Thanks for the video Patrick. Our foundries look a bit different but we've pretty much got the same stuff. There's no small amount of work behind what you've built! Muller is cool. The roto tiller gearbox is a neat idea. A little concerned about your ventillation though. What was that workspace used for in its previous life? Pete
Growing plants! But I have got some venilation, not shown in the video. My venilation conists of, one large attic fan screwed over a window, four windows, and two workspace venilation fans, like these. Sometimes an open door (if the wether is nicer). Patrick
Ok, OMM I have a half answer to your question. It take 2.7lbs of propane to melt 5lbs of aluminum, and to multiply that time 2 you get 5.4lbs of propane to melt 10lbs of aluminum, and to divide the first answer by 5 you get 0.54lbs of propane per 1 pound of aluminum. But that is not perfectly accurate because, the aluminum will melt much faster once there is already some molten metal in the crucible, which means it would take a little less propane to melt one pound of aluminium, and a little more than 2.7lbs of propane to melt 10lbs of aluminum. By the way my biggest crucible can only hold 5lbs of aluminum. And when I was conducting this test I cast myself an aluminum sand ram. View attachment 10848 Didn't pour fast enough, but it will still work! Patrick
That doesn't seem right, it seems like way too much fuel!! I've only that measurement on my furnace once and I used 800gr (1.76lb) of propane to melt 5.5 kg (12.1lb) of aluminum which works out to 0.15 lb of fuel per lb of aluminum.
One pound of propane contains 21000 BTUs. One pound of aluminum requires 400 to 500 BTUs to melt. So, furnace efficiency is what determines propane use in pounds burnt per pound melted. I guess a normal small scale furnace must be something like 10% of ideal efficiency. I guess that is not as bad as I might have guessed. Denis
I thought 2.7 was rather high too so I went to AA and checked the data I posted for my A6 furnace. Mine was under a pound. That's a very nice setup you have Patrick. Indoor foundry work must be sweet.
It's not mentioned by the OP but first melt from cold start will take much more fuel to heat the furnace, subsequent melts much less which could be impacting the data. Best, Kelly
Point taken, a lot of factors affect efficiency, starting temperature and mass of the furnace being major ones. Even so, the OP's numbers it still seem high, the numbers I gave earlier were from a cold start and they work out to approximately 15% efficiency. BTW, if anyone's interested in doing these type of calculations for themselves, at 100% efficiency, it takes 1 kilojoule (Kj) to melt 1 gram of aluminum starting from room temperature and propane contains 46 Kj per gram, diesel is 43-47 Kj/g, veg oil about 36 Kj/g . And for you non-metric users, 1 lb=454 g and 1 btu=1.055 Kj , and for the electric furnace users, 1 Kwh=3600 Kj
Sure is! It wasn't exactly room temperature, because its not a heated building not that it should use so much more fuel. But the way I tested it was, I weighed my propane tank before I started melting, and then afterwards. That is probably not supper acurrate. And I will see if I can test agian today. By the way how do you measure your propane Rocco? Patrick
If by chance you happen to be doing more than one melt, it would be interesting to see the difference in efficiency between a cold start and a hot start. I measured the propane the same way you did, weight before minus weight after. I'm not sure how accurate my weigh scale is but I'm thinking ± 50g is probably a reasonable guess.
I question also whether you may be running too hot, more propane than needed with the extra heat going right out the exhaust. I was running like that early on and started turning down the heat and the amount of aluminum I could melt per tank of propane went way up. In a perfect world the exhaust temperature from your furnace would be not much higher than the pouring temperature you want use. So measuring the exhaust temperature with a pyrometer can give you a good indication of excessive temperature.
Sort of along that same lines, another thing you can do to improve efficiency is to limit, to the greatest extent practical, the amount of non-combustion air that enters the furnace, all of the air entering the furnace should be coming in through the burner with the flame adjusted to nearly neutral, that way you don't have air getting a free ride through the furnace taking heat with it.
Hmmm, what you say makes a lot of sense I'll do some expermenting. I also did some melting today, and it took me 2.8 pounds of propane for the first 5lbs of aluminum (starting cold), and about 1.5lbs of propane for the second 5lbs. That is 4.3lbs of propane per 10lbs of aluminum, and propane $1.80 gallon and 4.22lbs of propane to the gallon rounded up is... about $2 for 10lbs of aluminum and $1 for 5lbs of aluminum, scary. And I've got some questions. #1 Do you think that the floor of my furnace being on the same level as my burner inlet makes a differnce? As in the first two photos. #2 Do you think my forced air burner is adaquate? Shown in photos 3 and 4. I'm working on it. So don't rush me. Patrick
Ahhhh!!! It's the magical hair dryer and hazard fart weed burner! I get it now! Don't forget to post your channel in our sticky thread. >>>>>>>>>> http://forums.thehomefoundry.org/index.php?threads/members-video-channels.188/ I'll take this one for ya... "#1 Do you think that the floor of my furnace being on the same level as my burner inlet makes a differnce?" NOPE! The only concern about your current setup is if your crucible springs a leak, it's going to come out your tuyere. Could be an issue if your foot is there or a propane line. The main thing is the flame isn't directly hitting your crucible. That will shorten it's life, but I see you have a plinth so you should be good. Yes, your hair dryer is probably enough to start out with. You could step it up a wee bit. Look for a used microwave blower assembly on ebay. They are cheap and put out a stiff breeze. More breeze means more fuel ya know.
