FireCharger

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Introduction: FireCharger

Introduction:

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!

The Genesis:

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.

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.

Materials:

1 'Tidy Cats' litter container

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)

Duct Tape

Plastic Staples

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)

Motor Mount:

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.

Brush/Stump Removal:

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.

Forge:

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!

Compost Accelerator:

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.

Bubbleblower:

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.

-Post Script-

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!

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    43 Discussions

    I think you could have accomplished the same thing with an electric hair dryer and a length of pipe with duct tape sealing the connection. I mean if you already have electricity, a $15 hair dryer puts out a lot of air in a hurry.

    2 replies

    You certainly could do that. That misses a few of the subtle problems I had to contend with: power consumption (hair dryers are notoriously inefficient), weather proofing, and durability. Also, ethically speaking, I'd rather recycle some good old-fashioned American garbage than buy some Chinese-made garbage at Walmart. Thanks for your comment.

    I lived across the street from the passive solar house experiment in Raleigh at NC State my first few years in college. That was in the early 80's. Too bad people did not adapt their lives in that direction. I have now lived in a late 70's passive solar house since '99. We don't have air conditioning and rarely use the heat pump. I supply the house wood furnace with just a bow saw. We cover the green house in summer with tipi covers to create a cold summer house. This past winter I started flipping the bow saw and cutting with teeth up. This seems far more effective than teeth down. I run the small limbs over those big teeth by placing the saw between my legs and stepping on a stick on the bottom of the bow. I really just used limbs this whole winter and spent far less time cutting.

    Kudos to the author. I used a car blower motor to add air to my brick smoker/grill using your ideas. Connected it to a small solar panel system I use to ventilate the attic. It works because the sun is generally out during both activities. oh, and to those who use a hair dryer, check your local thrift or secondhand store. They also might have a kitchen blower or other fan.

    2 replies

    Variable speed leaf blower is about $60 USD at the home supply stores.

    This is excellent! I'm going to use this idea to supplement my double barrel stove I'm building to heat the workshop :).

    Thanks very much for you taking the time to make this :)

    1 reply

    The microbe idea actually works in a real-world application: aerobic wastewater treatment systems. There is a pump sending oxygen into the first tank where bacteria are constantly breaking down the solid waste. The liquid waste flows over the top and is mixed with chlorine on the way to the second tank. From there it is pumped out to sprinklers.

    2 replies

    What do you suppose is the best practical application to, say, a compost pile? I've considered using PVC conduit with air holes at the base of my heaps, but I'm concerned they might restrict the pile from being turned with a pitchfork. Would you even need to turn the pile with such airflow? Food for thought I guess. Thanks for the insight.

    We always turned by hand. I so wished we had a machine. Worked well enough except the one time our 5' high 12' cylinder dried out and the sun set it on fire.

    1. What is the purpose of the light?

    2. Why did you use the plastic flexible ducting and not he metallic type?

    3. Have you considered a dimmer switch on it to control air flow?

    Those questions aside this was a good build for anyone that has access to second hand materials that are typically free, otherwise a leaf blower and metal pipe are the way to go.

    4 replies

    It appears the light in the bucket is the most popular question, so I'll address that first:

    1. When I'm using this device (whether it be boiling syrup or burning brush), I'm usually burning well into the night. The fire is usually a worksite of sorts, so I'm regularly grabbing wood from a pile, or cleaning the rim of the fire of debris, or just trying to figure out where I set my beer,

    2. It can be a safety hazard walking around a fire at night (in sometimes adverse weather conditions) so having an auxiliary light is helpful,

    3. The kitty litter container is translucent, I had the ability (and hardware) to wire the light, so heck, why not? Seemed like a no-brainer at the time.

    Second, the vinyl ducting vs. aluminum ducting:

    I originally used 'flexible' aluminum ducting on my first prototype. It functioned, however, I found it's inflexibility too be frustrating. If the direction of the airflow had to be adjusted, the entire unit needed to be moved around. It led to the development of the inflammable piercing nozzle as the contact point with the heat, and the not-so-inflammable vinyl ducting that allows for free movement. I think it's a good balance.

    Third, dimmer switch:

    Great question! I have thought about it quite a bit, and honestly, I haven't come across one without having to buy a new one. Lame, right? I'm cheap, I can't help it, and I've come to accept it. I know this much though: it can't be a dimmer switch for a light (can't handle the modest amperage) so that means it has to be a control switch for a blower motor (which are relatively common in these days of Amazon.com, but $30 is a little rich for my blood). Maybe Version 3?

    Thanks for the poignant questions.

    Please pardon the electrician here. Historically, all dimmer switches are resistive or voltage limiting and only for incandescent light bulbs because inductive loads like motors require a rheostat. Newer dimmers supposedly have been developed but caused loud hum and flickering on LED lighting. Amperage and wattage are not your reason. Single speed, inductive motors are best left that way so they don't burn up from low voltage supply. Cheapest method is get a variable speed leaf blower instead. (still loud and about $60 USD).

    would a bathroom extractor fan work? or not enough air flow as i was thinking you wouldn't need the big fan and big box as the plastic ducting would fit right on.

    1 reply

    NO. Most bathroom fans would make you cold if they were powerful enough. Most room fans are weak and not for forcing air like portable lollipop and box fans. A kitchen wall exhaust fan is more like it IF you need it QUIET. But nobody throws them out. If you must JUST BUY something quickly. Get a small shop vacuum with a blower port for the hose and duct tape it to at least 6' of 1.5" or larger metal pipe. It will be returnable. If it strains, poke a hole in the duct tape with a pen to vent some pressure or use a larger pipe to the fire. Object is to spend little or nothing and not have to wait for something to get tossed out. Harder to adapt, but some leaf blowers have variable or two speeds. I also own a two speed pet drier which is a very strong blower too. I think you want somewhere around an 1.5" pipe that can roll a tennis ball without blasting it airborne. You don't want it to scatter your ashes either. Stow that messy soap mixture and put clean water in the fire bucket. It quenches the metal better.

    Dear god.... You could shoot a very soapy mixture through the nozzle and make a foam sprayer...