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Pit building ratio calculator
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Tom C
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Joined: 21 Jul 2007
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Location: N. California

PostPosted: Fri Aug 21 09 12:46 pm    Post subject: Reply with quote

paulhayes,

The 1/3 is a general rule of thumb and people have made smokers with fireboxes of all sizes. My smoker's firebox is closer to half the volume of the cooking section and works fine.

The problem you face with a smaller firebox is the chance that you may not be able to get a fire hot enough or big enough to heat the large cooking section you have. The pipe size you mention is still about 21% too small for 1/3 volume needed. I would be concerned about using it if it were my smoker. I'm not saying it absolutely won't work, just that I don't know.

Tom C
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paulhayes



Joined: 15 Aug 2009
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PostPosted: Sat Aug 22 09 12:12 am    Post subject: Reply with quote

Tom C.

Thanks for the insight I would hate to spend the time and money on a good cooker and it not be worth the trouble to use, I try and use the thinking of whatever you build it is only and good as the weakest part. I believe that I will use the 26" X 36" pipe that way I will have the proper amount of air space. Once again thanks for the info.

Paul
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Tom C
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PostPosted: Sat Aug 22 09 1:44 am    Post subject: Reply with quote

You're welcome Paul, good luck with your project.
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paulhayes



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PostPosted: Sat Aug 22 09 1:30 pm    Post subject: Reply with quote

Tom C wrote:
You're welcome Paul, good luck with your project.


Tom C.

Well after carefull thought and consideration I have decided to go with an offset cooker with a square firebox on one end with a deflector plate and a few tuning plates to even the heat out. This seems more logical to me seeing that I want to use a trailor that isn't real wide (60" or less) and this way I will not have to worry about the heat from the firbox destroying my tires because the box will be on the end away from the tires. And the box is square so that will be easier by buying a door that I seen on this great site and easietr to mount without warpage.

Thanks Paul
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Tom C
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PostPosted: Sun Aug 23 09 3:37 am    Post subject: Reply with quote

Hi Paul,

That should work out fine for you! I'm looking forward to seeing pictures of the build.

Tom
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paulhayes



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PostPosted: Sun Aug 23 09 12:38 pm    Post subject: Reply with quote

Tom C wrote:
Hi Paul,

That should work out fine for you! I'm looking forward to seeing pictures of the build.

Tom


I am going to try and get some picturtes through out the build andget them up here if I can figure out how to do it.
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paulhayes



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PostPosted: Tue Aug 25 09 12:43 pm    Post subject: Reply with quote

Tom C.

I hvae been wondering which would be better to build the racks out of 1" tubing or 1" angle and would you place the grate material on top or bottom. I feel that the tubing would be stronger and have less warpage, what do you think. also I have been thinking of placing bearings on each corner of the racks so that they will slide out with very little effort when loaded and of coourse they will have stops so that they can't just roll out and fall down (just a thought)

thanks Paul
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Tom C
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PostPosted: Wed Aug 26 09 2:26 am    Post subject: Reply with quote

Both are used by builders, I used 1/2 tubing because that's what I had on hand. Your smoker is larger but I don't know what size grates you plan on building. If you use tubing I would place the the grate material on top. If you use angle iron I would pace it on the bottom.

Here is what mine looked like


For my outside shelf I used angle iron and mounted it from below.



As for bearings, I think there is a good change they would jus get bound up. In the first picture you can see that I used angle iron for supports on my grates. Once you have cooked on them a few times, there is enough grease or oil to allow them to slide very easy. Even after a cleaning.
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paulhayes



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PostPosted: Wed Aug 26 09 9:38 am    Post subject: Reply with quote

Tom C.

That is a nice smoker! Did it cook well the first time when you used it or did you have to make mods. as you went? Doyou have a high temp flat gasket on the door or is it metal to metal seal? I have found some of my supplies such as hinges at a local hardware/parts store the same one that the BBQ stores sell for $15 a pair for about $3 each or $6 a pair and they have many sizes and also have zirk fittings on one end for greasing. They are actual trailer supplies.
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Tom C
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PostPosted: Wed Aug 26 09 1:35 pm    Post subject: Reply with quote

Thanks Paul for the comments on the smoker! I'm very proud of it and it has cooked well from the start. I have had to learn the finer points to making it hold the temps I want in any weather for long cooks but it's been half the fun.

I originally made six tuning plates for it but have found that I can get the temps even across the cooking section just fine with only three of them. The positioning of the plates and adjustments on the air intake give me a lot of control.

The seal you see around the door is a standard wood stove seal. When I was welding the left door hinge on the smoker I got the too hot and it popped up a little making the door leak a little. I did everything I could to get it back in shape. I was able to improve it a little but it still needed something to seal it up. Some one here on the Ring suggested the seal and it worked great!


It sounds like you are really getting your parts together and thinking out the project well, that's great! Just take your time and it will come together for you. It took me 5 months to make mine working evenings and weekends on it. There were time where I just took a break to think about how I wanted to do something and how I could do it best. I really think that extra time made a difference on how happy I was with the results.

