Can't get the fire high enough...

[burninghXcsoul]

I recently restored an old rusty forge and am having problems maintaining a decent fire.  The forge did not come with one so I made one out of a brake rotor and some 3" exhaust pipe.  I initially had as a tuyere some 1/4 plate with a bunch of 1/4 holes drilled in it covering the 3" hole for the air intake and I could not for the life of me get burning coals above  the 2.5" high brake rotor.  I then welded up some scrap rebar I had laying around into one I thought might let more air into the fire.  This did not really help much.  

I am using bituminous coal that a friend of mine recommended and what he uses and he is a full time 2nd gen blacksmith so i dont think it is the coal.  It lights up easily with newspaper and some sticks and cokes fine I guess (I am completely new at this, this is only the second time I have used this forge).  I had made one out of an old well tank and a hair dryer and used it a couple of times before buying this one so I am super inexperienced but my homebuilt one performed better than this. 

I have gotten the timing pretty much perfectly on the ratchet clutch system.  This thing throws out what I would assume to be enough air, with alot more force than my old hairdryer.  

Could it be the shape of the firepot?  I lined it and sloped the sides with a mixture of bentonnite clay and sand that I got from reading this forum.  It looks like all the others I have seen.

I just cant seem to get the fire high enough to heat things above the 2.5" inch lip of the rotor.  I started out trying to make some tongs and I used some 3/4 square and round stock but I pretty much have to either dig the ends into the firepot to get it a decent color of orange otherwise just laying it on top of the rotor just gets it a dull red color.

This is going to sound stupid I know but whenever I watch youtube videos of people forging, it seems they have this huge mound of coals lit and I can't get anything close enough to put my stock straight across and heat it.

 

Attached are some pictures.  If need be I can try to take some pictures of it actually on fire but the main idea is that no matter how much coal I heap on top and no matter how much I pump the handle like a madman, I cant get much to burn above the top of the rotor.  Thanks.

 

 

[SReynolds]

From bottom pick (the side on view) looks like the top of the rotor is just a freckle above the cutouts on the forge table?

red flag there as you have no firepot. Where be your firepot. It would be about 2 to 5 inches deep depending on the make/model etc.etc. These old units used about a 4-5 inch deep pot. That is filled with fuel and is burning. White hot when air is applied. The fuel (coal and coke) are surrounding the fire pot. There is coke above the fire pot for say three inches above it.......for a total of about 6-8 inches deep overall from top of fuel to bottom of fire pot.........

Now.....looking at the 3rd and 4th pictures; there is no firepot. Just a hole in base of the forge table. appears the hole in base of the table (your tuyere) is a hair below the table cut-outs. Not gonna work.

That is me. I didn't graduate from college in forge design, but I have several and they ain't looking like that.

p.s. this may be an odd question, but; did you fill that brake rotor completely with sand/clay mix ????(!!) ?????

Fire pots. Forges with fire pots. The black rivet forge; that entire thing is the fire pot! The item that looks like your grate; that is the 9" base of a 8 inch deep fire pot. The blue forge is not mine. I found it here on the site.....again.............with a fire pot that is no less than 5 inches deep.

[Kevin Olson]

You need a deeper rotor. Find one from a pickup truck. Heres mine. Its 3 inches deep and 9 wide. Thats a nickel to show hole size. It has no filler to slope it. I just left it square in the bottom. 

[burninghXcsoul]

Sorry, my pics could have been better, from the top of the tuyere to the top of the rotor is 2.5 inchs.  I didnt fill the rotor in completely with clay, just enough to slope the sides and form it into a bowl shape that is 2.5" high.  

There was no firepot that came with this forge, but it was only $75 and a fun winter project.  I had read here and other places people use brake rotors as firepots so thats what I used.  So what your saying is I need to make one thats deeper?  

How will that make the fire higher?

[SReynolds]

why do you need the fire higher? how deep is it/how high is it? Use the term deep. Not high. I have a firepot 8" deep. It is level with the forge top. It has cut-outs I can slip the steel stock into and through the fire. So my fire isn't high. It is level with top of forge.

There is a (popular?) smith on this site that has (perhaps) hundreds of youtube videos. The one for firepot design is called maintaining a coal fire. His firepot if I recall is 1.5 inches deep. I have a tough time believing that but it obviously functions. However, the fuel is piled well above and around that firepot. And....the base of the firepot looks to be (if I recall) about 4"x 6" (at the bottom) and yours is maybe 3.5" round. 

[Kevin Olson]

Refer to Glenns post here. Its pinned. Its called "forges and fires"    There us a diagram cross section of a coal fire. That will help. 

[Daswulf]

Are you taking the clinkers out of the pot while forging? The can take away from getting it burning well but that's usually after a little time in. Are you emptying the ash dump? If it builds up it could obstruct airflow.  Also from the look of the design of the ash dump, does air blow out around the dump? Could be losing volume through that.  I use about a 2" deep rotor and have no trouble getting hot coals above the rotor lip when I pile it up. Then again I am using an electric blower but there's no reason a good hand crank blower shouldn't do the same. My blower isn't a beast or anything. 

[rockstar.esq]

Lots of rivet forges have no separate firepot.  You simply mound the coal higher over the tuyere to get a "deeper" fire which gets you a neutral or reducing environment.  The shorthand explanation here is that a netural or slightly reducing environment won't cause so much scale and may play a vital role in successful forge welding.

One thing jumped out at me right away.  As a rookie I'd have days where I just couldn't get the fire hot, and other days where everything would work fine.  It seems really simple; add air, and the fire will get hotter.  That's true provided you get your fire to what I call a "critical mass".  Anything less than that critical mass, and it's like the additional air simply blows around the piddly fire.

I'd be out there working the bellows or blower like crazy and the fire would be barely treading water.  Last summer I had an "aha" moment when I noticed how experienced smiths at a hammer in were starting their forges.  Most of them used a soup can with the top and bottom removed.  They stacked newspaper, hardwood charcoal, then coal in the can over the clean tuyere and lit the paper.  They gave just enough air to get the charcoal going, then they increased only enough to blow the charcoal smoke out of the can.  They kept cranking until the coals consolidated and fell a bit in the can.  Every time the coals slid down a bit, they'd add a piece or two of coal and increased the air volume until the smoke was blowing free of the can, but no more.  Only when they had a full can's worth of literally red coke did they pull the can straight up.  As a rough explanation, I'd say one soup can's worth of fully lit coke is the minimum "critical mass" to really consider the fire ready to work with.

It's weird how it works but by going slower to start gets you to working heat much faster.  I don't see many experienced smiths cranking their blower like a madman, regardless of what equipment they're using.