Critique my burner design.

[Kurt]

I'm planning a furnace.

 

I'm not sure what anything's called just yet. I believe I'm going for a dragon's den burner? Maybe? It's a pipe on its side lined with refractory and you put the knives in sideways, parallel to the pipe. I saw a bunch in the "Show us your Forge" thread. The final design in the first post is roughly what I'm after.

 

 

Is that sufficient? Or am I missing something important? The end of the blower will be blown in to the top center of the circular inside chamber of the furnace. Will that get me enough heat? (What is "welding temperature", and why should I care?)

 

For the furnace I'm thinking of an 8" or so tube 15" in length coated with 2-3" of 2700 F refractory cement (the outer refractory will be mixed with vermiculite in about 2/3 cement, 1/3 vermiculite) with an opening at one end and a narrow (1" high) slit at the other end.

 

Hotspots? Oversights? Suggestions?

[Dee]

first thing i would question is :

where the propane is coming in ... you dont just have it screwing from the bottle to the burner ... right?

its really only a trickle of gas that needs come through ..

 

and i dont know about the leaf blowers that are there ...

but over here they are pretty hefty things ..

if you are in the states, id go with one of the small squirrel cage like blowers.

(apparently surplus centre has them often)

this will also allow you to attach the blower without duct tape and plastic ... which might end up melting on you anyhow.

 

if you have a read in this thread:

here

and this one:

here

 

there is some good info and pics from Mr Keyes there that might help.

 

welding temp is about the highest that you will need a forge to get to if you are going to be looking at forge welding at some point.

personally i think its a good idea to make a forge to that kind of standard just in case you are going to be looking at doing forge welding at a later date.

it means you dont have to refit your forge when you suddenly get the urge to see sparks fly.

 

instead of going straight for the cement coating,

id personally look at getting a kaowool lining in there first.

its fairly cheap and i takes a lot of heat .. and it can be coated with any of the clays after.

in fact its a good idea to coat the kaowool .. as if you dont you can have small particles of the fibre floating around when you forge.

not nice to breath in.

 

Mr Fogg also has a bunch of info on building a Fogg style forge on his site.

you might want to take a look there and see what style you want.

 

good luck

[Ken Kelley]

If you are new to the hobby I urge you to start with a proven design for both your forge and your burner. Once you gain experience you can always branch out and experiment to your heart's content. Let me stress that propane burners are inherently hazardous and you really don't want to monkey around with them too much. Don Fogg's burner design is simple, inexpensive, and effective. The Darren Ellis design I use is a little more involved but not all that much so. Either will provide more than enough energy to achieve welding temperatures or maintain forging temps in any reasonably well built forge. I also urge you to build your first forge using ceramic wool for a lining. It's cheaper than cast refractory and easier to work with. If you damage it, it's a simple matter to tear it out and reline. Please rethink using a leaf blower for the air source since you don't need a tenth of the volume of air most put out. A simple squirrel cage blower of 25-100 cfm will do nicely. Have fun with your build but be careful and safe.

 

Ken

[Kurt]

Over here, squirrels are our friends.

 

I'm in Canada, and I've never heard of a squirrel cage blower. Sounds mean, to be honest.

 

When I say "leaf blower", I'm not talking some huge ass blower that runs off gas and can start a small tornado. Think $50 new, with a weight of less than 5 pounds, 75 cfm, cheap little electric one. A DC motor I can modify to run at whatever speed my heart desires, it's an easy thing to do.

http://www.canadiantire.ca/AST/browse/2/Ou...af%2BBlower.jsp

 

I just came back from Home Depot (hardware store), 1" steel pipe seems kind of small. Is one tube enough to get it up to temperature?

 

As far as the propane attachment, I have a 50 pound tank with a hose (and a valve), and I plan on keeping everything on that end far enough away from the hot end that I should have no problems. That will screw on to the pipe (I still have to check which kind of end the hose end is) and you know the rest from there.

 

I have a fireplace with plenty of loose ashes, they provide excellent insulation. In the winter, if we bury some embers one night, the next night we don't even have to light the new fire, we just put some paper on top of the unearthed embers and blow. I don't suppose there's a way to use that?

