First Time Build 100# Propane Cylinder (Help Please)

[Fishgod]

Hello All,
Some day I would like to build a dream smoker but my skill is at about 1 out of 10. So instead of heading down to the local steel supplier and buying expensive pipe to practice on, I thought I would build a smoker out of an old 100# cylinder I found on craigslist for dirt cheap. I have borrowed a welder from the neighbor across the street. I have an angle grinder and other various tools. I have little to no welding experience but hey that never stopped me before. I have some scrap metal to do some practicing on. I have been searching and reading various forums and I think have come up with a plan.
I will have a fabrication shop cut the steel to dimension for the firebox and baffle plate. I also plan on having them cut the door and ventilation out.
I have calculated the numbers using the calc here on and used the formula that is on smokingmeat. Wanting to make sure my numbers are correct and built correctly the first time. You all with experience please take a look and give me guidance.

The Cylinder is 47in in diameter by 40in long. I have not cut into the cylinder yet but I'm guessing on my ID numbers.

Smokingmeat Numbers:
14.59 x 14.59 x .7854 x 39.5 = 6603.87 / 231 = 28.59 Gallons

6603.87 x .004 = 26.42 x 1.25 = 33.03 FB/CC opening in square inches(Increased by 25% because of the small cooker size)

6603.87 x .004 = 26.42 x 1.25 = 33.03 = 32.60 Area under the RF plate in square inches(Increased by 25% because of the small cooker size)

6603.87 x .004 = 26.42 x 1.25 = 33.03 Area required at the end of the RF plate in square inches(Increased by 25% because of the small cooker size)

6603.87 x .33 = 2179.28 minimum volume of the Fire Box

6603.87 X 0.001 = 6.6 FB air inlets in square inches

6603.87 x .022 = 145.29 Exhaust Stack Volume in cubic inches


FB to CC Opening:

Radius
7.295
Segment Height ED
3.5
Chord AB
12.46

Fire Box (126%)
Height 16 inches
Width 12.375 inches
Length 14 inches

Exhaust Stack 3in Pipe 20.55 inches

Air Inlet
Lower: 1.25 x 4.25
Upper: 1.25 x 1.25

Baffle Plate
12.375 width

Smoker Builder Numbers:

Diameter Length Volume (in³)
Cook Chamber Size 14.59 in. 39.5 in. 6,603.86 in³

Length Width Height Actual Volume (in³) Recomended Volume (in³) % Recomended Size
Firebox Size 14 in. 12.375 in. 16 in. 2,772.00 in³ 2,201.29 in³ 125.93%

Chimney Diameter Rec. Chimney Volume Rec. Chimney Length
Chimney Size 3 in. 138.6 in³ 19.6178343949 in.

Length Width Intake Area (in²) Count
Air Intake 6 in. 1.5 in. 8.32 in² 0.92

Throat Area (in²)
Throat Size 22.176 in.

[ajfoxy]

I'm sure someone will cast a friendly eye over your calcs and let you know if they are sound.

[inkslinger]

I am about to undertake the same size build, with the same skillset and qualifications you have.

Ill be following your threads to see how you are coming along. My calculations were all similar to what you have here. I am, however, not working with accurate dims just yet. Im picking up my 100# tank this weekend.

My build will be a center feed reverse flow. 100# cook chamber and a 20# fire box. Both reclaimed propane tanks.

-Benjamin

[Squiggle]

[Fishgod]

Thanks all,
Benjamin, I don't have exact measurements yet either. Just external. I am going by a guesstimate of 3/16th wall thickness.
Currently I have the cylinder off gassing. I opened it up Saturday and there was a little bit of pressure coming out. Later this week, I'm going to pull the valve and put a half pound of TSP and a large dose of Dawn dish liquid in it then top it off with water. I will try and mix it up while I'm filling it. I will let it sit that way for a couple days. I will then mark out the door and do some cuts while it is sill filled with water. I just don't want things to go Boom.

[inkslinger]

Later this week, I'm going to pull the valve and put a half pound of TSP and a large dose of Dawn dish liquid in it then top it off with water. I will try and mix it up while I'm filling it. I will let it sit that way for a couple days. I will then mark out the door and do some cuts while it is sill filled with water. I just don't want things to go Boom.

