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First Forge Build Plans


TRR1143

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Hey everyone, I've been reading a lot on the 101 threads on this forum over the past few days and have come up with a design and a few questions that I wanted to run by some people before I went out and made too many mistakes. This will be my first forge and I'll likely start out making the usual beginner blacksmithing projects, leaves, bottles openers, hooks and such. Eventually I'd like to get into tool making, blades, and damascus work in the future. Nothing huge and ornamental like railings or anything like that. My design was based in part on the oval Chile Forge and on the muffler build thread I found on this site/YouTube, as we had a decent sized muffler laying around that looked perfect for the job. Now on to the design.

Forge Body

As I mentioned above, I'll be using a large muffler for the shell. The dimensions are roughly 11.5" x 7.5" for the oval cross section and the muffler is 20" long. I am currently targeting a length around 16" for the design, but I feel that 16" may be too long? More on that with the burners though. For the front and rear openings, I like the idea of attaching some brackets for sliding fire brick but would be open to other ideas.

Forge Lining and Floor

After reading a lot on the site I feel the Kaowool, rigidizer, refractory, IR reflective setup would work well. I would also have a high alumina kiln shelf as my floor. I'm currently planning on having 2x 1" layers of the rigidized kaowool, 1/4" - 1/2" of the Kast-O-Lite, and then a layer of the Metrikote to polish it all off. I believe I read about also coating the kiln shelf as well, would the Metrikote work for that application? My target cross section after the lining would be something around 3.5" high and 6"-7" wide for the forge chamber, more of a D shape. I can do the math with the insulation layers to know what to expect but I suspect that the wool will compress slightly during installation/rigidizing and I would plan to use the refractory to create my desired cross section in the end, but wouldn't apply more than 1/2".

Burners

This is perhaps my greatest area of uncertainty.  Running the volume numbers for the dimensions listed above, at around a 16" length chokes out a range from 336 to 392 cubic inches, based on a 6" or 7" wide chamber. I am considering building my own Frosty T burners and am familiar with the 350 cubic inches rule of thumb. My case here appears to borderline the need for two 3/4" burners. I feel that with the 16" length, a single burner simply wouldn't be able to heat the space evenly. So my main questions would be should I go for a two burner set up, evenly spaced at 1/3rd and 2/3rd the length of the forge and would two 3/4" Ts work out or should I go for two 1/2" burners? I don't really want to shorten the forge length too much, as I feel projects will grow into the extra room but if that sounds too big I am open to design changes here. Additionally, if I go the two burner route, I'm tossing around the idea of using an insertable wall to basically split the forge when I'd only need to use one burner if that makes sense. If anyone has any suggestions or thoughts on this topic I would appreciate it. I would plan to aim the burners at an angle to hit the near 1/3rd of my floor plate.

 

This is my design concept in a nut shell and I just wanted to run it by some people who actually know what they're doing to make sure I haven't overlooked something or thought up a glaring error. Please share your thoughts or suggestions about anything in the design.

Thanks!

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6 hours ago, TRR1143 said:

I believe I read about also coating the kiln shelf as well, would the Metrikote work for that application?

Yes it will work just fine for that too.

 

6 hours ago, TRR1143 said:

I feel that with the 16" length, a single burner simply wouldn't be able to heat the space evenly. So my main questions would be should I go for a two burner set up, evenly spaced at 1/3rd and 2/3rd the length of the forge and would two 3/4" Ts work out or should I go for two 1/2" burners?

You seem to have your ideas lined up well. Yes; go for two 1/2" "T" burners.

The one critical item you haven't spoken to is how to orient your burner's flames.

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Thanks for the information Mikey.

In terms of flame orientation, the target for impingement would be the burner side of the kiln plate. I've read about placing the burners between 1 and 2 o'clock on the shell, angled to the near side of the floor plate. Due to the oval shape, I'd think an orientation closer to vertical would work best, maybe just north of 45 degrees from horizontal. I've attached a crude sketch of my idea, not to scale obviously. Let me know what you think.388661811_ScreenShot2018-12-29at7_32_51PM.thumb.png.fbdfb609d4cc297cc01d87b9e425b03e.png

 

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  • 1 month later...

Just a follow up here, I've been making progress on the weekends when I can, as school has started back up, but aside from that I've been thinking about propane plumbing. I've talked with some local people and family members that have led me to the follow plumbing route for my two burner setup:

Propane Tank -> Regulator -> 1/4 turn ball valve (E-stop) -> hose to T Joint -> 1/4 turn ball valve (burner on/off) -> need valve (fine psi control) -> copper tubing -> T burner flare fitting

Does this seem reasonable? Reading some on here I can't see if needle valves are a good idea or not but people I've talked to recommend them. 

