novasbc's 250 gallon propane tank build

I wrote a calculator based on DaveOmak's linked thread, and got the following for my 250 gallon tank:



Interestingly, my measurements ended up with it showing 288 gallons instead of 250.



With these numbers, I can at least plan the firebox size.  I still need to add the calculations for the firebox volume and dimensions, but my wife will kill me if I stay at the computer any longer today..

Just to clarify, I just used that trailer to pick up the tank :).

I ended up getting a 3500lb axle from Magnum trailers in Austin for a good price.

Havent had problems with the lights so far, knock on wood.

jarjarchef said:

I remeber reading somewhere on SMF of someone using a Harbor Freight trailer and having issues with the electrical system. Their lights would flicker and not work consistently. They ended up having to tack weld the joints to fix the issue.

I know the cart before the horse, but I just had a squirrel moment....... sorry..

Click to expand...

Okay, so I have my calculations:, the reverse flow plate / firebox opening height needs to be 11.89 in.  From this, I can figure out how tall to make the firebox, and cut the doors.

I've been trying to search, but haven't found the exact answers to my questions.  I plan on starting a guide for building RF smokers to help newbies in the future :).

Doors

• I like the look of the flanges, and have read Ribwizzards post multiple times.
  • I have an angle grinder with a 0.040 metal cut-off disc that I was thinking of using.  It seems this method tends to generate the least amount of heat and warping.
  • It seems folks generally weld the hinges on before removing the doors, how do you do this, and then later weld the flanges on?  Or do you just not have a flange on the top?  Seems like that would be the place you'd most likely lose smoke and heat.
• Firebox opening
  • How far in do you cut the opening?  Far enough to make it a 90 degree angle?
  • Assuming that is the case, what does the firebox side look like?  I'm having a hard time imagining that, I have seen pictures of the tank side, the finished product, but not what has been done to prepare the firebox for mating to the tank.

Thanks!

I plan on including a storage area for wood, and a lockbox for various barbecue tools and miscellaneous junk I decide to bring.

I'm thinking of taking two pieces of metal (perhaps channel, maybe square tubing), and notching them, bending them to come together at the hitch, then reinforcing the bend with a weld.  I think I've read posts on here about folks doing that.

Any recommendations on what metal would be good for this, and what sizes?

Thanks!

Got the initial work done on the frame this weekend.

I was a newbie to using a welder (I even have had my Lincoln 180 mig welder from Home Depot since March of this year), and a cutting torch.  Fortunately, I decided to do the work to get the tank mobile (on the frame and axle) at his place so he could help me and supervise (he's a great welder).  Also, he has a backhoe that makes it easier to lift the tank into place when we get to that point.

I bought the material for the frame and tongue Saturday morning.  I decided to build it out of 3" channel iron.  I did not realize that it came in different thicknesses, and so as to avoid underbuilding it, I bought the 6 pound per foot variety.  Fairly heavy stuff, in retrospect, I could probably have gone with less.  I may only use it for the outer frame, tongue, and supports for the tank, due to weight, and where I want supports for other things, jump to some angle iron.

I'm debating putting down some expanded metal on the frame, to make it easier to throw things on it, like wood, a cooler, etc.  I also may put a propane burner onboard to be able to cook a pot of chili, a toolbox for my barbecue supplies, and a spot to secure my ice chest.  Seems like they would be handy additions.

Instead of bending the channel iron, I ended up just making a box, as I didn't get the pieces cut to the right length by the metal supplier.  So, I think I'll bring the angles for the tongue to below the frame.  My car hauler does something similar.

I'll get a chance to work on it again around Christmas, where my goal is to get the tongue and hitch on, and get it on the axle.  It's possible I'll get to drop the tank on it as well.

I've been trying to learn how to use some 3d modeling tools to do something better than pencil and paper for the design, but I'm not very proficient at it, and haven't made much progress, oh well.

One major decision I still have to make is the position of the 3500lb axle with matching springs.  I'm thinking I'll have to put the hangers back as far as I can on the frame as possible.  I just don't have a good feel for how much the firebox + warming cabinet are going to weigh versus the things I put in front of the axle (including part of the tank itself).  Perhaps we will have to mount the hangers once, get everything fully together, and then move the axle forward when I have a better idea of the tongue weight.  I'd not like it to be overly tongue heavy.


