Corin

Well it is probably time I throw my 2 cents in. First up, subject to Glenn and Dales approval, I can run a 1/2 day forge build workshop, Gas forge naturally, I could do a basic kit forge including everything you need to build a working forge. Cost would be around $200 (materials only I won't be charging time naturally). I can provide a huge BBQ suitable for cooking for large groups of people (we have cooked for over 200 people on one of them), and gas to run it. Anything else I can do to help just let me know. Regards

If it is forge and burners we will be doing we can most probably use my shop here at work. Heaps of burners to play with, Plasma cutter and Mig and any amount of cleaned out gas cylinders of all shapes and sizes to use as forge bodies. All gas equipment available including custom hoses. Western Sydney (Auburn). Nothing for forging though, so if its forging your want to do, Phil's will be better. No worries re the photo's as I was mostly taking pictures of people working I somehow missed you..... ;)

Cheers fellas! Blame me for the cold! lol If it makes you feel any better I am still crook Anyhow Just want to say thanks to everyone for a great time. The boy and I learnt a lot, and came away with some fantastic ideas. I will definitely be staying longer if it is a go for next year, and I am thinking seriously about running a gas forge building workshop next time. If it is OK with Moony. If it goes ahead I will provide all materials at cost (including refractory, burner and gas components,) That might pull some numbers for you Dale. Maybe if there is enough demand we should not wait till next year and do something sooner, heck I am keen if you are. I took some pictures, here are a few...

Good point! The foil thing does work and is used just as you describe I have seen it on a knife forum, It works incredibly well, better than air adjustments. Having said that I still believe the most versatile forge is one in which you can adjust the air for operations such as this. The result is not bad, even pretty good, though it does require constant monitoring of temperature and continual adjustment to ensure a good result. I heat treat once a month, its no big deal, and not worth the foil... I too find the door on mine very limiting and yours I note is even bigger! In the last couple of years I have wroked on more and more 20Lb cylinder forges with doors in the side. Normally as high as the ones with front doors. These were all owned by farriers doing the big horses, Clydesdale and such. Great concept but poorly executed because they all had the same problem, very hard to get stuff hot with a gaping hole in the side of the forge, still with your front door concept applied to the side, or front and side doors it my work really well, and would definitely add a huge level of versatility. The side door should be no higher than 2-2.5" though if the ones I have seen are anything to judge by, and you would need to play with the position of the burner so that the flame does not just shoot out the side. A tall chamber is very beneficial in terms of combustion, the hottest part of the flame, is the tip of the light blue turquoise section where the dark blue starts. If you do not have enough height you will get a cold (relatively) spot under the burner and circular forges carry the heat in a swirling motion, also normally better than square forges. Here is a typical forge burner flame. you should be aiming to have the floor of your forge about a good couple of inches" longer than the length of the light blue section from the burner nozzle.

I just checked out your door design... sorry but I am going to have to steal that for my next one! That is a great solution and would be a significant improvement on mine I use door reducers cut out of ceramic wool and cemented, they work OK but inevitably crumble away and break. I probably should rename this thread the most versatile gas forge... perfect is the wrong word, sorry about that.... anyhow, there are some interesting comments there. I would not own a forge without air adjustment, for two reasons... 1) I work in the combustion industry and it is a point of pride to ensure the combustion in my forge is adjusted correctly to the application, and 2) I use my forge for heat treating near finished products (knife blades and machined die sets normally), and when heat treating I do not want any scale to form. I do not know how to prevent the formation of scale without air adjustment (in a gas forge). I can machine a die to within a few thou and hold it at 900c (1650 f) for 10 minutes, quench it in oil then pretty much wipe it clean with only discoloration and very very little scale if any. Without air adjustment I would have to rough machine the die, heat treat and then after hardening and tempering, re machine hardened steel, Knives are exactly the same. The less grinding or machining I have to do on hardened material the happier I am. On the other hand the over rich mix I use for HT is terribly inefficient so when heating up from cold I open up the air and give plenty of gas.... If I do that it gets hot enough to melt 1/2" round steel bar in about 2 1/2 minutes. I don't understand why a faster heating forge would loose heat faster.... would that not depend on the amount of heat you put in and the type/ thickness and quality of refractory?

Thanks for the input mate! I You right about the fun thing and probably about the electric forge too I have no experience with them... but I will be sticking with gas! I think a lot of people who build forges tick a few things off the list, some more than others... I am happy with my own but like your multitool analogy it does have limitations. I would still love to know what the generally accepted heating times from cold to forging and welding temps are, and the ideas on minimum width of door too. I tried to in the original post, but clearly this was always the weakness in the discussion "Clearly the perfect forge depends on the job, so lets narrow it down to the most versatile forge" for the widest range of uses.

yeah I am probably looking for Utopia! I definitely think it can be done though, there are a few designs out there that come very close. What were the best features of each of your forges? Why three?