I would appreciate any thoughts, thanks!

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That will work out okay, but you will probably end up with needle valves on both burners; they are just handier than fooling with the regulator for fine tuning; especially since separate burners seldom tune the same way. However, this is what I call "an add on later on" type decision :rolleyes:

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Have you thought of positioning your burners high on one side of the forge and aimed horizontally toward the other side, so that their flames shoot over the work pieces, and have plenty of distance before impinging on anything? This is the position I am starting to recommend for oval forges.

 

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I think you've thought this out well and I'm on the same page as Mike Re. aligning the burners horizontally at the top of the vault. 

You have the propane supply about how I do it though if you align the burners horizontally you can use rubber hose up to the burners as they won't get hot enough to burn. Angled up slightly would be a sure thing.

The sliding wall to change the volume has been used and works well, the only potential problem is the refractories fusing together. Keeping the sliding wall bottom edge dusted with soapstone dust will take care of that issue. Just don't breath more of the dust than you can avoid, talc, soapstone, jade are all asbestos in various forms. Due as I recall to different molecular water contents.

I'm really looking forward to seeing that baby in action.

Frosty The Lucky.

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  • 3 weeks later...

Finally lit the forge for the first time today. I just wanted some advice on tuning the burners. Fairly sure they're a bit fuel rich but I wanted some expert opinions on what exactly should be done. I have 2x 1/2" T-burners. First picture is the front flame, second is the back.

 

 

IMG_7817.jpeg

IMG_7818.jpeg

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Is that 1/2" measured from the shell? The front burner is putting out more volume or at a higher velocity forcing the exhaust mostly out the rear. Were I to guess from 3,500 miles away I'd say check the jet on the rear burner for a burr or obstruction. Provided the rest of the construction is the same. IF the jet in the front burner is trimmed back from the throat farther it could be burning harder/faster but I'd expect it to be leaner.

Frosty The Lucky.

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I’ll go ahead and swap out that section of tubing and see how it goes. Would you recommend I trim the mig tips back a hair, say 1/8”? 

I'll also add that after the forge got around a nice orange color that back burner flame began to flicker every now and again as well.

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One change at a time! Then test to heat in the forge and take notes. Get them burning evenly before you start tuning.

If they actually need further tuning after you do get them burning evenly I'd try trimming them less than 1/16", probably 1/32" at a time. They're darned close now and 1/8" is a major adjustment. Also make sure the jets are aligned with the tube when you reassemble them, they're easy to bump. 

I'm not surprised the back burner started stuttering, most of the exhaust is going out the back and is being taken in by the back burner. 

Frosty The Lucky.

 

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I replaced the tubing on the back burner and I'm not sure it's gotten any better. The flame in the back is now smaller and slightly green. The front flame also shows hints of green at times as well. I've checked the jets and they look lined up properly. If I remember correctly, green = fuel rich and that should be a sign to trim the mig tips?

 

Slight edit: The back burner tube itself was slightly tilted out of alignment with the flare I cast in the refractory, I tweaked that a bit and now both flames look to be the same size, the rear flame is definitely more green, and the front is only a hint green at times.

IMG_7821.jpeg

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The green is probably just copper oxide knocked loose when you changed the tubing. Not uncommon.

The close one appears to be burning off the nozzle. If the burners are close to the same there shouldn't be that much difference. It still looks like the one in back isn't drawing as much air. It's richer and not so long nor hot.

The front burner looks to be acting like it has to much pressure. So, leave it alone and see if you can get the rear burner drawing enough air. 

Just to make sure, they have the same parts, same: T, tube, gas fittings, jets, nozzle flare, etc. all the way back to the regulator. Yes? You made them as close to exactly the same as you could right?

If so something is tweaked or blocked somewhere. Do you have torch tip files? 

Frosty The Lucky.

 

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Frosty, I forgot to take another picture so that last one isn’t the most up to date, my mistake. Everything for each burner is as close to the same as I could get it to be going back to the brass tee flare fitting that splits my main propane line. 

I don’t have torch tip files, but they sound like a good idea to have and I’ll pick some up. I’m away from the forge during the week so I won’t be able to work on it again until Friday. I’ll probably give that tip on the back burner a clean and see how it goes from there. 

Thanks for all your help. 

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