Tom
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paulhayes



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PostPosted: Wed Aug 26 09 10:02 pm    Post subject: Reply with quote

Tom,

Thanks for the picture of the cement and close up of the seal. I will be taking my time on this smoker, trying to make evrything come together as well as possible, I am one that sometimes gets in a hurry and by doing so things don't seem to work out as well but on this project I want it to be as close to perfect as possble not to mention I want it to cook good without much hassel. I will be working on getting my trailer size down pat today and seeing what I need to order that way I can get the tank mounted on the trailer and it will be mobile to pull to the shops that are helping me with the plasma work and such.
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paulhayes



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PostPosted: Wed Aug 26 09 10:45 pm    Post subject: Reply with quote

Tom C wrote:
Both are used by builders, I used 1/2 tubing because that's what I had on hand. Your smoker is larger but I don't know what size grates you plan on building. If you use tubing I would place the the grate material on top. If you use angle iron I would pace it on the bottom.

Here is what mine looked like


For my outside shelf I used angle iron and mounted it from below.



As for bearings, I think there is a good change they would jus get bound up. In the first picture you can see that I used angle iron for supports on my grates. Once you have cooked on them a few times, there is enough grease or oil to allow them to slide very easy. Even after a cleaning.



Tom,

Looking closer at the 1st photo it looks as if you have a second wall inside of your cooker that you added on each end is that correct? If so what is the purpose of it?

Thanks
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Tom C
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PostPosted: Thu Aug 27 09 2:02 am    Post subject: Reply with quote

Paul,

No I think that's just the angle of the photo. I did put a deflector to push the heat down under teh tunning plates but that's it.

[img]

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ClydeDale
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Joined: 21 Aug 2009
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Location: Hopkinsville, KY

PostPosted: Fri Aug 28 09 10:24 am    Post subject: Reply with quote

Does the outlet in my fire box need to be in the very top or can it be a few inches lower due to the vacuum developed during the heating process? I would like to keep the fire box as high as possible on the rear of my new build to avoid any ground clearance issues.
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Tom C
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PostPosted: Fri Aug 28 09 1:16 pm    Post subject: Reply with quote

I'm not sure how to answer that one. You might be ok but then again, if you somehow restrict airflow it will be a problem. You might want to post some pictures so I and others can see what your thinking. You might also try taking a look at this posting. Alien BBQ did a great job on this. It explains how smokers work and might answer your questions

http://www.thesmokering.com/forum/viewtopic.php?t=20771
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paulhayes



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PostPosted: Sun Aug 30 09 1:24 pm    Post subject: Reply with quote

Tom C.

Well I have just finished getting everything set up to haul my 250 gallon smoker to the factory that is going to heat treat my tank at 775 degrees for 4 hours in a large furnance, so that when we cut into the tank and it will not have any memory or adverse springing to it, hopefully it will be in there by Thursday of this week. I have put everything on paper and will be building a smoker that can either be a reverse flow or just a standard offset with tuning plates once I cook on it with tuning plates I will be able to make it a reverse flow if I don't care for the way that it cooks or have trouble getting it to cook properly. (there will be exhaust stacks on both ends with the ability to completely shut either on off. The folks at this facility will be also sandblasting my cooker. I do have a question does it matter how far into the cooker you put your exhaust stack when placing it on top or should it just weld directly to the top with no pipe inside of the cooker?

Thanks Paul
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Tom C
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PostPosted: Sun Aug 30 09 3:12 pm    Post subject: Reply with quote

Hi Paul,
Sounds like you are on your way! As far as the stacks go, most of us try to bring the stack down as close as you can to teh cooking grate if you have room. Mine was off to the side and did not interfere with the cooking grate.

Post some pictures of your project when you can!
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silver smoker



Joined: 17 Aug 2009
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PostPosted: Fri Sep 04 09 11:27 pm    Post subject: Reply with quote

Tom C.- Just a heads up on the new separate calculators. You need to add a section on the cooking chamber dimensions for a square/rectangular calculation using l x w x h. I added my own in the spreadsheet, but some my not realize that it is editable.
I would like to thank you immensely for the spreadsheet, as my old thermodynamics books are a bit dusty.
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Tom C
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PostPosted: Sat Sep 05 09 7:31 am    Post subject: Reply with quote

silver smoker,

I think there is just enough room for that. Very Happy
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darylcincy
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Joined: 24 Nov 2008
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PostPosted: Wed Sep 09 09 9:29 am    Post subject: Reply with quote

Tom C I really like the way you redone the pit build calculator, it easier for me to figure out than the old one, Nice work!

One question how can I figure in the chimney calculation if I'm using a square box stack, like say a 4 inch square stack measures 5 inches across so I know its more volume than a 4 inch round tube but not as big as a 5 inch tube? How can I go about figuring a square chimney in ?

Thank you for your time.
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