Ha so this is a can of worms and I bet you all had some ideas of your own when you saw this topic! So... Here is the question, what is your idea of the perfect gas forge? I want to generate a reference list of characteristics that every forge builder should consider when settling on a design. Sure such a list probably exists someplace on the net, but I am keen to hear your own thoughts on what makes a forge better than just good. I have worked on probably over 50 different forges over the years. Servicing burners, tuning burners, modifying burners or just making other peoples projects work. Working on forges got me into blacksmithing, but there are so many different combinations of burner and chamber design and some of those combinations are clearly not as good as others, in terms of temperature. There is of course more to the perfect forge than just temps though. Clearly the perfect forge depends on the job, so lets narrow it down to the most versatile forge The key things I have been asked to do to forges will give us a start. 1) The ability to reach welding temps and beyond, in a reasonable time. 2) The ability to control primary air and hence minimize oxidization of material 3) must heat up reasonably quickly, say less than 5 minutes 4) provision for a thermocouple or pyrometer to sense temperatures for heat treating. 5) must be reasonably efficient on fuel. 6) Have idle and full flame control, so it can be easily turned down but not off. 7) Must be able to accommodate long materials 8) must have a wide enough door for wide and curved materials. How wide is enough? What would you add to the list? can you quantify any of the above? How fast should a forge heat, how efficient etc. I look forward to hearing your thoughts on what exactly constitutes the perfect gas forge.

I suggest you put the whole thing in the car, along with your regulator, hose and any other equipment you have, and bring it down to my place (Picton) on Sunday. I am absolutely certain we can get it working for you. If you are interested send me a pm I will give you my phone number. Corin

where is the sound coming from exactly?

Thanks Jack I was wondering! :blink:

Keep us posted!

Picture, drawing, anything....

Hi Mate, These burners are about as simple as burners can be. Look at the range from companies like My link Harbor Freight, Wallmart, whatever tickles your fancy. If you listen to all the guru's on the net they will all tell you they won't work due to back pressure... This is not true. In most cases it has nothing to do with back pressure and everything to do with combustion air. Here is a picture from "Efficient Use of Fuel" Published by "His Majesty's Stationary Office" in 1944 I have newer publications with different pictures but this is actually one of the better pictures I have seen that clearly illustrates what we are talking about in forges. The text I have added is the amount of air required for a propane burner, the original figures were for towns gas. Methane is natural gas by the way. The second burner is almost exactly the same as your harbor freight burners. note that a little more than half the air for combustion has to come from around the flame. sticking the burner in a forge will not allow this to occur, but by pulling it back a fraction and making the hole a bit bigger, air is drawn in with the flame and combustion will occur within the forge. Not rocket science... but sort of... (if this had anything to do with "back pressure" the flames would not enter the hole, in fact we are now adding more air into the forge. It is just a different way to do it) Now look at the last flame, this is what any well designed natural draft forge burner does (pulls in all primary air), and exactly what a blower (fan forced) burner does. for controllability and ease of use it will always be the best option. These will always be the best option for forging, but any cheap burner with a decent flame will work if you mount it as Old Boiler has now. The first flame is the most spectacular of course, and the most useless for forging, though I once used a flame like this to forge a house.... Here is a picture of a steel house being tested for forest fire survival using approximately 100 Gal of propane every minute.

If your cylinders are filled correctly and upright, (If possible in the trunk of the vehicle) The chances of having an issue are probably less than actually driving the car. Dilution air is not a bad thing in any case, In Australia for this type of usage in a Garage type workshop the maximum size is on 20# cylinder inside, with no more than 100# of total storage inside and outside on the property. for a factory or warehouse type situation it is on 45kg cylinder per 540 Square foot of floor area. It will no doubt be different where you live, I cannot help, but I am sure someone else on here can. Regards Corin

