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Hey guys been a while since I’ve been a regular here. A lot has happened since I left as well. But I need some help so here I am to ask you guys for some insight. As the title of the thread states I’m currently in the process of building my first offset smoker. And like everything else I do, I overdo it. So I have a 500 gallon tank that measures 37 1/8” in diameter and that puts the center of the tank at 18 9/16”. The Feldon calculator only called for a 17” diameter hole from the fire box to the cook chamber, I opted for a 21” opening. So I laid it out on the main tank as follows. 18 9/16” as my center on the tank. That line became the top of the firebox hole opening which I used a compass to lay out a 10.5” radius circle thus giving me my 21” opening. The firebox tank is a 120 gallon tank that measures 30” in diameter and 44” deep. The problem lies in the fact that the bells on both tanks have dissimilar shapes and radius’s. So my question is this, how do I properly lay this out without making it look like I scabbed it together. I’ve been welding and fabricating for 20 years. Just not very well versed in this type of fabrication. Pics below to illustrate what I’m talking about.
Last edited by Tuscany; 03-23-2022 at 06:03 PM.1973 Lincoln SA 200, Already replaced shunt coils, Idle board (SOLD)1984 Miller Dialarc 250HF, Miller water cooler, 250 AMP water cooled torch, you know the worx.
Reply:I guess my question is, is this really as simple as finding where I want on the firebox tank to put a 21” hole and use the compass to lay it out, cut it out and it will fit up with no major gaps etc? Or is there much more to this than I’m thinking about here?1973 Lincoln SA 200, Already replaced shunt coils, Idle board (SOLD)1984 Miller Dialarc 250HF, Miller water cooler, 250 AMP water cooled torch, you know the worx.
Reply:I have no idea but would love to learn the down and dirty simple trick if there is one. Other wise if Geometry is required Id like to learn that or steps and process for figuring out the openings as well.Lincoln, ESAB, Thermal Dynamics, Victor, Miller, Dewalt, Makita, Kalamzoo. Hand tools, power tools, welding and cutting tools.
Reply:I did a quick google search how to calculate the openings on dissimilar size propane tanks for attaching a firebox to the cook chamber
Reply:This thread may give a better understanding of maximizing the firebox size to the cook chamber so you use the correct size firebox and put out enough heat and smoke to keep the temps at the optimum heat zones for what you are cooking.https://www.smokingmeatforums.com/am...tutorial.9870/Lincoln, ESAB, Thermal Dynamics, Victor, Miller, Dewalt, Makita, Kalamzoo. Hand tools, power tools, welding and cutting tools.
Reply:Using a regular divider won't really work because of the curve on the piece your cutting . I would tack on a 1/2" or so rod, squared to the tank at the center of cut. Take a piece of 1" or so square tube and drill a 1)2" hole and then another hole at 10.5" ( if that's the radius of the smaller hole) sized to fit a scriber long enough to follow the curve. As you scribe out the smaller circle onto the larger, you will be moving the scriber in and out from the tank as it follows the curve of the larger tank. Hopefully my description makes sense. I'm sure there is a mathematical formula to do that but this method will allow you to be off center and still mark out an accurate circle .
Reply:If you haven't skimmed it, you might want to check out Aaron Franklin's book A meat smoking manifesto, IIRC, he has a section on cooker construction that may be of help in general.
Reply:
Originally Posted by M J D
Using a regular divider won't really work because of the curve on the piece your cutting . I would tack on a 1/2" or so rod, squared to the tank at the center of cut. Take a piece of 1" or so square tube and drill a 1)2" hole and then another hole at 10.5" ( if that's the radius of the smaller hole) sized to fit a scriber long enough to follow the curve. As you scribe out the smaller circle onto the larger, you will be moving the scriber in and out from the tank as it follows the curve of the larger tank. Hopefully my description makes sense. I'm sure there is a mathematical formula to do that but this method will allow you to be off center and still mark out an accurate circle .
Reply:
Originally Posted by Tuscany
I appreciate everyone’s help so far. My compass allows me to draw out a circle up to 32”. It’s what I used to lay out the first one on the big tank. In theory couldn’t I just center punch where I want the one leg of the compass to sit then scribe a mark for the 21” hole with the other leg? Wouldn’t that accomplish the same task as what you’re saying?
