My Gas Forge Build

I found these fire bricks from a old wood stove.
I’m off to pick up some pipe fittings nowhttps://pin.it/ibxyrlunvwr4dy

 

Don't forget some high temperature clay to seal the joints, ceramic wool helps as well. A pottery supply store should have both used for kiln repair

 

Thanks John,
Yes I did not know about the clay
Have a great day
Daniel

 

The best part is to come, firing up the fire breathing monster

 

I have lots of 1” sld 40 pipe in stock
Plus I can thread
Will this be ok for the burners using a 1-1/2x1 reducer?
Or should I use 3/4”

 

1-1/2" reduced to 3/4" makes a good Venturi at about 9" long with a slight flare on the flame end. This is what mine look like.

 

Yes the shape of the burner port inside the forge chamber can be cast in refractory as part of the forge itself. If the taper is maintained at 1:12 and the burner tube is centered in the port it can be very efficient, but likely won't work very efficiently outside the forge.

I made my burner to work both in the forge and on its own outside the forge. I found it easier and more accurate to taper the inside of the nozzle and have it attached to the burner. Attached with set screws it can be adjusted and set to work over a wide range of pressures. As a bonus, I made it out of stainless steel which stand up better in an oxidizing environment.

There are several ways to make the flare. One is the taper is made by removing material inside the nozzle, another is to forge/expand the nozzle to create the 1:12 taper. Michael Porter has a great book on the subject called Gas Burners for Forges, Furnaces and Kilns.

Dan

 

Dan what is tacked on the top?
Onto the 1- 1/2”nipple

 

On my way out to pick up the 1-1/2” reducers
Hopefully I will find a 30lb regulator today

 

I made a bracket for the gas system. It's a short length of schedule 40 3/8" pipe and a piece of 1/8" steel to hold the gas jet directly in the centre of the intake. A setscrew holds the gas system in place, but lets you slide it in and out to get the best burn. The idea is that it is preferred to have the gas flowing directly into the burner vs. making a right angle turn like in the Reil design. Note that Tim's (Mythtaken's) side arm burner also sends the gas straight into the burner, but the air is coming in at the side and mixing with the gas.

Efficiency is improved when there are smooth direct paths for the fluids to move. Rough edges, steps, blockages all reduce efficiency. I ported the inside of mine like one would port and polish the intake and exhaust ports on an engine head to improve flow. I took a die grinder and smoothed all the rough casting from the inside of the reducer and the step where the burner tube meets the reducer.


Dan

 

Caveat. I am not an expert. Perhaps @FORGE can give us a lesson in fluid dynamics. He makes a very efficient burner.

 

I should end up with 438 cubic inches inside this forge.
I think I have enough bits and pieces to make 3 burners.
Each burner has its own valve
And I plan to make a plug or a sliding door to block off half the forge to save on the gas when doing knives.
Thanks for the tips guys
I just need to find some time now to put this together
Daniel

 

Polishing will improve flow of liquids and gasses, correctly shaped roughness can make even greater improvements. Chances of getting polish good is high but near zero on the roughness due to small size partly and lack of million dollar research budget.
A cousin gave me a nozzle to experiment with that may work much better for a forge and for a quenching system we thought up. just have to get off my rear and start building the assemblies

 

Daniel, those fire bricks look a lot like the ones I used to buy from Canadian Tire which were only rated for about 2000ºF and definitely melt at welding temperatures.

Magnus

 

There about 1.25 thick
Thanks I will look into this

What are fire bricks made of....and where can I find good bricks that will take welding temperatures ?

 

Dan, at one time I would have agree with you on polishing. I now find that the rougher and bumpier the surface the better the gas and the air mix.
In fact on my latest burners I drove a 3 inch long coil spring inside the burner tube on the flair end to mix the gases and it also keeps the flame from blowing out on the end of the burner. If you really want a venturie burner to work put a small blower on the end of it. If you know someone in the plumbing business that scrapes high efficiency water heaters those blowers are perfect for a forge.

 

I agree on the turbulent flow for mixing post fuel injection. My thoughts are that on the intake side we want laminar flow to get plenty of air in. A similar smoothed trumpet shape is seen on velocity stacks that are used on the intakes of some performance engines. The smoother the funnel walls the better the laminar flow, the larger the air volume for the given pressure differential. Venturi burners are essentially Teclu burners by design, only we want larger volumes of fuel/air than these laboratory cousins.

 

The good ones are made of metallic oxides (alumina, silica), I'm not sure what the ones I melted were made of. Pottery supply stores should carry K26 insulating firebrick (I've found the K23 ones to be a bit weak for a forge). Pottery Supply House is based out of Oakville (is that close to you?) and also does internet sales.

Magnus