Venturi VS Blown Burners - One Man's Opinion

(Portions of a letter composed 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 five 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 kind.

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 bladesmithing.

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.

Ron

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