timgunn1962

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About timgunn1962

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  1. I did a bit of playing with jet sizes and found the Butane jetting to work very well on Propane forges. I think the factory jetting is intended for “normal” heating applications which use both primary and secondary air. For Propane forges, there is usually no secondary air so the Propane jetting runs pretty rich and not quite hot enough for welding. The Butane jetting is smaller, so runs less rich and a bit hotter when burning Propane: certainly hot enough for welding bladesmithing steels, though I don’t know whether it will manage WI welding temperature. It’s still rich enough to limit scaling in the forge, so there’s some scope for reducing the jet size further to get even higher temperatures if needed. The Amal jets are available in closely-spaced increments and the sizing is pretty intuitive.
  2. Try increasing the size of the hoses. If you can double the diameter of the long section, the area will increase by a factor of 4 and the pressure loss will go down dramatically (the physics gets complicated, but a first approximation is that the pressure loss varies as the square of the velocity, so you'd get something of the order of one sixteenth of the pressure loss along the same length at the same flowrate). Shorten the hose and the pressure loss will vary with the length (as a first approximation). Ten feet of 1 1/2" hose will give "about" one fortieth of the pressure loss of your twenty-five feet of 3/4" hose. If you go for 1 1/2" hose upstream of the tee, get the tee as close as possible to the burners and use the 3/4" hose (that you already have) between the tee and the burners, things will probably get a lot more manageable.
  3. It sounds to me like you probably don't understand the physics well enough to be asking the right questions. The lines between blowers and pumps can be blurry at best.It's certainly not as simple as changing from one to the other at a defined pressure. "200-300 CFM" is a very wide range when considering the pressures needed to drive flow through a tube. I'd suggest an online search to find the catalog for "Rotron Regenerative Blowers" and read the technical stuff near the back. It'll either give you some answers or will give you a better idea of the appropriate questions. There is a "friction loss per foot of tubing" chart that should prove particularly instructive.
  4. Can you buy jets for the burner separately? If it needs secondary air as it stands, with the choke fully open, to get the maximum temperature that you need, fitting a smaller gas jet will increase the primary air:fuel ratio and reduce or eliminate the secondary air requirement. I would find out what jets are available, if any, and how fast you can get them, before butchering the burner mountings. That way you can see what you get and decide whether to try different jets or cut-and-shut if it does not do what you want.
  5. On the 3/4”, I think the threads in the body are 3/8” BSPT, which will be “about” the 15mm-ish you mention. Personally, I would use a 3/8”BSP hosetail with the barbed end sized to suit the hose. I use O-clips to secure the hose. If your configuration has the burner at top-centre, pointing downwards, there is likely to be some chimney effect and the heat transfer up the burner when it is shut down may make using hose unwise. Rigid metal tubing may be better.
  6. Stuff happens. I think we all knew what you meant. Occasionally making a mistake is normal: it certainly doesn't mean you should stop thinking. I only pointed it out because it's the internet and someone encountering this thread at some point in the future might otherwise pursue a path of extreme frustration.
  7. 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.
  8. "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.
  9. Reinventing the wheel springs to mind. That sounds a lot like an Amal injector, but without the facility to vary the mixture at will.
  10. 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.
  11. Turning the pressure up often works.
  12. 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.
  13. 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.
  14. 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.
  15. 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.