# Vertical boiler build



## Amber (Jul 29, 2011)

I've been doing a fair amount of research on what type of vertical boiler that I'd like to build. There are a lot of different configurations for vertical boilers! There are monotube boilers, multi flue tube boilers, water tube boilers of various kinds, dry firebox boilers, wet firebox boilers....lots of choices! 
I have a bit of analysis paralysis right now.
I'm leaning toward the wet firebox design because it's more efficient for solid fuel burning, and multiple firetube flues. I want a fairly deep firebox for burning solid fuel, but I also want to be able to install a gas burner if the solid fuel doesn't work out so well. I'm looking at a couple of prototype designs for what they called a submerged flue boiler. In that design, there's an extension of the boiler water jacket that goes higher than the top of the flue plate, and that's where the steam is collected from. Under normal use, the water level is kept above the top of the flue sheet. It's probably not necessary in a copper boiler where corrosion of the top of the flue tubes is not a problem, but it is an interesting design.
I am also thinking of putting 1 large flue tube in the middle of the boiler, surrounded by smaller flue tubes, that way I could run a "superheater" tube down the big flue and back up. I just have to figure out how to make the superheater tube. I'm guessing that I would need to silver braze a U fitting onto 2 tubes for that, I doubt that the copper tubing can be bent to a tight enough U shape to fit down the flue tube.
I have a 4 inch copper pipe for the boiler shell and a 3 inch pipe for the firebox, and for the upper steam area if I do a submerged flue boiler. I just need to figure out how deep to make the firebox as compared to the length of the flue area. I have about 13 inches total to work with so I was thinking about 4 inches for the firebox and about 8 inches for the flue tube area, give or take a bit . I have to make the flue sheets, which means I have to split a piece of pipe for the material to use, or I have to find sheet copper of sufficient thickness to work with. I also need to get various supplies for the boiler such as rivets and fittings.
At least I have an idea of where to start now.


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## HMeinhold (Jan 2, 2008)

Amber,
for my A-Climax build 
http://forums.mylargescale.com/18-live-steam/26243-skew-bevel-gears-ride-climax-build.html
I also need a vertical boiler about 6" diameter and 10 1/2" tall, similar to yours. I also want to switch between coal and gas. So far I have seen many different vertical boiler designs, all of them steaming pretty well. It seems that this type of boiler ls not very design sensitive. However you should be careful using different flue sizes. The cross section should be closely matched ("normal" tubes and larger tubes with superheater elements inserted), as the resistance of tubes changes with the power of 4(!) with the diameter. So an unobstructed tube with twice the diameter of a normal flue will have 16 times more gas flowing through. 
I have also seen varying tube diameters, down to 1/4" ID, which seem to work fine. I will probably go with 3/8" or 1/2" ID. 
I am not even sure if a wet firebox is necessary, as the wall thickness of our little boilers is comparatively large, which means heat conduction between the (dry) firebox and the water is pretty good. 
I will discuss my design with an experienced large scale live steamer. You can follow up on the results in the thread mentioned above.
You also asked about T-boilers. Bill Allen will describe one in his thread about the Byers locomotive:
http://forums.mylargescale.com/18-live-steam/41921-john-f-byers-build-log.html
Regards


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## Torby (Jan 2, 2008)

I'm picturing a vertical boiler bigboy.

Sorry. Thread back to you.


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## BigRedOne (Dec 13, 2012)

I think Bill built a T boiler for the "Hot Rod Ruby" thread.

I'm interested in seeing updates, build experience, tools used, your design and build process. I'm in the planning stage of a boiler for my Roundhouse steamer.

Matthew


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## Amber (Jul 29, 2011)

I figured that I would go with either 3/8ths or 1/2 inch flue tubes for the vertical boiler. I haven't found any hard copper tubing smaller than 1/2 inch locally, but 3/8ths soft copper tubing is easy to get.
I've found a fair amount of discussion about the wet firebox vs the dry firebox in the various things I've read lately on vertical boilers. What I got out of it was that a wet firebox is not necessary to have a decent steaming capability in a vertical boiler that's gas or alcohol fired, but it does add some efficiency to a boiler that burns solid fuel. With a boiler that is as small as a 4 inch vertical boiler with a 3 inch firebox, I'm not sure how good of an idea it is to burn solid fuel, I'm guessing it will have to be stoked fairly often, which means following it around to keep up with it's fuel needs. I'm guessing a solid fueled steamer needs fuel more often than water.
I'm sure the whole fueling issue is easier if you're riding the engine, but those are bigger than what I want to tackle.

