Deep Fryer / Boiler
The burner is made from the scrap end of 2-7/8 drill stem, a piece of 1" black pipe, and some 1/8" flat stock.
The length of these pipes doesn't seem to matter.
I just used whatever was in my scrap pile.
The top of the burner is set down in the stand about 1-1/2".
This gives plenty of room for the flames to flare out around the pot.
Don't laugh too much about the rings. I don't have a ring roller. These were bent with a vice and a hammer.
The two pipes are joined using a piece of 1/8" flat stock.
I don't know how critical the diameters of the pipe are.
You need the bottom part to be small diameter to make a ventrui.
This draws fresh air in the bottom and lets it mix with the gas to get a good burn.
You need the upper section to be a larger diameter.
If it's too small, the speed of the gas/air mixture is too fast.
This will make the flame blow out the top and go out.
It might be better to have the small diameter smoothly transition into the large diameter.
I didn't want to go through the trouble of trying to build a cone shaped piece.
The sharp step between the 1" and 2-7/8" pipe doesn't seem to cause any problems.
It may actually help the gas and air to mix better since there's some turbulence at the step.
The small hole at the side was for a flint striker made for a coleman lantern.
I found out later the burner gets so hot it ruins the temper in the spring that holds the flint against the striking wheel.
No spring means no pressure on the flint and no sparks.
It was a nice idea, but I'll have to find some other way to do a built-in lighter.
I may try a very small jet in this hole to act as a pilot light.
The jet for the propane is stuck up into the center of the 1" pipe by about 3/4".
You can have the jet be below the pipe. You get a little better mixing that way, but it also lets the wind mess up the gas flow.
Putting the jet up inside the pipe a little protects it from wind.
The ghetto hose clamps were used for testing the position of the jet. I've since replace this with a proper way to screw down the tube. I found out the valve isn't needed either. You can adjust the pressure via the regulator. It's too hot to be reaching under there and fiddling with the valve anyway.
The jet is made from 1/4" copper tubing. I cut a short length of tubing and put it in the clamp that goes with my tubing flaring tool. I didn't use the flaring die on it though. Instead I took a round blunt nose punch and went around the tube lightly tapping the punch with a hammer. This makes the end of the tube roll over and close off the tube. After I had the end of the tube well sealed off, I filed a flat spot across the end. Then I took a #70 drill bit and drilled the jet hole.
I originally tried to run this burner on a fixed pressure regulator for a normal propane grill.
I think that regulator only puts out a pressure of a few inches of water column.
It burned ok, but the heat output was too wimpy.
Here's the burner running on an adjustable propane regulator for a cutting torch.
This is about 2psi.
This is about 20psi.
There's not much change in the flame, but you can definitely tell there's way more heat output
Without the pot the flame shoots straight up. When you put a pot on the burner the flames flare out and surround the pot.
Holy inferno, batman!!
It's hard to see since the flame is so bright, but the pieces of flat stock that support the pot are glowing red. The top half of the burner is red hot also. Now we're cooking with gas!
This test run took 2 gallons of water from tap water temperature to a full rolling boil in about 7 minutes.
One BTU is approximately the energy to heat 1 pound of water 1 degree F.
2 gallons of water is 16 lbs.
Initial water temperature was around 80F.
16 lbs of water heated 132 degrees F in 7 minutes gives around 18000 BTU/hour.
That's 18000 BTU of delivered heat. There's tons more that was lost to the air.
I should find some way to measure the amount of propane going into the burner and try to compute the efficiency.
Here's the improved way to mount the jet. The bottom connection is a "B" size left hand threaded fitting for fuel gas on a cutting torch. With the same fitting on the propane regulator I can use a standard hose to connect the two (be sure to get the proper grade hose for use with propane)
I've also built a foot controlled "gas pedal".
With this you can turn the heat up or down with your foot.
This is great when you're finished frying a batch and you don't want the oil to overheat while you're scooping it out.
You can stomp the pedal right before you dump in a cold batch.
With the high output burner, you're back up to the proper temperature quickly.
The pedal base is 1/2" steel.
It's heavy enough it won't move around during use.
The pedal doesn't push down. It rocks back and forth, and there's no return spring on the pedal. So it'll stay at the same setting when you lift your foot.
The handle on the ball valve is connected to the foot pedal via a nut on a rod. Adjust the nut and jambnut so the ball valve just cuts off when the pedal is in the off position. The small valve on the side is adjusted to let just enough gas pass to keep the burner lit when the pedal is off.
Again the fittings are standard fuel lines for cutting torches.
One line comes from the regulator. The other line goes to the burner.
Here's the setup ready to cook!
With the pedal wide open, set the pressure on the regulator to set your maximum heat.
Then with the pedal off, adjust the small valve to set your minimum heat.
You can then use the pedal to set the heat anywhere in between.
Also see the griddle and single burner stove I built.