timgunn1962

If 1:12 is the "fast" limit, it seems like longer tapers would be "slower", so you'd be looking at 1:13 and onward.

"Very close" is perhaps a tad optimistic. The gas flow at any given pressure varies with area, which varies as the square of the diameter (assuming the geometry of the hole entrance and exit remains the same). .0485"/.043" is 1.128 times the diameter, giving 1.272 times the area. On those numbers, the burner would run 27% richer than it would with the #57 drill. I actually get 3/64 = .046875 .046875/.043 = 1.09 times the diameter, 1.188 times the area and about 19% richer than the #57 drill.

Reinventing the wheel springs to mind. That sounds a lot like an Amal injector, but without the facility to vary the mixture at will.

The real answer is "whatever works best for you". There are waaay too many variables for a single answer to cover all the possible scenarios. Even the color of the DB will vary in different ways with different setups: some will tend to richen up more than others once the openings become restricted.

Turning the pressure up often works.

I can’t see the video. Not enough air is very similar to too much gas. Try .030” tips. And I’d get a couple of .024” tips in case you need to go leaner still.

Can you fire it up in low light and see whether you have a significant amount of Dragons Breath? This will tell you whether you are running rich (fuel-rich: lots of DB) or lean (fuel-lean: little or no DB). There is a considerable amount of misinformation about burners. Many folk will tell you that you need high CFM from a forge burner because they have successfully used a burner that claims to have a capacity of 200 CFM (for example). Usually, the fans in question are rated for an open inlet and outlet and can only produce a small pressure rise when throttled. If the fan can flow 200 CFM with a fully-open 3" discharge and the discharge is reduced to 1", that's 1/3 of the diameter and 1/9 of the area. That 200 CFM fan is now closer to a 25 CFM "system". Using a vacuum cleaner, which is designed to produce a large pressure rise and to move air against the restriction imposed by the hose, you are likely to be getting a large proportion of the vacuum cleaners rated airflow to your burner. I am pretty certain this WILL be waaay too much air, but checking for DB in low-light is the best way to be sure. We usually want to run with a fuel-rich (reducing) forge atmosphere to minimize Oxidation of the workpiece. I calculated that each CFM of airflow will burn with 0.308lb/hr of Propane to produce a Stoichiometric forge atmosphere (Stoichiometric is a precise technical term which probably corresponds quite closely to "neutral" in smithing parlance). A rich mixture will require even more gas per CFM of air. Googling "shopvac specifications" gets a first hit for a spec that shows 5.1 cubic metres/minute, or 180 CFM, and 1525mm of water column, 60" WC. Peak rated power is 1400W. Even if you were only getting half of that shopvacs rated flow to your burner, you'd still need 0.308 lb/hr/CFM x 90 CFM = 27.72 lb/hr of Propane per hour. I've just used the first spec I found. Your vacuum may have a completely different spec, of course. In your position, I would fit a tee and two valves to the air line: one valve to throttle the air going to the burner and the other to regulate the amount of air being bled off from the tee. The air would come out of the vac into the tee unrestricted and both the exits from the tee would be restricted by the valves. To help understand what is going on, I would fit a U-tube manometer to the existing steel air pipe so that you can measure the pressure. Once you have things set up to your satisfaction, it is worth piping the bleed-off air to an air curtain in front of the forge to keep tongs/handles cool. It's worth keeping this in mind when you put things together.

It would help to know what type of blower you have. If your blower cannot tolerate inlet throttling, there's a pretty good chance it will not tolerate discharge throttling either. If it can't take throttling and can't be speed-controlled, you might find you need a tee with one leg to the burner and the other bleeding off surplus air. If you do, then it is a really good idea to route the bleedoff to an air curtain in front of the forge, keeping your tongs/handles cool. Ball valves work and can be cheap, but have horribly non-linear characteristics and, with 90 degrees of travel, do not give fine control. Many use gate valves with some success. They are designed as shut-off valves, rather than control valves, but are reasonably good at controlling flow in this application, thanks to their fine-threaded adjustment: typically 10-20 turns from fully-open to fully-closed. Globe valves are normally the "correct" tool for the job, actually being designed to regulate flow and having similar fine-thread adjustment to the gate valves. That said, anything that works well enough to get the job done is good and the cheapest thing that gets it done well is optimum for most of us.

