Gas forge question

[Steve McCarthy]

Because of the mess and availability of coal, I'm going to build a gas forge. I've read a lot and looked at a lot of forges. My question to people that know is, do you suggest forced air or venturi? From what I've read the advantage of forced air is a less picky set up and less fuel consumption. So far the only disadvantage I've heard of is the noise. I'ld really apperciate feedback from who ever has experience with both.

[HWooldridge]

I have both and prefer forced air for the reasons you've mentioned. Depending on the blower used, they are really no more noisy than a venturi (unless you build a BIG one). It doesn't take much pressure to move air and gas so a 60-100 CFM blower is enough for a typical 2-3 burner design. A needle valve in the gas stream will allow you to control the mix to compensate for different atmospheric conditions or types of work. A venturi type can be adjusted to a certain degree but not as much.

[Steve McCarthy]

Thanks for your thoughts. Is a gate valve in the air flow necessary as well as the needle valve in the gas line?

[HWooldridge]

I don't use an air valve on mine but I only have a 2-burner and am using a 60 cfm blower. Something much larger would likely need a degree of air control. Rather than a gate valve, you can cover the blower inlet with a piece of sheet metal and achieve the same thing.

Depending on what you want to heat, a variety of gas forge sizes would be convenient. This winter, I am going to build a long three burner for taking 24 inch heats on pickets - I already have a very small single burner, aspirated forge that will barely hold a horseshoe but is very economical for points and short forgings.

[Frosty]

The basic differences between a gun (blown) and naturally aspirated (atmospheric, venturi, etc.) burners are:

Guns cost more to build and are tied to power but are easy to build and tune and aren't too sensitive to back pressure or stray breezes.

Naturally aspirated is inexpensive and not too difficult to build depending on design, skill level and equipment, are not tied to power and develop plenty of heat but they are more difficult to build and tune because they rely on precision to induce the proper ratio of air to fuel. They are more sensitive to back pressure and breezes.

Either one will produce the same BTU output per cu/ft gas provided they're properly tuned. This goes for ANY type burner.

Most of the noise associated with gas burners is a product of combustion. Just turning the gas on in a NA burner delivers a gentle breeze sound and a gun burner is a bit louder because of the fan impeller blades. Light them up and both types roar like a jet engine. Heck, my coal forge makes more noise when I light it.

Which you choose will depend on variables YOU have to evaluate. If you like fiddling with tools, devices and such, have more time than money or want power independent portability than you probably want to build a naturally aspirated burner.

If you DON'T like fiddling with tools, have a few extra bucks, or just want to get on with it a gun is probably what you want. If you use a 12v blower you can be reasonably power independent only needing a car battery when away from home.

Frosty