T Burner Illustrated Directions

[ymber]

Alright I'll take some measurements of the forge and run the numbers. It's kinda long and thin so it might lend itself better to multiple burners. I might just take the excuse to build a new forge if I'm doing a burner already.

 

Where you talk about the air intake carrying capacity, what is that? I understand a 1" wide air intake would work out at an area much bigger than 2x3/4" so is it fine to have oversized air intakes as long as it doesn't cause a problem for getting the jet gap down to 0.5D?

[tinkertim]

A Normally Aspirated (NA) burner uses a fine jet of fuel gas (Propane) to draw in the required amount of air for the required combustion (tuneable for Rich or Lean, depending on requirements).

Getting the right jet sizes, tube lengths, Tee sizes takes a fair amount of development work to get a burner to run right.

Please follow the recommended sizes and ratios to have a chance of getting a burner that will stay lit, and will then allow you to tune it, with the assistance of the original designer (Frosty).

If you pick and mix sizes of tube and random sizes of Tee, your burner will not stay lit, or burn really inefficiently.  You will then ask the forum for help, and they will say "Did you follow the build instructions?" and you will say no, and then they will say "Well follow the build instructions and then get back to us".

Once you have followed the original build recipe, and have got your burner running, and have then tuned it with assistance from the Forum, then you can play with sizes and specs to make your own mods, but for the first burner Please follow the original build recipe first. It will save you so much time.

Good luck,

Tink!

[Another FrankenBurner]

If your intention is to work on large/long knives, long and thin is fine within reason. Just use two smaller burners.  Unless the current forge is built poorly, why build another. If you want to do more generalized forging, long and thin isn’t as much fun to work in. 
 

The jet gap is a starting point for tuning. 
 

You don’t want to go crazy on over sizing the air inlets or burner performance may suffer. As Frosty stated, it’s a ratio game. 
 

As far as I understand it, nominal pipe sizes are close between the two standards. If that is the case, select the next size up from the mix tube. If you want a 20mm burner, use 25mm air inlets. If you want to build 25mm, use 32mm inlets. 
 

If you give your forge internal volume, you may get recommendations on what burner(s) will work well. 

[Frosty]

10 hours ago, ymber said:

a 1" wide air intake would work out at an area much bigger than 2x3/4"

Didn't do the math did you? Or did you mean two, 1" intake ports is more than 2x a 3/4" tube? A T burner has two intake ports making 1" almost 4x the tube capacity. Oh darn I almost did the math. <sigh>

Carrying capacity is how much material will flow through a path at a given pressure/velocity. The larger the diameter the greater the capacity but it isn't a linear ratio and math far above what I can do. The reason is fairly straight forward though. The area is the square of the diameter where the circumference is a simple multiple. That means the larger the pipe the less skin contact friction there is in relation to the volume of material flowing.  

Frosty The Lucky.

[ymber]

I'm looking for a more general purpose forge really. As it is this one was built by a bladesmith for knives but he never got it working right and the other guys at the shop say he's not been around for a while. The construction is kinda crude and the insulation looks like it needs redoing to get it running nice. I'm thinking I'd have a better time if I built something like Larry Zoeller's simple gas forge design.

I just realized when I ran the numbers late last night I used the diameter instead of the radius to calculate the circle area. This makes a lot more sense when I calculate things right. A 1" BSP nominal run diameter on the T is 1.309" actual diameter. Apparently a nominal 1" BSP T has an actual run diameter only 0.006" smaller than a nominal 1" NPT T (1.309" vs 1.315") so it should be essentially the same for this purpose. πx(1.309/2)^2 is just under 1.35. If I'm going for AI=2D that should be 1.5, is that ~0.15 square inch difference an expected part of the original design or have I made a mistake? While I'm second guessing my working, AI is the area of a single intake and not both combined, right?

[Another FrankenBurner]

You are thinking too hard. We can be friends.

I thought I had gathered that the pipe actual dimensions were very close between the two standards and that threads were the big difference.  In which case, if wall thickness are also fairly close, you can just build per the instructions.

Building another forge is just part of the blacksmith way I think.  Plot to build that perfect forge and as soon as it’s done, start plotting the next with improvements.