From what I can find on t'internet, 14 nanometre seems to be about the optimum particle size for getting the concentration high. I don't know what that relates to in terms of specific area. The commercial rigidizer I've used in the past had a Specific Gravity of a little over 1.1. The best I managed to get with Cab-O-Sil M5 was about 1/7th of that concentration: an SG of around 1.015. This was multiple volumes of the Cab-O-Sil in a volume of water. It was the low achievable concentration that had me researching particle sizes and concentration online. Low concentration seems to be no real problem if you have time and good drying conditions: you just make multiple applications.

That looks a lot like a Devil Forge burner in the photo. If it is one of theirs, they seem to be pretty well sorted, in my rather limited experience of them. You can make the flame hotter/ less-reducing by opening the choke and cooler/more-reducing by closing it. You can increase the amount of flame (heat input) by increasing the gas pressure and reduce the amount of flame (heat input) by reducing the gas pressure. The adjustments will be progressive, but not linear. Have a play with the adjustments in the dark and see what happens to the temperature and Dragons Breath. It shouldn't take long to get a feel for what does what.

I'd roll a kaowool plug to put in the back as you suggest. That will reduce both the volume and the open area (no back port, though you can leave a gap in the middle of the plug if you need a pass-through), then I'd roll one or two layers of kaowool inside the front end to reduce the open area to little more than is needed for workpiece access. That will reduce the heat loss considerably and let you turn down the air and fuel. There will be a limit to what you can do before the mixture speed through the burner drops below the flame speed and you get the flame burning back into the burner tube, so watch for this. You also want the open area to be at least 5 times the burner area, preferably 7 times. If you just have a front opening and make it 2 1/2 times the burner ID, you'll have 6 1/4 times the area. I'd probably just use kaowool initially, use it outdoors and wear a mask, until I had some idea of whether it was giving the desired result. Then coat the kaowool and immobilize the fibres for longer-term use. I'd try very hard not to do anything irreversible unless/until it does everything it needs to do.

I don’t know how easy it will be to get K26 IFBs in Belgium. The K26 seem to be made in the USA and the JM26 equivalents are made in Italy iirc. The specs don’t usually include anything on resistance to thermal cycling. I think it’s basically a case of forge builders in the USA having found that the K26 IFBs seem to hold up better than others that have been tried. I don’t know of a source of KastOLite30 in smaller-than-full-bag quantities in Europe. If you have to buy a full bag of 25kg, 55lb, I’d probably try casting a lining in the IFB Forge you already have first and keeping the rest for planB.

Which gas jet are you using in the T-Rex? lots of folk seem to go for the biggest jet available, thinking more gas = hotter. It’s not quite that simple and in many cases a smaller jet will get hotter and use less gas. We tend to want to burn rich/reducing to reduce scaling in the forge, but going too rich reduces flame temperature. It might be worth investing in a set of mig tips in the next smaller sizes and giving them a try. It’s not guaranteed to improve matters, but it is cheap and the odds are pretty good: It’s certainly a lot cheaper in time and effort than building a ribbon burner and a couple of hours should tell you whether it improves things.

With the caveat that I'm also not a caster, it looks to me like you want to flux liberally to prevent Oxidation and open up the choke fully. If it's a Devil Forge burner, mine seemed to be slightly rich of stoichiometric when fully open: it seemed like someone in Lithuania had put in the effort to do it right. Turn down the pressure because it'll get a lot hotter with the choke fully open. I'd try 5 PSI and adjust from there to suit your setup. If you go too low, you'll get the flame burning back up the burner tube once things warm up.

No. I'm pretty sure it's right. I certainly hope so, because I've been using orifice plate flowmeters for 30 years on the basis that the flow is proportional to the square root of the pressure differential. We only run a low pressure differential across the orifice plates at work (and low line pressures). Things can get a little more complex as the pressure differential increases, but it's a good enough rule for most things most smiths will encounter. The gas jets we use for burners obviously run much higher pressures than orifice plates, but they are still effectively "just" orifices and the flow being proportional to the square root of the pressure holds quite well up to "about" 30 PSI, when the flow becomes "choked". The use of "long" orifices (e.g. when we use MIG tips) probably introduces a bit of deviation from the square relationship as well, but it's still good enough for government work. https://en.m.wikipedia.org/wiki/Orifice_plate https://www.eclipsenet.com/uploadedFiles/Pages/Product_Information/Eclipse_Engineering_Guide/Engineering_Guide_EFE825.pdf https://www.tlv.com/global/UK/calculator/air-flow-rate-through-orifice.html

