Burn Pile, forced air blowers

[AlanB]

Need to have several burns in my new yard to clean up debris. Want to do several smaller very controlled burns, and thinking of taking a fan, a yard blower, or maybe a squirrell cage blower from an AC unit, ducting it through an large diameter pipe of some type and blowing it into the center of a fire, then just feeding a hot center fire either by hand or with the tractor.

Kind of envision getting something like a forge fire going in the center that will keep things going as I add fuel from the sides.

I will also need to burn some stumps as I accumulate them and think it would be helpful to work them down as well.

Anyone done something like this with forced air or some other system of making a fire burn hotter and more centralized or any additional suggestions.

Not wanting to start a "Burn Safety" thread, just a simple thread about how to make the fire burn hotter / cleaner / more thoroughly with a minimum of work and time invested.

 

[schmism]

i suppose you could use a metal culvert to direct the air with a sqirel cage from a furnace.

ive had many burn piles out at the property. I aways hand feed my piles to keep them manageable and burning hot. (ive been known to tend with the FEL a couple of times also)

 

[Bird]

Alan, the only problem I see with using fans and blowers to get the forge effect is controlling the air flow. You need enough to make it burn hot, but not enough to scatter ashes and sparks. But it can certainly be done. This reminds me of when I was a kid, less than 10 years old, and my Dad was driving a truck selling and delivering welding supplies. Of course when he delivered new bottles of oxygen, he picked up the empty bottles, and sometimes they weren't completely empty. So I've seen him lay one of those oxygen bottles on the ground, aim it into a fire, and slowly and carefully open the valve. Pure oxygen blowing into a fire will burn or melt just about anything.

 

[tallyho8]

After hurricane Katrina I had to cut up, move and burn about 100 large trees on my property. The first thing I noticed was that if you let them dry a couple of weeks after you cut them, they burn much faster and hotter. I made many piles about the size of a pickup truck. The first pile I had was mostly pecan since it burned hotter and lit easier than my hackberry and tallow trees. When the first pile burned down most of the way I would push the next pile into it with my tractor and I repeated this process many times. The next morning I would come out and push a new pile into the ashes and it would immediately start burning. I only used one match to light the first fire and just kept it burning after that for several weeks. Even rainstorms did not put the fire out completely where I had to relight it. A pickup size pile will usually burn most of the way in less than 2 hours even with large pieces of trunk in it.

My next door neighbor used a leaf blower to forge his fire of just-cut trees and my house, trucks and yard were covered with ashes.
The blower also sent large volumes of burning ashes into the surrounding area and I guess we were lucky not to have any wildfires.

 

[dmccarty]

I have seen commercial blowers that are inserted into a trench. That seems to keep down the ashes/embers from flying around. I know in some local counties if you can burn you have to use a blower unit to burn quickly and cleanly. The burns I have done have not needed a blower though it might have helped starting the fire. Once they got going I wish they could have been turned down....

Another option is to have the wood chipped up which is what I want to do with the pile we have now. There is a thread or two regarding chipping with large equipment here on TBN somewhere.

Later,
Dan

 

[riptides]

I usually start with a hole in the ground and build the pile ontop of it leaving just enough space to direct my yard blower down towards it.

You get it started, turn the blower on. and with enough debris ontop of the pile, I have never had a problem with ashes.

 

[RonMar]

I use a small blower to get and keep a good core fire under my larger burn piles. Some of these piles have been setting for 30-40 years and are as much soil and moss as wood. I break them up with the tractor as best I can, but the wood is still saturated with water. It is like burning wood that has been buried. This is the same reason stumps are such a pain unless air dried for quite a while.

It is amazing what a little forced air will do for a fire. What I use is a 4" radioshack 12VDC fan(120MM, about 4.7" square). It is basically a large computer case fan and has a metal frame and plastic blades. This is connected to a little flange ring with 4 screws(forget where I got that, but think it was part of an old bathroom fan housing). The flange ring is the same size as the 4" steel and aluminum ducting found at most hardware and home supply stores. With the ring attached, the fan just plugs into the end of the piece of metal duct, but you could attach the fan to the duct with duct tape quite easilly. I use a 4' length of galvanized steel duct now. I had a 4' piece of aluminum(rigid dryer duct) but it progressively got shorter and shorter as the end was melted by the blast furnace temps it creates down in the pile. The aluminum was easier to straighten as the tube will inevitably have wood fall on it as the pile collapses. I usually collapse the end of the duct a bit to spread out the airflow to feed a larger base. This is also good for blowing air under a log to get to a fire built alongside the log.

I power the fan with a 12V 7AH gell cell battery scavenged from an old Uninterruptable Power Supply. This battery when fully charged will power this fan for nearly 24 hours. Since it is 12V, I could use any vehicle battery also. A garden tractor battery would run it for days.

With the small forced air input, the core fire superheats and that heated air has to force it's way out under the rest of the pile. Once the core fire is going good, most of my larger piles will have as much steam comming from them as smoke. At some point they will reach critical mass and really take off. That is when I start tending them with the tractor and pushing the partly dried wood around the edges into the middle.

I have used leaf blowers, shop vacumes and even the airflow out from under a mower deck. All are noisy, some consume fuel. I also don't necessarilly like having my garden tractor setting and runing right beside the fire. With the exception of the leaf blower at idle, They also provide way too much air(even the idleing blower was a little much) and will burn away all the lower fuel too quickly and cool the air over the fire before it has had a chance to dry out the upper wood. Too much air also separates the lighter coals and blows embers and sparks about instead of allowing them to concentrate their heat.

I thought about making a slightly larger one out of a auto heater blower, but then I would need qite a large duct to distribute the air without creating too much air velocity and that would be hard to get down into the pile like I do now. It would also need a larger battery and be more cumbersome to work with. The little electric is quiet, relatively inexpensive, trouble free and in my case gets the job done very well.

 

[SteelDust]

For smaller piles I use a leaf blower and a propane weed burner to get them going.


Larger slash piles or stumps, I go and rent a brush fan from the local rental yard.

 

[AlanB]

Ron, you just gave me an idea, I think I will take the blower out of the boat, plug it into my jump start battery, and hook it into a long piece of pipe. That would be cheap (already have everything) easy, couple pull plugs and a hose clamp, and quiet,,,, Think I will try that this weekend.

Steeldust, what is a "brush fan"?

 

[RonMar]

Good Idea. A boat blower should work well, already designed to connect up to duct pipe. It will pull a bit more current, but should also deliver a bit more air. You might also want to check that it is rated for continous duty. They are typically used to vent the bilge on gas inboards before startup to avoid fires so they are usually only run for shorter periods. But they are typically brushless(no sparks). Brushless DC motors are typically rated for the longer duty cycles.

"Cheap" and "Already Have Everything" are my favorite prices Let us know how it works out.

Brush fan = portable gas powered fan(looks like something a powered parachute pilot would strap on his back). Fire departments also use them to ventilate/desmoke houses after the fire is out.