[Frosty]

Ha, Ha, Ha, nice try, I don't check math either. I stopped using "pi r squared" a long time ago when I stumbled on an easier formula, ".7854 d squared." It eliminates a step and is accurate to 4+ decimal places. 

Lots of guys, especially old school guys build really long forges to make blades and for the most part waste at least 4x the fuel and or do serious damage to the steel. You can only realistically forge 4"-6" at a time so everything at forging temp outside the forged zone is suffering crystallization (grain growth) and decarburization to no purpose. Forging crushes crystal boundaries and refines the metallic structure so it is less brittle and prone to failure. Normalizing refines grain structure and should NOT be skipped. 

The forges 101 section of Iforge is a large section discussing forge construction, pros, cons, favorites and much hated designs. Larry's plans are solid and proven but a lot of progress has been made in the time since his site's last update. I admit I haven't checked his site in a few years, he may be updating again, I've been wrong before.!

For guys who don't know just what they want to make yet, I like forges that can be changed easily so they can experiment without spending lots of money on every change. Below is a forge our club built at a forge and burner work shop a few years ago. It is a clamped together version of a "brick pile forge.

The (Insulating Fire Brick) (IFB) are Morgan Thermal Ceramics, K-26. They have a working max rated temp of 2,600f and withstand the kind of thermal shock a propane forge generates. We used Plistex as a "kiln wash" to act as a final flame face to help armor the IFBs from the heat, abrasion and the high temperature chemistry that happens to forge liners in the presence of propane flame and forge welding fluxes. 

It's fired by one 1/2" T burner and is approximately 175 cu/in. I don't recall. This pic was taken less than 5 minutes after lighting it, the proud new owner didn't wait for it to heat up before putting the stock in. They make welding temperature easily and a number of the pro bladesmiths in the club only use their old forges for heat treat and they make axes and swords amongst EDC blades.

Frosty The Lucky.

[JHCC]

17 hours ago, Frosty said:

I stopped using "pi r squared" a long time ago when I stumbled on an easier formula, ".7854 d squared." It eliminates a step and is accurate to 4+ decimal places. 

On a side note, 22/7 is a perfectly adequate approximation of pi for most smithing purposes. When I was making the wedding archway a few months ago, I made the curved portion (a 7' diameter semicircle) with an 11' circumference, which is only 0.05311" longer than 7π/2. 

[Frosty]

I'm not clear. Is that the formula or an example? is the formula xpi/2? (I can never find the pi symbol. )

Frosty The Lucky.

[Mikey98118]

On 7/25/2022 at 3:57 PM, Frosty said:

The forges 101 section of Iforge is a large section discussing forge construction, pros, cons, favorites and much hated designs. Larry's plans are solid and proven but a lot of progress has been made in the time since his site's last update. I admit I haven't checked his site in a few years, he may be updating again, I've been wrong before.!

If today's insulating bricks had been available when Larry built his gas forges, I think his old site would look a lot different.

[Frosty]

Everybody's would. Manufacturers engage in constant R&D to keep up with the competition. The best refractories are highly desirable if you're doing HOT work, especially commercially. 

Have you heard anything form or about Larry, Mike?

Frosty The Lucky.

[Mikey98118]

Not for years. I was scrapping with someone he was supporting, and he didn't want to be put in the middle of it; I agreed with his position on the matter. But before it was done, his life had pretty well been turned inside out over other matters, and the next thing I heard was that he was living somewhere in Oregon. He had turned over his burner pages to ABANA, and I had to figure he wanted to drop off of everybody's radar; again, that was his private business...so that's there things stand. I'm sure he still has a computer, and can re-engage anytime he wants. Until he wants, I have no business looking for him.

[Frosty]

That's more than I knew and I certainly don't intend to pry. I'll wish him well and let be. 

Frosty The Lucky.

[JHCC]

He was at Quad-State last year; we had a nice chat. 

On 7/26/2022 at 12:21 PM, JHCC said:

the curved portion (a 7' diameter semicircle) with an 11' circumference, which is only 0.05311" longer than 7π/2. 

On 7/26/2022 at 12:38 PM, Frosty said:

I'm not clear. Is that the formula or an example? is the formula xpi/2? (I can never find the pi symbol. )

Frosty The Lucky.

