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ymber

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  1. I think I'm settling on the low pressure bypass design with a open/shut valve on the main line. Looking at some of the builds people have done like that they're getting +-5C at welding temperatures from it and I reckon there's more precision to be had from it with good tuning. Thanks guys, changing the design early will save me a while messing with hardware that isn't meant to do this. Mangling an analogue valve into a digital system described the original plan pretty well. Now I'm looking at building the forge before I start on the electronics. I want to do mostly bladesmithing in this forge and some smaller general blacksmithing. The largest things it will need to fit are axe heads or large knives and hopefully damascus billets down the line. I'm planning to run a dual burner setup with a pair of 3/4" T burners so I'm thinking 500in^3 is a good volume for the forge interior. That should be able to get up to welding temperature running 15PSI or less of gas from the tank so fuel efficiency should be alright. It's a quite similar design as in the video at https://www.youtube.com/watch?v=QuoKVMZgLgo. I'm planning to use a 12" diameter 15" long water pressure vessel for the shell. With the ends sawn off, 2" thick ceramic wool insulation, and a 1/4" layer of castable refractory over the top of that I get 7.5" internal diameter and 13.5" long for 596in^3 total internal volume. I expect to lose 100in^3 of volume on the bottom for fire bricks to make it D shaped which gives me about 500in^3 in the end. I'm planning to use the MonkeyForge kiln wash recipe since I can't get Plistix in this country. I'm thinking since I want to use this for precise heat treatment as well as forging the dual burner design is the way to go since it will heat the forge more evenly. If I have a blade in a pipe in the forge while it's holding a steady temperature I should be able to get precise soaks for heat treating stainless steels. That's my plan, does anything there sound wrong?
  2. It looks like what I'm looking for is called a proportional solenoid valve. They're the right size, spring return NC, they have a signal input for partial opening, and they're designed to take fuel gases. There are other kinds of modulating valves but all the ones I can see with propane safe seals are big expensive ones for way bigger fuel lines than I'm working with so it looks like proportional solenoid valves are the way to go. Now I'm trying to work out how the control input works. It says the control signal is PWM but the graph on that data sheet shows a DC analogue signal as the control variable, not a PWM duty cycle. If I can control a proportional solenoid valve from the DC analogue output of a 3 state PID controller that's ideal. Otherwise I might look at running the valve off a microcontroller board and just write my own control algorithm for it. I'd have to connect the thermocouple through an amp circuit or something that way but I could probably make it work. Looking at this stuff I increasingly understand why people just rig a gas bypass.
  3. I'm getting around to building a new forge and I've got a notion to build one that can hold precise target temperatures so it can double as a heat treat furnace. I want to use a PID controller with an S type thermocouple on the input and a modulating valve on the gas line connected to the controller output. I'm not very familiar with PID controllers but looking at most of the existing solutions for this, people are using solenoid valves connected to the controller through a solid state relay. I don't like that solution because it doesn't allow for throttling the gas, only turning it off completely so oscillation around the target temperature is quite high and you have to deal with the non ignition hazard. I see Denis Tyrell's solution to that and the non ignition problem where he has the low pressure gas bypass around the solenoid valve and his results are decent but I'm sure a modulating valve is a cleaner solution and with a well tuned controller it could reduce oscillation to near zero. I'm currently trying to work out a controller and valve combination to do it with. Most PID controllers I see are relay output but I'll probably need something with DC output to control a modulating valve. It's the valves I'm having trouble looking for. I need something that's 1/2" BSP, can take propane, and takes some kind of control input that I can get out of a PID controller. Is anyone familiar with these kind of setups? My plan is to put the valve on the main gas line before it splits to a pair of 1/2" T burners. NA burners seemed like the way to go here since the fuel/air mixture is somewhat self regulating as the fuel line pressure reduces which simplifies the whole setup as I don't have to throttle separate fuel and air lines proportionally. I've had good success with my previous 1/2" T burner and I reckon the tuning range on them is good enough to work for what I'm trying to do here.
  4. I can't find anyone selling matrikote in Britain. At this point I think I'm going to have to mix my own kiln wash. I'll call the Morgan distributor and see if they have a list of smaller retailers when they're open again next week. It looks like I was wrong about what happened to the fire bricks. I thought they were cracking from getting hit with tongs but the burner is actually melting them. I guess if it can turn refractory bricks to liquid it's burning hot enough.
  5. There is a Morgan distributor in Merseyside but they don't take small orders and as far as I can find they're the only UK distributor for Morgan. I can easily get Vitcas bricks though and they should perform pretty much the same. Martikote isn't giving me any hits either. I did find another kiln manufacturer and ceramic supplies distributor to ask while I was looking though. There's something called Batt wash that's high alumina but it doesn't look like it fires hard. Apart from that it looks like people in this country mostly mix their own kiln washes.
  6. It's been working pretty well for me. On thin (~5mm) stock it will heat it up to pale yellow in 15 seconds if I remember to put a fire brick over the front. Just made that last night. The ends were supposed to be more fishtail looking but I was using an oversized cross peen hammer and I couldn't get a good angle with it. It turns out there's a box of old rusty hammer heads at this shop and one of them is ideal for what I needed so I'm fixing it up. I just need to sand, fit, and oil the new handle. The next project is tongs because none of the ones already here are very good. I need to make some big enough to hold a hammer head and then I want to turn another one of the old hammer heads into a hot cut hardy. That should be a good test of how this forge handles bigger chunks of metal. I've not been able to source any Morgan bricks in this country but I've found some that will do the job just as well. My sticking point is kiln wash. I've asked around a bunch of different ceramics suppliers and nobody can source Plistix and none of them know of any similar hard firing, high alumina kiln washes that you can get here.
