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I Forge Iron

Naturally Aspirated Ribbon Burner. Photo heavy.


Frosty

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It  just occurred to me the yellow/orange flames may be crayon rems burning out. I'd just let it run and get good and hot. That should take care of any wax, wrapper, whatever is left. Heck, did you use Crisco as a release agent? The residue has to burn out too. 

It looks good John, maybe a little fine tuning but that's no big deal.

Frosty The Lucky.

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The mold for the block got coated in (rather old, stale, and partially dried out) Crisco; the crayons got a coat of cooking spray. They did NOT want to come out at all, and I ended up having to drill them out. There is probably some wax that got pushed into the plenum, but I think that was what the white smoke coming out of the T fitting was. That hasn't shown up for the last burn or two.

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Hi there,

I'm Tim,  a wrinkly engineer (mid-50s) from Bristol in England, who has been reading up for months, so that I don't ask the silly questions (too much ;) ).

Anyway, after building an IFB forge, fitted with a 3/4" AMAL Propane injector & 9" iron nipple, I have been using it sucessfully for over 6 months, making tongs and tools, and the occasional blade to practice quenching & tempering.

I then got caught up in the NARB thread and started planning my own multiport burner.  Just as I was finishing the design, Judson Yaggy posted up his NARB based on a drilled-out IFB, just like I was building! Cool!

So I went ahead and finished off my NARB. The plenum is folded and welded-up stainless plate, with 2 3/4" pipe bosses welded to the sides (one on the long side and one on the short, so I can mount it in different orientations and just use a blanking plug on the un-used boss).

So it lights and burns OK, and with the AMAL injector I can adjust how rich or lean it burns. In free-air it looks ok to me, (but I am Red/Green insensitive so not the best judge).

The issue I have is that when fitted into the top of my forge and turned up to ~5psi, the plenum starts to glow red-hot, with a dull-orange-hot patch appearing on the top.  Now I know the plenum is going to get pretty hot, and I know stainless steel is a poorer conductor of heat than mild steel, so its possible that the heat isn't getting disipated as effectively as it would be if it was mild steel construction.

I was concerned that I might get ignition in the plenum, but for the 15mins I ran it, it seemed stable and the plenum didn't appear to get any hotter.

Any suggestions/observations regarding this Plenum glow?

 

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On 2/22/2019 at 7:58 AM, JHCC said:

coat of cooking spray. They did NOT want to come out at all

Dripping with cooking spray didn't work for me so I rolled the crayons for the second burner in stale Crisco. In a most satisfyingly messy manner. :) Most of those crayons pulled out with the bottom of the most that had the crayon holes in it. The couple that didn't came free with a little twist and gentle pull. 

A very liberal coat of Johnson's paste wax didn't keep Kastolite from sticking with authority to the sanded and painted plywood.  

Frosty The Lucky.

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Welcome aboard Tim, glad to have you. 

It's burning inside the plenum. The outlets are too large so the Fuel Air Mix (FAM) velocity is too low to prevent it burning back once it warms up a little. And I MEAN a LITTLE. The intense IR from the forge isn't effected by the FAM flow, so the thin walls between outlet holes absorbs heat faster than the flow can cool it. 

Once hot and burning back it looks like the flame is right inside the plenum's margin and the flame exiting the outlets is what's left over. I have 19 crayon sized outlets driven by a home made T inducer. My T burners are nowhere near as effective as an AMAL "injector". 

I think you need more than a little tinkering here Tim, looks to me like you're looking at a tanking this one for a redo. I made a plenum with tabs so I could screw it to 2" x 2" wooden test burner blocks till I found the number of outlets and inlet orientation that worked best. 

I test fired them all in a brick pile forge once I got a decent flame. 

Frosty The Lucky.

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Hi Frosty,

I initially based my hole diameters on Judson Yaggy's NARB dimensions, where his 5/16" holes come out as 7.9mm, so I converted to 8mm for my outer 2 rows, and 7mm for the inner row, so I could widen out as needed.

The initial testing with these dimensions kept blowing out, so I widened the inner row from 7mm to 8mm and it seemed much more stable. I also added ~10mm depth of flare at each hole exit, taking it out to firstly a 9mm and then a 10mm step flare. These step flares are probably why the holes look bigger than they should, but at their narrowest, the holes are still 8mm (~5/16") in diameter.  Judson's NARB was functional at these dimensions.

