Hefty Posted November 1, 2022 Share Posted November 1, 2022 Curse my upgraditis!! I've only recently got my first gas forge up and running but for a number of reasons (mainly keeping my noise-sensitive neighbour happy) I really want to change to NARB. Yes, I could just build another forge but I'd rather save money if I can, by modifying this forge to install 1 large, or 2 smaller, ribbon burners. My main question is: what would be the best tool/method to cut through existing castable refractory? Cheers, Jono. Quote Link to comment Share on other sites More sharing options...
BayardStrachan Posted November 2, 2022 Share Posted November 2, 2022 I used a diamond tile hole saw to drill a burner port, I'm pretty sure you can get diamond cutoff disc's for an angle grinder Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 2, 2022 Share Posted November 2, 2022 A tungsten carbide abrasive reciprocating saw blade should work nicely, Any old 1/2 drill bit to make the starter hole, I assume you're making a ribbon burner port and aren't going to use the cut out. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 2, 2022 Author Share Posted November 2, 2022 Bayard, yep, I do have one, but I'm not sure if an angle grinder will reach where I would need to cut. I can use a normal cut-off wheel for the outer shell and then cut away the ceramic wool with a knife, but I'm not sure if the disc will protrude enough to cut from the outside and I don't know if I can position the grinder correctly through the front opening. I also have a 32mm (1 1/4") diamond hole saw that I might be able to use to overlap holes. Frosty, I don't have a reciprocating saw of my own, but yes, I think that would work for the length. I'll have to see if I can borrow one. Now that I think about it, a slightly oversized opening with a more irregular shape from overlapped drill holes might be better for getting new castable to adhere to in order to make a new mounting slot for the ribbon block. Cheers, Jono. Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 2, 2022 Share Posted November 2, 2022 You can use a keyhole saw, they come in abrasive blades. Yes you can drill a series of holes and clean it up with a chisel no problem. Just don't make the mistake I did when I welded the NARBs TO THE FORGE SHELL! Don't make it a permanent part of the forge so you can modify, fix, replace, 86, burners without having to tear the whole liner out or as in my case take a grinder to the shell. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 2, 2022 Author Share Posted November 2, 2022 Yep, I've read of your regret before. My plan was to do similar to what I did with my current burners and cast the opening around something non-stick that is the same dimensions as the outside of the block, then weld a mounting bracket to the shell and use some set screws, or similar, to hold the burner in the bracket. Quote Link to comment Share on other sites More sharing options...
BayardStrachan Posted November 2, 2022 Share Posted November 2, 2022 3 hours ago, Hefty said: Bayard, yep, I do have one, but I'm not sure if an angle grinder will reach where I would need to cut. Ah yes, didn't think of that Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 2, 2022 Author Share Posted November 2, 2022 Hmmm, next question: my forge is an old 9kg gas bottle with 2 x 1 inch layers of rigidised ceramic wool and a castable refractory flame face, heated by 2 x 3/4" T burners aimed down at an angle at the edge of the cast floor. If I still need to use 2 x 3/4 burners because I'm not altering the volume of the forge, where should I place them? I'd like a bit of swirl, but if possible, I'd also like the burner intakes to be down low to avoid chimney effect. One block will be in the space where my current burners enter at the top right. Any suggestions as to where to put the second? Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 2, 2022 Share Posted November 2, 2022 Okay, lets use the clock face to indicate where we're aiming things I've thought about using two burners to make a strong swirl but it's hard to describe. So, I'm envisioning your burner at 2 o'clock and the forge floor on a plane from 4 o'clock to 8 o'clock. the edges AT 4 & 8. Where is your burner aimed? Just imagine a line from your burner to where it hits the floor, it could be 5,6,7 or 8. Make sense? Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 2, 2022 Author Share Posted November 2, 2022 Yep, gotcha. My burners are currently at about 2 and aimed at about 5 o'clock. Although, I guess I could change the aim when I mount the block. Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 3, 2022 Share Posted November 3, 2022 Hmmm. could mount the second one at 8 o'clock aimed at 11. If the burners were far enough back in the liner they wouldn't be heating each other and the flow should make as strong a swirl as it gets. If the stock starts spinning in the center of the forge you might want to rethink it a bit. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 4, 2022 Author Share Posted November 4, 2022 Another thought is: could I just make the ribbons a little more square and keep the two next to each other? You based your NARB on existing plans that were quite a long rectangle. Do you know if there is a large change in performance or construction requirements for a shorter, wider shape? or if they are too close to each other, will that cause other issues? Sorry, I have trouble settling on one idea and more time to think about things than to actually do them, so the thoughts just go round and round! Jono. Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 4, 2022 Share Posted November 4, 2022 Yes you can. The proper term for these is, "Multiple outlet Burner." Ribbon is just one shape, long and narrow you can make the things just about any shape though you may need to modify the plenum is it's very strange. Ring burners are common and what you describe would be common shape. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 4, 2022 Author Share Posted November 4, 2022 So NARB should really be NAMOB! Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 4, 2022 Share Posted November 4, 2022 That's a BINGO! Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 4, 2022 Author Share Posted November 4, 2022 So regardless of shape (within reason), the main consideration is outlet area in relation to maximum burner tube cross sectional area, right? Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 4, 2022 Share Posted November 4, 2022 Pretty much but don't ask me about calculating outlet # to burner ratio, I never came up with nor discovered one that worked. My intuition tells me the shape of the burner block matters too, the closer to a mono dimensional shape the easier I THINK it will be to get even flames across the block. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
tinkertim Posted November 4, 2022 Share Posted November 4, 2022 I did my NARB development using a half Insulating Fire Brick (IFB) to try out combinations of hole sizes and patterns. Once I found one that worked well, I coated the flame face of the NARB with kiln-wash for protection. Works well for me, and is easy to replace. My 1st attempt would burn back into the plenum behind the IFB, but the second attempt worked really well with a 3/4" burner, and I've been using it in my oval mop-bucket-based forge ever since. Hope this helps. Tink! Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted November 4, 2022 Share Posted November 4, 2022 That shows inlets on two sides. Is that just to show that you can use it in either orientation, or is there actually a function for both of the potential inlets as shown? Quote Link to comment Share on other sites More sharing options...