Hi Mate, Firstly, the safe fill level is 80% of the total internal capacity of your tank. You will notice the capacity is stamped with the other information around the top of the cylinder. Normally this figure will have the Prefix WC (water capacity)and then a figure in Gallons of pounds. For Propane, there are 4.2 Lbs per Gallon Therefore, for a normal 100# cylinder you should be filling with 23.8 Gallons If you overfill, there are serious repercussions. As the liquid warms it expands, like mercury in a thermometer. When there is no more vapor space above the liquid, the pressure builds rapidly (the liquid itself cannot compress). At 375 PSI the relief valve opens and liquid is released. The liquid expands 274 times at atmospheric pressure and only about 3% gas to air mix is required to make a nice explosive mix. A very small release can be very dangerous very quickly, particularly in a confined space. I will post a video that illustrates this quite well. Ignore the news reporter, this was a typical overfill accident. A very long time ago through careful calculation and experimentation, taking into account worst case scenarios it was decided the safest fill level was 80%. I see no point exceeding it, though you are of course free to do as you please. I buy my short pattern inspirators from Gameco (and there is a conflict of interest because I also work there) My link The part number is NGB-1 and for what they are they are quite expensive.2 Ipswich.mpg

Very Useful links, thanks mate!

what we refer to as a ribbon burner in the gas industry is quite different from what I have seen in forges. In short I do not have much experience at all with burners with blowers of any type. I have read up on these burners for forges and they look very interesting. In my opinion, I rather have a forge that does not require a blower, and is really easy to make. There are spots in my forge that are hotter than others, but that is actually quite useful, as it allows you to heat thicker sections more than thinner, once you know where the hot spots are. I see little benefit in ribbon burners for what I do. If I ever get around to making a long heat treat forge (24"-36") I will definitely be considering these though.

Hi Jack, interesting thread! Not so sure I would be comfortable living next door to a few of those folk. Your info is good, especially the fan calculations. We have used fans before to get that little bit more... it is interesting to know how much. I made a comment. I could not comment on everything I wanted too. Not enough hours in the day! Don't be sorry about BTU Pounds etc.... really I work in any units, here it is mj/h, kPa, Kilograms, liters and Deg C. we import heaps of equipment from USA and most stuff that comes here from Europe is kilowatts and bar, I am very used to conversions! Take care mate, I hope it is starting to warm up for you. We hit 45 C today. Looking forward to cooling down!

There are a lot of good points on this thread, some well made. There is some misinformation also. Yes it is best to use more cylinders, or larger cylinders to get the vaporization you need. Yes a fan works well to increase vaporization. like wind running through your radiator. Yes lying cylinders down is bad. (liquid relieving to atmosphere expands 274 times to vapor, 2.4% - 9.6 % vapor to air makes an explosive mix, hence much much greater risk. For forktruck cylinders you will note the relief valve is at the top when lying down in the vapor space always present (see below). Cylinders are never filled completely. WC on the cylinder collar denotes water capacity. Cylinders are filled to 80% to allow for thermal expansion of liquid. No,a relief valve going off is not like a BLEVE, It is scary as all hell if it finds a source of ignition, and the ensuing fireball has and will kill. I have tested relief valves, seen first hand a big one going off, been involved in forensic cases where people have been killed, and I have videos that will make you think twice! LP Gas relief valves are generally pop acting, they can go from closed to fully open in a split second. Yes Heating a propane tank is perfectly safe, in much the same way as walking up the middle of a busy highway is safe..... as long as nothing hits you. The issue here is purely if something goes wrong. sure at 113 F you have only 200 PSI in the tank, but at 149 F you have 375 PSI and that relief valve will open (hopefully). If the contents reach about 204 F No amount of pressure will keep propane as a liquid. My link If you do heat, and I am not at all in any way, suggesting you should, make sure. Really sure, like absolutely, you only have one shot at this, positively sure, that you cannot over heat. That heating elements can't short out. That you can't possibly continue to heat an already hot cylinder. That thermostats are backed up by over-temp cutouts. That the over-temp cutouts will absolutely positively work no matter were the fault occurs. Bad things can happen if even a small section of wetted cylinder gets really hot quickly enough. I feel I have a good understanding of propane, I am very comfortable with heating in very controlled conditions. I work on Direct fired propane vaporizers that literally boil propane in a tank with a flame underneath. As comfortable as I am with that, I know it is not worth my time or the equipment to make a system to safely heat cylinders at home, I just use two 20# and keep them over half full. easy. It does not get below freezing here so it is not as hard for me as many of you. If you have cash and a good gasfitter you could always consider the right tool for the job. my link I have set up a thread for propane questions, if you have any, feel free to ask, Propane is my day job... I can calculate your forges BTU's and vaporization capacity for your cylinders or tanks. I am happy to help wherever I can. Ask Propane questions here!