I can see from the glowing IFB core that spacing out the holes more would help to reduce heat build-up in the core, so I can easily knock out the old IFB and drill out a new one. The Plenum was designed to be a slight resistance fit over the end of a firebrick, so I can get 3 to 4 test blocks out of a single IFB, saving casting and drying time is short with the fire cement bonding the IFB in place.. Once the design is optimised I was planning on casting a more heavy duty version, but for now, IFB is fine for development.

I don't think its helped by the vertical mounting position, and for my future Butane Tank forge, I will be going for a side entry slightly down-facing position.

Thanks for the feedback, I shall continue my development.

Tink!

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I like the plenum design. 

Port size/quantity seems to be a bit of a balancing act.  You need enough ports to let the inducer breath but they need to be small enough so the FAM velocity is above the propagation rate.  You stated that it was blowing the flame off at the smaller holes, was that before the flares?  I think you want the streams moving fast enough to be close to blowing off at start up.  This is where the step flares may help hold the flame or starting at a lower pressure and increasing once the block heats a little.  As the block heats and begins preheating the FAM, the propagation rate increases, so you want the FAM streams moving fast enough to prevent roll back.  

Before you scrap the block, block one/some of the ports and see what happens. 

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I think the increased exposure to IR tapered outlets represent make keeping the burner block cool enough to prevent burn back much more unlikely.

Trying to slow the flow by modifying outlets is doing it the hard way. if it's too fast, add an outlet.

Casting, curing, etc. is why I used wooden test blocks, I only needed them to survive maybe 30 seconds to evaluate the flame. Once I got it close I fine tuned the inducer.

Frosty The Lucky.

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Frosty - need some help here!  (and serendipitously, this is an example of using wood blocks to test!)

Had a few hours to play so I threw together a NA ribbon burner using a DIY hybrid style burner I had around.  I thought I'd try using smaller holes since I have a lot of 1/8" sprue wax I can use and I wanted it for a small forge (I figured the flame face would be shorter).  So here's 2 videos of test blocks burning; one with 36 holes (first), and one with 72 holes.  Its a 1.5" wide x 5.5" long block (I'm using a 2x2 for the test). 

Question: how do those flames look?  72 holes are definitely more stable.  Is the ox/propane mix solely from the burner, or do the number of holes effect the mix as well?  

Thanks in advance!

 

 

 

 

On 2/24/2019 at 5:19 PM, Frosty said:

Dripping with cooking spray didn't work for me so I rolled the crayons for the second burner in stale Crisco. In a most satisfyingly messy manner. :) Most of those crayons pulled out with the bottom of the most that had the crayon holes in it. The couple that didn't came free with a little twist and gentle pull. 

A very liberal coat of Johnson's paste wax didn't keep Kastolite from sticking with authority to the sanded and painted plywood.  

BTW - I've worked a lot with molds (used to teach a mold making class).  In this case Vaseline is your friend.  It will prevent sticking even to wood.  In addition, I found an old container of A&D diaper rash ointment (my son is 16 now), and it works great as a mold release since it is thicker than Vaseline and won't get rubbed off as easily.  Probably better then Crisco...

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32 minutes ago, D.Rotblatt said:

72 holes.

I cannot see your videos but I am very interested. I also used 72 holes the size of coffee stirrers powered by a 1/2" tube.

My flame kept blowing off unless it was super choked and very rich with not much velocity. 

I have also tried the 3/4" Mikey ejector with it and was fractionally better. I was thinking a larger intake than is necessary like in the hybrid burners would get it closer.

I am interested in the more smaller holes idea so I will be lurking about.

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On 2/24/2019 at 4:57 PM, tinkertim said:

the plenum starts to glow red-hot,

Listen to the others, but just for comparison; my plenum never gets so hot that I can't touch it....even at welding heats in the forge.  The flame should never enter the plenum (except maybe a blowback when shutting off).

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2 hours ago, D.Rotblatt said:

Question: how do those flames look?  72 holes are definitely more stable.

If it were me I'd go with the 36 holes or maybe add just a few more.  You have a little flame lift in open air, but still didn't blow the flame off the block at 10 psi.  It will behave a little differently inside the forge, and once the forge chamber is hot you probably won't see the flames lift off the block at all. 

Where you probably will see a difference is the turn down range in your forge.  The 36 hole version should result in cooler plenum when running, but it will also almost certainly be able to be turned down further before backfiring occurs when your forge is hot.