The burner looks like a Devil Forge burner. I got one to play with a while back and it seems pretty good and pretty well-tuned. With the choke fully open, it should make welding temperature, but still be richer than stoichiometric*. As you close the choke, the mixture will get richer and the flame temperature will reduce. It's reasonably progressive and the range of flame temperatures available is pretty useful. Try again with the choke more open. It should work. If it doesn't get hot enough, open the choke more. You have 2 adjustments with a choked Naturally Aspirated burner. The gas pressure adjusts the amount of gas going in. The choke adjusts the air:fuel ratio and therefore the temperature of the flame. As you close the choke, the amount of air available to burn the gas goes down, reducing the flame temperature, and more Carbon Monoxide will be produced. Carbon Monoxide is deadly, so the only properly safe place to use the system is outdoors. I know 2 smiths personally who have suffered Carbon Monoxide poisoning during 2018. Both were heat-treating and had choked down their burners to get flame temperatures around 1500 degF: lots of Carbon Monoxide. They had previously used their forges inside their shops for forging and/or welding (both processes with more open chokes, higher temperatures and less Carbon Monoxide formation) without problems and did not realize that they were increasing the Carbon Monoxide production dramatically when running choked. One just felt ill, realized the problem and stopped. The other was found unconscious on the floor and taken to hospital. Please be safe. The physics of NA burners means that, once the choke is set, the air:fuel ratio stays pretty constant as the gas pressure is varied. The gas flow varies as the square root of the gas pressure. To double the gas flow, you need to increase the pressure by a factor of 4. * I have a background in burners, rather than smithing, and tend to think in terms of the stoichiometric ratio. Whilst the stoichiometric ratio seems like it "should" correspond to a blacksmiths "Neutral" flame, I have a strong feeling that scaling is still a significant problem at stoichiometric and that applying "Oxidizing", "Neutral" and "Reducing" descriptions to air:fuel mixtures based on the effects seen on the workpiece will be more subjective and less precise.

Where was the choke when you tried it?

Is that degC or degF? What exactly is it about the way it performs that you are having issues with? You have Dragons Breath. This is indicative of a pretty rich mixture. NOTE: This is not necessarily a good thing or a bad thing: Think of it as just a thing. In general we want to run a reducing atmosphere, which is by definition a rich mixture, in our forges. I don't know many smiths who have run lean mixtures, which are by definition Oxidizing, but the few I know who have very quickly looked for ways to make them reducing. The flame temperature varies with the air:fuel ratio and the maximum flame temperature occurs at or near the stoichiometric ratio. On the rich side of stoichiometric, which is where the Dragons Breath indicates your burner to be, increasing the jet size will further richen the mixture and reduce the flame temperature. Unless you want to run at lower temperatures for Heat Treat, it seems very unlikely you need a bigger mig tip. What size is the burner tube?

I'm getting "unsupported format" for the file, running Windows 10.

As I understand things, the Iron Oxide is reduced to Iron by Carbon Monoxide during the smelting process, rather than directly by the Carbon. You need a *lot* of Carbon and quite a lot of Oxygen/air to produce enough heat and Carbon Monoxide to reduce the Iron Oxide. Enclosing a small amount of Carbon with the Iron Oxide will not do it.

Good mixing and accurate control of flame temperature tends to be much more difficult with oil than it is with gaseous fuels. Hard firebrick is a good idea because it is pretty tolerant of the temperature gradients you are likely to have where the flame hits the wall, and is resistant to erosion. If you are going with hard refractory, a properly hard one with a high temperature rating would seem wise. Check the manufacturers data sheet for whatever you intend to use. Some have a minimum recommended thickness and others have a maximum.

I suspect Larry Zoeller has to deal with folk with all levels of technical knowledge and experience on a fairly regular basis, and the only safe option is to assume complete ignorance (and perhaps even stupidity) unless there is very clear evidence to the contrary. If the question was simply "Is it safe to use tubing from an ice-maker for my gas lines?" with no further information and only yes/no options for the answer, the answer would have to be no. If the question was "I have found some tubing which seems to be suitable. It came from an icemaker. I have checked the dimensions and condition of the tubing and it seems to be annealed copper tubing to ASTM xxx. I have sourced the correct fittings, have made a couple of trial flares on it and they seem to be ok. I have assembled the fittings, pressure tested to 60 PSI and found no leaks. Just trying to cover all the bases: is there any reason you can think of, that I might not be aware of, to feel it might not be safe?", the answer might be rather different. If the latter is actually the case, I'd also be interested to know his reasoning. Almost all of the refrigerant tubing I get to see is brazed or soldered, not flared.

