Rich S.

Hex Forge - idea for your review

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Read the (gas) forges 101 and had some questions about a slightly different propane forge design based on the old vertical forges 20 years ago.  Had one for a year or so and loved it.  Broad and even heating band, easy to adjust air or gas with extra valves and fan, just let steel cross the 12” inside diameter to heat it, or dangled the knife inside the vertical forge for heat treating.

Started chasing a fine woman around with kids…you know the rest.  17 years later, ready to restart but don’t think much of the current forge styles.  Believe forges heat metal best as a radiant oven and disagree with the burner blasting straight down on the metal.  Also, dislike the metal just resting on the floor, basically getting heated on one side. 

So, rethinking propane forge and want some feedback on peoples’ expectation of this idea, which am calling a “hex forge” to keep it simple.

Intent is a propane forge to heat and weld objects such as knives to 18”, hammer heads to 3-4 lbs., rr spikes, and simple scroll work.  Believe steel object inside the forge would be sized from flat bar to hammer heads of 3” x 3” x 9” long.  If openings are 3.5” x 5” wide, some scroll work could be done.  A pass through opening on rear accommodates long knives and implements.  Want burner flames to rotate around interior, without hitting floor first.  Floor will have special tiles/boards to resist flux.  Several ceramic bunks will hold steel elevated to heat the steel from all sides.  The side the burner flames first reflect from may have special coating or boards to withstand flames.  Starting with two ¾” T burners which can be turned down if needed.

Steel shell is hex with 6 5/8” per side but with the bottom dropped an additional ½ to accommodate the ½ floor casting.  Two 1” insulation blankets for interior sides, rigidtizer and some reflective coating.  Ends are more steel with 2” insulation and pass through openings.  Burners are mounted on left side about 2.25” above the center, about 4.5” apart (keeping it simple.)

HEX 4 SUBASS 1.JPG

a cross-section thru the first burner is shown here, giving interior view....

HEX 4 SECTION 1.JPG

Floor casting is ½” thick on bottom with ¾” wide ribs sticking up to support the steel to be heated.  This also centers the working object near the forge center and allows heating from all sides.  The floor casting needs to withstand flux, but not direct flame contact.  The upper right insulation panel may need extra help to withstand direct flame contact.

Interior volume is 560 cubic inches including the floor casting and ribs.

The horizontal burners are mounted 2.25” above the forge center, with say a 3” x3” hammer head projecting 1.5” above the forge center.  Thus, the center of the burner would clear the hammer head by ¾”, which should work for the first and second side wall reflections.  Flat steel objects would get more flame clearance.

Sorry to make it long, but in your experience, does the hex forge have merit?

3rd pic is a longitudinal cross-section which shows the blue support bunks for the steel being worked......

HEX 4 SECTION 2.JPG

Thank you all for your ideas.

 

STOP playing with font sizes

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Interesting idea, but I'm not sure how practical it would be.  I'm imagining catching stock on the relatively thin vertical supports and thinking that between the thermal cycling and mechanical damage they may not last long.  It also creates multiple pits for scale, crud, and flux to build up and potentially become heat sinks.  I'm not trying to pour cold water on your idea.  I just tend to look for potential pitfalls when I'm brainstorming with my own ideas.  If you try it I'll be interested to hear how it works out for you.

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The design has merit, however the vertical ribs would be a problem with small stock falling between them making removal a chore if you could reach them.

Also Welcome to IFI, I always recommend this thread to help with getting the best out of the forum.

https://www.iforgeiron.com/topic/53873-read-this-first/

 

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Forget the complicated floor. Use K26 highly insulating and tough firebricks from eBay; they are cheap, and cost very little for shipping because they are super light.

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Check out the Build a Gas Forge at the Forge Supplies page of my web-site.  You can find it and other contact info on my profile page.  Much simpler than your proposed design, it does create the swirl effect.  I agree with others about the floor.  I have a soft fire brick inside my forge and prop work pieces up against it.

Let me know if I can help you.  I prefer e-mails.

Wayne

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I like the hex idea. My first thought on the floor beams was, “what is something small falls in between?” I think it’s a clever idea, but agree with earlier posts about the practicality of that design element. Nice job with the cad drawings too!

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If you want to keep something off the floor of the forge there are all sorts of "kiln furniture" items available. such things as small cubes, triangles, short cylinders, as well as kiln shelves that are as small as 4" x 6". All of these would be low profile, and would be removable and re-position able.

Alan

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I've given thought to and experimented with circulating fire under the work as well. Two things became evident right away: First, if you let your forge floor come to heat then conduction through direct contact heats the stock much faster than re-radiated heat. Second, it only takes a LITTLE space under the work. I used round soap stone in the experiments and was reasonably happy with the results.

My next forge will have a corrugated floor on about a 1/4" scale. Though it's not going to be a horizontal cylinder or vault.

