burner depth

[Njaak]

Grinding an offset ellipse onto 2" pipe to within 0.005". That sounds... hard. I might be able to pull it off with my bench grinder (8" wheels) but the OD of the chamber is 9" so much fidgeting. It's a fun challenge and would save a pile of $ though.

[Mikey98118]

I will admit that short arc MIG welding is little trouble to pick up, so long as you buy a high quality machine (I would suggest Miller these days), and an auto-dark helmet. The next stumbling block is to make sure that you have a 20 amp circuit available for it, if you buy a 120 volt model; running one on a 15 volt circuit is why they don't work worth beans for most guys.

[Njaak]

Appreciate the advice and I do have a stepson who's an electrician so I will get him to sort that out for me.

[Frosty]

The equivalent of dropping a decimal! <GASP> Bummer I don't know you well enough I could kid you suitably. Maybe another time, I guess. It's not like I don't do that sort of thing regularly. Sometimes I'll make the same mistake checking, especially if it's something I do all the time.

You're still making the same fundamental mistake as in the first forge, it's at least 2x too long. Heating 19" of steel will ruin it rapidly, you can not forge enough sufficiently to refine the grain structure and it WILL burn out carbon content and scale WILL reduce the bar thickness every single time you take it out of the fire.

The burner to volume ratio is one well tuned 3/4" burner per 300-350 cu/in volume. You can get more than 350 cu/in with a more recent forge liner design, 2 layers of rigidized 1" 8lb. ceramic blanket refractory, covered with 3/8" +/- water setting high alumina 3,000f castable refractory. A good kiln wash is icing on the cake, making the liner a little more effective and more robust. 

You might want to do what I do when reading technical material I'm not familiar with, take notes, w/ chapter and page.

You're trying too hard to make a precision instrument, these things don't work that way. Rather than trying to align your burner flame tangential to the liner align it so it impinges the far wall or floor at an angle. This will induce a good strong circular circulation and you can forget trying to plan a taper intersecting a cylinder. This isn't a jet liner, it's a home made furnace. 

Molding the liner to serve as the nozzle flare is a good plan but you don't start the taper at the ID of the burner tube. Start the taper at the OD of the mixing tube. This starts it as a step nozzle and not only improves performance is Much easier to make.

I've been watching your conversation with Mike and I'm coming to the conclusion you didn't spend much if any time in the shop as an engineer. I worked with engineers for more than 20 years some very good, the worst were competent. They were constantly asking me how to do basic shop type work some really simple things like hanging a shelf without it falling off the wall. 

It didn't make any of them some how lesser guys, they just weren't trained in the same trades I was.

I see above you're worried about grinding an elliptical hole in a cylinder to a forgiving spec and worrying about silver brazing. These are metal shop 101 jobs. Shop guy tip #1. Use a hole saw with an extended pilot bit. #2 Silver brazing can be done with a Bernzomatic SOLDERING torch.  

Mig welding an inside corner between schd 40 pipe and sheet steel is NOT a beginner's task. Be prepared to practice for a while.

I'm not dissing you when I say you're trying to design a machine you don't understand. If you'd like a nearly guaranteed functional and effective forge to learn with I highly suggest a brick pile forge using Morgan K-26 IFB, Plistex, kiln wash and clamp it together with angle iron and all thread. The pic below is one of about 30 built at a club burner and forge clinic a couple years ago. The ID is 4.5" x 4.5" x 9" and is powered by ONE 1/2" T burner. The pic was taken less than 5 minutes after it was lit. They reach easy welding temp as seen in the pic. A number of the professional bladesmiths in the club use the one they made rather than their other propane forges. They make knives, axes, swords and wootz steel. 

There's no shame in using a proven design. 

Frosty The Lucky.

[Mikey98118]

Grinding a perfect oval for your you pipe in a forge shell isn't hard, if you understand how. First, spend fifty bucks for a Votoer 480 what rotary tool (this is actually a full power die grinder) through Amazon.com. Next cut, and grind a hole for the shell. Lean the pipe through it in the direction you want it to end up, and ink mark the forward and real areas of the hole that you can see will need enlarging. Remove the pipe, and grind some of those two areas away. Rinse and repeat, until the pipe sits exactly where you want it. This is a self teaching process. Each succeeding elongation gets faster. But perfect fits are certain, so long as you don't cheat the process.

Dang! that should have read "your and watt" not "you and what"

[Njaak]

Ok, to recap:

1 - feel free to tease, I'm used to it, my kids and wife are pros.

2 - Correct, I only spent about 18 months in a shop as an engineer, mostly on CAD drawings and particle physics for electrostatic precipitation. Then moved to audit functions and then policy... etc. Mostly my diy skills are limited to bicycle mechanics, and home renovation. 

3 - I'm starting with few tools. Drill press, 2x42 belt grinder, 8" bench grinder, hand held angle grinder, Dremel rotary tool, tap and die set, and hand tools. Zero machinist tools, nor any real experience with them.

4 - Reason for current length was twofold: (1) I had the tank, and (2) I wanted to heat treat longer pieces... and didn't really know how to do that at home without a kiln or forge of sufficient length. I still don't know how I'd do that... I have a kiln I use for HT in stock removal knife making but it can only handle pieces up to 10" total length.

5 - point taken re: not a precision build and tangential flames.  Direct impingement on side wall is fine by me.. but how that induces swirl is hard to sort out. Turbulence, yes.