Reply:Could you use a projector to cast the circle onto the object? Maybe go for the horizontal diameter you want & the rest would fall into place?Millermatic 255Dynasty 280 DXReady Welder IHypertherm 30XP
Reply:Drill a bunch of holes in the circumference of your circle in a piece of plate, position it, put rods through the holes so they touch the tank, then mark the points of intersection & sketch your opening?Millermatic 255Dynasty 280 DXReady Welder IHypertherm 30XP
Reply:I would think it possible to scribe one or both tanks to get a fit up. Since you have tanks positioned in 2 pictures close to how they will join,will the small tank not fit into cutout in larger tank so that small tank can be scribed? Most propane tank builds I've seen use a flat plate to trasition between firebox and cook chamber.
Reply:You might look at Allen's channel and see if he tackled something similar before. https://www.youtube.com/channel/UCLV...OoNd7rg1CfnKlwMiller Multimatic 255
Reply:Unless the surfaces of both parts you want to join are spherical, it will not be possible to join them directly with circular holes without having a gap. In this case you could use a short piece of fabricated 21 inch diameter tube to join them, which would also make locating the cuts easy to scribe.
Reply:You could get both surfaces at one time by using angle or channel. Mark the point touched on the smoker and box as you butt it against the smoker. Compensate for thickness. You can make a pointer on the ends. The seam might be an issue?
Reply:I see a bumper sticker here... My smoker ate your smoker. Considering i have a 120 gallon tank that i was possibly going to use as a smoker....the size you are using for a fire box.
Reply:That's a BIG smoker! looks like it could smoke a whole carcass.The hole is probably not round nor planar due to the nature of the compass on a non spherical or flat surface.Down and dirty way I would do it (to keep already cut hole):Match shape/profile of already cut hole with wire (copper, steel, whatever). *don't forget to make orientation marks*Use the wire profile as a guide to cut and grind the book-matched hole on the other tank.Let the tanks kiss, and watch the sparks fly!Easier way to do it (cut larger, new hole):In the future if you want to make it a little easier, Use a known flat/round hoop to mark/cut out your holes (instead of a compass).Any holes should mate up perfectly and it will just be a matter of getting the location correct (use center of the holes to determine that, just like a compass).Last edited by SlowBlues; 03-24-2022 at 03:01 PM.
Reply:Mine just a baby at 60 Gal, but I put a flat end on my firebox, held it in place and then traced out the cut with soapstone..The hole between the firebox and the cook chamber is larger than desired but it's pretty easy to install a restrictor plate once the firebox is mounted..Firebox in position, sort of
Marking out the cut line
Inside, once the firebox is attached
Baffle/Tuning plates installed
End result. (two chimneys so I could try normal and reverse flow)
Last edited by frieed; 03-24-2022 at 03:52 PM.MillerMatic 252, HTP 221 w/cooler, Hypertherm PM45, Lincoln IdealArc 250 AC/DC, victor Oxy/Acet"I'd like to believe as many true things and as few false things as possible"
Reply:
Originally Posted by SlowBlues
That's a BIG smoker! looks like it could smoke a whole carcass.The hole is probably not round nor planar due to the nature of the compass on a non spherical or flat surface.Down and dirty way I would do it (to keep already cut hole):Match shape/profile of already cut hole with wire (copper, steel, whatever). *don't forget to make orientation marks*Use the wire profile as a guide to cut and grind the book-matched hole on the other tank.Let the tanks kiss, and watch the sparks fly!Easier way to do it (cut larger, new hole):In the future if you want to make it a little easier, Use a known flat/round hoop to mark/cut out your holes (instead of a compass).Any holes should mate up perfectly and it will just be a matter of getting the location correct (use center of the holes to determine that, just like a compass).
Reply:I put the firebox on the bottom of my smoker. But,I march to the beat of a different drummer
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Miller 211Hypertherm PM 451961 Lincoln Idealarc 250HTP 221 True Wisdom only comes from Pain.
Reply:
Originally Posted by John T
I put the firebox on the bottom of my smoker. But,I march to the beat of a different drummer….
Reply:
Originally Posted by Tuscany
Hard to do that on a 500 gallon trailer mounted rig. Especially with no real rigging/lifting equipment.