Just my 2 cents based on my own experimentation with these burners.

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7 minutes ago, Buzzkill said:

If it were me I'd go with the 36 holes or maybe add just a few more.  You have a little flame lift in open air, but still didn't blow the flame off the block at 10 psi.  It will behave a little differently inside the forge, and once the forge chamber is hot you probably won't see the flames lift off the block at all. 

That sounds logical.  I have a gun ribbon burner on my other forge (first one I made, 19 normal crayon sized holes), and it doesn't hold a flame in open air, but works like a charm in the forge - my observations are consistent with what you are saying, but I have no comparison.  

One thing I can say, is both numbers of holes were incredibly stable.  It was a complete guess as to the number of holes and it was my first try.  Using crayons to burn out is a great idea, but looking at all the commercial burners out there, it seems the holes are much smaller.

BTW: I have some old sprue wax, but you can buy enough for a lot of burners at amazon - not too cheap though, around $18-25 a box.  Just look up 8 gauge sprue wax.

 

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3 hours ago, D.Rotblatt said:

Question: how do those flames look?  72 holes are definitely more stable.  Is the ox/propane mix solely from the burner, or do the number of holes effect the mix as well?  

Those are SMALL holes! 72 looks a lot better, the flames are: stable, shorter and lower velocity. The yellow streaks and rich flame in the second video is caused by the wood burning. Otherwise the FAM looks good. The Air/propane ratio is from the inducer (burner) not the burner outlets, though the back pressure balance can effect induction and FAM ratio.

Sounds crazy but I'd work up from 72 maybe try bracketing the right number and do 96 next. There are pictures of commercial NA multiple outlet burners with LOTS of really small outlets. 

Sprue wax eh? Is that $18 per 25 in a box? Crayons aren't cheap here either. Vaseline it is. I have a couple ideas I want to try once it's warm enough to make more burner blocks.

Frosty The Lucky.

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Hi Another FrankenBurner,

Initially 12 holes at 8mm and 5 holes at 7mm, the flame burned fairly stable outside the forge, and facing upwards, and I could adjust the FAM through rich to lean pretty well.

But when I mounted the NARB upside down in the top of the forge (as seen in my previous photos) the flame would only stay on if the FAM was adjusted to very rich, so yellow flames were pouring out of the forge openings at both ends. When I started to lean out the mixture, the yellow would go and then the flame would pop and blow out. I was probably at a couple of PSI at this stage.

It was after this that I took the 5 x 7mm holes up to 8mm, yet still had the same behaviour, so added the step flares to the holes. The flame would now stay on in the forge without blowing out, but we see the burning in the plenum now.

Hi frosty,

I think my holes are too close together, as the web between them is what glows the hotest, but the holes around the edge don't at all. My next test will be with more widely spaced holes and maybe slightly more of them and slightly smaller, maybe angled outwards to give more material between each hole at the hot face?

Thanks again for your feedback guys.

Tink!

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Here is my updated IFB burner hole layout for my next round of testing.

Compared to the V1 version, the V2 has more, smaller and wider-spaced holes to try and minimise the overheat of the IFB webbing between the holes.

With my area calculations I have undersized them very slightly, so I can over-bore them a few at a time and monitor the flame behaviour, to keep the flame out of the plenum this time round. :)

I'll build it and hopefully do some testing at the weekend and will post up results.

Tink!

 

NARB_V1-vs-V2.jpg

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11 hours ago, Frosty said:

Sounds crazy but I'd work up from 72 maybe try bracketing the right number and do 96 next. There are pictures of commercial NA multiple outlet burners with LOTS of really small outlets. 

Sprue wax eh? Is that $18 per 25 in a box? Crayons aren't cheap here either. Vaseline it is. I have a couple ideas I want to try once it's warm enough to make more burner blocks.

Thanks Frosty!  I was thinking about the Joppa Glassworks burners.  I read about them years ago and have his book on building glass furnaces (I used to do a bit of glass blowing).  I'll give more a try and see what it does.  Exactly what should I be looking for in the flames?

As to sprue was, it's $18 for 2 oz, and 25 or so for 8 oz.  Don't know how many that is, but 8oz is plenty.

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I looked at a number of commercial multiple outlet burners when I was messing with the idea of making the thing. Joppa is an early hit when searching. Right now I'm going on memory as to what they looked like, I remember lots of small holes and: pale blue almost opaque, short flames. It looked almost like a very short bristle brush. 

