air in the fire

[IronPuppet]

Hello there. So far, I am unable to buy coal of any kind around this town where I live. I was using charcoal brickets and someone on this form said I could use wood. This was good news because I have a large collection of scrap wood I have collected over the years because my shop is heated with a wood stove.

So I have been having a go with wood in my forge. This all seems new to me and I was wondering if I could ask about air supply, or rather, the ideal air supply.

I have an old Electrolux vacuum for my air power and so there is no shortage of force in my air flow. I have an old tap mounted in the air line so I can control the air flow from a slight whisper to a full on blast, that is so strong, I might add, that when I turn it up all the way, it blows all the embers and wood aside.

I notice that when I have a lower flow of air that I get more red hot coals and it seems to take a long time to heat anything up and it doesn't get to a bright red, just a dull red.

When I turn the air power up then the fire becomes more active and it gets hotter. The sweet spot is hard to find and the air blast seems to be cooling the metal, but when I do get the metal in the right spot then it does get closer to bright red.

I want to know if a constant air flow is a bad idea. Is it better to pulse the air flow by turning it up and down? (like a bellows would blow)

Right now my air flow is coming from a pipe sticking through the bottom of the fire pot. I was wondering if I made a dish or a box with 4 holes in the corners or a series of holes around the edge and placed this upside down over the air pipe to divert the air flow and filter it out to different points in the fire. What do you think of this? An attempt to spread out the air flow to feed the fire with air from multiple holes. Or is it better with just one hole, like the pipe?

Any thoughts would be appreciated.

Christopher

[irnsrgn]

Christopher, you have several problems that need to be addressed.

1. Your forge needs modifying, the fire pot is way too big, add some clay so the top of the air opening in the bottom is flush with the clay on the bottom. You need a smaller deeper fire pot, check out Building a forge
to make your firepot smaller and I would say the top should be flush with the top edge of the tire rim. You need to add something on the outside to make the top larger also. Tack weld the piece you cut out of the rim back in to facilitate making the firepot.

2. You have to make the wood into CHARCOAL FIRST. SEE BP0338 Making your own Charcoal http://www.iforgeiron.com/blueprints...-charcoal.html or look at the drawing and explanation below.

3. Once you have a decent smaller deeper firepot it will not take much air to bring things up to a welding heat. The ideal location for a piece to be heated is about 5 inches above the bottom of the firepot in the neutral area of the fire, lower and it is in the oxidizing area, higher and it is in the carbuerizing area.

4. A bellows gives a constant air flow.


expanation for drawing below:
1. Take a 55 gallon drum with one end cut out, and a 1/2 inch hole poked in the other end centered, fill with smaller short chunks of dry wood, place chicken wire over the top and secure in place around the top with baling wire.

2. Carefully upend the barrel and place a fire brick under one edge as shown in (drawing A), using shavings and kindling start a fire as shown, when the wood in the barrel catches good, remove the brick and mound loose dirt around the barrel except a small air opening shown by the Arrow in drawing B).

3. Drawing B shows smoke coming from the hole in the top, light this smoke on fire, it will burn on its own after ignited, when the flame goes out on its own, drop an old 1/2 inch bolt in the hole and close the air opening at the bottom.

4. When the barrel is completely cold, turn it over remove the chicken wire, dump the contents out and you have charcoal, you will need to break the bigger pieces up into usable pieces about the size of walnut or smaller.

5. A Charcoal fired forge burns lots of charcoal and has lots of fleas or sparks that rise in the hot air and fumes, so be careful of starting grass fires.

6. You can use wet charcoal at the sides of the fire to help maintain the small hot fire needed for smithing, not the large bonfire you have now.

[irnsrgn]

Chris if you have a wood stove in your shop, you have an ideal charcoal maker. In the winter when the stove is burning when you have a good bed of charcoal glowing, just remove it and put in a 5 gallon metal bucket and put the lid on to smother it, when cool dump in a 55 gallon barrel or barrels for a supply of charcoal when the stove is not burning, remember to replentish the stove with fresh wood after removing some for charcoal

[oakwoodforge]

Christopher, THE Irnsrgn gave you some very sound advice there. I use a forge something like this everyday, if you add a few shovel fulls of dirt, clay, kitty litter ( new - not used ) or fireplace ashes will give you a nice deep fire pot of a use-able size. To give you an idea for scale, IN MY forge I like to have 10-15 cm of burning charcoal between the air-gate/ tuyre and the steel to be heated then another 10-20 cm of charcoal on top. With a slow -N-Low air blast, This makes for a reducing fire, very little free -or- un-burned O2 in the sweet spot. = no bad scale problems.

Regarding your particular air problem , you may have too much air pressure and just not enough CFM of air flow. Your vacuum blower will work , you just need to control the fan speed, its currently much too fast, a woodworker's router speed controller or any rheostat rated for motors would be just the ticket.

Hope this helps


Jens

[easilyconfused]

Originally Posted by irnsrgn

Chris if you have a wood stove in your shop, you have an ideal charcoal maker. In the winter when the stove is burning when you have a good bed of charcoal glowing, just remove it and put in a 5 gallon metal bucket and put the lid on to smother it, when cool dump in a 55 gallon barrel or barrels for a supply of charcoal when the stove is not burning, remember to replentish the stove with fresh wood after removing some for charcoal

I use the wood stove in our shed to make charcoal and it works really well, just be careful because it may smoke up your shop. I usually pull out the whole bed of embers which is about a 1/4 of a 55 gallon drum since it is a large furnace. I've used both soft wood and hard wood to make charcoal and the only difference I've noticed is that you go through more soft wood but I've successfully welded using both. Proper fire maintanence is the key.

[evfreek]

Hi Christopher. You really need some real charcoal. There are no restaurant supply houses around who have it? Some of my buddies in Texas had a way to make charcoal. Fire up a BBQ grill with lots of wood. Cook something which takes a lot of cookin' like pot roast or brisket. When the wood is good and charred up, run it through a "Texas sieve" (a torched out brake drum with rebar grille welded in). Encourage the charcoal to fall through by striking the wood with a piece of rebar. Put the hot lumps in an airtight metal container like a cast iron dutch oven.

Forging over wood is tricky. You really want to get some good coal or charcoal. I have seen people do it. You need a very deep fire with wood. Something like 12 inches. I have never done it. But, I have done something like it. When running low on charcoal, I use charcoal below the steel, and wood above it. The wood acts like the insulation. Bits of charcoal periodically fall into the fire, replentishing the charcoal already in the firepot. Help them along occasionally with a poker. A layer of fuel is required above the steel, but it does not have to be charcoal. The layer below should be, though.

[Finnr]

I use a lot of Royal Oak lump charcoal when I am not able to get coal. It works very well and is available in most big box stores. I am in the process of building my own charcoal cooker to make my own as my woodworking shop generates lots of scrap.
Finnr

[son_of_bluegrass]

You've gotten some good advice above. Since you need to rework your forge anyway you may want to think about a side blast. I find side blast works better for charcoal than bottem blast.j

ron

[Archie Zietman]

side blast forges definitely work better for charcoal. I'm not sure why, they just do, they are also easier to build. I often forge with wood, and I just need a deep fire and it works fine.

[easilyconfused]

Dunno if it's just this but I've noticed that since I switched to a bottom blast for my occasional coal use, there have been more 'fleas' and the smaller pieces get blowen away from the heart of the fire.