When a woodfire is accelerated by charged air, it is transformed into a powerful force. Do you need an on-demand incinerator, metallurgy forge, or stump-burner? This device will suit that need and more!
I was first introduced to this problem while cooking maple syrup in my backyard. It was difficult to keep consistent heat on the evaporator pan without having to use the cured (and expensive) cordwood I used to heat my home.
While digging through a dumpster one evening, I found a bathroom ventilation fan. With a few small modifications, it was transformed into FireCharger Version 1.0. The motor was still mounted in a large electrical box, so I wired a light bulb on top, and used some old aluminum ducting for the exhaust. I then pointed the blowing air into the base of the fire and Voila!
I was able to burn green or over-seasoned wood at high enough temperatures to achieve a rolling boil (this technique is common in maple syrup arches). I then turned this new-found device on a rotten brush pile that needed to be hauled to the stump-dump. I burned through it it a few days while enjoying a white-hot, nearly smokeless bonfire. It worked well for a few seasons, but in the meantime I horded as many electric blower motors I came across in preparation for bigger and better things.
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Step 1: Motor Installation
The problems I experienced with the original version were addressed in V.2.0, and later enhanced in V.2.5. These included: weatherproofing, inflexibility of exhaust duct, fire plunge-depth, portability, efficient lighting, and overall aesthetics.
1 Blower Motor Assembly (holy crap! Don't buy a new one, dumpster dive)
4" Flexible Vinyl Ducting
1/2 an Outdoor Floodlight Fixture(optional)
3/4" Plywood Scraps
Misc Deck Screws
46 oz Steel Can (V-8 Juice, or 'SIimer Hi-C EctoCooler')
3' Length of 1 1/2" Steel Pipe (size and length may vary)
Using scraps of plywood, make a mount that will support the motor in the litter container. Make sure it can squeeze into the small opening in the top. Cut a hole if needed to supply the intake, the screw them together. Attach the motor with more wood screws, then mount the light (optional).
Slip the motor assembly into the container; mark holes on the front and side for the ducting and the intake. Remove motor, cut holes, then set back in container. Screw it to the bottom and sides from the outside (using gasket if provided).
Cut a small hole in the top (or side) to supply the power cable. Run the vinyl ducting through the hole in the front and loosely place it in front of the blower's exhaust, then use duct tape (liberally) to secure to the front of the container.
Step 2: Piercing Nozzle
Steel Can Coupling:
The simplest way to join flexible vinyl ducting with a heavy steel rod is to use a 4" diameter steel can. The cans I have used came from large 46 oz cans of V-8, but I'm sure there are other brands out there that use them. Anyone remember Hi-C cans? Boy, I must be getting old.
The process is simple; trace the pole on the unopened end of the can. Drill a hole in the center, then use a tin snips to cut wedges (about 12) and leave them hinged on the can. Use a pliers to bend the hinges out (careful, sharp edges; wear gloves). This now leaves a hole for the steel rod to be threaded through; make sure to leave a length inside the can for stability. Wrap duct tape around the exposed, jagged edges to secure them to the rod (use tape liberally). Now simply insert the end of the vinyl ducting into the other end of the can and duct tape it shut.
*There is an awesome irony with the term 'piercing nozzle'. Other Firefighters out there might know a piercing nozzle is used to inject water through an otherwise impenetrable surface to extinguish a fire. This nozzle instead is used to accelerate a fire by injecting air directly to the center of the embers.
Step 3: Implementation
I briefly mentioned a few uses for this device earlier. I'd like to take a minute to go a little more in depth on how this device can be used to it's full potential, and it's most interesting qualities.
The Clean Burn:
By accelerating a fire with forced air, the temperature increases. The hotter the fire, the cleaner the burn.
I used these devices to burn down a giant maple stump. My only other recourse was to bring in some heavy (and expensive) machinery to dig it out. The fire was fueled by brush that I would have otherwise had to haul off to the local forest service burn pile.
As the blower operates, occasionally the piercing nozzle get buried in hot, charged embers and begins to glow red-hot. Metallurgy is not my forte, but I'm confident that these temperatures are appropriate for metal forging. Check out these instructables.
Backyard Maple Syrup Production:
Maple Syrup is created by collecting diluted sap from sugar maple trees in the spring. You then boil the liquid so the water evaporates and leaves the sweet, sweet syrup behind. One of many hindrances in this activity is gathering the fuel source (traditionally wood) to run the evaporator. Using this device, you can burn less-than-optimal wood (not the precious cordwood you burn in you house to keep your family warm).
The Tire-less Bonfire:
Nothing gets a bonfire going quite like a tractor tire, just don't stand downwind. Instead, skip the tire and just charge the fire with fresh air to burn it clean, and hot!
I haven't tried this yet; it's still in the theoretical stage. Compost is broken down by microbes. Microbes need air and heat to grow. Injecting air into your compost bin hypothetically should increase the speed of decomposition. There is some science to support this, however, it might as well be anecdotal for me at this point.
Ok, I'll admit it. I'm getting to the bottom of the list. Really scraping the barrel here. But perhaps you could build a Bubble Machine? You know, the kind of thing they use at kid's birthday parties . . . or raves. It would just need a pinwheel with bubble rings attached, so as the air turned the pinwheel, it also blows bubbles, and the wheel dips into the soapy mixture.
Thanks for making it all the way through my instructable; your patience did not go unnoticed. Please check out some of my other works, and let me know what you think. I have a strong appreciation for the openness of this online community, and constructive criticism is welcome!