Reply:Ok for those wanting to know (I’m hard headed and impatient so I frequently learn the hard way). The idea I had, does not work. I repeat, learn from me. It’s not as simple as drawing two of the same sized circles and cutting them out. The firebox tank essentially looks like a saddle for a pipe fit up. So I guess I’m going to weld the tank back together and try again. Lol.1973 Lincoln SA 200, Already replaced shunt coils, Idle board (SOLD)1984 Miller Dialarc 250HF, Miller water cooler, 250 AMP water cooled torch, you know the worx.
Reply:
Originally Posted by Tuscany
Ok for those wanting to know (Im hard headed and impatient so I frequently learn the hard way). The idea I had, does not work. I repeat, learn from me. Its not as simple as drawing two of the same sized circles and cutting them out. The firebox tank essentially looks like a saddle for a pipe fit up. So I guess Im going to weld the tank back together and try again. Lol.
Reply:Paper, cardboard, posterboard paper etc is always a very usefull tool in mocking up and getting the perfect fit prior to doing any cutting.You could also use the trick previously mentioned with wood circle and drilled holes with rods. Long bbq wooden skewers would work in a pinch for cheap pins.Last edited by N2 Welding; 03-24-2022 at 06:14 PM.Lincoln, ESAB, Thermal Dynamics, Victor, Miller, Dewalt, Makita, Kalamzoo. Hand tools, power tools, welding and cutting tools.
Originally Posted by Tuscany
Ok for those wanting to know (I’m hard headed and impatient so I frequently learn the hard way). The idea I had, does not work. I repeat, learn from me. It’s not as simple as drawing two of the same sized circles and cutting them out. The firebox tank essentially looks like a saddle for a pipe fit up. So I guess I’m going to weld the tank back together and try again. Lol.
Reply:
Originally Posted by M J D
No kidding. I tried explaining that earlier. Think of it as hole sawing a piece out of a round tube. When you flatten out the slug it becomes oval shaped
Reply:If I were to cut the sides away where they are hitting on the cc tank would the top and bottoms mate up being that theyre still 21 in diameter on both holes? Or is this completely fuxxed?1973 Lincoln SA 200, Already replaced shunt coils, Idle board (SOLD)1984 Miller Dialarc 250HF, Miller water cooler, 250 AMP water cooled torch, you know the worx.
Reply:I wouldn't do a thing until someone with actual PIPE-FITTING experience chimes in. my $0.02Miller 211Hypertherm PM 451961 Lincoln Idealarc 250HTP 221 True Wisdom only comes from Pain.
Reply:
Originally Posted by John T
I wouldn't do a thing until someone with actual PIPE-FITTING experience chimes in. my $0.02
Reply:I have this gizmo for projecting holes on to curved surfaces. Never tried it on a hemispherical piece though. And it's not cheap. I suppose a guy could tack a platform on to hold the magnet if it wouldn't reach from the side wall of the tank.
Reply:
Originally Posted by Tuscany
If I were to cut the sides away where they are hitting on the cc tank would the top and bottoms mate up being that they’re still 21” in diameter on both holes? Or is this completely fuxxed?
Reply:Now that you have two 21 inch circular holes in the tanks that don’t fit together without gaps, just make a short piece of 21 inch circular pipe to join them. It has to be easier than welding them back up and then making a jig to make the proper cuts. It will look better and be more tolerant of fit up errors.
Reply:
Originally Posted by Bradley256
Now that you have two 21 inch circular holes in the tanks that dont fit together without gaps, just make a short piece of 21 inch circular pipe to join them. It has to be easier than welding them back up and then making a jig to make the proper cuts. It will look better and be more tolerant of fit up errors.
Reply:You absolutely can just grind where there is interference until the openings match. This isn't a pressure/critical weld, don't sweat it too much.Just mark where you need to grind and try to go slow (the going slow part is hard after putting the pieces together for the 50th time to mark interference).
Reply:Can you just hold the firebox tank up against the main tank hole, then trace around the edge of the hole (marking on the firebox tank) from the inside of the main tank? That would show you where to cut.... ??-Ruark"Become one with the puddle, grasshopper" - Welding InstructorLincoln 3200HDHobart Stickmate LX235TWECO Fabricator 211i
Reply:So I think I may have found a simpler solution to all of this. Here’s what I’m thinking. Roll the firebox 180° so that the hole that was cut is now on the bottom. Then spin it 180° And use that cutout and hole as the door for the firebox. I mean it is a 21” opening and with it on the bottom would make fire management and cleanup much easier. Just make some hinges and handle and figure out how to make a round door seal with 1/4” flatbar. But what better way of owning my f up than figuring out a neat way of incorporating it into the build. I would even leave the threaded bungs as permanent vents (although extremely undersized. Thoughts? If I could figure out how to photoshop what I was talking about I would. But here’s some reference pics.
