Venturi VS Blown Burners - One Man's
(Portions of a letter composed in 2002 by Ron Reil with minor editing)
The burners now available
of the Venturi design, both to build yourself and to buy through HybridBurners, are
light-years ahead of those available a few years ago. Over the past two
years Mike Porter in Seattle, Rex, and I, have put in hundreds or perhaps
even thousands of hours in design and testing to develop the full potential
of Venturi burners. I was the least involved because I was critically ill
for almost a year of that time, but kept connected with them via the Net.
These burners now run very hot, much hotter than Damascus welding requires,
and have a range from a cigarette lighter flame to a small jet engine, and
they are instantly tunable across the full pressure range for an
oxidizing/neutral/reducing flame by a slight adjustment of the choke. They
are simple, clean, and independent of external power requirements of any
A blown forge will work
very well, but you will not be gaining anything over a good Venturi burner
forge but complications, noise, and difficulty of tuning, although the tuning
may be almost identical depending on the blown forge design. You will not
be gaining more controllability with a blown forge. You would
have 5 years ago, but not today. Everyone on the net knows I am a total advocate
of naturally aspirated burners, and have been for a number of years, ever
since I developed the Reil and EZ burners, but it is not a blind dedication.
The Reil and EZ burners, as first developed, had a very narrow operating
range, 2 psi being the low end, but now these burners operate from zero gage
to whatever you wish to crank them up to, 40, 50, 60 psi, although I never
exceed 10 psi for Damascus welding, and normally go no higher then 8 psi.
I have a shop that I spend many hours in every day of the week, and I require
a forge that can do whatever I require of it quickly and efficiently, in
fact a number of forges....the latest, for big scroll work, still not completed.
If there were a better way to heat my forges I would be using it.
You could build a Side-arm
burner that would meet your needs, but there is no substitute for the T-Rex family of
burners. The perfection of Rex's machining, and tuning of the geometry of
the burner, has created a burner that operates smoother, and across a greater
pressure range, than any other out there, commercial or home made. Most of
his burner models will actually run perfectly right up to the operational
limit of an orifice produced gas stream...that being the velocity of sound.
He has even gone so far as to perfect the "step" distance for each burner,
that being the enlargement from the interior burner tube diameter to the
interior of the nozzle diameter. He was one of the first to realize that
the step distance was a critical parameter that needed tuning also. Mike
was also deeply involved with this development.
There is another
consideration that you should think about too. Most blown burner forges are
chamber burn forges, that is, the cold gasses are mixed and then injected
into the forge chamber to burn. This has several distinct disadvantages.
One is the injection of cold gasses into the chamber. The chamber will have
areas of relatively cold unburned gasses circulating around in it that may
or may not be of consequence depending on the geometry of the chamber. The
other is the fact that such a design injects raw oxygen into the chamber
that can make its way to your iron, and that is a concern. The Venturi burners
employ a nozzle burn, and the burn is mostly complete within 2"- 3" of the
burner nozzle, so the gasses entering the chamber are at or above chamber
temperature, and the oxygen has been completely consumed.
I will add a few comments about
forge designs, and perhaps bring up some factors
you may not have considered. Satinite has been replaced by ITC-100 for about
5 years now. Satinite is a refractory wool stabilizer and nothing more. ITC-100
is a Zircon sand, or similar material, based IR reflective coating that reflects
98% of the IR radiation that strikes it. Most of the heating in a forge is
due to IR radiation, not conduction from the chamber walls or floor. The
idea of building forges with massive solid refractory walls for the heat
reservoir the walls provide in order to more quickly heat the iron is simply
not supported by the reality of thermodynamics. By reflecting almost all
of the IR back into the chamber it becomes much hotter, several shades of
yellow or yellow/white hotter, depending on the gas pressure, so your metal
will heat much more rapidly. Also you can realize about a 30% savings in
fuel, depending on how you run your forge. You may use ITC-100 on refractory
wool, poured or rammed refractories, or ceramic tiles. It works equally well
on any kind of refractory material.
You may be committed to
building a forge that has a minimal heating length, the distance between
the two openings in the side of the vertical pipe forge design, and I am
not sure I understand your reasons for being so self limiting, but here are
several things to consider. By building a horizontal pipe forge that is set
up with idle/full control valving, and individually valved burners, you will
enjoy a further savings of fuel by being able to use only as many burners
as needed for the particular job, and also being able to instantly drop the
forge from welding heat, if that is what you are doing, to a low idle pressure
while you are at the anvil or power hammer, and when you return to the forge
instantly "ramp up" to welding heat. This design for your plumbing can save
you as much or even more than the ITC-100. I don't know what island
you are going to, but I spent a lot of time in the Aleutians doing precious
metals exploration, and I know the cost of supplies there, and this would
be a huge benefit to you up there. Further, if you will look at the forge
design I employ for my main forge, the four burner one, I use a bottom slotted
movable back wall inside it. I don't do many blades, but do a lot of other
long items where I want to heat only a small portion at any one time in order
to protect the surface of the part I am not working. For these items, I move
the wall up so I am running one burner only, and then I can slide the item
in so that it slides under and past the wall, thus allowing me to heat only
a few inches at a time, and preventing the remainder from heating and scaling.
If I need to heat 20" of metal for straightening, tempering, or bending,
I just slide the movable back wall towards the rear of the forge and light
another burner(s) as necessary. I never use more then two at any one time
now. I needed three on occasion until I switched to T-Rex burners. Unless
you are planning to have a number of forges, you will be greatly limiting
your abilities with a vertical pipe slot forge unless you are truly a one
trick pony. If you go with a forge of this type, you will need at least one
more forge for general smithing needs if you do anything other than
A vertical pipe forge
is not a do-all forge, and in fact is extremely specialized, to a degree
that is unsuitable for most shops. Based on my experience in the Aleutians,
I suspect you will be having a lot more use for your forge and metal working
abilities than just to make blades. I have spent time on a number of islands
up there, and if I had my forge with me I could have made a lot of money
with it in some of those locations, especially when I was living in Dutch.
Just some thoughts that you may or may not be interested in.
I hope I have answered
your question in all of my ramblings on. You can't do better then Rex's burners.
Buy one T-Rex 3/4" burner, hook it up to test it, and see for yourself. I'll
bet you will want several more before you head up there.
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