forge question

D

dolby77

Joined
Nov 9, 2013
Messages
6
Hey Guys,

I'm pretty new to this whole process and I'm trying to set up a small forge. I have the venturi burning but my forge doesn't seem to be getting red hot. Is it too open to heat up or am I not waiting long enough (I waited about 10 minutes and still not red)? I put in a blade and the handle, which was sticking out of the forge, got red hot and the blade was still not. The propane tank as an 1" of inslwool and two coatings of satanite. Check the link to get an idea of what I'm talking about. I know the forge isn't secured well...I was just trying to see if it was working.

http://imgur.com/hfVJoIq

Any help / suggestions / information would be great

Thanks
 
Looks like the forge body is to small for that size burner do you have a hole in the back also? How far is the burner inside the forge body?
 
Haha that is a funny little guy, sorry it just made me laugh. Yeah that forge is really small for that size burner. Good job on the burner but yeah the forge I would go larger with the forge body. No reason not to since it looks like you made a good burner.
 
oh yea... You got to change that up a bit. You took the time to build a decent burner. Now take the time to build a nice forge.
 
Well, I made two...one with a hole in the back and one without. Neither heated up nicely. The burner is about level with the satanite on the inside.

So you think if I just tried a propane torch it may work?

thanks for any suggestions


tump said:
Looks like the forge body is to small for that size burner do you have a hole in the back also? How far is the burner inside the forge body?
Click to expand...
 
Something with a chamber after insulation that is 4"x12" would be good. With 2" of kaowool and your satanite. Should get to forging temps.
 
Well that burner should support a forge chamber around 200 cubic inches. So a 8" diameter cylinder with 2" of kaowool per side would give you a 4" chamber diameter. You could go any where from 12" to probably 16" and still hit welding temps. I guess. My forge is being rebuilt if I ever make it home. I was forging way to cold in a fire brick bodied forge.
 
Yeaaa it is a bit on the small side, but I thought since I didn't need anything huge for what I wanted to do, smaller would be more efficient. I guess I still don't understand why it wouldn't heat up properly.

quint said:
Haha that is a funny little guy, sorry it just made me laugh. Yeah that forge is really small for that size burner. Good job on the burner but yeah the forge I would go larger with the forge body. No reason not to since it looks like you made a good burner.
Click to expand...
 
Go to your local AC shop and ask if they'll give you one of their empty coolant tanks. Perfect size for that burner. I put two burners of that design into my propane tank (20# propane tank, not the little bottle like you have) and they get me almost to welding heat. One burner gets it forging hot with no issues.

J-
 
dolby77 said:
Yeaaa it is a bit on the small side, but I thought since I didn't need anything huge for what I wanted to do, smaller would be more efficient. I guess I still don't understand why it wouldn't heat up properly.
Click to expand...

All the heat is in that blue flame out the front of your forge body. Basically that little forge is just an extension of the burner, nowhere for the heat to be trapped and stored.
 
What homebrew said. Small is fine but too small and there is no vortex of the flame inside the forge. That vortex and a slightly larger body allows more heat to be maintained in the forge.
 
The forge is WAY too small. Most of the combustion is happening outside the body cavity.

Does your tank have a regulator on it? What pressure are you running?
 
The chamber is definitely too small.

I think this is probably causing a restriction at the hot end of the burner which slows down the mixture passing through the burner tube and prevents the "Venturi" part drawing in the amount of primary air that it should. The result is that you have a rich mixture and too low a temperature inside the forge. Once the gases get out to the atmosphere, they can finish burning and generate more heat in the process; likely the reason the blade kept cool but the handle (in the secondary flame) got hot.

What is needed is either less gas or more primary air.

Because a Venturi should give a reasonably constant air:fuel ratio over a reasonably wide range, just turning down the gas pressure will also turn down the primary air. I say should because the restriction due to your small chamber most probably upsets the relationship.

If you really need to stick with what you have, you could try fitting a smaller gas jet, along with a choke. This might get you running but it's far from certain.

It looks like your setup is a drilled hole, so it is a lot of faffing about to do.

I'd get 3 or 4 of the jet tubes and probably a couple of sets of 60-80 number drills (because it's way too easy to break them).

Start with a hole half the size of your present one or, failing that, the smallest hole you can actually drill, fit it, test it, drill the next size up, test it again and so on.

The first one or two probably won't even burn. There's a good chance that the first one that does burn will tend to burn very hot and the flame will run back down the burner tube. You can try increasing the gas pressure a bit to try to stop the flame running back down the tube, but there will be a limit imposed by the forge restriction and you'll probably have to keep going up on jet sizes.

Once you get to the smallest jet size that gives a stable flame, it will probably be way too hot and show no dragons breath. Fit the choke and choke down the air gradually. As the dragons breath increases, the temperature in the forge will come down and you should be able to get things about where you need them.

Keep the original jet tube. When (not if) you make a bigger forge, it will not be as restrictive and you'll need the bigger jet.

Unless you are deeply geeky and will actively enjoy the process of tuning the burner, take everyone else's advice and build a bigger forge.
 
It's not a forge issue, but a burner issue. I'm guessing, only becuase you haven't told us, that your burner has a .035 mig tip for a jet? The forge you are trying to use it on is basically acting as a flare. With that size of forge, a simple propane torch would have adequate BTU to forge small metal with.
 
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