Gas Forge Design Questions...?

Kalindras

Kalindras

Joined
Aug 24, 1999
Messages
933
Hey, All!

Hope everyone's having a great New Year, so far! I know my luck is finally starting to pick up, at least in the shop area!!

I am, however, still having a few problems getting my forge started, though...and I was hoping some of you Mad-Scientists and Tinkerers could help clarify some things for me. I've practically lived at the NTBA site and Ron Reill's pages, but there are a few questions that are sort of vague, still--I figure they were left vague to allow for adjustment, but I need a benchmark to start from.

Well, first off, I've laid hands on a 2' long piece of 12" OD, 1/4" wall steel pipe ($15, Mobley Pipe and Steel on Broadway in Carrollton, for any locals--Don Chapman runs it, and he's a Knut, so he's willing to help out!). Great! Now, looking at it, it seems so...well...BIG! I meant to go kinda largish, since I figure I'll be smithing more than just knives and swords, from time to time, but I'm also worried about efficiency. It has been suggested that I get one of the 100-lb. propane tanks, to prevent freeze-up and pressure fluctuatuion, but I can't afford to fill that sucker every month!! Part of my thinking was that I usually wouldn't need to heat the whole length of a 2' chamber, but that it might be useful for heat-treating larger pieces evenly. I know I'm rambling, but you guys are my best resource, so try to stick with me, okay? All that said...

Several questions: 1) Is the pipe just too big? 2) If so, what's a more practical size (length-wise)? 3) If not, then how many burners will I need to put on it, so that I can get welding heat out of it? And finally, 4) Is there any wheel already invented that might let me use this forge at full size, and also cut it down, when I'm working smaller stuff, so I'm not wasting heat and gas?

And once I settle on a size, I'm looking to line it with the home-made refractory from Perlite and such on this page: http://people.ne.mediaone.net/wasser/NEMES/MakeICR.html

Has anybody out there used this? How well does it hold up? Is it safe? Or should I just use KaoWool/Satanite?

Here's to finding out, since I'm really twitching to beat some steel!! Thanks in advance for any guidance lent! :D
 
Sounds like it should work.Not much of anything with kao wool being the worst will hold up to borax in a forge.I have a 14 inch pipe 2 foot long standing upright lined with wool and has one burner that works great.I have a 1 foot 10 inch pipe up right that is wool lined that works great and I have a 5gallon bucket on side with castable in it with one burner that will heat the full length of the bucket that I weld in at the present.I liked the big uprite but it was wool lined and I had to patch it everytime I would weld Damascus in it and it didn't have a place to set the billet so it had to be held with tongs or a handle all the time.I think that 2 foot is a little long but for heat treating a long piece might work fine,other wise you cant work very much of a bar at a time anyway and really 6 inches heated is about all you need to heat and work at a time anyway.
Bruce
 
Howdy,

I have what you have and lined it with onelayer of kao wool then put hard fire brick in the bottom, that I shaped to fit, then two more inches of kao wool. Fired it a couple of times and then sprayed with ITC 100 let that dry and topped the whole sheebang off with ITC 296? I'm not sure of that last # . Anyway I used the forge with one burner, based on what you'll find on rons site, for a year with no real trouble except a hot spot in front of the burner. I modified the same forge to take a three burner set up last year and it works great. the hard fire brick seems to stand up to the flux from welding very well as I haven't had to change it yet and it's been in there for three years. Also Ron has a forge on his web site that has three burners and a moveable rear wall. The burners are set up so that they can be used all at once or individually depending on what you want. If you want a small forge you simply move the back wall forward and light only one burner leavbing the other two shut off.



Bill B????
 
Well, dang, Bill...

Leave to you guys to find the page I missed. Where is that, over on Ron's page?

Also, though, Bruce brings up another question for me...I had always sort of figured that I'd be laying this pipe on its side, since that was the configuration of many of the plans I'd seen. But between you, Don Fogg's page, and some work I saw Jerry Fisk do at SOS '01, I'm beginning to wonder if I shouldn't go with an upright?

What are the pros and cons of upright vs. horizontal? Is either one better/more efficient/heats more evenly? Also, is there any benefit to a venturi jet, as opposed to a blower? I'm sure it's quieter, and it uses less electricity, but how about control? Does it get as hot?

:D :confused: :D
 
The only problem I have with the uprite is that the borax builds up in the bottom and I have to take the forge apart every once in awhile to break the gunk out of the bottom as it starts plugging up my inlet hole,and as I said before I would have to hold the small billets with tongs the whole time it was in the foge.I would try making something from stainless now though to set it on.I liked it best as the heat rose up and would actually be hotter than the lay down model with a evener heat through out the entire width of the forge.
The lay down model is easier to keep the flux cleaned out of,but it has hot and cold spots which I am not used to,but it works fine.
Everything I have is forced air,but I have friends that are using ventury style and they don't seem to have any trouble.It doesn't seem to have the heat that can be gotten from a forced air style,but it will weld a billet together.The main reason I didn't set up a ventury style was at that time I didn't know what size hole to put in the inlet pipe for the gas...I will try a smaller size forge than I am using now with a ventury setup for heat treating before long..
Bruce
 
I've used a 14" diameter x 24" tall vertical forge on the Don Fogg model with a forced air burner. The burner is near the bottom and inserts at an angle so that the burning gases swirl around the interior, and the idea is that much of the oxtgen is burned up by the time the heat reaches the upper portion of the forge where the access holes are. This forge easily adjusts from a barely orange interior for heat teating to welding heat with no problem. I'm not sure a venturi type burner would work as well on this type of forge. Adjustments are made by just covering the intake of the blower with a swiveling metal plate to restrict air intake and by adjusting the gas flow with a needle valve. I did experience some scaling on this forge but it probably was caused by having several people using it at the same time for different purposes.

