math help

[ironmutt]

ok so as title says math help i have a 8.75 outside diam. pipe .25 wall thickness so 8.25 inside 24 inches long  if i put 2inches of kaowool  it should come out to 320 Cubic inches  so a single t burn should work  or  i was considering a 2inc wide 12 inch ling ribbon burn  to spread the heat around  am i on track math wise or am i off my rocker 

 

[Frozenforge]

Close enough on the math. I have no idea / experience on the ribbon burner part.

[Charlotte]

Read the Info on the supplier site.   but length seems a little long for even heat

[Mikey98118]

A typical forge built from a propane cylinder, which ends up with an 8" diameter interior will start out at bout 19" long and end up with a 16" to 17.5" long interior, depending of whether 2" ceramic blanket or or the much denser ceramic fiber board is used for end enclosures. Such a forge will mostly be heated to an even temp with a single 3/4" burner, with the last couple of inches at ether opening running somewhat cooler. For more even heating you would need two 1/2" burners placed at one-third, to one-third, to one-third distances apart.

Compare this to the much longer and narrower forge you are contemplating, and maybe some more research?

[Buzzkill]

If you get a 2 inch wide, 12 inch long ribbon burner to function correctly I'm definitely interested in the details.  Off the top of my head I'm thinking you'll end up with about 20 inches by 4 inches inside dimensions.  If you center the ribbon burner you'd only have 4 inches on each end that was not in line with your burner.  That seems feasible to me, but what I don't have any knowledge about is how a ribbon burner will work in that space or if you can even reasonably make one that long and narrow and still have it perform correctly.  Hopefully there's someone who knows more about ribbon burners who can help here, but I question whether you can get even mixing and pressure to the holes furthest from your gas/air input into the burner.  Like I said though, if you do get this to work I am eager to hear what you did and how you did it.

 

BTW, if my estimated dimensions are correct, the volume is around 280 cubic inches, assuming a cylinder shape.  If you were going with the full 24 inches and blocking off the ends with brick or something it would be around 340 cubic inches.  But that would also give you 6 inches on each side of your proposed ribbon burner to heat. 

[Frosty]

Multiple 1/2" burners spaced about like Mike suggests though I might go 3. It's easier to turn them down than try to get them to burn at max. My calc says 340sq", close enough to not make a difference and I didn't figure closures.

Trying to get even heat in a 24" long 4.25" dia. tube would be an interesting exercise in how long you want to let it run. If you can even get a 3/4" NA burner to tuned for it I think you'd have about 10-12" screaming, destroy the Kaowool HOT and the temperature diminishing to the ends.

 if you'd like to join me on a little imaginary voyage put what you know aside for a moment come along.  Visualize being a fire tamer. The fire it's a living creature being shoved into a closed space and must escape or die. As fire tamer there are a couple approaches you can take like most forges leave lots of escape routes, big doors, cracks and voids in the walls. What incentive does the flame have to go anywhere in particular when everywhere is of equal attractiveness? So, to make Mr. fire go where you want put it's escape where YOU want it.

Visualize this long narrow forge as an aquarium and the flames as yellow Goldfish. They live happily in an aquarium at one end of the "forge" fish, subway tube. Come feeding time the food is released in several small exit ports at the far end. Little click click sounds signal food and here they come. There are "things" on the floor so they stay near the top till they get to the other end and take a quick dive into the little feeding ports and make their way back home when full. All in all the Goldfish are pretty evenly distributed through the tube.

Okay, come on back from sight seeing around in my head. That's basically how I solve certain problems I free associate till I find a workable analogy and start playing with it.

Maybe if a person mounted a 3/4" NA burner at one end and the exhaust port were at the same end a strong enough flame velocity might carry it to the far end and back. This might MIGHT make for an even heat in a narrow chamber that long. Be fun to play with, A good time to use a brick pile. Hmmmm?

A better model would be clear plastic tube and smoke, you could put the exhaust ports exactly where they'd do the most good.

Frosty The Lucky.

[timgunn1962]

What do you want to do in the forge that needs 24" of length?

I ask the question because it makes a big difference to the amount of heat input required.

If your requirement is to get 24" of Wrought Iron to welding temperature, your burner needs will be completely different to those for getting 24" of Carbon steel to Austenitizing temperature, for example. 

[ironmutt]

i am wanting to do longer stock  like pickets and twisted ballisters   but because of  logistics i need the back of the forge closed for right now i figured with  central located  burner  located in the middle of the  side angled up to the curve to cause swirl it would  heat over all better  but still have a hot spot in the middle i was  considering  build it with a  fire brick  cut to inside demsions with a mouse hole like off tom and jerry  to block off most of the back of the forge  as needed but still let me poke a peice all the way in i can move it forward and back as needed  with the end closed off with plate and layer of wool  i have some 24in long  hard shelf for the floor i can cut down to 3 in wide   to put on the bottom  

 

[Charlotte]

Forging is usually done on about 6" long area at one time.  Long pieces tend to bend.   One of my friends builds beds with Iron head and foot boards.  He lays out his pattern on a platen table, puts clamps and fixed points at critical points then bends the pieces with a big propane heating torch to his pattern.  Even heavy stock bends like candles left out in the hot sun when heated. 

I've seen vids of a big time famous sculptor bending long pieces from a long oven but he had a crew to help him handle the long red hot spaghetti.   

[ironmutt]

i under stand working only six inches at a time  hence the  mouse door plug to allow  for heating in the middle with out heating up end that s still in the far end of forge with out stick out the end  i would love to have a lay out table  i could just go to town on with a torch  but  i dont have room for it right now . i have 2 anvils  a forced air  propane forge made from firebricks and refrac cement , 1/2 pipe side arm design  with a pink 1960 hair dryer blower attached at the side and  a turky fryer frame with a interior demention of 6''wide  6''deep and 4'' tall   so right now if i want to do any thing larger then 6 inches i have to forge weld to gether every six inches or now mig weld it together, a quench bucket and a assorted stacks of scrap it sits inside cause it walks away on its own if i let it play in the yard, my recently aquired post vice and stand i built and a mig welder all cramed in to a 8ft x 11ft area i still have to walk throu to get in and out of my house  witch is also why i want only one opening on the forge  so i only have to  keep a close eye on the front since the longest piece i plan to do is 36''  i figure 24 deep should allow for  doing one end up to the middle  then quenching doing other end  same way 

[timgunn1962]

From your description, it's sounding to me like you want a pretty normal forge with both ends open, but with a tubular heat-shield arrangement on the back end to eliminate fire risk, and even heating over the full 24" is not required? 

If that is indeed the case, I'd build a 24" deep forge with a closed back, stick a single burner about 6" in from the front end, and treat it as a 12" long open-ended forge from the design point of view. I'd certainly expect a 3/4" burner to cope with it, though I have yet to try a T-burner.

Assuming you use Kaowool (I would), you'll want 2" of it on the closed end and you'll want to ensure there are overlaps so there is no direct heat path through the joins. From experience, I'd suggest that unless you have arms like a gibbon, it's probably easier to do this from the outside and MIG weld the end on once you've got it right.