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  1. #1
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    Default Casting Tools Part 2 - Burners

    Hi All,

    Here are three LPG burners, the first two are normally aspirated, the last one (most recent) is forced air.

    The design is pretty simple, you have a LPG cylinder with an adjustable regulator, the one I use is a standard CIG (BOC) 0-400kpa, mostly I run in the range 0-150 kPa...

    A gas jet, which can be as simple as a brass tube with a small hole pointing down the pipe, I've used gas tips so I can play with nozzle sizes, TWECO 14, I think from memory.

    The next thing is a means of adjusting the mixture, this is just a series of slots that are covered with a sliding tube.

    If you are running the burner in free air, then you need a flare on the end to reduce the gas velocity to less than the flame velocity, otherwise it will blow itself out, once the burner is inside the furnace, that problem goes away. A temporary flare of sheet metal is easy enough to make anyway.

    Ok that's the basics.

    This is the first one, normally aspirated, gas jet directed straight down the pipe, and sliding mixture adjustment.




    The extra sliding section, was an experiment to see if the position of the gas jet relative to the air inlet section ending made any difference.. as a burner it worked fine, but struggled with larger bronze pours, so onto the second generation..

    This one has a flared section for the air inlet, and the gas entry point is where we expect the air velocity to be the highest, just at the end of the flare (remember bernouilli)





    This is the best normally aspirated burner yet, we can melt 1 kilo of bronze in 7 minutes. The secret is more air and more gas. Unfortunately we couldn't get to cast iron temperatures, for that we need... more air more gas... so the next one is forced air.

    Initially we used a vacuum cleaner (make sure you connect to the correct outlet), and ran that off a variac, it worked fine, but was very noisy, and way too big for the job. We melted zirconia fibre blanket with that cranked up, so I got a spa air blower, the kind that you use to put bubbles in your hot tub... (my hot tub goes to 1400C ) Big plus was that it's completely silent. and small.

    Going to forced air, meant that I had to bring the gas in from the side, not ideal, but, I thought a quick shut-off valve would be a handy addition, so it quickly got over-engineered.





    The other upgrade for this burner, was to get some titanium tubing, going to cast iron temperatures was a problem with the steel tubing on the previous burners.
    So it ended up over-engineered and you could make the same thing much simpler.

    The blower speed is still controlled by a variac and the fuel/air ratio is a combination of gas pressure and blower speed.

    The burner tuning is done by observing the flame colour as you adjust the mixture.

    A rich mixture has a green tinge to it.
    A neutral mixture is a nice clean blue long cone.
    A lean mixture is a blue with short cone and reddish tinge.

    This is a picture of one of the earlier normally aspirated burners, being tested, note the flare.


    Regards
    Ray

  2. #2
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    Default

    I'm starting to get ideas of stealing your ideas..........
    Thumbs up for taking the time to post all of this up.
    Matt
    Warning Disclaimer

  3. #3
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    Default

    Quote Originally Posted by matthew_g View Post
    I'm starting to get ideas of stealing your ideas..........
    Thumbs up for taking the time to post all of this up.
    Matt
    Hi Matt,

    No problem, happy to provide as much information and help as I can.

    Next installment will be the furnace, but that will be in a couple of days time. Then we can move onto the cope and drag, sprues and risers, cores and vents...

    It's always good to remember that this stuff isn't rocket science, the Greeks (and others) were doing bronze casting 2500 years ago...

    Regards
    Ray

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    wish I lived around the corner from you

  5. #5
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    Default

    Very nice Ray... I have read that you can use a hybrid LPG/sump oil burner to attain temperatures suitable for melting cast iron...

    You use the LPG to get it started then switch over to the oil.. Other then that there is the usual coke fired furnace, but coke is probably hard to get although I could bail up one of the 20 to 30 coal trains that pass by here every day....
    Gold, the colour of choice for the discerning person.

  6. #6
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    Quote Originally Posted by eskimo View Post
    wish I lived around the corner from you
    Now your'e talking... I could do your casting, and you could do an aircon for the workshop...

