Burner comparisons

[Salem Straub]

Damn, Fox Creek, you took the words right out of my mouth. I would be interested to find out from some blown burner guys what orifice size they use. I have the feeling that it's commonly a fair bit larger than a #60 drill. The discussion should not be about what pressures are being used but how many CFM propane are being burnt. (Or what BTUs/Hour you get).

Much ado has been made about the "fussiness" of naturally aspirated burners, but they are actually pretty darn simple and reliable once you build a few. Or the first one, if you do it right. It seems to me that with a good running venturi burner there is less to potentially go wrong as it is a more simple system. If your blower died with your forge running wide open and you didn't notice right away, the results could be bad.

A very real advantage for me in the past with venturis has been the lack of electrical service in a rural shop off the grid. The first that I built was simple and a gas hog. Each burner I've built has been a little better than the one before, and a burner like the T-rex which I don't have the shop to build is much better yet. I've been pretty satisfied with side-arms.

Another factor I think that people sometimes neglect to factor in is the efficiency of their forge insulation. The greatest venturi burner in the world is going to burn a ton of gas to get welding heat in a forge with too big of a chamber and only one inch of cerablanket for a liner, while even a poorly designed blown burner will eat substantially less gas to weld in a forge with 2" of Kaowool and ITC-100. Either burner will suffer in a forge with too small of an exhast opening or heat chamber, as well. Perhaps someone should attempt an efficiency trial with two identical forges side by side, one with a blower and one with venturi, run at the same heat for the same amount of time, monitoring gas consumption.

There are more options available with the blown burner, such as waste oil fuel and ribbon burners that really make me want to experiment further with them. I'm not really biased either way, venturis have just made more sense for me and I feel that they don't get the recognition they deserve.

 

[Mike Krall]

Thanks for the link, Stacy. I've looked over the supplies on Ellis' site a half dozen times, but hadn't ever seen the forge gallery. Based on the consistent stream of input from the forums for the last six months, I decided not to do a one brick or a soup can from the get go. Planning on a 6 or 8 inch pipe, probably 12-14 inches long, with firebrick doors ala Indian George, with 1" of Kaowool with a thin coat of satanite and then ITC 100. Still thinking about burner options, but you have really got me convinced to go blown. Like I said before, I intend to go with a thermocouple and PID for temp awareness, but not to go all in with the SSR for temp control. I've sold a few knives recently, so the funding is in place, now I just have to get past a bathroom remodel and I'll get after the forge building.

I'd be looking for thin wall 7". An old fire extinguisher approx 16" long on cylinder section is perfect... I find them at the dump so an extinguisher service outfit may give one or two to you. One layer ceramic blanket with coatings and one Zoeller side-arm or "Z" Burner with SS flare. Either of those will take 350cu.in. to welding temp. I wouldn't figure to weld in this forge, though a person could make a SS bottom tray to catch the flux. If this forge were 14" the cu.in. would be 279. The 8" with one layer at 14" would be 395cu.in. Either way, a side-arm burner is well matched with the volume for forging.

In some ways, T-rex burners are the best thing a person could have for a forge. They are expensive on first look but they are precision instruments too. I think, if a person was to compare gas use for heat, over time they would pay for themselves pretty easily. They are very controllable, too.

Mike