# What is the best calculator to use for a reverse flow build

Discussion in 'Reverse Flow' started by lovelife, Mar 16, 2016.

1. ### lovelifeSmoke Blower

I live in Europe and we have different kind of tank sizes. Most likely I will be able to find two 1600 liter tanks which is 422 gallon.

My father in law is going to build them but he doesn't speak English, so I will be doing most of the research.

I was wondering what the best calculator is online to use? Once we start the build I will start a new thread and keep everyone posted for who is interested in seeing the progress.

I appreciate all feedback!

3. ### lovelifeSmoke Blower

Thanks you so much Dave. Hopefully I will be able to follow and understand all the steps.

isaac likes this.
4. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

One step at a time.....   write down the answer and continue....   It's a bit unnerving but when you get done, you will have an understanding of what's going on.....

5. ### johnboybakerFire Starter

Thanks for the link Dave I saw it and it helped me also. Thanks for asking the question lovelife

6. ### lovelifeSmoke Blower

Hi guys,

I received my tank today (check my other thread) and started doing some calculations.

I all went well until I reached the smoke stack calculations....

Exhaust Calculation..

ESV in cubic inches_____________________________ ... = Stack Length in inches (36" +/-)
0.7854 X Stack Diameter X Stack Diameter

I do have the ESV number which is 16201.9 cubic inches. Just not quite sure what to do with the empty space on that line....

Sorry about that, hopefully someone can push me into the right direction.

7. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

Cook Chamber 16201 c.i.

Volume in cubic inches X 0.022 0.017 = Exhaust Stack Volume in cubic inches, above the CC.... (ESV)
(The increase in volume ~30% shows a dramatic improvement in equalized temperatures across the cooking surface... edit 6/19/15 )

Exhaust Calculation..

ESV in cubic inches_____________________________ ... = Stack Length in inches (36" +/-)
0.7854 X Stack Diameter X Stack Diameter

Adjust the diameter of the stack, until the proper length is achieved... be sure to measure the actual internal diameter of the pipe used..
this is for round stacks only..

Last edited: Apr 1, 2016
8. ### lovelifeSmoke Blower

Thanks for the reply Dave. I was missing the point that I had to divide the numbers.

Anyway, I came up with his:

356

------------------------------            = 36.18

(0.7854x3.54x3.54)= 9.84

Stack diameter:  3.54 inch  = 9cm

So if I make my exhaust stack 36 inches tall it recommends me to use a 3.54 inch diameter stack.

Does that sound correct? It seems off...? I must be doing something wrong

*edit: Just checked Feldons calculator. When I use a 7" pipe, it needs to be 35" long. I guess I made a mistake in my calculaton. Does 7 inch sounds more reasonable? That would be 1350 cubic inches volume instead of Dave recommendation of 16202 cubic inches...hmmm...

Last edited: Apr 4, 2016
9. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

I do have the ESV number which is 16201.9 cubic inches. Just not quite sure what to do with the empty space on that line....
That is the CC volume...

ESV is the CC volume times (X)

Cook Chamber 16201 c.i. Volume in cubic inches X 0.022 0.017 = Exhaust Stack Volume in cubic inches, above the CC.... (ESV)

10. ### lovelifeSmoke Blower

Yeah not sure why I said that. In the calculation I did use the 356 cubic inches number though...

11. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

Feldon's bases it's numbers on the size of the FB....  My calculations are based on the size of the CC....  The 2 calculations are totally different...

12. ### lovelifeSmoke Blower

I understand Dave. I am just trying to figure out the diameter of the exhaust stack I'll need and have some trouble with that.

13. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

Use a ~3" ID pipe 36" long and you will be happy....   3" exhaust pipe from a muffler shop or 3" black iron pipe from a plumbing shop...

14. ### lovelifeSmoke Blower

Thanks Dave.

I got confused and was convinced I did something wrong when I started to read other peoples threads on the internet and reading that they were using 6, 7 and 9 inch diameter pipes...

Does the thickness of the steel of the pipe matters at all? I guess not...right?

I really appreciate your time and help a lot!

15. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

The inside diameter is what's important.....

16. ### lovelifeSmoke Blower

My fire box need to have a minimum volume of 0.40m³.

My RF plate is going to be around 0.77m wide. A firebox of 0.80x0.75x0.75  (0.80 being the side that connects to the CC) would have a volume of 0.45m³. The dimensions of the fire box don't matter as long as you have the minimum volume right? So all in all would these dimensions be alright?

Yes....

18. ### lovelifeSmoke Blower

Thanks Dave!

Also, I have a question about the doors. Some cut them right on top at 12 o clock or 0C. Others cut them a little lower. You would think at 12 o clock you get the most space, but it will be harder to open. A weight on top of the doors will be needed, correct? 12 o clock has my preference, you will get the most space out of your smoker.

19. ### daveomakSmoking GuruOTBS MemberSMF Premier Member

You do not want meat tight to the top of the CC....  make sense ???    So, leaving 5" above the meat will not be a problem....  You do need air flow all around what ever you are cooking....

....click on pic to enlarge.....

20. ### lovelifeSmoke Blower

Thanks again. Always a big help Dave!