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Building a smoker

 
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joemac



Joined: 14 Jul 2012
Posts: 6

PostPosted: Sat Jul 14, 2012 4:51 pm    Post subject: Building a smoker Reply with quote

Greetings all. I stumbled upon this website a few days ago and am thrilled to have a "home" for cooking info.

I'm in the process of designing an electric smoker. I have 95% of it designed and am more or less torn on a couple things.

My construction is looking to be a sheet metal box approximately 20x20x36 with 2 inches of mineral wool and a wood exterior. I plan on having 2 x 500 watt heating elements made from electric charcoal starters controller but an Omega Process controller that I got from ebay.

First question, I've been going back and forth on what material to use for the interior chamber. Steel is pretty cheap, but would need to be painted to protect it so i'm trying to avoid that, aluminum is a little more expensive but wouldn't need to be painted, and stainless would probably be the best option, but cost significantly more. Do you think I would have any regrets going with an aluminum interior vs. the stainless?

Second question. Do you think I would need external ventilation to get fresh air into the system? I'm not planning on having the system air tight so I'm sure there will be some leakage, but wasn't sure if I would need more than that.

In the past, I've just used my propane grill to smoke meats by placing an closed aluminum bread loaf pan full of wood chips over a single lit burner to create smoke and indirect heat. It has worked very well, but a bit of effort to maintain a proper temp.

Thanks for any input.

Joe

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Dilbert



Joined: 19 Oct 2007
Posts: 1008
Location: central PA

PostPosted: Sat Jul 14, 2012 5:26 pm    Post subject: Reply with quote

I have not built any - so keep that in mind . . .

most commercial & home builds do have inlet and outlet vents - note they also have some provision to make them larger / smaller / regulate air flow.

if the cabinet is too well insulated and too well sealed, it will hold the heat - meaning than little / lesser outside heat input is required (i.e. elements will not be "on, alot") - and those are the doohickies that heat the wood chips/pellets/etc to produce the smoke.

in operation there's balancing act of
- enough air exchange to produce the density of smoke you want
- not too much air exchange such that the heat source cannot maintain the set point temp

check out this link - similar set-up:
http://www.netcookingtalk.com/forums/showthread.php?p=264238&highlight=smoker#post264238
ChileFarmer and others I'm sure will be happy to share their experience / knowledge.

off-hand thoughts -
consider locating the electronics not-at-the-top-where-the-most-heat-is.....

and - incorporate flexibility in where the temp. sensor is located (longer cable/whatever) as apparently finding "the right spot" sometimes requires experimenting.
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DrBiggles



Joined: 12 May 2005
Posts: 355
Location: Richmond, CA

PostPosted: Sun Jul 15, 2012 6:03 pm    Post subject: Re: Building a smoker Reply with quote

Hi Joe,

Neat project! I've made a few of my own hot smokers, but returned to the commercial varieties due cost/time/efforts. I'd rather be eating than tuning, building the rig. I'm lazy.

Regarding your first question, you mention that the interior would "need" to be painted. I've been hot smoking for approximately 25 years or so, I think. I've never heard of this, or used a smoker that had a painted interior. If you want to, you can line it with any of those expensive materials you choose. I would suggest using the least expensive steel you can find, 1/8" thick would be more than adequate. Once the box is built, wash and dry thoroughly, then rub with cooking oil. Run the smoker at 250 degrees F or so for a few hours. Mission complete.

Second question, you're going to need to get the smoke out of the chamber. This means an intake and exhaust. Intake can be installed, for instance, on the lower left-hand side, down on the bottom. Exhaust could be on the upper most portion on the right side. What you want to be thoughtful about is that the intake will carry the lovely smoke over your meat and out the top. Over time you may find that there could very well be dead spots or places in the smoker where there is less smoke available to the product. You can either build baffles, or just plan on rotating the meat in the smoker every hour or so. This would be the easier of the two.

Keep your psyche at the ready, 1000 watts of 110 power may not be enough to maintain temperature the smoker's temp with a full or 2/3 load. While one of the smokers I put together was a tad larger, 1600 watts was only able to maintain a 200 degree F range at the very top. There was only enough umph to smoke 2 slabs of baby back pork ribs. My smoke generator was on the lower left side and the exhaust was in the center on the very top. It was very clear I was going to need 220 or at the very least a propane powered heat source.

