To answer that we would need to see it lit with the crucible inside. Is that a piezo igniter hanging on the burner wand?
I use exactly the same setup, hair dryer and all although the pipe is about 14" long and the propane comes in about 8 " from the furnace. I'm not certain of the effect of more mixing time on combustion, but I know my pipe gets hot. I've tried my vacuum cleaner blower and, at least at the beginning of the burn, it was too much. Even with the router speed controller turned all the way down I still couldn't get good performance. Maybe because of the pressure aspect, I dunno. When I switched to the blow drier it did fine. I know the burner performs differently as the furnace environment heats up and maybe the vacuum blower would work better in a red hot furnace, but by that time I'm switching over to oil anyway so I just switch out the whole kit. Pete
Agreed, we need to see it in action to be able to say much about your setup. For my small furnace that runs on about 5psi propane, a hair dryer is sufficient, it can't keep up with much more gas than that. In the big furnace, I use a shop vac turned way down low instead as it preheats using propane, but only so that I don't have to switch blowers once I switch it over to run on diesel or wvo... Jeff
I'm not a big fan the HF style torch, as you draw propane from the tank, tank pressure drops due to cooling and alters the mixture of flame, I like having a regulator on the tank you can adjust it for a consistent near neutral flame, I use an old acetylene regulator, it work great.
Yes, but it no longer works. I did some melting yesterday, and from a cold start it took me 2.6lbs of propane to 5lbs of aluminum, and from the hot start 1.5lbs of propane to the 5lbs of aluminum. All I changed from sunday's and monday's pour, was I didn't turn my hair dryer high. I also took note that there is little or no flame when my blower is on, and plenty of flame when my blower is off. Note my camera's exsposure is turned down for visiblity sake. These first three photos are shortly afrter my hot start with the blower. The last three photos are about the same time but no blower. Oh, and Jason thank you for subscription! Very encourageing. Soo... if I increase air flow I lose fuel efficiency? I'm a little confused. I'll try a regulator, probably need to pick one up. Patrick
There is a thing called natural draft. This is a thermal syphon. Anybody who has an airtight woodstove knows what I'm talking about... I live in one of those R2000 homes. It is sealed up so tight, the only intake are leeks coming from bathroom exhaust fans which have gravity louvres(and the hot water tank exhaust). In the dead of the winter (-15°C) I do not have any windows open. I do have a 6 inch flue. To get the fire started I always crack open my sliding glass door about 2 inches. This adds positive pressure to the inside of the building and create a natral draft. Inside it is 20°C, outside -15°C. The cycle starts before any fire or wood or smoke. I build my paper, wood, cardboard pile then fire it off.... At this point there is a fine adjustment of the door being open or closed. This could take up to 10 minutes. Once the flu is syphoning and hot coals are generated I can start adding larger chunks of Split-wood... and reduce syphoned air. This means I can close the airtight's door and use the dampers. At this point in time, I can close the sliding glass door. I can maintain 300-400°C on double wall stainless steel exhaust pipe for three hours with the flu fully open. I can maintain with the same load eight hours at 200°C with the flu choked, after achieved temperature. My fuel is wood. It's air to fuel ratio is enormous at the beginning. But levels out. I could keep re-feuling (wood) every 3 hours, to get an inside temperature above 35°C. (And I've done this before to shorten family parties past 10 o'clock at night). If you want to think about this as a race car (or a big 18 wheeler diesel truck), there is a lot of fuel and air spent getting up to speed. Very little to maintain speed.
If you increase air flow, you must increase fuel flow or your mixture changes and you end up either rich or lean. Too rich, flames goes out, too lean, flame goes out.... Done correctly, the result will be a faster melt up to a certain point, beyond that is where you discover the law of diminishing returns. THAT is when your efficiency of your furnace construction is put to the test. It all boils down to how much heat you put into it vs to how much it loses. They all lose heat! Some less than others.
My burner is made from a HF torch. That torch has a built-in regulator. A speed controller on your hair dryer will help. I use a light dimmer switch on my blower to keep the flame on the lean side.