    Thanks .RC, There are a lot of advantages in a dual fuel system, I think the cost of oil is cheaper per kilowatt-hour, and I'm pretty sure I've read that you can use waste oil (like sump oil) certainly worth investigating further.

    Regards
    Ray

    Edit I wouldn't bother bailing up a coal train, just put a few bumps in the track and I'm sure plenty would fall out..

  7. #7
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    Quote Originally Posted by RayG View Post
    I think the cost of oil is cheaper per kilowatt-hour, and I'm pretty sure I've read that you can use waste oil (like sump oil) certainly worth investigating further.

    Cost of oil should be free.. In AME many years ago there was an oil burner for melting cast iron..... I will see if I can find the article... It also mentioned in the article you can use copper as a replacement for ferrosilicon..
    Gold, the colour of choice for the discerning person.

  8. #8
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    I have researched oil burners in past. Just googled "Backyard casting". First position gave meA homemade waste oil burner

    I have started building one but is low in priority at this point.

    Dean

  9. #9
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    I played with an oil burner but went off it very quickly..the stench it made was really quite objectionable, and tended to linger for a long time on still days. Its a shame, because I really like the low cost aspect of this.

    Of course I may not have been doing it right...it was a fairly rudimentary setup...and I gave up on it very quickly (in favour of charcoal only for melting Al)

  10. #10
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    Quote Originally Posted by 19brendan81 View Post
    I played with an oil burner but went off it very quickly..the stench it made was really quite objectionable, and tended to linger for a long time on still days. Its a shame, because I really like the low cost aspect of this.

    Of course I may not have been doing it right...it was a fairly rudimentary setup...and I gave up on it very quickly (in favour of charcoal only for melting Al)
    One thing I remember seeing in my research is the fact that there is no smoke etc when operated correctly. The main attraction for me is the low cost and the ability to just turn it off. I have managed to melt a partial load of brass, probably 200g using heat beads, but it is hard to work out how many are needed at the start. Too many and it costs more, too little and it costs more cos it takes longer to get up to heat after adding more.

    I have about 300+ litres of sump oil stored up from a long period due to the difficulty to dispose of it correctly where I am. I am sure there are thousands of litres sitting around the area sheds. If I can get it to work it is dirt cheap for me. I believe the oil must be filtered first tho. Nothing too serious but try to remove the solids.

    I was going to draw off the top 90% after sitting to allow it to settle then run that 90% through an oil filter from a car using gravity and time or a pressure system with compressed air at about 10 to 15 psi. First I have to strain off moths and leaves etc. Set this to run somewhere out of the way and provide fuel in advance. I also have heaps of fine and ultra fine stainless mesh as discards from work. The ultra fine is about 3 ft diam disk. The remaining 10% needs more careful treatment due to possible water etc.

    Thats what I am going to try anyway.

    Dean

  11. #11
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    Yeah I read that, and mine did indeed burn without smoke, however it still smelt horrible....I gave up on it before the neighbors started complaining but if I didnt it surely wouldnt have been long before someone whinged.

  12. #12
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    Quote Originally Posted by 19brendan81 View Post
    Yeah I read that, and mine did indeed burn without smoke, however it still smelt horrible....I gave up on it before the neighbors started complaining but if I didnt it surely wouldnt have been long before someone whinged.
    The joys of living in the bush. I can run up my big chainsaw, angle grinder, cutoff saw or anything else I want anytime I want. All I have to consider is fire restrictions during season. Take sensible precautions. I love it. If I have a water hose available and suitable clearance around I could operate an oil burner anytime except fire ban days and nobody would know, let alone complain. I don't have mobile phone reception but that is a plus for me. A good excuse to turn it off.

    Dean

  13. #13
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    Yep, that certainly would make oil burners an attractive option as they are definitely cheap and you wont need to worry that your property will smell like a mitsubishi owners convention as there will be no one around to smell the fumes.

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