James,
I recently fabricated my first two rocket stoves using $25 in parts per stove, and gave one to my local volunteer fire department fundraising auction. It takes just over an hour to make one and it works great. The fuel/vent stand is key for ensuring air flows under the fuel for maximum combustion. The pot grill is key for ensuring maximum heat transfer to your cooking pot without choking the fire.
It was pretty nice the other morning making scrambled eggs without having to use propane, electricity, or the fire pit. The rocket stove is one of the most efficient wood fuel stoves ever devised.
You can find a photo of one of the finished stoves, here.
The following is how I made the rocket stoves:
Materials
– 5 gal steel paint pail from commercial paint store, with lid $12 (or free if you find a used metal paint can)
– 18″ x 24″ wire deck from Lowe’s SKU# 319519 $5
– 4″ galvanized duct elbow $4
– 24″ piece of 4″ galvanized duct $4
– small sheet metal screws
– Wood ashes
Tools
– Saber saw with metal blade
– drill bits and drill motor
– tin snips
– pliers
– vise
– electric hand grinder with metal cutting wheel
– half round file
Fabrication
– Cut the wire deck with the cutting wheel to create both the fuel/vent stand and the pot grill
– Bend legs of fuel stand at stable angle so that top of stand lines up with center of vent pipe when raised off of bottom of pail about an inch
– Taper front end of fuel stand so that three inches of it can fit into vent pipe without binding. Leave two small studs protruding so that they can fit into notches cut into vent pipe
– Mark paint can on side where vent pipe would be centered and draw 4″ circle
– Do the same in center of paint can lid
– Remove foam seal in paint can lid
– Drill starting hole with 1/4″ bit and wiggle to widen hole enough for saber saw blade to fit
– Cut out both circles (don’t worry much about the quality of these holes
– Attach vent to elbow and fasten with three sheet metal screws, avoiding screw at top of vent where fuel will be shoved through
– Measure width of bottom of paint can and cut duct with grinder cutoff wheel so that the pre-assembled 90 degree angle will easily fit in the bottom of the can (it will protrude properly once the duct is centered vertically in the can)
– Attach remaining section of duct to other end of angle duct
– Pre-install duct into both holes to confirm fit, and mark top end of duct at 1/2″ above top of lid and cut off excess duct with grinding wheel
– File cut edges of both ducts with half round file to reduce risk of sharp edges
– Fill paint can with wood ashes and slightly compress with hands as you fill it, while maintaining duct centered in can
– Put lid on and crimp closed with pliers
– Mark horizontal duct 1″ in from edge to align with the two attach stubs and drill clearance hole for fuel stand stubs
– Cut clearance notch in duct slightly above clearance holes to allow stubs to slide along duct and drop into place into the clearance holes like a detent position
– Cut remaining piece of wire deck so that you can bend four support legs and bend the outside corners in a bit to fashion a grill
– Cut the support legs so that the grill stands at 1/2″ (or slightly under) above the duct edge (this may take trial and error, but you want to maximize heat transfer to your pot without choking your air flow)
– You’re done. The commercial guys sell an adjustable pot skirt which directs the heat up the sides of the pot. I might make one of those as an accessory one of these days.