20x36 Reverse Flow - First Time Build

[Big T]

I still think you'll be ok and if you think it's getting too warm you could add a heat shield.

[10pinto]

Is there a reason that you have a square stack, just got me thinking is a round stack better than square ?

[Kcd2016]

Is there a reason that you have a square stack, just got me thinking is a round stack better than square ?

I just drew it square, haven't built it yet. I assumed that I'll end up using a square stack simply because we have a bunch of square tubing laying around the yard here. I've asked the question before and was told that a round stack is more efficient, IE a 4x4 square tube is the equivalent of a 4" diameter tube even though the square tube has more volume. (Someone please correct me if I'm remembering this incorrectly)

If there are other reasons I should run a round stack someone please let me know!

[temurf]

Is there a reason that you have a square stack, just got me thinking is a round stack better than square ?

I just drew it square, haven't built it yet. I assumed that I'll end up using a square stack simply because we have a bunch of square tubing laying around the yard here. I've asked the question before and was told that a round stack is more efficient, IE a 4x4 square tube is the equivalent of a 4" diameter tube even though the square tube has more volume. (Someone please correct me if I'm remembering this incorrectly)

If there are other reasons I should run a round stack someone please let me know!

Kcd, I seem to be remembering being told something similar. I think it has to do with the way air flows in a circular motion. In a square stack, the air gets slowed down in the corners and creates turbulence so the volume of air exiting the top of the stack is roughly the same as that of a round stack.
A lot of people have square stacks that work just fine.

[JohnBFryJr]

If there is any truth to that I sure would like to know. I just got a piece of 6x6 square for my stack.

[Pete Mazz]

You guys remember correctly. I wrote another calc to get the equivalent size if using non-round stack but if it's square just use the same dimension as if it was round.

[Kcd2016]

Its got wheels!

[Big T]

It's a good feeling when you get it to where you can move it around.

[temurf]

Looking good.

[KarateDoc]

It's coming together nicely

[Squiggle]

[Kcd2016]

What do you guys think of a round bottom fire basket design? I'm calling on the experts to check my dimensions that this thing isn't too small. So far about 99% of the critics around the shop have said my FB looks to small.



Direct link to enlarged image: http://i.imgur.com/H6C4UzO.png


Direct link to enlarged image: http://i.imgur.com/Ijkyhcc.png

[Rodcrafter]

Your FB should be about 1/3 of your CC that is a good rule of thumb. As for the basket I like it fine it will keep the stuff burning together nicely.

If there's going to be air intakes next to the end plate use a hole saw and cut some 1-1/2" holes in it. I stole that idea from Fortycreek and it was a good idea.


Making memories!

[Big T]

I ran the numbers on your drawings through the SB pit calculator and it says that your FB is 105% recommended volume.

[Kcd2016]

Thanks for the reassurance.

Rod, in regard to the holes in the end plate, my intakes are on either side of the fb, you can see where I've placed them in the first pic in my previous post. Are you referring to having intakes in the door?

I wanted to go with this style of fb for the benefit of having that plate to shield the fb door to help prevent warping. How much space should I have between the baskets end plate and the fb door? Should I plan a space between the rear plates too? I'm trying to maximize space here since we're only 16.25" deep to begin with.

[temurf]

I like it.

[Squiggle]

I'd look at putting something above the slide rails to lock the basket in & prevent it tipping when you slide it out.

[reelfishy]

I like the fire basket.

[Kcd2016]

Thanks fellas. I also drew up some simple hinges for the cc



This has got me thinking about what to do about my gasket situation. I understand that a hinge on the cc door is necessary, but what's everyone's experience with gaskets vs no gasket on just the fb door? (Speaking without experience) It just seems to me that if the fb door fits reasonable well that any air leaks through the door can just be compensated for by closing the intake a little more. Is this not the case?

Also, I've read that folks like to glue a rope gasket to the fb with RTV silicone that is rated to ~650F, isn't that fire box getting hotter than that - much hotter? If it does, but the glue is still gluing is anyone worried about fumes starting to come off anyway and getting sucked through the cc?

If I use a romex style gasket or even the red RTV stuff on the cc do I install the hinge before or after the seal?

Finally, I come from using ceramic cookers that do use the romex felt style gaskets and they typically put one on the lid and the base, does anyone recommend doubling them up on our smoker builds too?

[Big T]

I've never used a gasket on the FB door and I haven't had any issues. I make sure the door flanges are flat against the FB and let it ride. If I was building an insulated FB I would probably install a gasket. I don't think you need to double the gaskets if you have a tight seal with one gasket.

[Squiggle]

& if you do install a gasket, install the hinges first but use a shim to space the door, usually about half the gasket thickness to allow the gasket to compress.

[Kcd2016]

Will do!

I'm taking votes on hinge profile shape. It goes from mouse ears to toucans ... or maybe telephones. I'm leaning toward the second from the left. I'm also open to any other suggestions or ideas

[Kcd2016]

(double post)

[Kcd2016]

I'm going with hinge #2. I've drawn it up in CAD and attached a PDF so that I could share it if anyone else wants to use it in the future. It's suitable for a 20" OD cook chamber with 2" or less wide flange on the door and 3/16" gasket material. I hope...

The idea is that you can print this drawing out at 1:1 scale (on legal size paper) and tape it to your plate steel, center punch your pivot points, and cut the whole hinge out with a circle jig.

IF someone actually does decide they'd like to use this note that there are 2 pivot points at the bottom of the page, the lower left one is at the center of the cook chamber to pivot for the red half of the hinge, and the one just a hair above is the pivot point for the blue half of the hinge. This is to compensate for the door offset by the gasket material.

If y'all are interested let me know, I can try and take detailed pictures of the process that I have planned in my head and report back.

[Gizmo]

This looks like some nice work. I would move the stack as high as it will go to help insure more even exchange of "smoke out - fresh air in" for the entire system.

The stack shape is never the issue as far as the cooker is concerned - only cubic volume as determined by the overall system size. Heck, one fella back a few years ago had some hexagonal pipe and built the neatest looking stack you ever saw.

I never heard any more about that cooker after he posted the pics - he probably couldn't find any six-sided smoke to put through it - but that's a story for another day.