Torby, I think you would need at least 2 vertical boilers for an articulated engine, but it would be an interesting looking beast...


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## xo18thfa (Jan 2, 2008)

I've seen the return bends on the superheater loops done two ways. One way is bend the copper tubes to about 45 degrees, cut thru the bend parallel to the tube and silver solder them together. It makes an arrow point that fits nicely in the flue. Another method is drill two holes, side-by-side in a small chunk of bronze. Drill an angled hole to connect. Silver solder the copper tubes in the block. Whittle off the excess material.

Check figure 3-8 on page 39 of Harris' book. Modify that into a superheater, would be an option.


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## xo18thfa (Jan 2, 2008)

Amber said:


> ..... wet firebox is not necessary to have a decent steaming capability in a vertical boiler that's gas or alcohol fired, but it does add some efficiency to a boiler that burns solid fuel. .....


I disagree with that. Vertical boilers have a very rapid flow of gas thru the flues. In fact the flow is too fast for efficiency. To prevent that, vertical boilers should have a turbulator in the chimney. A turbulator is a length of sheet metal strip twisted into a candy cane spiral and inserted into the chimney. The slower flow keeps the fuel's energy in the firebox longer. And since most of the steam in a boiler is produced from the firebox, you want to fuel burning in there longer. Slower flow caused by the turbulator also helps ensure all the fuel is combusted.

The turbulator is determined by trial and error. Too much and it chokes the fire. Too little burns more fuel.

Dryside fireboxes radiant a lot of energy out the side unless they are heavily insulated. 

Go with the wetside IMHO.


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## HMeinhold (Jan 2, 2008)

Bob,
first my apologies for not having mentioned your Nina T-boiler, especially as I have one right under my nose, built by Ron. 
Recently I have seen a coal fired vertical boiler with a dry firebox which worked surprisingly well. Due to the wall thickness (about 1/8") heat transfer between the firebox and the upper part of the boiler is pretty good. Remember how difficult it is to maintain some temperature difference while silver soldering. With a full sized boiler this would not work, as the ratio between wall thickness/heat transfer would leave the dry walls overheated.
Regards


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## Amber (Jul 29, 2011)

Good information about the turbulator, I'll have to try that when I get to that point.


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## xo18thfa (Jan 2, 2008)

Hi Henner. How's everything?

Turbulators work very well. Especially on gas fired boilers where there is built in draft from the velocity of the fuel gas.

Dryside firebox boiler work, there are plenty of them around. It's only a few more steps to do a vertical right, the way the real ones are.


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## Amber (Jul 29, 2011)

I seem to have a bit of a problem with building the wetside firebox. The piece of 3 inch pipe seems a bit thin to me, compared to the other pieces that I have. The 4 inch copper pipe is plenty thick enough, it's slightly over .100 thick. The 3 inch piece on the other hand is around .045 thick, as best I can measure it with the caliper. The 2 inch pipe that I have is around .059 thick. I have about 4 feet of the 2 inch pipe, I was going to use that to make the flue sheets with. If I split it lengthwise, I can get a sheet about 6-1/2" wide, perhaps a bit more, depending on the saw kerf. That's plenty wide enough for the material for the flue sheets including the flange.
Anyway, with the 3 inch diameter piece of pipe being .045 thick, I'm not sure if it is thick enough to handle 100 PSI in the boiler. I could be wrong about that, but I'm not sure. 
The difference between the .045 wall thickness of the 3 inch pipe and the .059 thickness of the 2 inch pipe is pretty obvious when you compare them side by side. I guess I'll have to go back and read the materials chapter of the E book again to see what I can find out.
The other thing I'm wondering about is if using solid fuel in a small boiler is more trouble than it's worth. I have to wonder how often I'm going to have to put fuel in it to keep up the steam pressure. You might have to tweak the gas valve when you're running it on butane or propane, but probably not as often as you might have to shovel in wood or coal.
I know that you have to keep up with the water level, but I'm guessing that's not as often as putting solid fuel in the firebox. If this was a ride on, or ride in engine, that would be different, you'd be with the engine constantly to keep up with it.


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## clifforddward (Jan 2, 2008)

Amber, you should look online and obtain a copy of the Australian Model Boiler code document that is available...plus reference your K.N. Harris book and others I've heard you mention. There is an accepted standard for thickness of copper for the various parts of a model boiler...you should abide the recommendations, even if we don't have regulatory demands here in the USA....those of us building boilers for our own use still build to the safe and accepted standards...not good enough to "guess" at the best thickness to use.