You want reasonably short nearly opaque pale blue flames right at or only barely separated from the block. That's what I try for anyway. The slower the flame the longer it stays in the forge heating the liner. It has to be fast enough to keep the block cool enough it doesn't burn back though. 

The more I think about it has me wondering if tapering it more narrow at the outlet end wouldn't be better. More surface area inside the block to cool and more velocity AT the outlet so it won't burn back as easily. The narrow outlet will also shield the inside surfaces of the holes from more IR. 

Instead I think I'll see if I can come up with a thinner burner block that doesn't conduct heat very well.

Frosty The Lucky.

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7 hours ago, Frosty said:

You want reasonably short nearly opaque pale blue flames right at or only barely separated from the block. That's what I try for anyway. The slower the flame the longer it stays in the forge heating the liner. It has to be fast enough to keep the block cool enough it doesn't burn back though. 

Thanks!  That'll help.  It's pretty much what I'm getting, just that they're off the burner a bit.  Buzzkill suggested that it was better to have them off the burner, thus keeping the burner block a bit cooler - I know from the little experience I have in ribbon burners that once in the forge it's a whole different ball game.

The Joppa burners are ceramic, and look like honeycomb - very small holes close together.  I don't think that would work with Mizzou (which is what I am using), as it is too coarse.  Even so, the small holes seem to work well on my test...knock on wood!  

7 hours ago, Frosty said:

The more I think about it has me wondering if tapering it more narrow at the outlet end wouldn't be better. More surface area inside the block to cool and more velocity AT the outlet so it won't burn back as easily. The narrow outlet will also shield the inside surfaces of the holes from more IR. 

Instead I think I'll see if I can come up with a thinner burner block that doesn't conduct heat very well.

Weren't we talking about that a few pages back?  I believe I suggested it would be easy to make a 2 part plaster mold for the waxes.  Just soak the plaster in water until no bubbles are coming out and then pour wax into the mold to make tapered forms.  I used to do molds like that all the time for sculptural pieces.  Still do for guards and pommels if I'm doing a re-creation.  

In my case, I think the smaller holes, close together will also help in cooling the burner block.  I'm thinking about thinning the block itself, but I haven't figured out what to put as a form - maybe build a wax box to pour the mizzou around. The idea of tapered forms for the nozzles might be easiest.  

___

One last question.  The flames toward either end of the block where further from the face of the block, getting closer toward the middle.  Would a baffle help that...or does it really matter either way?  I do notice on my gun ribbon burner that the flames toward the ends of the block are not as hot as the center...that burner does have a baffle and is 8" long.

On 2/25/2019 at 7:58 PM, 671jungle said:

I also used 72 holes the size of coffee stirrers powered by a 1/2" tube.

Mine is powered by a 3/4" inducer (burner) rather than a 1/2" one.  But frosty suggested more holes...I'll try it and post and we'll see!

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I assume Joppa and other commercial multiple outlet burners are made with high temp materials and I have no idea what. If I knew what kind of ceramics Joppa burners were made with that's what I'd be using if I had to pay for time at a pottery shop to fire them correctly. 

 

12 hours ago, D.Rotblatt said:

Weren't we talking about that a few pages back?  I believe I suggested it would be easy to make a 2 part plaster mold for the waxes.  Just soak the plaster in water until no bubbles are coming out and then pour wax into the mold to make tapered forms.  I used to do molds like that all the time for sculptural pieces.  Still do for guards and pommels if I'm doing a re-creation.  

Yes we were and I haven't forgotten the method. 

Here I was referring to minimizing the surface area exposed to IR from the forge liner. I've run one of the Kastolite burners outside the forge for a couple hours and it didn't get close to showing color, it barely got hot enough to toast a piece of white paper so what, 350-375 f.?

Being contained in the forge chamber on the other hand is a whole different environment and unless I run mine at at least 3 psi. it gets hot enough to burn back in use.

Yes, the uneven flame length is due to uneven flow in the plenum. I put a baffle about half way across the plenum from the inlet in the one the outlets and inlet were in line. The flames weren't "perfectly" matched but probably close enough. Then I thought of giving introducing the inlet at 90* and using the far wall of the plenum to disperse the flow and it worked well enough. There's a little difference but I don't feel it's significant.

I don't know what's going on in your gun Multiple Outlet Burner. (MOB) I'm thinking I'd mess with the baffle and see.

Frosty The Lucky.

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