I don't see the dimensions of the furnace interior but an A3 is a small crucible. I suspect you will spend a lot of fuel heating and cooling your furnace versus the charge since it is quite massive in comparison. Anytime you open the lid there will be significant heat loss from the furnace. This and burner tune are probably the chief contributors to variations in fuel usage per melt. This one area where the advantages of (my) resistive electric furnaces are really apparent. It loses no energy through a vent and does not have to heat all the combustion air. It's only appreciable losses are through the furnace wall insulation and I can touch the outer skin with my bare hand. I do have a power meter on it but and it's been a while since I've even thought about power per melt but after the initial heat, it will melt 10lbs of aluminum in about 15 minutes with 8.5kw of input. The duty cycle is less than 100% for the last half of that time so even at 100% duty cycle and 15 minutes that's only at most 2.125 kw-hrs of electricity to melt 10lbs or .215kw/lb......for me that's about <21 cents to melt 10 lbs or 2.1 cents/lb, and I never run out or have to fetch or store fuel. Set up time is usually a couple minutes. I charge the crucible, plug it in, turn on the switch, and walk away to do something productive. Melterskelter mentioned it takes 400-500 BTUs per lb of aluminum. Me thinks that it's pretty close to 400 BTUs/lb. That's about .12 kw-hr/lb of aluminum melted. So at worst my electric is .12/.215 = 56% efficient. I estimate my furnace is only 50% duty cycle for the last half of the melt and at that it's 75% thermal efficiency. Best, Kelly
That's a good one OMM, and from a very reliable source.................Iowa State University...... Best, Kelly
I root for the Cyclones at all times......except when the play the Hawkeyes....my Alma Mater!!! Best, Kelly
Aha, I also did post grad at Iowa City. So, my loyalties are with both! Thought you’d stir up rivalry, huh?! ;-) Denis
Yeah that was a fun video Patrick. I cast the same bell in the same way (as your failure) and got the exact same result. I haven't tried to recast it yet. We're asking the aluminum to fill a pretty thin cross section, especially if you're using extruded aluminum. I'll use your sprue position and give it another try. Your snap flask works pretty well. I haven't gone that way because I use weights on all my molds and would be concerned about sand collapsing. I use petrobond, and a load of that hitting the dirt would be an awfully wasteful mess for me. I've had enough runouts of my molds in the past so I always weight or clamp them. I could make jackets for the molds but that seems like a lot of work for very little return in our environment. By the same token I've also had some messy pours so between parting line runouts and metal running off the top and down the sides, most of my flasks are burnt to hell and need replacement. Pick your poison I guess. Pete
Well done Patrick. You're off to a great start......and with a couple successful castings, so the addiction begins You have a nice foundry. One thing you might consider is connecting your chimney to its upper section (still removable to access the furnace), space the bottom of the vent several inches off your furnace lid with a couple of blocks or legs, and center the furnace vent in the chimney. This will cause the exhaust system to act like an ejector, similar to a naturally aspirated burner, and draw air into the exhaust stream from the gap near the lid. This will have two benefits. It will dilute/reduce the exhaust gas temperature in the chimney, and reduce the additional air draw induced in your furnace caused by the convective chimney affect, which in turn should allow you to maintain a better tune to your burn and furnace temperature. I'd also suggest that you stick a thermocouple in your chimney just to see what kind of exhaust temps you are seeing and insure you're not at risk of a chimney fire. It would also be a good idea to buy a CO monitor. I now you have a lot of ventilation, but with a good chimney system, I you may no additional ventilation to the room (though certainly cant hurt).....even better if you run the vent inlet over close to the furnace. You could also make a hood several feet above the furnace and put a booster fan in the chimney. With enough cfm, the exhaust will remain cool enough for the fan. Keep up the good work. Best, Kelly
Yah, I considered that. But that project will be for the future. I'll try the chimney setup you mentioned. The flux I use is this stuff. https://www.budgetfoundrysupply.com/aluminum-flux Thank You, for your subscription Matt! And I'm glad you guy's enjoyed the video. Make's sense, I realized that a snap flask would not allow me to weigh down the mold. Do you use a pouring basin? I don't "yet" but that would probably make it easier to keep things tidy. Patrick