A couple problems come to mind looking at your concept drawings: First, casting a hex is more work than a cylinder. Secondly you're sacrificing a LOT of usable floor for the hoped for benefit. Third is not having a flat floor to lay work on, the gaps WILL cause sags, especially when you consider the increased surface area of the standoffs will mean they're hotter than the rest of the forge. Lastly are all the pits to hide dropped work and dross.

A vault, (cylinder with a flat floor) shape has a couple advantages: It's easy to make, REALLY easy and not just by filling the bottom of a cylinder. I'd use sono tube and styrofoam or lumber to make a form and cast the thing. This is how I made my first propane forge. The semi-circular roof is a better lens than 3 flat surfaces so IR is more focused.

One of Bernoulli's principals of fluidics says, (to paraphrase from memory) ANY fluid flowing over a curved surface creates a low pressure boundary layer and flows faster. I used to think this only applied to the upper surface of wings but it applies to the inside of a curve as well as a fluid flowing through a pipe. Gas and fluid operate the same way.

Fewer sharp turns to make means less turbulence in the chamber and more even heating. I don't think the difference is significant but it's there. The smoother the flow of flame the fewer flame shadows and cool spots which is the point of building standoffs  into the forge floor.

We're on the dame basic page here Rich, I just think you've carried the working idea past the point of diminishing returns into the realm of detrimental. Of course that's just my opinion I could be wrong and not particularly surprised by it. ;)

Frosty The Lucky.

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I think the hex portion of the design is brilliant. Especially if the shape allows for additional modules to be added for larger forges (thinking these could be modular for one, two, four, and eight burner options). For the flooring, I like the concept of even heating, but there would need to be a flow from one floor section to the next. Otherwise, this design would have one area that could be drastically hotter than the next. I like the concept, but I think it needs a little refinement for even flow from back to front to deliver the even heating you want from the design. Personally, I think you are onto some great concepts and I hope you bring them to life. If you produced this and gave yourself the ability to make pull outs and inserts of improved versions of the flooring, you would end up coming up with a killer design. Version 1 is some great new ideas and with some tweaks, you could have something revolutionary.

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54 minutes ago, PaperPatched said:

as well as kiln shelves that are as small as 4" x 6"

I'm interested in that; could you clue me in as to where to look, please?

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Mikey,

The Ceramic Shop dot com in Norristown, PA has the 4" x 6" kiln shelves. I just looked and their smallest is 2" x 6"

Alan

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Im thinking, that if you only had one ridge at the front and back of the forge, and a kiln shelf which rested on top, and was slightly narrower than the whole forge-thus allowing the circulation of the flames around the kiln shelf, you would get the effect you are desiring without having the problem of stock falling between ridges, and it would be easy to remove and clean the kiln shelf or switch it out

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That's not a bad thought Andrew and it's only one more step to the "recuperative wall furnace" which is better still.

David: What's to prevent making any forge modular? Cylindrical, hexagonal, vault, square, etc. Make the end wall with the door removable, slide another module in place and hook up the fuel line. This is a lot more practical that it may seem at first blush.

Imagine you have a couple beginner students who don't know how to work close to others. This is REALLY common in a country with few shop classes. You have a couple single burner square forges, in two comfortably spaced stations. Later as they advance the class project turns into grills, railings, grates. The students can work safely together in fact frequently help each other. Now though they need to twist pickets, and various grill, grate, etc. elements. You simply put the two single burner forges together with maybe one that's under a bench and you have a forge long enough to make uniform heats on long stock.

Hmmm?

Frosty The Lucky.

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Frosty, you have a great point. I saw the octagon and just thought about the ease of placing walls together. But a flat side (rectangular or square) could do the same thing. Not sure about cylinders, but I know from other feedback from you that if you see it as doable, you have much, much more experience than me. After building my cylinder, I almost immediately thought that I should have gone with a square design. I love the idea of a modular body because I use only a small portion of mine for almost everything. But if I could “snap on” an extension to allow for larger stock, mostly for hardening, normalizing, and annealing than I would probably put a large value on that feature. As I say this, I have a grand total of zero projects where I would have used it to date. So I may be overthinking the whole thing. What are your thoughts for being able to extend the depth of your forge? Is it a requirement as you work on different projects? This is one of those areas where I don’t have enough exposure yet, so I would love to hear from someone like you that has real world experience for projects where the stock becomes longer. Do you focus the areas you work around what you have? Or do you solve the issue as it presents itself? Since my projects have been under one foot, I like having a small area to heat up for the forge. I can run it for ten minutes and I hardly use any fuel. Btw, have I mentioned I owe that to the feedback from this forum, for a small space and best refractory and IR? I saw a post tonight where an individual had used a different refractory and no Kaowool, and his forge was taking 30 mins to heat. I know that if he changes to what I would call the IFI best practices, he will heat up that forge in 5 minutes. Had to give kudos to the brain share here because in that one post, it shows how much I have gained from brains here. Anyway, I really would love to hear your feedback Frosty on the “modular extension” question. If it has value, I may look at something for my version 2 design.

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