tinkertim Posted November 5, 2022 Share Posted November 5, 2022 Either orientation. I have a blocking plug for the other. My brick-pile forge uses one port, my oval mop-pail forge uses the other. works a treat! Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 11, 2022 Author Share Posted November 11, 2022 Tinkertim, did you just use a normal drill bit to drill the IFB? And is it a Morgans 26 brick? I have what I thought was a morgans 26 for my forge door and it cracked in half after two decent forging sessions! I guess it's not a morgans brick! Oh well, I have enough castable now that I should be able to cast over/around it and make it one piece again. Then I'll get on to casting some burner blocks! Ok, I've trawled through the NARB thread but I'm not finding what I'm looking for. I think I've got my head around enough holes to balance back pressure between flame lift and back burning. I get the benefits of more, smaller holes and I thought I read somewhere about people trying thinner blocks so they self-cool more easily from the FAM through-flow but now I can't find it and I can't remember if someone tested this or was just discussing it. So: Is there any rule of thumb about thickness of the burner block to aid in preventing back burning? Cheers, Jono. Quote Link to comment Share on other sites More sharing options...
tinkertim Posted November 11, 2022 Share Posted November 11, 2022 Hi Jono. IFBs are normally quite soft and can be cut with an old hacksaw blade or drilled with an old HSS drill very easily. I say old, as the IFB will blunt your best drill bits quickly. I haven't experienced using Morgan Ceramics K26 IFBs, which I believe are longest lasting you can get. Many of my generic K26 IFBs have cracked in a few uses, but with my original brick-pile forge, they were held together with lengths of angle-iron and threaded rod, so that even if they cracked they would stay together. With my later Kaowool-lined oval forge I still used IFBs for movable doors. Regarding using IFBs for NARBs, it is very easy to experiment with drill patterns, and if you start smaller, you can easily enlarge the holes with the next drill size up, maybe a few at a time, to give you finer control as you creep up on that sweet spot of flame behaviour. My first NARB had holes that were too big, so the Fuel/Air Mix (FAM) wouldn't flow fast enough, and so would burn back into the IFB itself and cause the bits of IFB between the holes (webs?) to heat up to bright glowing. Another observation that others made was that if the holes are too big, then the IR radiation given off by the walls of a hot forge can get into those holes and heat up the webs as well. Anyway, when the first design above was used in my 1st brick forge, the flame burnt back into the plenum chamber and burned there, causing the stainless-steel plenum to start glowing yellow hot! The second drill pattern (27 x 5.5mm holes) seemed to be spot on for my 3/4" burner, and would give me a good range of turn-down without burning back into the plenum, and would let me turn it up to full yellow-white heat as well. So, once I'd got a good drill pattern for my NARB, I looked into coating the flame face to protect the IFB. In the UK it is hard to get Plistex or Matricote or other well-known-in-the-USA kiln-washes, so I followed a suggestion of Dan Rotblatt and made my own from Zircopax flour and a Colloidal Silica solution, that he used as an investment coating for metal casting, as well as lining his own forges. These materials were easier for a hobbyist in the UK to find, and worked really well for me. I've coated all of the flame-facing IFB surfaces with multiple layers of this DIY kiln wash and it seems to have really protected the IFBs. I haven't had to re-make my IFB NARB yet (but then I haven't used it for many Months) but I've been very happy with my NARB solution. It is much quieter in use and uses less Propane from my testing. Sorry for the Essay, but I hope some of it is helpful. Tink! Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 11, 2022 Share Posted November 11, 2022 Good essay Tink, thanks. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted November 13, 2022 Author Share Posted November 13, 2022 Thanks Tink, yes, that's a great essay! Quote Link to comment Share on other sites More sharing options...
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