Get it done and get cooking no matter how you decide to make it go. It's nearly dinner time!

xo, Biggles
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joemac



Joined: 14 Jul 2012
Posts: 6

PostPosted: Sun Jul 15, 2012 6:39 pm    Post subject: Reply with quote

When you made your smoker(s), what did you use for heating elements?

I guess I just figured it would need to be painted, if it were regular steel, to prevent rusting. The plan is to build the interior box to be removable for easier cleaning. I suppose if I built it from steel and didn't like the results I could always replace it.

I know there has got to be some ideal amount of air flow as too much may not allow the smoke enough time to effect the meat and not enough air flow...? What would be the downfall of not enough air flow?

I saw the Masterbuilt method of adding more chips without having to open the door by using a cylinder inserted in the sides and planned on creating something like that for mine. When not being used, I figured that could act as the air inlet and have been trying to decide how large to make my exhaust. I'd like to try and keep it as small as possible just to try and retain as much heat as possible.

I made an excel spread sheet including the thermal properties of the box (interior, insulation, and exterior thermal conductivity) and then figured how much power it would take to maintain a given interior temperature given a particular outside temp. On a very cold day in AZ (32F) to maintain an internal temp of 230F would only require 370 watts and would get to temp in 35 minutes. Once the food is put in, the power requirements obviously go up... do you guys have any sort of calculation for power requirements for a given food "load"?

I have thought about adding a third heating element. I suppose too much power and the heater for the smoke chips may not run enough. I suppose that could always be countered with more ventilation.

I've thought about putting one of the elements on the very top to possibly act like a broiler element, but not sure if that would be a good idea.

Thanks for the info.

Joe
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DrBiggles



Joined: 12 May 2005
Posts: 355
Location: Richmond, CA

PostPosted: Sun Jul 15, 2012 7:15 pm    Post subject: Reply with quote

Hey Joe,


joemac wrote:
When you made your smoker(s), what did you use for heating elements?

I guess I just figured it would need to be painted, if it were regular steel, to prevent rusting. The plan is to build the interior box to be removable for easier cleaning. I suppose if I built it from steel and didn't like the results I could always replace it.


Exactly. Start inexpensive and get your design and/or likes and dislikes taken care of.

joemac wrote:
I know there has got to be some ideal amount of air flow as too much may not allow the smoke enough time to effect the meat and not enough air flow...? What would be the downfall of not enough air flow?


Air flow is very important. If you can't get the smoke out, or not enough, and if your burning chips smoulder (brown smoke) the smoke will condense on the product and create a very bitter taste. Something that will cause you to smack your lips even 20 minutes after, remarking how "smoky" the flavor is. You may want to consider adding a smoke stack to the exhaust to create a draw in your smoker, maybe 12" high.

joemac wrote:
I saw the Masterbuilt method of adding more chips without having to open the door by using a cylinder inserted in the sides and planned on creating something like that for mine. When not being used, I figured that could act as the air inlet and have been trying to decide how large to make my exhaust. I'd like to try and keep it as small as possible just to try and retain as much heat as possible.


Here's the smoke generator I use in mine, http://www.smokedaddyinc.com/

It's darned easy to remove and install to another smoker when needed, pretty nice.

Intakes and exhaust holes are easy to deal with, can even find nice smoke stacks at your local hardware stores. I don't have any math available to calculate what would be appropriate for your use. If it were me I would put a 1.5" on the intake and 2" on the exhaust, baffle as needed.

This is VERY important. When in the process of cooking, regulate the flow of smoke by the INTAKE. You want the exhaust to be free flowing and not choke down. Smoke out good. It make take a few runs to see where your sweet spot in, chicken thighs are cheap and make great smoker fodder.

joemac wrote:
I made an excel spread sheet including the thermal properties of the box (interior, insulation, and exterior thermal conductivity) and then figured how much power it would take to maintain a given interior temperature given a particular outside temp. On a very cold day in AZ (32F) to maintain an internal temp of 230F would only require 370 watts and would get to temp in 35 minutes. Once the food is put in, the power requirements obviously go up... do you guys have any sort of calculation for power requirements for a given food "load"?


I personally don't, but my internal temp of the smoker once the meat was installed dropped like a rock. And this had nothing to do with opening the door to put the meat in.

joemac wrote:
I have thought about adding a third heating element. I suppose too much power and the heater for the smoke chips may not run enough. I suppose that could always be countered with more ventilation.

I've thought about putting one of the elements on the very top to possibly act like a broiler element, but not sure if that would be a good idea.