I was going to do water and dawn. What is this "TSP" you speak of?

[Fishgod]

It is a general purpose cleaner that can be bought at one of the big box stores (Home Depot or Lowes) (Trisodium phosphate or TSP). It is a powder. I saw a video of "How to flush a propane cylinder" and it was highly recommended. I did a search and it came up at Lowe's and it runs $4.38 a box. I believe the video said 2lb per hundred gallons. Since mine is only about 29 gallons I figured a half box would be ample.

Here is the link to the Youtube video

https://www.youtube.com/watch?v=nJ6UodIYxwU

[pr0wlunwoof]

I used bleach on my 120 gallon. Filled it all the way up with water to make sure it was empty of gas. The chemical they use to make the propane stink is horrendous. I think I had every fly in the county on the vent hole before I put the bleach in.

Sent from my Venue 8 7840 using Tapatalk

[Rodcrafter]

I will look at the calculator when I get to my computer in a couple of days. Welcome to the crew


Making memories!

[Big T]

. These are the numbers that the SB pit calculator recommends.


Sent from my iPhone using Tapatalk

[Fishgod]

BigT,
I was reading at another place that because of the small size of the cooker there is a lot of friction. So the theory is that you increase the FB to CC opening, space under the baffle, and the opening at the end of the baffle by 25% helps the flow.
That's why I'm asking questions and trying to learn from all those that have come before me.

[Big T]

I'm not sure about that but I have seen guys build cookers of all sizes and I haven't heard of any issues. I haven't built one that small but I have used the pit calculator for all of my builds and they work great.


Sent from my iPhone using Tapatalk

[Fishgod]

BigT,
Thanks. I have been wondering if this cylinder would be better suited to a standard offset versus a reverse flow. However I did see a thread where a guy used a scuba tank and turned into a revers flow smoker. Not sure if I am way overthinking this.

[Big T]

I'm pretty sure that you're over thinking it. I've seen a few RF's built from those size tanks and they seemed to love them. Here's one viewtopic.php?f=11&t=3883&p=55286#p55286 and there's a few more through out the RF section.

[Pete Mazz]

You won't get much friction loss from a tank that size. I'd only consider it if the tank was very long and small in diameter. Take a look at the calcs in my sig for anything else you may need for the layout.

[Squiggle]

I'm building one out of a 24gal tank, although I made the CC a bit bigger by making square doors. I've followed the pit calcs numbers & I have no reservations that it will work well, they are tried & true numbers.

[Rodcrafter]

Yep


Making memories!

[Fishgod]

Thanks for the Pit calcs. I got some better measurements and came up with these.
Tank Measurement: OD 47 x 41 (14.59 x 40.5)
Tank Volume: 27.62 Gal

Firebox: 14 H x 12 W x 14 L

FB to CC throat: 11 W x 2.503 H

Baffle Plate Space: 2.7 inch

[Pete Mazz]

You need 7 sq.in. of FB intake. More is OK since you can close them off. Do you plan to run charcoal or wood?

[Fishgod]

Pete, I'm planning on doing wood. I have a UDS for charcoal cooking.
I am planning on doing upper and lower intakes, 80% below and 20% above across from the throat.


Sent from my iPhone using Tapatalk

[Big T]

I would keep your intakes as low as possible so that you don't draw cold air past the fire and into the CC. Jm2cw


Sent from my iPhone using Tapatalk

[Fishgod]

Thanks BigT. There again, read on another place that you wanted an 80/20 split. They say the lower controls temp and the upper is used to flow the smoke/heat through the system. I do see that it will be drawing cold air into CC.

Well the cylinder prep has started. Got the valve off, filled it with detergent. Cut off a section of hose so that I can put the hose in the bottom of the cylinder. Seems to me that it will help force out any contents inside. I ended up with a sprinkler/fountain

[Big T]

You are officially on your way to smoking now!


Sent from my iPhone using Tapatalk

[Rodcrafter]

Go for it


Making memories!

[Fishgod]

I am going to stop by a local fabrication shop and see what they would charge me to cut out the pieces for my firebox. Not sure I want to be cutting steel plate with my angle grinder.