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4 Pipe Propane Forge Troubleshoot


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Hello everyone,

     We are building a large propane forge (Yes it must be this big, for our projects), and have a 4 pipe setup. Tested individually we orginally had successful burners individually BEFORE we attached them to the forge. After assembling, none of the spouts give more than a thick soft flame, no jets.

     Even individually they behave the same, thus according to what we can observe. I'm going to upload some pics and I'm hoping somebody with experience can notice something obvious.




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1 hour ago, MurrayBGC said:

I dont have a guage at the time, but everything is new, there should be no restriction. What is the general opinion of the design of the forge?

so because it is new there is no fitting in it with a small bore slowing the gas, also the regulator is rated at several hundred cubic feet of gas per second?

if the regulator was supplying the gas at a reasonable speed the bottle would soon have frost on it from the gas evaporation

kaowool is an insulator, refactory cement is not, soft firebricks are an insulator, hard firebricks are not.

I am no expert on gas forges, many others on here are but I would think two layers of inch thick kaowool is reasonable

when you tested the burners were they pointing down like they are now and with firebricks the same distance from the end of them

it looks to me like you have very little insulation so to get that forge hot you may need the gas from 10 of those bottles for a few minutes use

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I agree that your flame issue is most likely related to the tank and regulator sizing.  I would expect you to need at least one tank and 30 psi adjustable regulator for each of those burners.

The other major issue is the one that ID and TP noted: your forge construction.  Even if the side walls have 2" of insulation you appear to have included a lot of thermal mass with the hard bricks lining the sides.  Those will take a good while to heat up, and unless you are going into some serious production cycles you will have trouble.  The other issue is the forge floor.  Hard to tell from the photo, but is that a 1" thick kiln shelf with no, or little, insulation backing it up?  There you have not only a heat sink, but a direct passage to the forge exterior for that heat to escape.

Very curious what kind of projects you are doing that require that length of stock to be heated simultaneously.  Typically I see long twists or bends being done iteratively (in short sections added up).  If it is, say, a heat treating chamber for swords, there are better designs too keep the interior temperature stable.  In fact if you expect this design to heat stock evenly along the length I expect you will be disappointed as well, as there will likely be hot spots at each of the burner locations.

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Thank you for your advice.

To go into more detail, we have a (I believe) 1/4" or slightly thicker steel frame, insulated both under and over the firebrick with refractory cement.

As an Update:

We switched out all the pipes to slightly smaller diameters and redesigned the nozzles so that they could be adjusted. Seems to be working now using only two burners. 

So now we are going to see about setting up for a second tank to provide adequate pressure.

To answer your question, yes we are working on swords, longer axe heads, and other similar weapons. The nozzles are around 6 inches apart. If you think this will be an issue for even heating, what is your suggestion?

Again, we will have doors on both sides that can be closed and opened.




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when working on long items like a sword you only want to heat the area you are working or you will have problems with grain growth,

refactory cement is not insulation

with your burners arranged like that you will get some very hot spots and will burn through the floor in no time

I am no expert but would arrange burners to create a swirl of flame around the inside of the forge

get two inches of insulation inside those firebricks then ridigiser, then something heat reflective

not a good design for large items unless you are going to have 10 strikers to hammer out the entire item in one heat.

how many good swords have you made in the past?

1 even?

I bet you got the idea from on you tube maybe even from our old friend randumb


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Well since it is the first attempt at a larger forge, we have not created larger projects.

Our small forge of similar design works quite well, even with the direction of the flame.

I am also not an expert, as I spend more of my time actually working in the shop and collaborating with others for experiance, rather than living on the forum making conjectures over the work of others.

Insulting those you want help from, usually backfires

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I started working metal for a living in 1976 in case you are interested, mostly I make forges these days and have sold well over 500 of the present design.

I would consider pointing a burner directly at the side or floor to add to erosion in that area rather than hitting it at an angle which is better but you know more than me and have more experience murray so I will leave you to it

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I'm only saying that mocking me for lack of knowledge is counter productive to offering advice. I came forward purely with questions and objective facts. I've made no assumptions about the science of making a forge or weapon, other than that fellow smiths would take a genuine interest in helping teach the trade. I Am in fact interested in your experience and success making forges. That is, respectfully, exactly what I was looking for.

My discussion has been open minded and objective,  and I expect the same response from any adult on this forum. I apologize if I have offended anyone offering advice. It was not my intent.

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Perhaps rather than posting and making a bigger mess, you should stop and read a bit, if you had you would have learned a few things.

1) your placement of burners is going to create hot spots. A heat treat oven would not be set that way, and a wagon wheel would need an open side for the curves. that leaves swords or fencing,  any of these I would want to have a smooth even heat, not spot heats like this would give.

2) no insulation and small fuel tank is a disaster waiting to happen, its a large heat sink.

3) we dont get paid to baby-sit thin skinned people, we help because we want too, or not

4) no one was mocking you.   Most all of us know much more than you do, that is expected and no one should argue that fact,  and no one was mocking you,  just making what are clear observations to any experienced smith from the way you asked YOUR questions.  No one was mocking  you, if they were I would be  coming down on them rather than you.

5) public school lied to you, there are such things as wrong answers, bad answers, and even dangerously stupid answers, there is no room for being PC in a  smithy.


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Your burners are too poorly made, even in principle let alone precision, to work well if at all. Pick one of the many designs available and stick to the plans. No, 10 psi won't drive those burners let alone in such a long narrow chamber. That reg will NOT work even if it could deliver a high enough flow.

Pick a forge design and follow those plans. The one you have now is a deal killer, it won't work as you imagine.

Pull up comfy chair, bring a beverage and snacks then start reading the gas forge and gas burner sections. At LEAST get some idea of what you're doing before wasting more money.

Then get back and we'll give you a hand but lose the attitude I'm too old, been making the things longer than you've been alive and am tired of the same OLD attitudes and arguments.

If you don't like how I answer your questions say so one more time and I wont.

Frosty The Lucky.

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we are not mocking you but your attitude will mean you get less help in the future, If I who has never made a gas forge can see major flaws in what you are doing and those who know much more than me have not pointed out my errors then there is something wrong.

some on this thread are experts on this, for example check out the 'T burner' design and how the author has helped many people over many years make forges that work, you will find out who is who if you actually do any research on this but looking at your design it looks like you have done very little so far

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