  7. I finally got the forge fired up again and I got some photos in better lighting. There actually is some visible dragon's breath, I just couldn't see it in the bright sun. That's just after I lit it. Looks like a pretty good flame to me. Not exactly in focus but you can see how hot it's getting and there's still some blue flame visible in there. That's the dragon's breath. There's a similar amount coming out of the back vent. Fairly minimal and pale orange. That means it's running pretty well, right? I'd have some photos of it running in the dark but I stopped early because the soft fire brick floor of the forge started breaking to pieces from my tongs hitting it. I'll have to move redoing the insulation in there up the priority list.
  8. I didn't get a chance to fire up the forge last night but I did get a better photo of the jet gap. Next time I've got it running I'll try and get a better forge photo. It should be easy now that it's getting dark in the evenings again, I've just got a list of stuff that needs welding first. The jet gap looks like it's about 1/2D like the document says. It did seem to be burning pretty well. I had that problem working with BSP parts. I ended up using a cone seat union. They're mostly for pneumatics and fuel lines I think but they're widely available and the walls are thick enough that you've got plenty of material to drill and tap.
  9. I'm told it's some kind of pizza oven insulation with an unknown spray on it. That could be some kind of rigidizer or kiln wash, I'm not sure. The stuff feels like hard polystyrene with a slightly cotton wool ish texture. I only built the new burner, the forge was built by another guy before I was at this shop. The burner he built with it was a massively oversized T burner with mismatched threads mashed together with PTFE tape and chokes welded over the air intakes. I'm told it ran at 45+ PSI and sounded like a jet engine and several feet of fire came out of every opening. I don't have a whole lot of expectations for the forge - I'm working with it for now but I don't expect the refractory to last long and I'm certain it would melt under hot borax. When it degrades too far to work properly I'm planning to build a brick pile forge with IFBs and a proper zirconium silicate wash. You can't get plistix in this country but there is Vitcas Zircon Paint Coating and it looks like it's the same chemistry as the washes people talk about in the refractory threads here.
  10. The second photo was after 10 minutes when the forge had come up to temperature. I'll try to get some better pictures when I'm back in the shop next week.
  11. I started keeping a fire brick over the front opening to keep the heat in and that will stop me looking in it too. Almost all of the IR protective lenses I see are green. I was trying to avoid coloured lenses so I'd still be able to see what colour the steel is clearly and these grey ones claim they don't affect your colour perception. They're the lightest shade of IR protective lenses I've seen. What kind of lenses do you use?
  12. It looks like the leak around the MIG tip thread was a serious problem. I tightened it up and checked it with leak foam and now most of the problems I could see on Thursday are gone. I've got a feeling the tapered BSP thread in the top of the T is making it easier to get the gas seal just by tightening it than it would be with a parallel thread. All the connections between parts have good gas seals now without using any tape or gel or similar. That's what it looks like when it's just fired up. The photo doesn't show it very well but you can see a blue flame coming out of the burner. That's after leaving it for 10 minutes to get up to heat. The blue flame is much less visible at that point. There's never any dragon's breath but there is a very noticeable heat haze coming out of the forge openings if I don't put a fire brick over them. That's the burner. The jet gap looks shorter than I think it should. Would that make the flame too lean and explain the total lack of dragon's breath? The jet is possibly slightly off axis too but not by as much as it looks like in that photo. I got it fired up and forged a few test pieces and it's definitely workable now. Mild steel was coming up to orange-yellow temperature and with a fire brick over the front it didn't take long at all to heat 10mm bar stock. Do you reckon I could get even more out of the burner with some tuning?
  13. I got my new forge fired up for the first time today and I can feel eye strain from staring in it so I'm going to get glasses. Are grey polycarbonate lenses that offer UV protection, IR protection, and normal colour perception a thing these days? I'm looking at a pair from Uvex that claim all of that for £14.
  14. Yeah when there were wind gusts you could see it affecting the burner. I didn't want to try it indoors because I figured it's probably burning inefficiently and producing carbon monoxide so I couldn't say how different it is without wind. I'm planning to put together a windbreak and rain cover in the corner of the yard outside the shop to keep everything under. I'll be back in the shop tomorrow and hopefully some 0.8mm MIG tips will have turned up. I'll get some photos of the burner and how it works in the forge once I've sorted out the leak around the MIG tip.
  15. I've spent the last 4 weeks messing around with different parts trying to make the build work with parts that are available in Britain and I've finally got it burning. I had to go with a 1/4" BSP equal fuel line union instead of the 1/8" NPT to 1/4" flare fitting because the 1/8" BSP end of a reducing union was too narrow to tap for M8 without cutting right through the walls but it doesn't have the wall thickness in the first place to tap for M6. The jet nozzle is 1mm so about 0.11mm larger than the 0.035" in the design document but we'll see how that plays out in tuning the thing. Going down to 0.8mm would be an option. Right now the problems are a probable leak around the MIG tip thread and the hose is directly connected to the gas assembly which gets concerningly hot after it's been on a while. When I've got it tuned I'll write up a document for the build. It wasn't difficult to build in the end, it just took a while experimenting with parts to find out what works in this country. I'll report back with tuning results. VID_20220825_185727449.mp4
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