You have a blown burner, so you can control the temperature by varying the mixture. Leave the air where it is happy and increase the gas. If you richen up the mixture significantly, the flame temperature will reduce. If you richen it up enough, you can get it down to HT temperatures and this will allow long soak times at optimum temperature. You'll use a lot of gas and you'll need to run it outside, since the rich mixture will produce a huge amount of Carbon Monoxide (and death really doesn't improve your knifemaking). You'll need to reduce the size of the openings too. If you don't, the hot exhaust gases will flow out at the top and draw air in at the bottom. This extra air will cause the temperature to increase. As the mixture gets richer, the flame speed will get lower and the likelihood of a backfire due to the flamefront travelling through the burner block will reduce. As the flame temperature comes down, the heat input to the hot face of the block will come down and the likelihood of a flashback due to the back of the block reaching autoignition temperature will reduce. By keeping the airflow relatively high, and increasing the gas flow to get a cool-burning mixture, you will keep the cooling mixture flow through the burner block high and keep the probability of a flashback low. The extremely rich mixture will help to prevent scaling in the forge and may even help to reduce decarb. If you try this, use a thermocouple and do it outside. The thermocouple is mainly because judging temperature by eye outside is unlikely to give good results and the do it outside part is non-negotiable. Ribbon burners are very good for certain things, but they are not a magic bullet. Their biggest advantage is that they give short flames. To a large extent, flames are scalable. If you have a particular mixture composition and a particular mixture velocity, your flame will be X times as long as the diameter of your burner port. If we take an X of 4 (purely as an example), we could use a 2" single burner and produce a flame 8" long. Alternatively, we could put the same amount of the same mixture through a multi-port burner (ribbon burner) with 28 holes, each 3/8" in diameter and produce flames 1 1/2" long with the same burner port velocity. It is much easier to build a reasonably small forge that keeps the unburned mixture away from the workpiece if we only need an inch and a half to complete the burn and this is the main reason ribbon burners are used. Heat-treatment requires much less heat input than welding, or even forging. I have built forges (using commercial Venturi mixers) that can do everything from HT to welding in a single forge, but I really would not recommend it. For the same time, effort and money, I can build a conventional forging/welding forge and a dedicated HT forge, transferring the burner between them, and get much better performance. For the extra cost of a second, smaller, burner , the HT forge can be made to work very well indeed. I have built several electric HT ovens and am convinced the HT forges are better for a hobby knifemaker working in Carbon steels. The electric ovens are undoubtedly better for stainless steels, particularly those that benefit from ramp/soak programs. They need less attention in use, so are better for the professional as well. For the hobby maker though, the reduction in scaling (and maybe decarb) with the forge is a definite advantage. For my purpose-built HT forges, I normally use a 1/2" burner in an 8" diameter, 20"-22" long chamber and it is ample. The chamber is a 2-foot long 10" thinwall pipe lined with 1" of kaowool and has 1" kaowool board disks pushed in for the ends.

It doesn’t need to be expensive, or pretty, to make it finely-adjustable. A sliding gate will work and a couple of bent-up tabs of sheet metal on it can be enough to make things progressively adjustable with a long 1/4” screw.

You beat me to it. I was just about to post that if you are adding a couple of 90-degree bends and some extra pipe length to get the blower below the forge, do it in the larger bore pipe, not the smaller bore stuff. Looking at your blower, it seems to have about a 2" discharge. This reduces to 1" (maybe even 3/4") just downstream of the gas inlet. 1" pipe has 1/4 the area of 2" pipe and forcing air along 1" pipe takes much more pressure than forcing it along 2" pipe. Because of the way blower capacity tends to be quoted (maximum flow at zero pressure differential), you will have reduced your blower from a 75 CFM to a 19 CFM unit by reducing the area. This is not a problem since it is enough air to burn between 5.8 and 8.3 lb/hr of Propane: 5.8 lb/hr to Carbon Dioxide, 8.3 lb/hr to Carbon Monoxide. We tend to run rich (reducing) forge atmospheres with a mixture of CO2 and CO, so would burn somewhere reasonably near 7 lb/hr unless you have a way to reduce the air flow. The extra elbows and 1" pipe length will probably help to reduce gas flow and if that is 3/4" pipe you have used for the burner, you'll effectively have a 10.6 CFM blower able to burn between 3.2 and 4.7 lb/hr of Propane. It's still worth fitting either a globe valve or a sliding gate to bring the consumption down. If you can give it a threaded adjustment, you'll get much finer control than a simpler friction-held sliding gate.