 

Kaowool looks to be significantly more expensive than cement for me...

 

Maybe portland cement + ashes + vermiculite would do it?

 

I also found this stuff: http://www.canadiantire.ca/AST/browse/3/Ho...%2B710%2BmL.jsp

Edited May 8, 2009 by Kurt

[Geoff Keyes]

It's pretty common (in fact, I did it myself, when I was getting started) to assume that bigger is better. In fact, with forges, just a little bit more than you need is just about right.

 

Check out the links to the two threads that Dee mentioned, I've said most of what I want to say there.

 

1 1/2 inch pipe works better, in my experience, than 1 inch. A needle valve (or some kind of valve) where the propane comes in is a huge help.

 

Surplus Center AC Fan

 

Even this fan is WAY more air than you need. I use something similar, and I choke them down about 80% at the intake.'

 

People build the interior of forges out of all kinds of things. Hard surfaces last a long time, Kaowool heats much faster, and so uses less fuel. Have a look at this thread

Thread

 

Geoff

[Tony Havard]

Geoff has a good point about the air. I use a $10 Dollar General blow dryer on my forge. I bought it, took it apart, removed the heating coil and diodes and wired the switch straight into the motor, cut the plug off the end of it, crimped on two flat electrical connectors and run it off of my 19V craftsman cordless drill battery. Runs for hours and hours without ever pulling down the charge. Now back to Geoff's point on air...I cut a slice out of one side of my intake pipe (my piping is like the Don Fogg setup also), and made a small aluminum wafer to allow more air or less air. I've found as the forge is heating, I use a little air and after a couple of minutes and adjusting gas and air, I end up using 100% air flow, however, that's using a hair drying and not a squirrel cage blower. The hair dryer works perfectly for me at 100%.

[Kurt]

Just got around to reading those links. I think I'll probably copy that burner design, apart from my crude attempt at conveying my idea, it's essentially the same. Once I saw the size of 1" pipe, I considered stepping it up to 1.5", but figured I'd stick to things that have already been attempted.

 

As far as the blower goes, I guess a little experimentation couldn't hurt. What sort of cubic feet per minute am I aiming for? P.S. - Hyperlinking is disabled for that site. I think I read about 50 cfm is ideal?

 

Also, as far as cost is concerned, I'm trying to keep it to a minimum for now. HOWEVER, I might be able to snag me a government grant of $1500 towards start up costs, which would be awesome. I'm thinking I'd get a 100lb tank vs. my 50 lb tank (If I was to use the 50lb tank I'd put a heat sink on it tokee it from freezing), a nice wood lathe, and maybe some proper hammers.

 

Speaking of which, I was just planning on buying a 3 pound hand-held sledgehammer, taking the head off, and forging it in to a rounded wedge. I figure that'd make a nice fuller. (It'd have to be annealed first, of course). Opinions? I need to drive for a good 2 hours one-way to get to a place that sells smithing tools, I'm just outside the GTA (to the south) in Ontario. The good news is Hamilton (steel city) is only a few minutes drive away.

[Geoff Keyes]

This is pretty much what you are after in a forging hammer

 

Forging hammer

 

Trying to forge out a crosspien on a 3lb sledge is...uh...ambitious, to say the least. I'd want a powerhammer, or a good friend as a striker. OTOH, my local hardware store carries what they call an "engineers hammer" which is much the same. You might also try haunting junk stores, barn sales, yard sales. I've picked up some good tools that way. It sounds like you are out in the country a bit, you might just ask around farms. Many farms around where I live still have the remnants of simple blacksmith shops tucked away in odd corners.

 

Except when I'm drawing a taper, I hardly use the crosspien on my hammers. THe edge of the anvil, or the top of the horn, works about as well for drawing out.

 

Good luck,

 

Geoff

[Kurt]

That just looks like a drawn out sledge to me. Maybe I could cut a sledge head?

 

As far as an anvil, I have a slab of steel, no horn. I also have a railroad tie, but it seems a little inferior to a flat slab of steel.

[Geoff Keyes]

I suspect that what you have is a piece of railroad rail, a tie is wood. Wooden anvils don't work all that well .

