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Gas Forge Question


dbemery

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Yeah, you definitely need more air. There's no great way to diagnose the ultimate problem without knowing more about how you made your burner and your propane supply though.

I'll start with the most obvious to me...

1) There's no forced air going on here, it's just venturi action, right? That looks closest in design to a "sidearm burner." Is this your design, or just trying to figure out how to get someone else's to work? If the latter, I think you need a hair dryer, etc, blowing into the air intake.

2) Are you using a normal BBQ Grill regulator? (small disk in between the tank and the hose) Those don't supply enough pressure to get a proper venturi effect going, where the gas pressure creates enough suction to pull more air into the tube. I used this.

3) What's the inner diameter on the gas/air feed pipe? That looks pretty big. The bigger the diameter, the slower the volume of gas, and slow propane volume = very little suction = very little air. I used 1" diamter black iron pipe. Some people use 3/4" with a smaller jet.

4) What size of jet is your propane coming out of? A welding nozzle, or a drilled hole? As in #3, a larger hole = lower pressure than a smaller hole. You can increase the pressure with the regulator to compensate and get more volume at the same pressure, but we haven't established that you have pressure.



I'd invite you to look over my burner pages. I talk a little bit about theory (as best I understand it) as well as how I made mine, mistakes, and fixes.


http://kcrucible.wordpress.com/the-kcrucible-furnace/

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Gas forge- Additional information.

This is not my design. I bought the forge and an anvil from a neighbor whose husband passed on. The regulator is a Weldmark Oxy Acet
alyne with lots of adjustment. The venturi (lower pipe) is 2" outside diameter. The gas line is 1/2" od. 3/8" id.

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post-13716-032875800 1283988472_thumb.jp

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my forge is similar to yours. same basic design. it needs a blower, a hair dryer has been said to work, but mine came with a industrial looking squirrel cage blower. I'm not sure if it has a high enough output but my solid fuel forge runs off a bathroom fan. for less than $2o it has a great air output. I would suggest if you have a hard time finding a good blower, attempt to use one. they are available at any hardware store such as home depot or lowes.

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Based upon the photos I've attached, how to you propose that a blower (hair dryer, bathroom fan, etc.) be attached? At the bottom of the 2" pipe, at the square hole in the back, new hole???
Also, would I need to set up a reostat to the blower to control the air volume?

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Based upon the photos I've attached, how to you propose that a blower (hair dryer, bathroom fan, etc.) be attached? At the bottom of the 2" pipe, at the square hole in the back, new hole???
Also, would I need to set up a reostat to the blower to control the air volume?

based on the photo, notice the web like material around the bottom of the 2 inch pipe, that resembles duct tape. I would summize the previous owner had some flexible pipe similar to a dryer hose attached there and then the other end if it attached to an air source. and both ends taped to provide a solid seal. My solid fuel forge has a 2 inch pipe and ametal tape used for A/C duct to seal the fan to the pipe. it works well. with the length of the pipe it shouldn't get hot enough to care damage to a fan. you could make a small stand for a fan, or use a block, get creative.

since I see no evidence of a air gate to control air flow yes a rheostat of some sort to control the airflow if using a blower. a hair dryer shouldn't need much adjustment.
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The 2" pipe protruding downward from the gas line seems to act as an exhaust, not an air intake. When the fire is burn, it seems that unburned gas and hot air leaves the chamber through this opening.
I took my wife's hair dryer (set to low)and directed air both up the 2" pipe and through the square opening at the rear. The latter seemed to work the best, but there was too much air. So I think I will try to somehow create an air/gas combo at the gas input. I don't know how yet, but blowing air into the thing seems to be overkill. Thanks for all your help, and any additional suggestions are appreciated.

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That forge is based on the old abana gas forge plans. I built one of those and ran it profitably for years. It needs a blower period end of story. The air flow is usually regulated by a gate valve or sliding cover over the intake of the blower. Perhaps he never finished building this forge or the blower got lost at some time.

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That forge is based on the old abana gas forge plans. I built one of those and ran it profitably for years. It needs a blower period end of story. The air flow is usually regulated by a gate valve or sliding cover over the intake of the blower. Perhaps he never finished building this forge or the blower got lost at some time.


Please listen to southshoresmith. he is giving you the right advice. it needs a blower with a gate valve to regulate air flow. It sounds to me like you really dont know much about this. My suggestion would be to find a local club to get the help you need. Before you hurt yourself.
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The 2" pipe protruding downward from the gas line seems to act as an exhaust, not an air intake. When the fire is burn, it seems that unburned gas and hot air leaves the chamber through this opening.
I took my wife's hair dryer (set to low)and directed air both up the 2" pipe and through the square opening at the rear. The latter seemed to work the best, but there was too much air. So I think I will try to somehow create an air/gas combo at the gas input. I don't know how yet, but blowing air into the thing seems to be overkill. Thanks for all your help, and any additional suggestions are appreciated.

I agree with southshore. The reason it seems to be exhausting unburned gas and hot air is because there is no blower. Force some air up through the tube and you will no doubt see what it SHOULD be doing. Also, follow tireif's advise and get some help from a local blacksmithing org. Finally, I would get rid of the acetylene regulator and get one rated for propane. The hose too. May have worked but the hose looks like oxidized acetylene hose (was red) From what I understand (anyone correct me if I am wrong) propane will eventually deteriorate the rubber inside the hose and clog and similar results will affect the regulator except it won't clog; it will leak. Hope this helps. Good luck, have fun, and above all, play safe and get help. Local propane dealer should be able to help with hose and regulator resources.
Scott
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Some regulators and some acetylene hoses are designed to work for propane as well as acetylene---the regulator will usually be marked "for all fuel gasses" and the hose will be "T" grade IIRC.

Yes air should go up the 2" pipe. Yes it will exhaust if there is no air going up it. It would be easy to slit that pipe and stick in a round piece of sheet metal with two tabs: one to fasten to a pivot point mounted on the pipe and the other to grab to rotate it in and out of the pipe to control air flow.

When you get a good blower, (I use a 150 cfm with my Peot forge) you will need to adjust both air and gas to get the best burn at each level----I have my gas set to the general pressure I like and then adjust the air till the burn is loudest for the hottest burn and back off the air for a more reducing atmosphere for knife making.

You know that in the time it took you to take and post the pictures you could have had it up and working if you had just asked a local smith that's familiar with propane!

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let me repeat what has already been stated, please be careful.
used improperly this forge could be very dangerous. infact mine, working properly, has a tendancy to be a flame thrower for a few seconds whan i first light it

that square hole in the back of your forge is a pass through so you can heat longer pieces. it looks like the blower that was once used on your forge was a quirrel cage blower that had the air flow controlled by a gate across the intake. as for using the hair dryer, try moving it out of the hole and ust blow it towards to hole. the further it is from the pipe the less air gets into the pipe. you might be able to play with that combo a little bit and see if you can atlest get a look at what the forge is supposed to do. however you really do need a airflow gate of some kind. I recommecnd the sheetmetal in the slit design previously mentioned. keep in mind air and fuel both need to be adjusted to get a proper fire. here are some pictures of mine. the blower in mine can be controls with either an airgate on the blower of in the manifold pipe. I have it in the pipe next to the blower.
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The consensus that you need a blower is correct... The suggestion that you find someone with experience with propane forges to learn from is priceless. These forges are relatively safe for folks that know what they are dealing with. They can be widowmakers for someone who doesn't.

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