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## Amber (Jul 29, 2011)

I agree with you there, Cliff. I'd rather build a safe boiler than mess around with something that might be an accident waiting to happen.


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## xo18thfa (Jan 2, 2008)

The Australian Model Boiler Society Code (AMBSC) is in 3 parts. Part 1 is steel boilers, part 2 is (larger) copper boilers and part 3 is miniature (hobby) copper boilers. Part 3 is limited to boilers 77mm (3") diameter or less at 75 PSI or less. The AMBSC details construction materials, minimum thicknesses, construction methods, etc. It covers several types of boilers as well.

I don't have the part 2 for larger copper, so that's out of my league. So is steel.

AMBSC, part 3 is a great source. It's worth getting a copy. I don't think it's an online download anymore, you have to order a paper copy from them.

When it comes to safety, boilers require testing. It's generally accepted practice to test new boiler weldments to twice operating pressure. After all the plumbing and fittings go on they require annual testing to 1.5 operating pressure.


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## clifforddward (Jan 2, 2008)

Thanks for that reminder Bob...I had forgotten they changed to a purchase only model for the miniature boiler code....certainly worth obtaining for anybody considering manufacturing a live steam boiler. Here's a link to the index page for the part 3 document...looks like a link at the bottom for ordering a hard copy:
http://www.aals.asn.au/AMBSC/AMBSC_Code3.htm


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## Amber (Jul 29, 2011)

Well, from the calculations in the Harris book, it looks like I'll have to use copper that's at least .062 thickness for a 4 inch boiler at 90 PSI, and that' has an 8 times pressure safety factor built in. So I'll need basically 1/8th inch thick copper for the firebox on the vertical boiler. The 2 inch copper pipe that I have is about that thick, within a couple thousandths, so that will work, except that I would have to fabricate a firebox with it. I think that might be more of a pain than I want to do.


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## clifforddward (Jan 2, 2008)

Amber, if I'm not mistaken the Harris book has a very nice vertical boiler for solid fuel already worked out....let me check when I get home tonight and I'll be back in touch...As I recall it was a wet firebox boiler with multiple smaller flues in about the size you are discussing...all the thicknesses, dimensions and details are worked out...

Maybe you could provide some guidance...what are your priorities...use the materials you have on hand or make a boiler to a certain size even if it means purchase of new materials...if you could help us with key priorities it would be easier to provide assistance. I know copper is expensive so using what you have is of key interest, please give us a laundry list of what you have on hand and available...diameter, thickness, and how much...from there we can make suggestions.

Much is possible with what one has on hand....


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## clifforddward (Jan 2, 2008)

Amber:
I checked my K.N. Harris book....two vertical boilers laid out there in detail. Design #5 is a plain multitubular (Dry firebox for alcohol or gas burner), and design #9 which is multitubular coal fired design. Follow the dimensions approximately of either and you'll be certain to have a good firing boiler.

Two comments:
1) Design #5 would be MUCH easier to build.
2) Note both designs use many firetubes of smaller dimension (1/4" and 5/16").
This provides maximum heat exchange surface...to be recommended.

I would think your 4" diameter copper piece would be a good starting point...


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## Amber (Jul 29, 2011)

I think I might have to go with the dry firebox design, simply based on the materials on hand. The 4 inch tube is well over the necessary thickness necessary, and I can use the 2 inch tube for material to make the flue sheets as it's thick enough to use.
I'm going to have to make a former to use to make the flange on the flue sheets, that should be interesting.


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## xo18thfa (Jan 2, 2008)

What are you planning to run with the boiler? Reason I ask is 90 PSI is reasonably high. My 7.5" gauge 3 cylinder Shay, geared 2:1, propane fired, with a rather smallish boiler, can haul 10 adults at 70-80 PSI. If yours is for stationary or light service, 30-40 PSI is probably enough.


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## Phippsburg Eric (Jan 10, 2008)

Even the tube sheet should be reasonably thick...I would stick with the same thickness as the shell.