That’s the example. Since the formula for the circumference of a circle is diameter x π, then the circumference of a semicircle is (diameter x π)/2. 

Using the 22/7 approximation for π, the circumference of the 7’ semicircle is:

(7’ x 22/7)/2

22’/2

11’

[Frosty]

Dividing the circumference by 2 only works for a 1/2 circle. Isn't using 22/7 adding steps to the calculation? 

Approximating circumference in my head I multiply by 3.125 and for area divide d squared by .8. If I'm working a project and don't want to get out a calculator I have a pi tape, it has area and segment markings I've never used. WAY better than calculating the shape to cut to weld say 1.2" round to 3" round at a 30* angle. The marks are on one side the instructions on the other. I've always been a little embarrassed I've never used one for more than the elementary school level basics. 

Frosty The Lucky.

[JHCC]

41 minutes ago, Frosty said:

Dividing the circumference by 2 only works for a 1/2 circle.

Yes, indeed. If you're trying to find the circumference of a semicircle, dividing by 2 is entirely appropriate!

41 minutes ago, Frosty said:

Isn't using 22/7 adding steps to the calculation? 

Not really. Say you want the circumference of an 8" circle. 8 times 22 = 176. 176 divided by 7 = 25-1/7.  That's equivalent to 25.1428571429", while using π gets you 25.1327412287". That's barely more than 0.01", which is plenty close for our purposes. (Depending on how precise you want to get at that point in your actual practical application, you can say either 25" or 25-1/8", since 1/7 is a hair bigger than 1/8). 

Now, if you want to do the area of that same circle, r = 4, so r² = 16. 16 times 22 = 352; 352 divided by 7 = 50-2/7"² or 50.2857142857"². Using π gets you 50.2654824574"², which is only a hair more than 0.02"² difference.

One thing I particularly like about 22/7 is that since 22x = 20x + 2x, it's relatively easy to do the math in my head.

 

[Goods]

Honestly, for all of the work I’ve done, I’ve just used 3 instead of using 3.1415….
 

Note: all of this work has been basic “close enough” type items like quick estimate of material to get hang loop on the end of tools or the loops and rings for campfire tripods. If I ever get into larger or items needing more precise diameters, 22/7 or 3.14 will be the better method.

David

[Another FrankenBurner]

For close enough work with circumference, I multiply by three and add ten percent.

For the 8 inch circle, 0.8+24.

 If I need to be over, I add 15 percent.  1.2+24. 

[Mikey98118]

On 7/28/2022 at 6:15 PM, Another FrankenBurner said:

For close enough work with circumference, I multiply by three and add ten percent.

 

That is more than good enough for figuring out where to cut ceramic blanket.

[Mikey98118]

But adding 15 percent is even better, because a little extra blanket can be pushed into position, but a l little short is sloppy to deal with.

[Justin Keller]

Hi all,

I built two T burners and they seem to be working pretty well, but I'm not sure if my tuning is as good as it should be.  Here's the album of my forge photos: https://photos.app.goo.gl/ZY9SWdsHJQPRrUpa8, I'd appreciate input.

Thanks in advance,

Justin

[Frosty]

It looks pretty good to me Justin, maybe a LITTLE rich but pretty good. The orange flame is the calcite in the refractory curing. How hot does the forge get?

Frosty The Lucky.

[Mikey98118]

 

the calcite burning off obscures the problematic exhaust in all but two photos; they both show a huge amount of blue exhaust flame, which is not good.

[Frosty]

By problematic. . . too rich? If so, how too rich?

Frosty The Lucky.

[Justin Keller]

14 hours ago, Frosty said:

It looks pretty good to me Justin, maybe a LITTLE rich but pretty good. The orange flame is the calcite in the refractory curing. How hot does the forge get?

Frosty The Lucky.

I haven't been able to get to forge welding temperatures with it yet, despite running two T burners.

2 hours ago, Mikey98118 said:

 

the calcite burning off obscures the problematic exhaust in all but two photos; they both show a huge amount of blue exhaust flame, which is not good.

So too rich?  I should try trimming back the MIG tips to induce more air then?