I have not read the previous thread, do you have a link? Following is some basic information and properties on LP Gas that I will use in discussions regarding cylinder freeze ups (as opposed to regulator freeze ups.) Also is a general explanation of how vaporisation works in a propane cylinder Firstly Composition: In Australia and The USA LP Gas used in industry and for home heating (generally speaking) is 90% or more propane. In New Zealand and in Australian Auto Gas, it is a blend of Butane and Propane commonly a 50-50 mix, although there is a huge amount of variance in Austalian Auto Gas. In the Pacific Islands it is normally 90% + Butane. Before you go any further check what the mix is in your part of the world, because it will make a difference. At this stage I will only be discussing Propane, and high percentage mixes of Propane. Think of Propane just as you would water. It is colourless, odourless, (and probably tasteless ), it has three states of matter, Solid (like ice), Liquid (like water) and Vapor, (like steam) (we will ignore that it is flammable for the time being.) At temperatures below about -190 C (-374 F) it is a solid, just like water below 0 C (32 F) is Ice. If we warm it up above ---190 C (-374 F) it melts into its liquid phase. we can hold it in a cup (if we could survive the cold). OK so lets keep warming it up.... at -42 C (-44 F) it starts to boil. just like we cannot heat water above 100 C (212 F) no matter how big a fire we put under it, we can't heat propane liquid above -42 C. It simply boils into its gaseous phase. For every volume of liquid that boils off we get 274 volumes of vapour. These are facts,but we are overlooking something, this is for atmospheric pressure at sea level. Of course it is possible, to heat water above 100C without it boiling, by heating water in a sealed vessel we create pressure, this pressure prevents the water boiling. Think of a pressure cooker or the radiator in a car. http://en.wikipedia....ressure_cooking The more we heat, the higher the pressure will be. By putting the liquid Propane in a container capable of holding pressure, we can thus prevent it boiling when temperatures rise above -42C (-44F) as temperature increases so the pressure will increase too just like in a pressure cooker or a car’s radiator with water. At -1C (30F) The pressure in our propane cylinder will be 400 kPa (58 PSI). At room temperature 15 C (59F) the pressure in your cylinder is about 700 kPa (100 PSI) the size of the cylinder has absolutely no bearing on this, whether it is a few pounds of product in your 20# cylinder, or a correctly full 80 ton tank if both are at the same temperature they are the same pressure. Ok so what happens if we remove some gas? It should be quite obvious if you have read and understood the information above , that if we release all pressure quickly, the boiling point of the product reverts to -42 C (44 F), the liquid will boil rapidly. It needs energy to do this and this energy comes in the form of heat in the liquid and the surrounding air. The temperature of the liquid will drop to -42 as the pressure reaches zero gauge. To put this in perspective, if the valve on a 9kg (20 #) cylinder is opened to full (at room temp), it takes about 4-5 minutes for the liquid temperature to drop to -42 and the pressure to reach 0 PSIG and at this point the amount of vapour being produced is very small, governed only by the amount of heat that can enter the cylinder from the air around the cylinder. Think of what happens if you remove the cap off your radiator. The superheated water flashes to steam and boils off. This process is actually almost the same. (if the radiator had more water in it) So what if we only take out a small amount of vapour from our cylinder at room temperature? Only a small amount of gas removed will drop the pressure slightly in the cylinder. Slightly dropping the boiling point and causing some liquid to boil off the energy for the gas to boil comes from the heat within the liquid, and whatever heat can be conducted from the surrounding air into the liquid in the cylinder. If we take out more gas than what can be boiled off by the heat in the surrounding air, then the cylinder starts to “freeze” Pressure will drop, temperature will drop, first condensation forms on the outside and soon this condensation starts to freeze. The propane does not freeze it just can’t boil fast enough. Whenever we size how many cylinders or tanks and what size to use on a propane installation we need to consider this phenomenon. We do so based on gas consumption required and ambient temperature. It is also important to consider how much liquid is in your cylinder, as heat from the surrounding air must be transferred into the liquid, so hence the wetted surface area is critical. Normally cylinders are sized at 30% full. Think about trying to boil a pot of water by putting a heating element around the top of the pot where there is no water. The effect will be negligible. Insulating tanks is clearly silly, as heat cannot enter to boil the liquid propane, this will make things worse. Increasing the air movement around the tank will improve vapourization, in much the same way as air through a radiator helps cool the water inside, heat energy from the air passing past will transfer into the liquid better than still air, which will chill near the cylinder. Heating the cylinder is a clear winner, except that when things go wrong they really go wrong, More on this later maybe... There are appliances available, called vaporizers, specifically for this purpose, normally for industrial applications, but there are small models. I hope that all make sense, I am happy to answer any specific or general questions on this subject, and can provide more detailed information on request. Lets have some questions!

