Here is a photo of the first run of the test burner. The burner is a scrap of old steel pipe. It's held in a vise and has a raggedy sheetmetal flare on the end of it. The flare is needed just like on a "self-aspirated" burner. The valve on the MAPP® gas tank must be completely open to produce sufficient fuel flow. The blower is the same blower I used for my charcoal furnace when I first began metalcasting. This dirt cheap rig proved the concept works! This is a 1" burner pipe but the flame was similar to a 3/4" venturi burner flame. Click photo for a larger view
This is a comparison photo of some common gaseous fuels. On the left is the typical barbecue grill type propane tank. The popular "self-aspirated" a.k.a. "atmospheric" a.k.a. "venturi" burners require the propane capacity and pressure that these tanks put out. They also require a high pressure regulator. The yellow tank is a disposable MAPP gas tank. These are often used in place of propane in hand held plumbing soldering torches. On the right is a typical short propane tank and next to it is the taller version. Both are disposed of when empty. I have not tried these small tanks with an atmospheric burner but it seems to me that they are more suited to a "forced-air" burner because of their smaller gas quantity.
MAPP® gas (C3H4) is produced by combining liquified petroleum gas with Methylacetylene-Propadiene. It can produce close to the heat of acetylene but is as safe to handle as propane. A neutral MAPP gas flame is 5,301° F. (2,927° C.) MAPP is actually the trade name for the gas and is owned by Dow Chemical Corp. It is known as "Razergas" in Australia and is trademarked by ELGAS. The gas is stored in liquid form (like propane) and is available in disposable tanks as well as in bulk quantities and is used for welding, heating, brazing, flame cutting, soldering, flame hardening and metallizing.
A cylinder containing 70 pounds of Mapp gas can do the work of six-and-a-half 225 cubic foot acetylene cylinders. At 70° F. MAPP gas tanks have a pressure of 95-97 PSIG all of which can be used (unlike the safety limit of 15 PSI for acetylene) making it good for underwater work.
To get sufficient fuel flow from the tank the torch head must have the rubber gas restricting diaphragm removed and discarded. This lets about 10 times more gas flow out the tank once the valve is open, lovely... This is actually an older torch head design. Modern torches restrict the gas flow with a tiny hole in the brass torch neck (yes I've modified that type also!). A torch head should NEVER EVER be used with the regular soldering tip with this diaphragm removed!! It is sure to void the warranty. Oh... and it's probably dangerous also. :-)
The second modification is to cut the stem off the torch head (the thin tube and the part that the flame comes out of) leaving a short section of the stem and solder on either a hose barb or a section of brass nipple as I did.
Here is the modified torch head with a coupling installed to attach the hose barb. I probably should have just soldered the hose barb to the torch head. The assembly is now ready for the vinyl tubing.
Here are the two main type of regulators. The red one is an imported high pressure regulator. This type is required for the "self-aspirated" burners. This regulator can be adjusted to various pressures usually 0-30 or 50 PSI by turning the handwheel. On the right is a typical low pressure regulator as found on most propane barbecue grills and some other low pressure propane appliances. These regulators are preset to one low pressure output. Therefore a blower is needed with burners utilizing these to get the propane/air mixture moving through the burner.
Here is a clearer view of the Mapp gas foundry burner. In this photo I have the Mapp gas cannister in a special holder I built for it. You can also see the vinyl tubing and burner more effectively. Note the simplicity of the setup. Also notice the tape over the air inlet at the top of the blower. The tank was running low on propane and therefore the air had to be decreased to keep the air/gas mixture correct. Click photo for a larger view More experimentation including melting metal with Mapp gas is planned.