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## Amber (Jul 29, 2011)

Bob, the pop valve that I have from my first boiler build a couple of years is set at 60 or 65 PSI, I think, and that's what I'd be using on it. I just want to build it to be capable of 90 PSI with plenty of safety margin, should I decide to use it with cylinders that are capable of handling that pressure. It's my understanding that brass cylinders don't hold up well to higher pressures, and that's what I have right now. At some point, I would like to get larger cast iron or steel cylinders to use, but that will have to wait a while.
My goal is to build a vertical boiler 2 axle engine that will probably be a chain drive and run on 4-3/4s inch track. It would be for my 2 inch scale 2 foot gauge line, actually 28 inch gauge in that scale.


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## Amber (Jul 29, 2011)

Eric, I'll have to look on-line to see about getting a couple pieces of sheet brass in the proper thickness. I'm guessing that they need to be at least 5" X 5" square in order to be big enough to make the circle needed for the flue sheets. I have seen sheet copper on ebay that is 6" X 6" in a thickness close to what I would need. The 4 inch tubes are at right about .10" thick, quite robust.


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## Phippsburg Eric (Jan 10, 2008)

I would. Not use brass due to potential corrosion issues which can weekend the brass. I usually use a section of the pipe I am using for the shell as the end plates...just slit a section so you can unroll it. Anneal it first.


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## clifforddward (Jan 2, 2008)

Eric is right...very common to unroll some tube, flattening it out to make tubesheets or other flat parts. Copper tubing comes in standard thicknesses, "L" and "M" thickness is most useful for our needs. By selecting the right diameter and thickness, most any material needed for making boilers can be obtained. 

A few years back I found an old 20 foot long piece of 3" diameter "L" copper tube at a plumbing supply house....a full length left over from a commercial job...it was a bit dinged in spots, and the guys sold it to me at their wholesale price as it had been sitting around....I'm still working off of that piece.

Doing this with scrap copper tubing end cuts used to be very common...unfortunately the price of copper scrap means it is very difficult to obtain as scrap anymore. Still, much of the small length copper tubing available on eBay is end cuts, so that is an easy way to obtain copper sheet.


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## Amber (Jul 29, 2011)

I have to admit, it had not occurred to me to look for copper pipe on ebay. DOH!
I found just what I need to make the wet firebox for the boiler. There's a couple of sellers that sell 3 inch type L copper pipe by the inch. That has almost the same thickness as the 4 inch copper pipe that I have.
I looked up the specs for copper pipe on line, and it turns out that my 4 inch pipe is type M, nominal wall thickness .095. The type L 3 inch pipe has a nominal wall thickness of .090, close enough for government work. 
Now to order enough of that for the firebox, and get started on it.


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## Amber (Jul 29, 2011)

I ordered rivets for the boiler, now I just need to decide how to do the upper flue sheet. I'm wondering if flanging the flue sheet would thin the copper at the bend as you're pounding it out. I don't see how you could bend it without it getting thinner at the bend. Also, I'm not sure that I want to try to make the former necessary to make the flange. I was thinking about the possibility of making a collar that would go inside the top edge of the boiler, and the flue sheet could be held in place with the collar. That assembly would be silver brazed to make sure it stayed together and didn't leak.
I could probably use high content silver solder for that because of the mechanical strength provided by the riveted and soldered collar.


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## Phippsburg Eric (Jan 10, 2008)

The Australian steam guys did some pressure tests to the point of failure for boilers made with and without flanges. My understanding of the results was that either way gets the joint strong enough so that failure is somewhere else. Failure pressures were in the range of 800 1000 pounds. This assumes that you get good silver solder joints without holes or partially filled spots.

If you do an good job with the fit and silver soldering, flanging is not required. That being said, any thinning at the flange is not an issue if you do it right.


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## Amber (Jul 29, 2011)

Interesting, thanks Eric.


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## Bob in Mich (Mar 8, 2008)

*Amber,I see You have goten a lot of snow also.Down here on TV they say You got over 2 ft. of it.I see You are a Mich-a-gander in Live Steam.So You will have to go to Shay Days in Harbor Springs.That is as Closes as We come to the Upper. This is the closes Steamup to You that we have.Shay Days is in July.Let Us know if You can make it.*
*Happy Thankgiving*
*Bob*


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## Amber (Jul 29, 2011)

The Iron Mountain area didn't get too much snow yet. No more than about a foot here. Up by lake Superior, they got dumped on pretty bad. West of Negaunee, they got at least 40 inches.


