Ribbon burner questions

[Vombrown]

I'm about to start building my new larger forge. The inside diameter will be 8" diameter and about 24" long. I'm wondering how long the burner would need to be. Also wondering wether 3" or 2" square tubing for the burner body. Last thing is this, on all the designs I have seen, they remove a circle of steel in the central locations where the pipe is welded. Then weld in a piece inside the manifold drilled with holes. I'm wondering why you couldn't mark the pipe location, possibly dimple the area and drill it. Then weld the pipe on. It seems counter productive to cut out the piece and then weld a piece of steel in the exact same spot. I understand that this piece is only acting as a diffuser to help mix the gas and oxygen entering the manifold. Why does it matter that it is 1/8" lower than flush? I understand that some people weld in a thicker piece in this location than the manifold thickness. I have the materials here to build six or seven of them and I'm feeling like I might just do that. Test this littlle thing and possibly a few more engineering ideas I have.

Please keep in mind, I'm not looking for links to other pages and builds. I have done the homework on this.

 

[Wayne Coe]

Why does it matter that it is 1/8" lower than flush?

The space down allows air/fuel to spread out more.
For that length forge you should have a 9 or 12" burner using 3X3" tubing. I believe 2" would be to small.
Check out the attachments on my Forge Supplies page at www.WayneCoeArtistBlacksmith.com. You should find all the info you need there.
Let me know if I can help you.

 

[EdCaffreyMS]

I concur with Wayne, AT LEAST the size he indicates, and possibly even larger.

Here's the thing about forge burners and blowers....... if you oversize them for the forge, beyond what you THINK you need, you always have the option of dialing them back/down. However, if you under estimate, and the burner/blower is too small, once you've reached it's capacity (and if it's not enough for your needs) you're hosed...... the only option you have then is to build/buy a larger burner and/or blower. And in the case of a ribbon burner, the forge body is generally fabricated to fit the burner..... so in order to up size the burner, you'd likely have to refab the forge body in order to accommodate a larger burner.

In this case I am assuming that you want a forge that will not only be used for forging "straight" steels, but also for forge welding? If so, then I would say 3" X 14"-16" or more..... that way you will for certain have the capacity for welding heat when needed..... but there are caveats....... with a castable forge of that size, and that much thermal mass, don't be surprised if it takes 1-2 hours for it to reach welding heat. Fuel consumption must also be taken into account..... you'll likely need a full on propane tank....... I strongly suspect that even a couple 100lb bottles, cross linked, would "freeze up" before either was 1/2 empty. (because of the characteristics of a ribbon burner, it's not gona take a lot of fuel pressure, but it does require significant volume of fuel)

 

[Wayne Coe]

I really suggest that a forge not be more than 12" long unless you are heat treating really long blades or twisting long balusters. You can only forge about 6" at a time. Over heating will cause grain growth, excessive scaling and decarbonation.

Let me know if I can help you.