to the top of your throat opening.
Picture 1 looks like the BP is tilted downward and picture 2 looks like the BP is flat. They should be both level and could be the same piece of metal. Or am I just seeing things?

Post by **Rodcrafter** » October 16th, 2013, 7:05 am

I would say Gizmo is seeing what he thinks he is. I also see that the BP is not at the top of the FB it is in down a few inches from the top. This will cause heat to be trapped in the FB. The BP does appear to be reducing the air duct as the BP is 2 pieces first one in an downward angle then the other laying on top of it seems to have reduced the duct by approximately 1/3. These are more of your problem than the stack length, but the fact you have your stack at rack level again is not helping the air to flow through.

jm2cw

PetesMeat · Post by **PetesMeat** » October 16th, 2013, 6:21 pm

Hi Everyone,

To clarify, I have drawn a diagram showing the current setup of the smoker. I have also done another diagram showing your suggested changes, hopefully I have interpreted them right.

My only concern with the mods on the second drawing are, with the layout of the smoker, this means the floor will be about in inch below the food grate, which seems very close. Will this allow the smoke to go through, or im thinking it could maybe radiate too much direct heat to the food, or something like that.

Let me know what you think,

http://www.hocusproducts.com/smokerchanges.pdf

Thanks for all your help.

Pete.

Post by **Big T** » October 16th, 2013, 8:01 pm

Your second drawing is the correct layout for a reverse flow smoker, the first one is choking the throat down from the fire box. Normally you would want a 2 inch minimum between the baffle plate and your bottom rack, If you have room you may want to move your rack up about an inch.

PetesMeat · Post by **PetesMeat** » October 17th, 2013, 5:26 am

The problem is the opening into the CC is about the same height as the grill, so id have to raise the grill by two inches which wont be easy and will loose me lots of cooking space.

I wonder if I could move the firebox down.... Hmmmm......

PetesMeat · Post by **PetesMeat** » October 17th, 2013, 5:35 am

If I were to move the firebox down, this would make the throat opening smaller... How small could it be before it was too small?

Gizmo · Post by **Gizmo** » October 17th, 2013, 5:39 am

Run it through the pit calc to see...

Post by **Rodcrafter** » October 17th, 2013, 6:23 am

I would say you are on the right track move the FB down. Looking at the drawings, which are very nice thanks, I see that the first one does show the FB top is higher than the BP and throat opening. I say bring the FB down until the top of it aligns with the BP and the BP being flat across the CC at the same height as the throat opening. This should give you a few inches between the grate and the BP. And yes too much radiant heat from the BP will cause some cooking issues like over heating rubs on ribs, and stuff like that.

jm2cw

The Czar · Post by **The Czar** » October 17th, 2013, 7:01 am

Dang it ....Gizmo beat me to it....

Sent from my iPhone using Tapatalk Pro

PetesMeat · Post by **PetesMeat** » October 17th, 2013, 8:58 am

Hmm, it says 28.18 square inches. Pretty sure we can do that.

Now the final question. Will my argon bottle run out before I finish this. lol.

Post by **Rodcrafter** » October 17th, 2013, 10:05 am

It's only money, even easier to spend when it is other people's.
Lol

PetesMeat · Post by **PetesMeat** » October 17th, 2013, 10:56 am

I've taken the firebox off and welded a three inch piece of steel in to block half the throat. Now I need to do the same on the cc then I can bolt the two together.

Still not run out of argon but I had to go and get more tungstens hahahah

SmokerBuilder.com