Bruce, the problem you mentioned about not having any place to lay your work in the chamber was solved by just inserting a length of angle iron through the forge so that it protrudes from the access holes on both sides. This helps catch some of the welding flux also and can be scraped off later when the forge cools.

Much of the problem with the gunk on the bottom was solved by just leaving the bottom open and setting the forge on a wheeled metal cart with a table of poured concrete or refractory material.

I like this forge a lot and am begining to build one myself. The burner used for Don Fogg's 9" diameter forge uses a 50 cfm blower but I emailed him about the larger diameter welding forge (to see if he used the same burner described on his web site for it) and this is what he said in his reply.

"The burner for my welding forge is based on a 100cfm blower. The pipe is sized to the blower outlet and is 1.5" same configuration. Everything else is the same except that you might want to add some hard castible refractory or crushed hard firebrick in the bottom to absorbe the flux. I have also welded in a piece of metal on the bottom of the door half inch thick and extending into the forge a couple of inches to act as a shelf to keep the flux off the wall. It extends out past the door opening to serve as a shelf there too."
-Don Fogg

Hope some of this info has helped!
 
I meant to address another issue about freezing the small tanks. I don't understand fully the physics of the problem but a man who has been in the propane businees for many years told me that it was a relation between the amount of flow out of a tank and the surface area of the liquid propane NOT the size of the tank. So a 100 gallon tank, which has the same outer diameter as the smaller tanks for gas grills should experience the same amount of freezing since the surface area of the liquid propane is the same in both tanks.

I'd like some more input on this if anyone knows. I run a single Ron Reil designed venturi EZ-burner on my little forge made from a freon tank for extended periods and have experienced no freeze ups yet. Multiple burners on a small tank might change that but I've heard of using multiple small tanks with a switching valve so that when one tank begins to freeze you can switch to another tank. Seems like it might work well.

It's also possible that the 100 lb. tanks don't freeze up simply because of their greater mass thereby creating a larger heat sink base.
 
I had this problem years ago and the gas man explained it like this.
You are burning the vapers from the liquid gas,if you are sucking the vapers faster than the liquid can vaporize then the tank will freeze up as the liquid id so cold.The colder outside the less it will vaporize in the tank.
At least thats how he told me.
I have a 150 gallon permanent tank they come out and fill and I can no were near suck the vaores that fast with my forge as there is allot of room for the vapores to hold.
Bruce
 
Tanks Freezing.

This uses basic referation principles. Let's use carbon dioxide as an example. At room temperature Carbon dioxide is a gas. With that in mind, there are two ways to make carbon dioxide gas into a liquid or.

1. Pressure
2. Extreme cold

The manufacturing of liqoud CO2 is a little more complicated and combines both of those methods, but that is an entirley different discussion.

Another thing to think about is water? How do we turn water into steam and water vapor? By heat.

Now let's take a look at our tank, it really dosnt matter what gas inside is it wherther co2, propane, freon, etc. Remember the 2 ways to keep a gas a liquid? Obviously our tank isn't some 300 degrees below zero so that leaves pressure. Becuase the tank is warm, the liquid inside literally boils and creates gas. Eventually It reaches a certain pressure and ceases to boil. Technicaly if you had water in an enclosed conatiner that could handle the stress, it dosent matter how much heat you apply to it, once the steam inside reaces a certain temperature, the water will cease to boil.

The boiling is key. The boiling point of water is 212 degrees. The boiling point of propane is way below zero, I belive 108 degrees below zero. So as you use gas, the pressure lowers, the propane boils. As the propane boils, it's temperature lowers to 108 degrees below zero!

I hope that let's you understand WHY your tank freezes.

How do we stop freezing?

I'm not sure exactly what the most efficent method for a tank is, but let's look at an air condionter. You know how sometimes the coils inside can just freeze up? For those of you who havnet figured it out yet, that happens when your fan speed is not fast enough. If the air dosent move aorund the coils fast enough, there isnt' enough hot air to keep the coils from freezing.

I suppose the most efficent way to keep your tank from freezing would be too blow warm air around it, just like an air conditioner does. Of course the air blowing away from the tank is going to be cool, which could be a problem in the winter time. If you could somewhat control where the cool air from the tank goes, your all set. Of coruse in the summer time... cheap air conditioning!

Sorry if I ventured off the topic, but I hope that helps a little bit and you learned something! You can email me if you have any specific questions.

Have a good one!
 
Oh and as far as the surface area goes, if there were less surface it would take a more boiling action to build the pressure up.

Well it makes sense in my head anyway...

P.S. - While I dont work in the refigeration industy, my Pop-Pop did. He was one of the few guys in that industy that actually undertood what he was fixing. I learned much from him.
 
kalindras,

I was just looking on RR's website and could find no pictures of the movable wall on his large forge. I did find mention of it in several loctions, on the forge and foundry page. basically he is using hollow 3/4 inch square kiln legs that act as slides for the back wall to move on. They also act as a spacer that creates a 3/4 inch gap all around the back wall for an exhaust port.The forge is lined with two inches of kao wool and the back wall is made of kao board. I personally prefer a blown forge. I have mine indoors and it is situated very close to a wall. I could not do this if there were an opening on the back wall for exhaust.



Bill B????
 
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