Pwknives Posted February 4, 2019 Share Posted February 4, 2019 I just finished the build of 2 ribbon forges. These are the first I have built and I am having trouble with back burn. They light great but if I tune it to a reducing flame that produces a small dragons breath it will back burn once the forge heats up. If i increase the air supply to cool the ribbon it does not back burn but also does not get hot. The only thing I can think of is I have to many holes. My burner is 12"×3" with 35 23/64" (crayon) holes. 2" supply pipe feed by a 4" blower producing 300 cfm. I do have a gate valve after the blower. I am running a regulator but not a needle valve for a propane supply. I have tried several different mig tips for fuel supply .035 and .042. It back burns fast with the .035. I have tried Propain pressure from 7psi to 15psi I see in Wayne Coe build he uses 26 crayons. To reduce holes to test it do I have to cast a new burner or is there a way to plug these to dial it in before I cast a new burners? Or any other feed back would be much appreciated. If I had hair it would be pulled out by now. Very frustrating. Paul Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 4, 2019 Share Posted February 4, 2019 Welcome aboard Paul, glad to have you. If you'll put your general location in the header you might ve surprised how many of the gang live within visiting distance. Unless you want to up the air and propane you have WAY too many outlet holes. For experimenting just plug them with a little wadded up Kaowool or equivalent. When you find the number and arrangement of outlets you like make the plugs permanent with hard refractory. Easy peasy, Yes? The rule of thumb for what's happening here is: the larger the outlet the slower the flow whether it's a rocket engine or a garden hose. Yes? If the FAM (Fuel Air Mix) velocity falls below the rate of propagation the flame front goes where there's fuel to burn, the plenum or maybe clear to the gas jet. I don't know why guys making gun burners started using mig tips when just drilling a small hole in the final supply pipe works so well. Gotta remember the same rule for burning back in the burner block applys here, if the jet hole is too large the pressure from the blower will force air up the gas supply pipe and shut it all down. Yes? That's quite the forge you have there. Do you always run them together? I have to wonder if shutting one burner down doesn't increase combustion air pressure to the other enough to effect it? Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Pwknives Posted February 4, 2019 Author Share Posted February 4, 2019 Great to hear from you Frosty. I was hoping to pick your brain. I am a Alaska smith myself. Sterling. I will add .y location to my profile. Thanks. I was curious if plugging some holes with kaowool would work or not. Didn't want to build a bomb. That is what I will try now. I do not run the forges together. One box is for dry forging and the other for flux. I ended up using a mig tip because copper is easier to drill with those small bits then steel. Thanks so much for your expertise, I have been following your posts. And please stop in on your next trip to the peninsula. Thanks again PW Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 4, 2019 Share Posted February 4, 2019 Sterling! We're almost neighbors! Very cool, give me a shout if you need to come to the big city, we'll hook up. Heck I might even clear enough room to stand in the shop. Please feel free to pick what's left of my brain, it's my pleasure. Two points: 1, copper alloys are harder to drill than steel UNLESS the bits are sharpened to the correct edge angle. I've lost too many small bits trying to chase contact tips to larger DIA. Torch tip filles work much better and don't leave a burr to clean out. 2: Mig contact tips aren't copper, they're Byrillium bronze so be VERY careful of cutting and grinding them, byrillium is darned toxic. Small bits are a different skill set even though drilling is drilling at a fundamental level. Tiny bits need the target to be rock steady, down pressure light and rpm low. Not as low as if it were oversized bits. No shortcuts though, buy bits by the package they're cheaper by the dozen. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Pwknives Posted February 4, 2019 Author Share Posted February 4, 2019 Yes we are. And I will.take you up on that invite someday for sure. I plugged 9 holes. I am getting a sweet dragon's breath at 10psi. My question frosty is "what is the proper flame structure? I am welder and work with neutral flames with a torch. Do I want the same cone structure or what I call a oxidizing flame to prevent burn back? Guess the question is do you use so much air the cone leaves the block? Thanks again and I think I am getting alot closer. PW Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 8, 2019 Share Posted February 8, 2019 It's not an oxy fuel flame so the structure isn't the same, no primary cone, secondary sheath or tertiary. I've had to change my thinking about tuning the flame ideally it's a pale partially opaque primary with a nearly transparent tertiary. Oxidizing is a BAD thing in a propane forge it generates scale on the scale in the forge. You want a neutral or SLIGHTLY rich flame. Check out some of the recent burner flames in Burners 101. Mikey is better at reading what's a better flame than I, I'm still adjusting my view of what's right. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted February 8, 2019 Share Posted February 8, 2019 Acetylene was the king of torch fuels for more than seventy years; because its molecular makeup is carbon heavy, a truly neutral oxyacetylene from always has a primary and small secondary envelope. Only oxygen rich (lean) acetylene flames have no secondary flame envelope, and these are only good for cutting; not for welding, brazing or heat bending. So the average welder or fitter in a shop gets used to seeing only one kind of neutral flame, and doesn't adjust his thinking for other fuels and oxidizers (like air). We see what we expect to see Twenty years ago, It was a wrenching readjustment for me to realize I had fallen into that same trap. "...a truly neutral oxyacetylene from always...' should read "...a truly neutral oxyacetylene flame always...' Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 8, 2019 Share Posted February 8, 2019 Well in the olden days there were a few other reasons too---you could generate acetylene on site using calcium carbide A lot of the "old" shops still have an acetylene generator piled under a lot of junk. Didn't have the industrial support for a lot of the compressed gasses we have today. (Of course such generators blew up fairly often too.) Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted February 9, 2019 Share Posted February 9, 2019 Fortunately, business finally came up with an exceptionable substitute for acetylene--propylene. MAPP gas was nice, but still had similar explosive problems to acetylene (in the hands of idiots). TIG is an acceptable alternative for acetylene for welding ferrous metals, if no where near as fun Quote Link to comment Share on other sites More sharing options...
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