We didn't notice initially, but one of the pieces we cut for the frame lengths was bowed inward.  Made it tough to get it fully square, we put the angle iron in the middle temporarily to help, and used the help of some tow straps to get it square to finish welding it up.

Originally Posted by LenDecaturAL  
 
Leave a little extra in case you want to add a baffle so you may want to cut it at 12.25 unless you already allowed for one in your measurements.

Click to expand...

I'll have to look into what I get by running a baffle.  It wasn't something I had considered, thanks for that, and the description of cutting the firebox opening!

All in all, even though I haven't really done that much, I feel like a lot has been accomplished, especially since I am infinitely more comfortable with the welder than before.

Once I get it rolling, I'll take it back to my house, so I can work on it after I get home each day, rather than having to make a trip out of town on the weekends.  I'll make the cuts for the doors and the firebox then.  I also have to figure out how to get the reverse flow plate installed, assuming I am doing a double door setup.  I guess I'll have to put the plate inside in sections, and then weld them together once inside the tank.

Thanks, I have a bit to process here, but one question pops out at me.

I was planning on using the legs and welding them to the frame of the trailer. They seem very stout and are in good shape.

Is there a reason you specifically mention cutting the legs off?

Ribwizzard said:

Slide your plate in before welding firebox on.

Here is how i recomend performing the build.
1-Fabricate firebox completely, its alot easier to get all detail work on firebox done while you can still flip it over by hand. Do not weld the two plate at the seam that will be the corner that will insert into the notch in the cooking chamber.

2- while tank is still sitting level on legs, notch the top of the tank for your firebox as in you are installing it upside down. It is much easier while tank still has feet and its easier to mount firebox to tank rather than tank to firebox, this also allows you to weld the bottom seam before flipping it over, and you only have to flip over once.

3- now than firebox is welded on, flip it over and now the firebox will hold tank level. Weld top seam of firebox and cut legs off of tank and cut doors. Now that tank is level, it will be easier to know where to mark doors.

4- once doors are cut, reach inside tank with torch or plasma and using the bottom of cc as a guide, cut opening into firebox. That is why you dont weld top cornet of firebox,

Click to expand...

To be specific, when I measured things out, with the height of the axle, tires, springs, and frame, it didnt seem like I'd want to raise it any higher than the existing legs. So, I figured just to use the existing ones.

I've given up the idea of putting this into some sort of CAD program for now.  Here is what I am tentatively planning to do:


Just recently on another thread here, I realized that I have a "wide/fat short CC", because of my tank design (previously I didn't connect the dots).  I may have to alter my calculator to change values based on that, but I haven't figured that out yet.

I don't have the tank open, so I can't really do anything but run numbers.

The idea of flipping it over to avoid having the plugs on the bottom sound interesting, but unless I'm missing something, it's primarily aesthetic.  If I decide to build another, maybe I'll do that, especially if the legs aren't in good shape.  It just seems a shame to mess with such perfectly good legs, and not use them to attach to the frame.  It's not even legs, but metal that goes all the way across, in a cut-off triangle fashion.

Since my numbers are probably off because the original calculator assumed a "standard", modern propane tank, I guess I'll need to be sure of the 11.89" height of the plate/firebox opening, cut the opening, and then physically measure the width the RF plate will need to be.  Otherwise, it seems I could be completely off.  I'm basing the width of the firebox on the width of the RF plate, which I calculated at 30.15", but of course, that assumes the numbers are right for my tank.

Other than that, I think I'm going to use 1/4" for the plate and firebox walls.

My original plan was to get the tank mounted to the trailer frame, cut the doors, start a fire in it to burn whatever crap might be left in it, cut the opening for the FB, get the RF plate installed, and then mount the firebox.  It doesn't require me having to flip the tank over.  But, if I have some real benefits from doing so, I could figure out a way to flip it over, but other than aesthetics, it doesn't seem to be that important...

Based on my calculations, it seemed that the reverse flow plate needed to be 30.15" wide by 76.66 (tank length of 85.5" minus 8.84", which * the RF plate width of 30.15" gives me 266.53 square inches).