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## Amber (Jul 29, 2011)

I'm thinking about using a 3 inch copper pipe cap for the firebox, if the sides of the cap are long enough. I'm pretty sure that the pipe caps for type L and type M pipe are thick enough to hold the pressure, but I don't know what the length of the cap sides are so I don't know if the firebox would be deep enough. I suppose I could build the boiler with a half wet and half dry firebox. Using a pipe cap would save me the trouble of having to fabricate a lower flue sheet for the 3 inch pipe that would form the inner firebox, and I could mount the flue pipes in the end of the pipe cap with no problems.
I'm going to see if I can find the specs for the pipe caps on line somewhere, to see about thickness and dimensions.


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## Amber (Jul 29, 2011)

Well, about the only information I could find on the pipe caps is that the 3 inch cap has a side wall that's 1.6 inches long, not as long as I had hoped for, but long enough to be of some value in picking up heat from the fire, especially if I use butane or propane. The burner could be placed close to that point, or possibly up inside the bottom of the coupling. The lower part of the firebox could just be for holding the burner mounting.


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## Phippsburg Eric (Jan 10, 2008)

A cap should work well enough thou as you see it may be too shallow. It is good not having any seams.


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## Amber (Jul 29, 2011)

I was thinking that a half wet-half dry firebox would probably still heat the water more efficiently than just a dry fire box would. Of course, I'd still have to make the bottom ring for the half fire box, but the pipe cap would simplify the construction.


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## Amber (Jul 29, 2011)

Now I have to decide on the flues. The question is, do I use more 3/8ths inch flues, or less 1/2 inch flues? And also, do I put a large flue in the middle so that I can have a superheater? And, of course, the size of the center flue depends on the size of the copper pipe used for the superheater. I'm sure it needs to be at least the diameter of the steam delivery pipe. I'm not sure if a 1/4 inch steam pipe is big enough, or perhaps bigger than necessary for the boiler's steaming ability.


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## BigRedOne (Dec 13, 2012)

I think you need stainless steel for the superheater.

Did you calculate the surface area of both 3/8" and 1/2" flues?

In the boiler I'm designing for my Fowler, I calculated about 69,000 square millimeters for twelve 3/8" tubes, 51,000 for seven 1/2" tubes, and 52,000 for five 3/4".

I'm thinking smaller is better, though I don't know all the factors.


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## Amber (Jul 29, 2011)

From what I understand, going too small with the flue pipes causes problems with the draft. It's probably different for a horizontal boiler and a vertical boiler. I think it would be easier to get heat to rise through small tubes when they're vertical.


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## BigRedOne (Dec 13, 2012)

Do you have a copy of Model Boilers and Boilermaking, by K.N. Harris? He goes into ratio of flue diameter to length.

I think you want to take as much heat out of the exhaust gas as possible - any heat which didn't transfer before going up the chimney is wasted fuel.


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## Phippsburg Eric (Jan 10, 2008)

there is a cross over from where the flow is restricted and thus the fire dampened to free firing but less heat transfer. you want to shoot for that sweet spot


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## Amber (Jul 29, 2011)

Well, I had a change of plans due to not having the materials to build a 3 inch diameter firebox for the 4 inch boiler. About the only way I could do that now would be to make a 3 inch pipe section from a 4 inch pipe section, and I'm not sure I want to do that.
So, my next idea is run a single piece of 2 inch copper pipe up the middle of the boiler with a bunch of cross tubes in it for the water to flow through and be heated. I would put a propane or butane burner in the bottom of that. If I put the cross tubes in correctly, at 90 degree angles from each other as they go up the tube, I could run a superheater pipe down one side of the monotube, between the water tubes, and back up the other side in the same way. I have a lot of heavy wall 2 inch copper pipe, so I could probably make something like a cone shaped bottom section for the center flue, to fit a larger burner into at the bottom of the boiler. I don't think the "firebox" would need any stays, because it's still round, even though it's conical. I might put some short quills in the firebox to pick up a bit more heat from the burner. The more heat I can transfer to the water, the easier it will be to maintain steam pressure when it's being used.


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## Amber (Jul 29, 2011)

I haven't gotten past the planning stage on this boiler yet. I still would rather build the boiler with a 3 inch diameter firebox, I just need to get either a piece of heavy wall 3 inch pipe or a 3 inch pipe cap for type L and M pipe. I can get either piece from ebay, I just have had other commitments for the money for the last month. Hopefully, after the first, I'll have a bit of extra money to buy the part I need for the firebox. Since moving has been put off until next summer, I was able to get my drill press set up again to drill the various holes necessary. I need to make the upper flue plate, but I can't drill it until I make the firebox.


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