# Could use a little help please

#### cjordan

##### Fire Starter
Hey guys I'm sure these questions have already been answered a few times but I can't seem to find them.
Any help or advice is greatly appreciated.

I'm getting ready to build a side firebox smoker.

I used the formula for a reverse flow smoker to get my numbers, even though it won't be a reverse flow. Is that ok to do? Or is there another formula I should be using?

The pipe I will be using is 19 3/16 ID (19.1875) This is for the CC and FB

CC- 48" long= 13,879.34 CI

FB- min vol calls for 4,580.1833 CI

I've got a piece of pipe already cut that will equal 7,951.7071 CI. Would this be to much?
I can cut it down if I need to, just trying to save oxygen and gas if possible.

If I can use this over sized FB will that change the FB/CC opening, along with the air inlet openings, and also the exhaust stack vol?
Or can I use the numbers the formula calls for

#### JC in GB

##### Master of the Pit
SMF Premier Member
Wow, great questions. Mechanical engineering isn't my strong point. I will follow this thread to see what you have come up with.

#### cjordan

##### Fire Starter
Thanks Mr.Dave.
I used that tutorial to get my numbers earlier, in hopes that it would be the same numbers for a side firebox and a reverse flow.
When I get back to the house I will post everything I came up with to make sure I didn't miss anything.

I won't be able to post the numbers for my stack because all I have around the house is 6" and 8" pipe. If I ran the numbers correctly this would have me using a 6" pipe about 10" long. Seems pretty short to me but it is 20" pipe. When I go back to work Thursday I should be able to get some 4" pipe, just not for sure what the ID is till I get my hands on it.
Also having some issues understanding how to do the FB/CC opening calculations, once I get back to my numbers I want to study it a little bit more before requesting yalls help

#### daveomak

##### SMF Hall of Fame Pitmaster
OTBS Member
SMF Premier Member
You want your stack about 35-36" tall ABOVE the CC... It needs that to create a draft..... The stack can be oversized... Too small creates a problem....

#### cjordan

##### Fire Starter
Thanks Mr.Dave. I was under the impression it would need to be a certain inside diameter, and a certain length in order to draft/work correctly.

I figured to small of a ID would choke it back, but also thought to big of an ID would cause issues as well.
Now that I think about it... maybe it doesn't work this way, but I was thinking too big of an ID and too long would create no back pressure, which in turn would effect the way it would or wouldn't draft.

I'm sorry I didn't get a chance to post numbers last night, it was kind of late when we got in, and now we have a track meet today and a baseball game tonight. Not for sure if I'll be able to post them today or not, hopefully so.

I definitely want to build this thing right the first time.

#### JC in GB

##### Master of the Pit
SMF Premier Member
I wish you success! Would love to see your progress photos.

#### cjordan

##### Fire Starter
Alright guys here is what I've came up with so far. Can y'all please check over my numbers and help with the FB/CC opening.

The pipe I'll be using is 19.1875 ID

I'll be using 3/8 plate as the end caps, welded directly to the end so it won't change the length any

CC= 48"Long= 13,879.343 VCI
FB= 27.50" = 7951.707 VCI
FB min vol calls for 4580.1833 VCI so it'll be a bit oversized, at this length.

FB/CC opening calls for 55.517 sq"

Trying to use the circle calculator I know that using a seg height of 4.75" I get a seg area of 55.749, but I'm stumped after that. Any help would be greatly appreciated

FB air inlets calls for 13.879 CI
I'll have to play with numbers to figure out how many holes and what size they need to be. My plan will be to put half of them across from the FB/CC opening and the other half will be below the wood grate

The exhaust stack volume calls for 305.345 CI
If I use a piece of 6"ID pipe at 36" long this will give me 1,017.878 CI.
Since I'll be mounting the pipe even with the food grate it'll actually be a little longer than 36", it'll probably come out to somewhere around 46"-48" total length which will equal a good bit more than the suggested 305.345 CI.
Mr.Dave you said going bigger wouldn't hurt. Will going this much bigger cause any issue that you can see?

I'll be leaving tomorrow for two weeks so I won't get anything done on it anytime soon. Just trying to get my head wrapped around it while I have time.

#### daveomak

##### SMF Hall of Fame Pitmaster
OTBS Member
SMF Premier Member
Trying to use the circle calculator I know that using a seg height of 4.75" I get a seg area of 55.749, but I'm stumped after that. Any help would be greatly appreciated

The green area will be the opening... ED is the segment height.... Make a template and place it on the CC end plate.. Think about the fit up... maybe cut the top line up 3/8" to allow for material thickness... Think about how the RF plate will fit up... and do it..

FB air inlets calls for 13.879 CI
I'll have to play with numbers to figure out how many holes and what size they need to be. My plan will be to put half of them across from the FB/CC opening and the other half will be below the wood grate... I would go with 20% upper and 80% lower

The exhaust stack volume calls for 305.345 CI
If I use a piece of 6"ID pipe at 36" long this will give me 1,017.878 CI.
Since I'll be mounting the pipe even with the food grate it'll actually be a little longer than 36", it'll probably come out to somewhere around 46"-48" total length which will equal a good bit more than the suggested 305.345 CI.
Mr.Dave you said going bigger wouldn't hurt. Will going this much bigger cause any issue that you can see?
The stack volume is measured from the top of the CC to the top of the stack... The rest is just a connector... Your chunk is fine...