Posted by joew on January 31, 19100 at 19:25:55:

In Reply to: Re: Burnout furnace plans posted by William Boyer on January 30, 19100 at 05:54:58:

Never having built an oven using a steel drum, all i can offer is some ideas and opinions about related things i am familiar with. A few posts down the page refer to similar setups.

The common burner/blower set-up used on metal melting furnaces, using a 2" blower pipe with a gas-pipe inserted between the blower and the furnace might be needed. Search the net for examples and variations of this type of burner. These are simple and can be built from a couple pieces of steel pipe.

Gas powered ceramic kilns come in many types, downdraft, updraft, etc, using venturi or blower type burners. [Blowers are loud and they complicate matters. If it were me, i would avoid the blower if possible.]

Commonly a burner is pointed straight into the side of an oven (or straight up the inside edge) flames hit a baffle, and are further guided around the interior in various ways. They reach way higher temps than you'll need for lost wax burnout, at least to around 1700 F and go far higher. The burner/baffel layouts and variations for those ovens are illustrated on web sites related to companies that sell kilns. Search for 'Raku' kilns to see something very similar to what you propose.

For instance, at http://www.kickwheel.com/pottery.kilns.html, clik on the picture of the raku kiln (barrel shape with metal frame/pulley to raise the barrel) and read about BTU input and other info for various kiln sizes. These places sell parts, like burners, also.

The rate of temperature rise and top temperature attainable depends on how fast heat escapes compared to how fast heat is input. Even at full throttle a point is reached where heat losses (convection and radiation) prevent any further temperature rise. Heres where the insulating value of the oven is important.

There is no way to calculate how many btu/hour input you will need or whether a blower is needed without knowing the insulating qualities of the oven.

Good insulation conserves fuel. I'm a fan of lots of insulation. Can't have too much of it, imo.

In a well insulated steel barrel, one or two cast iron venturi type propane burners, like from a barbeque grill, may be enough to get the interior up to 1000 F in a hurry and keep it there without using a lot of fuel. I would even try the little camp-stove burners (must be all steel construction, no plastic, no rubber O-rings, etc). Trial and error will let you know if you need more insulation and/or a bigger burner.

Cast iron natural gas burners, as used for kitchen-oven and hot water heaters can be re-jetted to use propane. Ask a local HVAC technician for advice and parts.

Some hot water heater burners are a circular ring type. One might fit neatly into a 20 gallon drum. A discarded water heater comes complete with flame-out shutoff safety valves and lots of other nice stuff too.

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