Hi Mate, First up, A very big thank you for your time in assisting me to understand this. I do appreciate it, and understand you have no obligation to do so. Wow -30 Degrees! Down here we think its cold if it goes under 0 deg C! You are of course correct in assuming, from my perspective, in all discussions on burner orifices all pressures are upstream gauge, and differential is the same thing as we are discharging to atmosphere. You will also be pleased to know that I may have now reached a clear understanding of Sonic flows and identified and resolved my areas of confusion. I was looking for a restriction or a limit in flow after sonic flow is reached, per Phil's comment at the top of this page. I entered my formula into excel and a series of tabular results, for a 1/16" orifice. I then calculated results from my formula and worked out that for this orifice size the constant is 27.35 (I believe I still need to factor in a friction co-efficient to get this perfect for all orifice sizes, but I will get onto that later.) Suffice is to say with my formula (green dots) and a constant of 27.35 the variance from the tables (brown dots) is less than 1% The curves are perfect. I am very happy with my little formula even if it has little real world application. I wish I had excel when I did the calculations that lead to it! I was looking for a change in flow, but the curve clearly shows none. I then went looking for flow curves for other gases, and found this. My link I then realized the error in my thinking. In my application Sonic flows do not restrict mass flow on increase of pressure as was suggested, they limit velocity and increase density. Order is restored in my world Thanks again Jack, am I on the right track now? My apologies to anyone following this conversation that does not care but I do like to understand a thing! Also keep the messages coming if you have burner questions or questions on Propane in General, I am happy to discuss bottle freeze ups, regulators and their operation, in fact as I said at the top anything to do with propane.

This is very interesting to me. I must say I still don't understand, though believe me I am trying. A quick web search to try to learn exactly what sonic flow is, why it occurs and the specific effect on flows when it occurs is not revealing anything that clears it up, in fact much information appears to be contradicting. I then go back to combustion tables and measured flow through orifices in tabular form. I am looking for a change in the graphical curve around 15 PSI which there does not appear to be. Many many years ago I myself spent considerable time developing a mathematical formula for calculating flows through orifices based on available tables (themselves based on measured flows through measurement using displacement meters and orifice plates), I cannot write formulas in forum format so I will write it in Excel format. I am no mathematician and it is possible this could be simplified further but what is certain is that it corresponds within approximately 5-10% with tabulated data on flows through orifices F=SQRT(P)*POWER(D/2,2)*C Where F = FLOW IN mj/h P = Pressure in kPa D = orifice diameter in mm C = is Corins Constant 28.26 Sorry it is in metric but I can supply conversions if required, I mostly work in metric. No compensation is made for sonic flows from above 15 psi and yet this formula retains a high level of accuracy at those pressures. It is not perfect but there are many factors that influence flows through orifices and for working calculations for equipment sizing it has got me out of the proverbial on a number of occasions. Where can I learn more about the effects of sonic flows, are there any reference books of web pages you can recommend?

Sorry just realised it is open both ends. Block the back end with a fire brick during testing (it will heat a lot quicker, still about 30 minutes to full, but 10 should see you toasting marshmallows. I am guessing here but I want to see what this mud does when it gets hot. I am really curious about this mud and its properties. New technologies work great, but people were forging and even casting steel before asbestos, and ceramic fibre.

Great, that is exactly what I was hoping for, but that was only step one, the pictures hold more clues, and we may be welding in this baby yet. (don't get your hopes up, I am optimistic about the termite mud, but it is no ceramic fibre) The next step is to correct problems with you chamber. Remove all the bricks. There is not enough volume in there for that size flame. That termite mud should work OK on its own, it is not ceramic fibre, but give it a go, I am hoping it will surprise both of us. It can certainly take the heat. now next is a very important step. your table at the front of the forge should be level with the forge floor. stand two bricks on end on the table blocking the door, leaving about 75 mm gap between them in the center for you to but the steel through. Try and get them up as close as possible to the forge door. This is a crude fix, but let me know how this goes, I can then advise a more permanent solution. you may need to increase your table size (by clamping something bigger to it temporarily) and remove the swing door so you can get the bricks hard up against the forge. fire it up and leave it for at least 10 minutes, that termite mud will have a lot of thermal mass and will take a while to get up to temp, probably something like 30 minutes before you reach maximum. These two bricks do two things that will (hopefully) significantly improve your heating and temperature capacity. Give it a go an let us know how you get on. If you don't get what I mean with the bricks, let me know, this bit is important to get right. Corin