questions about reverse flow details

[wildbill]

Hello everybody – new to the forum but not to smokin’

I have a couple of questions about retrofitting an old New Braunfels Smoker that has a burned out fire box. I want to convert it to a reverse flow type and have been wandering around the forums looking for info. I have a couple of questions about this modification. One of the things that used to drive me nuts was the small firebox size – 17” x17” round - 3856 cu in. I would have to get up a couple of times in the night to re-load wood in it if I was cooking a large brisket or 2. I had long planned on making a bigger fire box and dampening down enough to let it go until morning. Using Aliens ratios and Dodis’s Excel chart I find that the original firebox – to - cook chamber was about twice what the recommended size of 6.25 in round. I would like to use a rectangular fire box and connect to the chamber the chamber with 6” pipe with a damper in between. Is there some factor that I’m unaware of that says the fire box and must be smaller to match the cook chamber if I stick to the smaller size for the connection? Also I haven’t come across any mention of the heating chamber size or the distance that should be between the cook surface and the baffle plate. Anybody have a definitive answer or know where to look?

Thanks and glad I joined – this looks like a great site!
WildBill

[Smokin Mike]

wildbill, check out the mods I made to my New Braunfels offset;

http://www.thesmokering.com/forum/viewtopic.php?t=67840

I hate to be the purveyor of negative news but I don't believe there will be anyway you can achieve an overnight burn. Under the best of circumstances you're probably looking at a refuel every 3 hours, regardless of firebox size... and firebox size is important. If you oversize and dampen it down then you wont have that nice bed of coals hot enough to produce thin blue smoke but more than likely a stale smoke. Remember this is a cooker not a wood stove.

If the overnight unattended thing is really important to you then you probably should check out a UDS or a Weber Smoky Mountain.

As far as placement of the reverse flow plate, since the cooking grates are halfway up I divided the distance between mid cylinder and the bottom, around 4 inches. It's about the best you can do to take advantage of what you have. I'm very pleased with the mods I made and have really increased the performance of the cooker.

Got any more questions, then ask away.
_________________
My current cookers: 80 gallon vertical tank
The Ultimate New Braunfels Makeover

[wildbill]

Thanks Mike for the info and the link to your mod. I had sorta given up on the larger FB for a couple of reasons and I know that two of the BBQ businesses in the town I live near (Johnson City,TX), when they cook overnight have some of the local teens tend to the fire.
My cooker is about 25 years old and the FB and the smoker body had burned out a few years ago so it got set aside. It deteriorated even more during that time. So I had a lot of repair to do to it if I wanted to make it serviceable again. With your helpful info I jumped on it and have the body back in business and have almost completed the rebuild of the new FB using a water pressure tank that was the same size as a base for it. I finished up the reverse flow pan and installed a drain tube. I'm about to add the ash pan and wood basket and install the new smoke stack. I have one other question about the stack - did you mount it directly to the chamber or did you extend it into the chamber and if so how much?
Thanks again for your great advice and I'll try to get some pictures out when I finish it.

wildbill

[Smokin Mike]

wildbill, Glad to hear you're making some progress at reviving your old cooker. I'm looking forward to seeing some pictures of your mods.

I made the new exhaust stack flush with the CC. I didn't want to take up anymore room inside the CC than necessary plus I'm not sure there's much to gain by extending it into the cooker considering that the unit is now a reverse flow and several design deficiencies that are common with that style smoker have been resolved. It has a much better draft than the original 3" exhaust.
_________________
My current cookers: 80 gallon vertical tank
The Ultimate New Braunfels Makeover