Start simple. Once you're rolling you can add fancy one stroke at a time and gauge how well that modification worked or not.

I used an electric dual burner hot plate on the bottom of my smoker. Here are my first adventures with one of my smokers:

http://www.meathenge.com/2008/09/heat_source_doe/

There is a link within that post that goes to another chapter in that story.

UPDATE: The link within the post has my old path from years ago in there, no good. Here's the correct url: http://www.meathenge.com/2008/08/operation_cold_1/

xo, Biggles
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joemac



Joined: 14 Jul 2012
Posts: 6

PostPosted: Wed Jul 18, 2012 1:37 pm    Post subject: Reply with quote

Thanks for all the great info and insight.

I was able to add 2 additional variables to my spreadsheet... I included a "food load" of X pounds and also just put in a way to simulate introducing fresh outside air and how much that will reduce the inside temp. On your smokers, do you have any sort of fan blowing fresh air in or just open ports for intake and exhaust using the heats own rising action to draw air in?

If I may, I have an idea why your hotplate only got up to 200F. My guess is that the device was shutting down because it was overheating. I suppose the only real way to know for sure would be to use an ammeter and see if it is continuously running the burner.

I really like the idea of the Smoke Daddy... I may try and build my own... I guess we'll see how phase 1 goes.

Joe
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joemac



Joined: 14 Jul 2012
Posts: 6

PostPosted: Tue Sep 04, 2012 9:59 pm    Post subject: Reply with quote

I have a question about smoking at higher temps. When I've smoked turkeys in the past, I would typically do them around 300-350 or so. Would this cause a problem with the steel and it's oil impregnation? I feel like it would all tend to burn off and lose it's effectiveness.

Thanks

Joe
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DrBiggles



Joined: 12 May 2005
Posts: 355
Location: Richmond, CA

PostPosted: Thu Sep 06, 2012 3:51 pm    Post subject: Reply with quote

joemac wrote:
I have a question about smoking at higher temps. When I've smoked turkeys in the past, I would typically do them around 300-350 or so. Would this cause a problem with the steel and it's oil impregnation? I feel like it would all tend to burn off and lose it's effectiveness.

Thanks

Joe


Hi Joe,

Do you mean the oil you rubbed on the steel inside your smoker? No, it won't hurt anything at those temperatures. And, not having a patina of oil on your steel inside your smoker isn't a deal breaker for cooking. Unless you're using an infrared smoker such as the Charbroil Smoker Roaster Grill or Oil-less Turkey Fryer. Those actually do require the very dark patina in the interior of the cooking surface. The darker and more even the patina, the more and more even the heat.

xo, Biggles
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joemac



Joined: 14 Jul 2012
Posts: 6

PostPosted: Thu Sep 06, 2012 4:01 pm    Post subject: Reply with quote

OK, good to know that it isn't required. Thanks again for all the help. I'm hoping to get more work done on it this weekend and will hopefully be able to post pictures.

Joe
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DrBiggles



Joined: 12 May 2005
Posts: 355
Location: Richmond, CA

PostPosted: Fri Sep 07, 2012 10:08 pm    Post subject: Reply with quote

joemac wrote:
OK, good to know that it isn't required. Thanks again for all the help. I'm hoping to get more work done on it this weekend and will hopefully be able to post pictures.

Joe


Pictures would be awesome. And, get on it man!

xo, Biggles
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joemac



Joined: 14 Jul 2012
Posts: 6

PostPosted: Mon Jan 28, 2013 7:31 pm    Post subject: Reply with quote

Well, it has been quite some time since my last post. I've been pretty busy but have been able to get a little bit of work done here and there, with a good portion done this weekend.

These are two picks from right before Thanksgiving. The first picture shows me doing some wiring on the control panel that you can see a betting picture of in the second picture. You can also see the top half of the smoker that doubles as an excellent work surface. The inside is 18 x 18 x 36 tall made of sheet steel. There is 2 inches of rigid mineral wool insulation around all sides with pecan stained 3/4" plywood as the exterior. The door has double panes of 1/8" tempered glass that are 24 x 15.




The two heating elements that I got are rated at 3100 watts each @ 240 volts, but since I'm running 120 volts, I only get about ~775 watts each. Which works out well, because each one draws about 6.5 amps so I can run both elements at once and use my smoker on any household outlet.

Not pictured is the top housing for the electronics that I just finished this weekend. I'll try and get more pictures a little later.

Joe
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