MEMBER ITEMS FOR SALE
Custom Knives | Other Knives | General Items
-------------------------------------------
New Posts | New PhotosAll Photos



Go Back   The Knife Network Forums : Knife Making Discussions > Custom Knife Discussion Boards > Knife Making Discussions > The Newbies Arena

The Newbies Arena Are you new to knife making? Here is all the help you will need.

Reply
 
Thread Tools Display Modes
  #1  
Old 02-21-2007, 07:46 PM
horseman1 horseman1 is offline
Enthusiast
 
Join Date: Feb 2006
Location: Elbert, Colorado
Posts: 90
Forge burner troubles

OK, I made the plunge and bought some O-1 steel today. Grinding on the sawsall blade and making all those mistakes gave me the confidence I needed I guess So, I suppose its about time to get the forge working then....

I took a look at Ray's mini forge on his (really nice) site and built one similar, but made it out of a (non-gavanized) mailbox. Durn nice too. I used a squirrel cage fan for the blower and everything seemed OK. Even welded up some mounts for all the parts! Except, I didnt think about it being so much larger inside than his... This of course caused me a bit of a problem . It might melt butter, but not too much else. Mapp gas didnt do anything either. I might have some pictures of this thing being made on the computer someplace, but I really dont think they are required. The simple problem is that the forge is way too big for the burner. My bad.

I have an idea that might work and I'd like your feedback on it. A few years back, I bought one of those propane flame throwing weed burner deals. As is is my usual mode of operation, I bought it for an entirely different purpose (just like this!). I bought it to thaw out the frozen water in a metal stock tank that I couldnt get an electric heater to. Anyway, I dont have that problem anymore and I was thinking about replacing the little propane/mapp gas torch with this big puppy. I would of course need to change out the diameter of the gas/air feed line too.

Also, not sure this is important, but I live just above 7000 ft above sea level if that matters at all.

Whachya think about that?

Thanks,

Kurt

Last edited by horseman1; 02-21-2007 at 07:50 PM.
Reply With Quote
  #2  
Old 02-21-2007, 09:00 PM
Doug Lester Doug Lester is offline
Hall of Famer
 
Join Date: Sep 2006
Location: Decatur, IL
Posts: 2,612
Re: forge burner trouble

I built a forge using a mailbox for a frame and I can get up to welding heat. That's with a propane venturi burner from Zoeller Forge. How much and what type of insulation are you using and do you have any refractory material inside it?

Doug Lester
Reply With Quote
  #3  
Old 02-21-2007, 09:15 PM
EdgarFigaro EdgarFigaro is offline
Skilled
 
Join Date: May 2006
Location: Tuttle, Oklahoma
Posts: 717
Check this out too.

http://www.knifenetwork.com/forum/sh...ad.php?t=41183

Kinda on the exact same topic you're on.


__________________
Beau Erwin
www.ErwinKnives.com
Custom knives
Bcarta Composites
Stabilized Woods
Reply With Quote
  #4  
Old 02-21-2007, 09:23 PM
NJStricker's Avatar
NJStricker NJStricker is offline
Hall of Famer
 
Join Date: Sep 2005
Location: Central Ohio
Posts: 2,193
Kurt,

What kind of insulation are you using? And what size mailbox?
Reply With Quote
  #5  
Old 02-21-2007, 10:34 PM
Ed Caffrey's Avatar
Ed Caffrey Ed Caffrey is offline
Super Moderator
 
Join Date: Jun 2002
Location: Great Falls, Montana, USA
Posts: 4,393
Send a message via AIM to Ed Caffrey Send a message via Yahoo to Ed Caffrey
Dimensions of the interior would help a great deal. I started to respond, but wanted to make sure I'd be telling you correctly. If it's a standard size mailbox, you SHOULD be OK with a
1 1/2" diameter burner, depending on the CFM of your blower. If it's one of the "rural" mailboxes (the huge ones) then I doubt your gona get welding heat even if you step up to a 2" dia. burner.

There are several other factors that come into play when using a blower..... the common variety of "squirrel cage" blowers will not handle back pressure, which is exactly what happens in a forge burner application. As the pressure increases, the blower pushed less and less air, therefore you get less heat. If the blower is less than 100 cfm, its likely you won't even get forging heat (above 1500F). Another issue with blower type forges is setting the gas inlet properly, and in such a manner that the air/fuel will get throughly mixed before hitting the combustion chamber. The easiest way to do this is to use a 12" piece of pipe attached to the blower, with the gas inlet just a couple of inches up the pipe. Connect that pipe to a 90 degree elbow, and then another 12" piece of pipe to the other side of the elbow. the end opposite the blower will of course go into the forge body. This setup allows the air/fuel to mix well prior to hitting the combustion chamber, creating more heat and using less fuel.
When working with a blower type forge REMEMBER THIS..... THE BLOWER IS ALWAYS THE FIRST THING TURNED ON, AND THE LAST THING TURNED OFF. To do otherwise is an invitation to disaster.


