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  1. #1
    Join Date
    Nov 2017
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    Geelong, Australia
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    Default First furnace build

    Made a start on my first furnace on the weekend. I'm going with the design from the book "The Artful Bodgers Iron Casting Waste Oil Furnace".
    Why that particular one? I managed to get hold of the book, it makes sense, and seems relatively simple while still being practical and sufficient to melt cast iron should I want/need to do that in the future.
    For a start it will just be aluminium and probably some brass/bronze.

    For those not familiar with the design, its a castable refractory inner cylinder surrounded by insulation (I'll be using ceramic blanket), foot lifted lid and the ability to melt directly in the furnace for breaking down large bits of scrap. Powered by an simple preheater type of oil burner.
    Inner diameter is 250mm and the outside roughly around 400.

    I was going to start with an old beer keg as the author had done, but stainless is a hassle to work with, and I remembered I had an old gas hot water service in the scrap pile. It was working OK but got swapped out for a larger unit at our old place as the ladies of the house demanded more hot water!!

    So, out with the Aldi plasma cutter and made a start....






    Steve

  2. #2
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    Nov 2017
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    Default

    Got the outer skin cut to length and cleaned up the cuts on both that and the lid.




    Steve

  3. #3
    Join Date
    Nov 2017
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    Geelong, Australia
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    Default First furnace build

    The water heater cylinder was about 380mm diameter and I really wanted a bit larger for the furnace outside to get a reasonable thickness of refractory without making the inside opening too small.
    So out with the plasma cutter to make vertical cut and inserted some 40x3mm flat (in 3 places).




    The opposite applied for the inner to contain the refractory. I cut another piece the same length off the cylinder and then removed a piece from the side so I could squeeze it up and make it smaller. When I squeezed it up I found that the original factory weld had softened the material and it wanted to bend there rather than staying nice and round. I'll weld it up and then find some way of massaging it a bit more round - although its mainly an outer former for the refractory so definitely not critical.



    Steve

  4. #4
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
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    71
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    5,942

    Default

    Looking forward to see the furnace in action. I could do with something like that myself for melting down scrap metals.
    Kryn
    To grow old is mandatory, growing up is optional.

  5. #5
    Join Date
    Jul 2010
    Location
    Melbourne
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    9,088

    Default

    Quote Originally Posted by OxxAndBert View Post
    The opposite applied for the inner to contain the refractory.
    Quote Originally Posted by OxxAndBert View Post
    although its mainly an outer former for the refractory so definitely not critical.
    Make up your mind ok I assume its a typo. If its the inner former, aren't you going to want to be able to get it out?

    Watching with interest. I made a half start on one years ago but things got it the way.

  6. #6
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    Nov 2017
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    Default

    No, that’s perfectly correct.
    There is an outer, then ceramic fibre insulation, then a relatively “inner” strong cylinder to contain the refractory, then the temporary former inside the refractory - which will be removed as you say.
    Clear as mud

    Steve

  7. #7
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    Nov 2017
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    Default

    Been doing a bit more on the furnace.

    Have the outer shell and outer former mounted on a frame with wheels.
    Cutout for the burner tube and preheater has been done and boxed out.
    Outer tube for the tapping point fitted.





    Steve

  8. #8
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    Nov 2017
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    Geelong, Australia
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    Default

    And the inner former that will be removed after the refractory has set.




    Steve

  9. #9
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    Nov 2017
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    Default

    Foot operated lid lifting mechanism mostly done.
    I’ll wait until the refractory is done to do the final details like some detects to lock rotation in the raised and lowered positions.





    Steve

  10. #10
    Join Date
    Apr 2018
    Location
    Drouin Vic
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    Default

    Looking good Steve. Have you got protrusions inside the lid to hold the refractory to the frame? Also I have to wonder about the metal dome over the lid; my lid frame is just a steel ring- an extension of the outer former- with bolts welded around the inside pointing radially inwards to anchor the refractory. I find the flat top of the lid useful, I sit chunks of scrap on there for preheating prior to dropping into the crucible, makes sure they're dry.

  11. #11
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    Nov 2017
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    Geelong, Australia
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    Default

    Thanks Pete.
    Ran out of gas for the MIG yesterday so still have some things to do to the lid, including something to retain the refractory. Was thinking about just running a ring of 10mm rod around inside the lip, but can easily add a few bits of rod too. I've noted the author's advice not to run any metal reinforcement actually through the refractory as it tends to crack it in use.

    Good point about the dome shape. I don't particularly want to redo the support arms but can easily cut the center out a bit larger to where the brackets attach, and cast that bit flat at least. Better than nothing.

    Steve

  12. #12
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    6,439

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    Hi Steve, Guys,

    If that hole in the lid is just to create a vent, just put a wire grid over it and the hot gas will do the rest.
    Best Regards:
    Baron J.

  13. #13
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    Nov 2017
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    Geelong, Australia
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    Default

    Slow progress - been busy working on the new press build....

    Got the refractory done in the lid tonight.





    Steve

  14. #14
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    Apr 2018
    Location
    Drouin Vic
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    Looking good Steve. The way you have the bolts to anchor the refractory is pretty much identical to what I did with my lid, it has stood up perfectly so far with no cracking.

  15. #15
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    Nov 2017
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    Default

    Thanks Pete. Good to know I'm on the right track.
    I was going to put a flange all the way around the lower edge to retain the refractory, but it all got too hard so just used the bolts.

    It sure is weird stuff to work. Closest thing I can think of to describe it is hard wet sand on the beach. If you poke at it then it wets up and becomes slightly fluid, but if you hit then its quite solid.

    The main body is ready for the refractory, I just need window when my helper is in a good mood and we've got a couple of hours to spare.

    FWIW - to mix the refractory I used one of those flexible buckets with the handle on each side, and a putty knife. Only mixed about a third of a bag at a time, and used the putty knife to sort of cut the water into the refractory. I could tip the bucket on its bottom edge and rotate it and give it a bit of a bump to make sure I was getting to the bottom everywhere. Worked really well in comparison to other stuff I've mixed in hard buckets previously.
    The instructions said to use only enough water so that you could just form a ball in your hand and be able to toss it in the air 30-40cm and catch it again without it crumbling. Very scientific...
    I did that and it seemed to be very dry when trying to ram it, but I persevered with the same each mix and it ended up wetting out well by the time I'd compacted it layer by layer to the top.

    Steve

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