6 - Frosty, that picture shows a clever use of thread and l angle. I love it!  Lots of material I don't have in that build but I'll start accumulating.

7 - I've got 2x1" kaowool already, and plenty of Satanite to work with... So that's what I hope to use rather than scrapping and starting with all new everything :/

Fixes to the current project:

1 - shorten the chamber to 9"? 10"?.. I'd like to keep the cylinder rather than going with bricks, since I have it and have some kaowool, but don't have any bricks.

2 - move to 1 burner, with side direct burner mount (not tangential).

4 - taper starting from OD of mixing tube, not ID of burner. Without tangential placement the amount of flare is even less. Those thread protectors are looking better and better.

 

 

 

 

[Mikey98118]

You can do the same thing with a hardened burner opening as with a burner's flame retention nozzle; that is to just use a parralel opening of the same diameter is the large opening in a flared nozzle, and run the burner's mixing tube back and forth in the center of that opening to tune the burner's flame.

In other words, the opening then serves the same purpose as a slide-over stepped flame retention nozzle.

[Frosty]

A drill press is probably the most versatile tool I use making forges and burners. 

I didn't say align the burner so the flame impinges the far wall perpendicularly. A 70* angle of impingement rather than 90 is good, 60 better but more shallow is starting to pass the point of diminishing returns. 

There's a trap we all step into though I'm getting better at avoiding it, maybe when I'm 90. Just because you have a thing doesn't mean you have to use it. If you build a shorter forge you don't have to throw that tank out, a heat treating furnace doesn't need the insulation, you want it to hold a stable temperature for a while. For example I anneal by shutting my propane forge off when it reaches critical temperature it stays hot enough to bring the steel to critical after it's off. I insert the piece and close it up till the next day. 

Anyway. Look into hole saws, be sure to buy a center piece that works with a large selection of sizes or buy a set. I have a Lenox set from 3/4" to 6" dia. in increments. 

The text books I studied to become a pipe and structural welder had page after page of how to calculate and mark intersecting pipe at different angles. Now I use a long 1/4" drill bit in the drill press and my 3 axis drill vise to drill a pilot hole in the target pipe. Then I use a length of 1/4" rod in the hole saw pilot and install the diameter hole saw I wish. The rod just rides in the pilot hole and keeps the hole saw from wandering. It makes the oval hole. In a large dia target like a forge shell I just cut the burner mount at the desired angle, hold it on the "tank" to match that angle and mark the arc with a piece of soap stone or sharpy and take it to the grinder. It's a 10 minute job start to finish weld. 

If you don't weld, cut short pieces of small angle iron to make tabs and screw or rivet the burner mount to the tank. 

Silver brazing is REALLY easy. 

Frosty The Lucky.

 

[Njaak]

All sounds good. I've got time set aside for mid August for the rebuild attempt. I'll post questions when they arise and pictures as the Frankemforge progresses.

[Njaak]

Frosty, I think now I'm going to build up a pile of bricks like the one in the picture you sent, then sort out if and how to convert the current mess into something for heat treating. 

To that end, are the bricks forges your club builds using 23 or 26 series bricks? I've read some varying suggestions (insulation value vs strength). My plan is to coat the inside of the chamber with 1/4" of Satanite.  I was thinking all 2300 series except the brick opposite the burner which is do with 2600.

Thanks.

[Frosty]

They're K-26 with Plistex brushed on like thick latex paint as the kiln wash. Satanite might work, it seems to be doing pretty well from what I hear. 

You can make a brick pile forge as large as you wish. The temperature in the club builds is pretty even and easily exceeds 2,300f and probably 2,600f. Kiln washed K-26 are holding up so far.

Frosty The Lucky.

[Njaak]

Great, thanks!

[Njaak]

I finished the pile of bricks!

Flame is stable, thermocouple installed!  Ramped up heating slowly over a couple of days. Tonight I'll test it out for real if all goes well

 

[Mikey98118]

On 7/31/2022 at 1:52 PM, Njaak said:

3 - I'm starting with few tools. Drill press, 2x42 belt grinder, 8" bench grinder, hand held angle grinder, Dremel rotary tool, tap and die set, and hand tools. Zero machinist tools, nor any real experience with them.

The next tool I would suggest you buy is digital calipers; this does more than any other machinist tool to bridge the knowledge gaps for novices in shop work; it will become your best friend, when you are trying to cover your six

[Njaak]

Mikey, I have digital calipers they're essential to custom bicycle work... the only builder hobby I actually got really good at (so far).

The pile of bricks forge works like a charm. Here it is with some A33 in the process of becoming a drift.  Burner doesn't overheat, and kept the temp super stable. I'm happy

 

Thanks so much Frosty for the picture of that build. It was worth a thousand YouTube videos.

 

 

[Frosty]

You're welcome Njaak, it's my pleasure. It puts a real smile on my face to see success, she looks HOT.  

If heat radiating through the bottom of the forge causes warping in the metal it's on a sheet of cement backer board on small stand offs takes care of it nicely. 

Frosty The Lucky.

[Njaak]

It's actually currently on standoffs the threaded rod has acorn nuts on the bottoms, and raises the base of the forge about 2 inches off of the sheet metal. So far so good 

[Njaak]

Oh, and yes, was keeping it at 1925 or so. HOT indeed