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 http://www.iforgeiron.com/forum/f7/building-forge-3016/
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-300-400/bp0338-making-your-own-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 .

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]

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.

[IronPuppet]

I spent today, so far, building a new fire pot. So lets see what you think of this. I am still going to cut out the back of the rim for long stock.

I still have to replace the clay that chipped out while hammering things.

Thanks for the tip on the side draft units, guys. I have an idea of how I can make an insert to change it to a side draft.

Christopher

[irnsrgn]

little fire pot looks to be about 2 inches deep, and 4 or 5 inches by about 6 inches, another 3 inches above the edge is where the clay should be filled to, and the fire pot should be orientated with the long way running from front to back not side to side. Remember a large inside the wheel bonfire is gonna use a lot of air and not give off the heat in the center needed for smithing. A bright orange is a good working temp for most things, when it gets just red it's time to reheat, if it only gets to red to start with, its not worth the effort to try, after all it has to be at a plastic state to make it move well and efficiently. Unless you want to spend all day pounding cold iron and chance having it crack from working it to cold.

[IronPuppet]

Thank you so much for having patience with me. Here I thought I was going to build the perfect forge the first time, and now I understand that it's a learning device. I will take your advice and build up the edge and add to the fire pot to get it to the right height. You said the fire pot is small. Is it too small, I'm wondering. Well, I'm going to rebuild it again.

Maybe third time lucky.

Christopher

[JerryCarroll]

Where else can you find help like the above posting?? Thanks to irn and others this site is priceless.

[irnsrgn]

Christopher you don't need to rebuild again, just reorientate what you have a quarter turn, its about the right size for the bottom of a fire pot, and build the sides up with clay 3 inches at about a 20 degree angle and the ends or front and back at about a 30 to 35 degree angle to make it longer at the top. I imagine what you used for the sides is not very thick so will burn out if you don't cover the bottom and sides with at least a half inch of clay.

It's not so much a learning experience as understanding the subject before starting the project. Experience is a cruel teacher, it gives you the test first, then the lesson. once you get it right you gonna have to throttle your air down with a rheostat or you will blow the fire up outa the firepot, try a router speed control. from a woodworking supplier or sears etc.

[Glenn]

In order to speak from working knowledge rather than present an armchair argument, I got up out of the armchair and went outside and built a wheel forge.


Blueprint BP0462 Wheel Forge is the result.

The wheel forge took 45 minutes to build. After 25 minutes of burning only wood I had metal up to red heat. That is 1 hour and 10 minutes of investment. I can report that the forge does work, but my version needs improvements. See BP0462 for details and a solution for using wood as a fuel.


Blueprint BP0463 Wheel Forge 2 is an improved version based on coal as a fuel.

After construction and before the first fire was built the forge underwent modifications. I will need to build a fire in this forge to see how it heats but already there are a couple of additional modifications planned. No one ever said it had to be right the first time. You just have to have something to base the improvements on.

That is 2 forges built from automobile parts at little or no cost. From nothing, nada, zip, to red hot metal is just over an hour including the construction time for the forge. It can be done.

There is already a spin-off idea for yet another forge of a different design in the works. The search is now in progress for the parts.

[Daryl]

In Saskatchewan, we have an unusual method of obtaining coal. Find a Home Hardware store and ask them to order blacksmith coal... you WILL get that 'deer in the headlights' look. Have them phone the Head Office in Ontario and they will find out yes, you can get coal. It is somewhat pricey to buy, though.

[Blacksmith Jim]

Fig. 28 looks just like the forge I've just started using. Its fun :)

[Glenn]

Blueprint BP0463 has been updated. The fire pot was too small and had no volume in the fire ball. This is a learning experience and takes some time to arrive at a working design.



More details are posted on the Blueprint.

[IronPuppet]

That's super, Glen! Very informative. Thanks for taking the time to work that out.

Rain for three days now and it looks like more today. I need it to be dry outside before I resume experimentation.

Thanks, Daryl, for the tip on where to find coal in these parts. I'll do that.

I'm always learning.

Christopher

[evfreek]

...
The wheel forge took 45 minutes to build. After 25 minutes of burning only wood I had metal up to red heat. That is 1 hour and 10 minutes of investment. I can report that the forge does work, but my version needs improvements. See BP0462 for details and a solution for using wood as a fuel.
...

Hi Glenn. Experimenting with using wood to forge is very interesting. Once upon a time someone posted on his experiences with wood pellets. He was able to get a pretty good heat. There is some kind of rule I heard of like 6-10X the fuel size for the firepot depth. That is why it is so hard to get a hot fire with big pieces of wood. The fire behaves like a shallow fire. Cold and oxidizing.

Actually, it is a little more complicated than that, and the scaling is non-linear in the good direction. In other words, the rule may become more relaxed with larger size fuel. I saw a wood fired forge in action that could get up to a sparking heat with scrap wood (like pallets and construction scrap). It had a firepot that was about 3 feet deep. Hmmmmmmmmm, this is about 6-10X.

This may help to guide the direction of your experimentation.

[Glenn]

I have run the Supercharged 55 Forge (Blueprint BP0333) on pallet wood, yard waste, and I even ran a whole apple tree through that forge. (grin). See post #25 this thread for a photo.

Your mileage may vary, but with my set up, the good size for wood seems to be a 2x4 and maybe 4 inches long. Smaller than that size is even better. This allows the wood to burn, form charcoal, and form a hot bed of coals. This not only heats the metal, but burns the wood creating charcoal to continue the process.

It takes a LOT of wood to fire a forge. On the plus side, your yard is clean of sticks, the woodlot is clean of ground clutter, and you make a lot of business happy by hauling off their old pallets.

Find a fuel and then build a forge to use that fuel. The experimentation is fun and you learn what works and what does not.

[IronPuppet]

irnsrgn said a couple of things that stuck in my head. One was that my stock was probably too thin, the other was that the sides should be sloped at 20 degrees and the front and back sloped at 35 degrees.

My new fire pot will be made of 1/4 inch steel plate. I got it from a friend who was dismantling some big "I" beams. The stock I got is long bits about 4.5 to 5 inches wide. To save on gas for the torch I cut out the pieces as shown below. now they are all ground up and flattened out and I will weld them together to make the 4 sides, then weld the sides together to form the fire pot. This will make the steel part of the fire pot just over 4 inches deep. The top 1 inch will be made up of clay. I also have bricks to make the sides taller for some uses.

This is where I am at right now. Due to the fact that I am welding the parts together to make the various sides I was wondering if there is any advantage to making the side parts rounded. Weld then together on a slight curve. This would give the fire pot a rounder shape rather than square. what do you experts think of that?

Christopher

[irnsrgn]

your getting there, forget the curves. if anything make it wider and longer. so you have more area at the bottom. Charcoal needs a bigger firepot than coal or coke.

[Glenn]

I fired up the Supercharged 55 Forge Blueprint BP0333 on only wood and remembered to take a photo. It does reach forging temperature.