 

Actually, lots smiths use a rail anvil with good results. The anvil I do most of my work on is a chunk of steel 5 x 6.5 x 30 inches. There is a pretty good discussion of anvils

 

Here

 

If you have the tools to cut down, or forge down, a sledge head, then by all means do that. My bet is that after doing one (more likely part of one) you'll think that $30 for a hammer is a deal .

 

Geoff

 

 

BTW, ballpien hammers can do some pretty good work, and it's easier to forge down the ball of a hammer than a two inch square piece of steel.

 

Just my .02

 

Geoff

[Kurt]

Nothing a little grinding can't take care of, or an hour or so with a hacksaw. My goal in the end is to have a flat hammer and a hammer that can draw out harder steels. A ball peen is kind of what I'm after, but, to steal an image, I saw this last month and it stuck in my head:

 

 

Credit goes to Greg Obach for the image.

Edited May 9, 2009 by Kurt

[Kurt]

WELL!

 

I've actually been doing stuff, I swear. I have the furnace done, save for welding the burner on and maybe a face plate to keep the insulation in.

 

The burner is giving me some trouble, however. A hairdryer blowing medium-string from about a foot away from the hole provides the optimum air flow. This is a problem. It burns wonderfully, but I need much less air flow than I am currently getting from a hair dryer. My solution: Computer fan. Electronics are a family hobby, we all do tons of random projects. But I digress.

 

Is there something wrong with my burner design? What can be improved before it's attached? When attached, will it act differently? How do y'all like it? (I also have enough insulation for a similar sized forge. Any ideas on what to use it for?

 

The bottom end. The empty hole is where air is blown in, eventually something will be permanently attached here.

 

The forge in all of its almost-complete glory. Just one or two more days...

 

An inside view. I used a ceramic fiber to line it with, as the refractory man recommended. It's like kaowool but newer, generation 3, woven fibers instead of loose strands. The floor is firebrick. I may jam some insulation in the corners if the fire doesn't swirl nicely. Also, a slit will be cut in the back to accommodate larger blades or air flow if necessary.

 

The back of the forge. This was taken mostly for myself, as those welds are my first welds ever. You can almost SEE the learning curve, forever melted in to the steel. The container is a hacked up old dryer drum. That was almost my first time using an angle grinder. In fact, before a week ago all I had was metalworking hand tools.

 

The burner. It looks simple, but took all day to make. I had tried to weld an elbow and a 1.5 foot length of pipe, but ended up scrapping that since it wasn't even watertight and just bought two 6" nipples and a coupling.

 

Roughly what it'll look like finished. You can take a moment to bask in the glory of my manly blacksmithing arm muscles.

[Matt Bower]

Is that a little plumber's torch running into the bottom of the burner? Won't that make it hard to hook up to a proper propane bottle?

[Kurt]

Yes, but no. I have a hose that hooks up to it from the tank you see hidden behind the furnace. It's not a problem at all.

[Matt Bower]

OK then. Can the orifice in the plumber's torch deliver enough BTUs' worth of propane per unit of time?

Edited May 29, 2009 by Matt Bower

[Kurt]

I drilled it out to 1/16" or something. I used the smallest bit I had, but I couldn't even SEE a hole before.

 

Is this one of those situations where I'm on my own? I think I can manage.

 

 

Strange thing, though. When the propane was injected through the side (you can see the white thread sealant) it didn't work for shit. Moving it to the bottom made it work except for the air flow thing. I think, at least...

[Geoff Keyes]

Ok, so you are using a BBQ tank, you'll probably have some issue with the valve freezing up. Try suspending it in a large bucket of water, it will keep the valve open and you can cool your soft drinks (shops are WAY too dangerous for beer during working hours, that's my rule). The gas valve on my system has a 1/4 inch opening, so you will probably want to drill that out to something like that. You only need a tiny hole if you are building a venturi. You also could get rid of the coupler and one length of pipe. You may want to neck down the burner where it enters the forge body, a little back pressure seems to help the burn.

 

Good luck,

 

Geoff

[Matt Bower]

Is this one of those situations where I'm on my own? I think I can manage.