__________________
WWW.CAFFREYKNIVES.NET

Caffreyknives@gmail.com

"Every CHOICE has a CONSEQUENCE, and all your CONSEQUENCES are a result of your CHOICES."
Reply With Quote
  #6  
Old 02-22-2007, 01:08 AM
horseman1 horseman1 is offline
Enthusiast
 
Join Date: Feb 2006
Location: Elbert, Colorado
Posts: 90
Thanks for the help. I feel silly thinking that this would work, but I'll have to get over it. . I didnt do my research before getting started.

I took a few pictures while I was making the forge. I dont have any of it completed, but these should help. I had planned on feeding mapp gas into the pipe from nothing more than a run of the mill plumbing torch along with air supplied by the blower shown in the picture. The blower is adjusted by the gate valve and the torch went into a hole in the pipe close to the mailbox,. I'm sorry I dont have the dimensions tonight , but I will get them tomorrow morning. There is two inches of inswool inside covered in refractory cement. There is two inches in the back as well.

I got it to work, welded up an adapter to plumb the blower in, but as you can imagine it didnt do the job heatwise.

Here are some pictures. I think I found at least one more problem. There is a fly in the cement! At least he got cooked pretty good even if the steel didnt.





Thanks,

Kurt
Reply With Quote
  #7  
Old 02-22-2007, 07:25 AM
Woodchuck Forge's Avatar
Woodchuck Forge Woodchuck Forge is offline
Skilled
 
Join Date: Feb 2004
Location: Salem Oregon
Posts: 634
From what I see your box is juat fine. You do however need a lerger infeed pipe. As Ed deshecribes in his post just 2 pieces of 2" pipe 12 " long with an elbo in the middle. If you have Wayne Goddards books $50 knife shop and the Wonder of Knifemaking he has a picture of what it would look like. You mighr be able to get by with 1.5 inch pipe. You just need more airflow not pressure but CFM. then get the propane mix right and your off and cooking steel.

Chuck


__________________
http://www.woodchuckforge.com
Avatar, Scott Taylor Memorial Scholarship Knife
Photo by Bob Glassman
Chuck Richards ABS J.S.
Reply With Quote
  #8  
Old 02-22-2007, 09:23 AM
Ray Rogers's Avatar
Ray Rogers Ray Rogers is offline
Founding Member / Moderator
 
Join Date: Jun 2002
Location: Wauconda, WA
Posts: 9,840
I agree with what the others have said. If you look at the burner design I used on the mini-forge you'll see that the propane torch is not the burner but only a fuel supply. This is an important difference! In your case, the forge body is too big for a propane torch to get the job done because there simply isn't enough gas available fast enough. If you were to build that same burner you see on the mini-forge and scale it up to a 1" nozzle and a 2" body as has been recommended by others previously and used a regular propane tank for fuel supply you would be fine if your blower has enough push. You can see this exact burner used on my big forge which is considerably larger than your forge body.

There is another thread going right now in either Ed's forum or The Outpost or maybe in General, I forget, but one of those brush burning torches is being used there and seems to be working well with only minimat modification.

If doing these other things is out of your reach at the moment, consider building a smaller forge body......


__________________

Your question may already have been answered - try the Search button first!






Reply With Quote
  #9  
Old 02-22-2007, 11:00 AM
horseman1 horseman1 is offline
Enthusiast
 
Join Date: Feb 2006
Location: Elbert, Colorado
Posts: 90
Ray,

I used the torch only for the fuel supply. There is a hole in the pipe where I stuck the torch in, about 8" before it got to the mailbox, so it mixed with the air from the blower. I built it using your ideas from the mini forge. It worked and I could adjust the flame fairly well with the gate valve. I just made the body way too big.

So, lets see if I understand the information you all have provided. If I increase the pipe size to 2", use a 1" nozzle, use the weed burner for fuel and my 100 lb propane tank and get a better blower it should probably get hot enough... I can make the inside smaller if I need to, but I plan on using it for general steel bending repairs as well.

dimensions and cubic inches:

The inside is 16" deep and 4" wide. Using Horsemans homemade math, I figure it roughly at 228 ci. Since the shape is not a cylinder, nor it is a rectangle this is the number I came up with for a hybrid of the two. Thats pretty big. I can make it a little smaller inside if this doesnt work.