1973 Lincoln SA 200, Already replaced shunt coils, Idle board (SOLD)1984 Miller Dialarc 250HF, Miller water cooler, 250 AMP water cooled torch, you know the worx.
Reply:Guess not.1973 Lincoln SA 200, Already replaced shunt coils, Idle board (SOLD)1984 Miller Dialarc 250HF, Miller water cooler, 250 AMP water cooled torch, you know the worx.
Reply:One thing is for sure those that don't know are learning the way not to do it LOL
Lincoln, ESAB, Thermal Dynamics, Victor, Miller, Dewalt, Makita, Kalamzoo. Hand tools, power tools, welding and cutting tools.
Reply:MJD's post (#6 in this thread) is a way to project a circle onto the non-planar portion of your cylinders. And the approach using the sharpened soapstone extended from the exterior of the firebox is also a great approach. There is also a drafting approach that you could use (had to learn it back in the 80s to show how to merge two non-flat parts) but I've lost too much grey matter to even begin trying to do it now...but circling back: Either the soapstone approach or the offset compass approach detailed by MJD would get you the closest fitment between your two cylinders.Dave66=================Millermatic 211 (Transformer Based)Primeweld TIG 225X
Reply:Looks like a propane tank?I am surprised I do not here more exsloption from propane tank conversions Dave
Originally Posted by Tuscany
Hey guys been a while since I’ve been a regular here. A lot has happened since I left as well. But I need some help so here I am to ask you guys for some insight. As the title of the thread states I’m currently in the process of building my first offset smoker. And like everything else I do, I overdo it. So I have a 500 gallon tank that measures 37 1/8” in diameter and that puts the center of the tank at 18 9/16”. The Feldon calculator only called for a 17” diameter hole from the fire box to the cook chamber, I opted for a 21” opening. So I laid it out on the main tank as follows. 18 9/16” as my center on the tank. That line became the top of the firebox hole opening which I used a compass to lay out a 10.5” radius circle thus giving me my 21” opening. The firebox tank is a 120 gallon tank that measures 30” in diameter and 44” deep. The problem lies in the fact that the bells on both tanks have dissimilar shapes and radius’s. So my question is this, how do I properly lay this out without making it look like I scabbed it together. I’ve been welding and fabricating for 20 years. Just not very well versed in this type of fabrication. Pics below to illustrate what I’m talking about. Attachment 1737766Attachment 1737767Attachment 1737768Attachment 1737769Attachment 1737765
Reply:Tuscany, you do realize that the Feldon calculator has a reason for a 17" opening between the firebox and chamber. The smoke stack has to be sized properly to get the correct air flow through the pit.If the air flow is off your smoke will be blue and give your meat a bad taste. The stack is just as important as the opening for air flow.
Reply:
Good as new.1973 Lincoln SA 200, Already replaced shunt coils, Idle board (SOLD)1984 Miller Dialarc 250HF, Miller water cooler, 250 AMP water cooled torch, you know the worx.
Reply:Can you place the small tank in position as close as possible & put a light in the big tank, then trace the shadow? Even if you have to cut a chunk off the small tank to get is as close to the correct position as possible, the circle of light should be close.
Reply:Eclipse method. Cool idea
Reply:Just make a 17" circle in both fire box and cooking chamber and then make a 17" circular tube to connect the two and call it a wrap!Lincoln, ESAB, Thermal Dynamics, Victor, Miller, Dewalt, Makita, Kalamzoo. Hand tools, power tools, welding and cutting tools.
Reply:
Originally Posted by N2 Welding
Just make a 17" circle in both fire box and cooking chamber and then make a 17" circular tube to connect the two and call it a wrap!
Reply:
Originally Posted by John T
You clearly don’t understand.
Reply:
Originally Posted by John T
You clearly don’t understand.
Reply:
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发表于 2022-5-19 11:02:44