 

Well, I don't think I've seen this particular approach before. But this stuff ain't rocket science, and you seem to be thinking the right way. No worries.

[Kurt]

I've adjusted my setup a little, the propane comes in from the middle now, which seems to eliminate the back-burning somehow. I'm not complaining.

 

One more question: My 20lb propane tank and the valve are on full blast when the hairdryer is on full blast. Is this normal?

 

Another one more question: () My flame is just hitting the opposite wall and producing a hot spot. Any tricks to getting a swirl?

 

I took some videos and pictures to better illustrate my current progress:

 

 

A control picture. This is the propane torch I use to safely light the burner.

 

The burner. I don't remember what hairdryer setting it was on, but it appears to be medium.

 

An inside view.

 

A video of me messing with the burner. As you can see, it's not burning consistently yet. I may have fixed that problem by moving the propane inlet midway along the pipe section (by flipping a 6" section around), but since I'm still using my mom's hairdryer, I haven't fine-tuned anything yet.

 

 

http://www.youtube.com/watch?v=3KNdcTkdM3s

An inside view, running. You can see the hot spot.

 

http://www.thermalceramics.com/site.asp?si...4&pageid=47 I bought the "Cerablanket", for those interested. Kaowool +1.

Edited May 30, 2009 by Kurt

[Matt Bower]

Most burners won't stay lit outside a forge without a flare on the end of the burner. But burning outside the forge isn't what counts, and the back pressure of the forge seems to help in many cases. If it burns when it's in the forge, that's what's important.

 

The flat bottom of the chamber is going to make it tough to get a real swirling action. Most folks don't seem to worry about it in forges. Casting furnaces are a slightly different proposition.

Edited May 30, 2009 by Matt Bower

[Kurt]

Just wanted to let those interested know that the forge works great.

 

It only gets things light orange (just under yellow) at its hottest, though. What is considered welding heat?

[Geoff Keyes]

Heat a piece of steel up to whatever your forge will do at it's hottest, leave it in the forge. Take a 1/4 inch rod of mild and bring it up to the same temp. Touch the rod to the larger piece, if it feels tacky, it's at welding temp. The colors are at best a guide. What looks orange to you, might be yellow to me. Welding temps for 10xx steel are in the 2300 F range, which is about 500 degrees hotter than you want to do most of your forging.

 

Did you drill out the tip of the gas inlet? Lack of fuel might limit your temps. I build my forges so that, running at about 25-50 of wide open, I get temps from 1600 to 2000 F. That way, if I need to get 3000 F, I can. I hardly ever do.

 

Geoff

[Kurt]

Thanks.

 

There's a nice spot at each air speed where the flame isn't spitting out and the flame gets real loud and white hot right where it hits. It's hard to explain but I'm sure you know what I mean.

 

I took apart my hair dryer tonight (and tried some cider finally, great stuff!), and found out that apart from the heating element and switches, all that runs the fan is a 12 volt DC motor. I hooked it up to an 18 volt supply and a homemade dimmer, and now I have a great fan, which can blow more air than before, maybe even enough for welding now. Leaving a piece in the furnace, it only got yellow. I estimate I'm getting around 1000 C as a temperature. Which means now I might get near melting. MAYBE.

 

In other words, some assembly tomorrow and some steel orders on Monday, and I'm in business. Time to make some profit!

[charred]

why dont you finally just make a knife and see if you even like it.

[Kurt]

Preparation. I will, don't worry, I just want to do it right the first time. The last few days I've had the furnace running, I didn't mention it, but I've been hammering away some rebar and scrap steel, partly for fun, but the rebar will be made in to tongs. You see, the first knife I make is going to be very special, as I'm sure everyone's first knife is. So I want to make it good. So I read, ask questions, and let y'all know what I'm doing so that someone will hopefully tell me how wrong I am in doing something, so I can correct it before it's irreversible. Sorry if that's bugging you, I'll quit it with the bloggier posts.

 

I found an oddity that I thought was worth mentioning:

 

The steel pipe of the burner got really hot all the way down to the bottom yesterday. Today, after welding it in place, it's cool to the touch everywhere but the top-most elbow.