Do I have a plan?

Thanks for the help,

Kurt
Reply With Quote
  #10  
Old 02-22-2007, 11:54 AM
Ray Rogers's Avatar
Ray Rogers Ray Rogers is offline
Founding Member / Moderator
 
Join Date: Jun 2002
Location: Wauconda, WA
Posts: 9,840
Kurt,

BTW, while I'm thinking of it, you mentioned that you live at 7000 ft. Yes, that will likely affect the performance of your weed burner. Venturi burners can be very sensitive to altitude and air density chances. This is why when you buy one ready made and they ship it rom sea level where it worked fine to you it just doesn't do the job until you twiddle with it for a while. Forced air burners aren't subject to this probem (or, rather they are but you don't notice it because they are fully tunable).

You have a plan but you may not need the weed burner if you build the larger burner. Instead of the weed burner, run a hose from your 100 lb tank to your high quality adjustable (from 0 to 30 psi) regulator which I hope you have and then from the regulator directly into the side of your 2" pipe just above the air inlet. If you do that and if you have enough blower, that arrangement will heat a forge that size very easily.

If you decide to use the weed burner then you don't need to build the 2" burner. This won't get as hot but maybe if you can set up where you can add your blower to the weed burner you can create a hybrid burner that will be hotter than the weed burner (a venturi burner) but not quite as hot as the 2" burner (a forced air burner).

Ed's advice on lighting the forge is worth repeating at this point. Make sure the air goes in first, then the fuel, then the match. When shutting down, the air is the last thing to be turned off. Also, I found it useful to put a ball valve on the fuel line at the point where the propane enters the 2" pipe. If there's a power failure and my blower shuts off that gives me a very fast way to kill the fuel flow. Not stopping the fuel fast enough can lead to what might be euphemistically referred to as a 'bomb' .....


__________________

Your question may already have been answered - try the Search button first!






Reply With Quote
  #11  
Old 02-22-2007, 04:10 PM
horseman1 horseman1 is offline
Enthusiast
 
Join Date: Feb 2006
Location: Elbert, Colorado
Posts: 90
"If there's a power failure and my blower shuts off that gives me a very fast way to kill the fuel flow. Not stopping the fuel fast enough can lead to what might be euphemistically referred to as a 'bomb' ....."

I hadnt thought of that Ray. We get power failures here too often to ignore your and Ed's warning. I'll bet a normally closed gas solenoid valve (like used in a propane furnace) is available to do something like that for us automatically if the juice were to go away. It would probably require a 24 volt transformer but not much else. I suppose I better get it working first and then worry about the modifications

Thanks all. I'll let you know how I make out. If it doesnt snow this weekend I'll get some time to do some work/play.
Reply With Quote
  #12  
Old 02-22-2007, 06:26 PM
Ray Rogers's Avatar
Ray Rogers Ray Rogers is offline
Founding Member / Moderator
 
Join Date: Jun 2002
Location: Wauconda, WA
Posts: 9,840
A solenoid is a cool idea but maybe overkill. I intentionally over state this stuff to make sure the point gets across that this is a serious issue.

In real life, if the blower quits the gas pressure will probably keep most of the flame going out the front of the nozzle. Over time the nozzle will get very hot without the air to cool it and that heat will creep backwards towards the mixing chamber. If enough heat gets back there for a long enough time it could damage your gage or maybe a valve seal or even the regulator. If enough damage happens to let air seep in to that fuel rich mixing chamber with all that heat.....but, this takes maybe 5 or 10 minutes for things to get that bad, maybe longer.

A more likely scenario is the power goes off, the blower quits but the gas continues to burn mildly but not completely due to the lack of air. A minute latwe the power comes back on and a lot of extra fuel ignites and send a gush of flame into your laundry room closely followed by the front of your forge.

Anyway, you can see that you NEVER want to wander off and watch tv while the forge heats up. As long as you're right there when something goes wrong and can switch off the gas there isn't too much to worry about....


__________________

Your question may already have been answered - try the Search button first!






Reply With Quote
Reply

Tags
blade, forge, forging, knife


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -5. The time now is 08:22 AM.




KNIFENETWORK.COM
Copyright © 2000
? CKK Industries, Inc. ? All Rights Reserved
Powered by ...

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
The Knife Network : All Rights Reserved