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Thread: myfordboy imitation furnace build

  1. #41
    I can put my hands on the outside of my furnace when it's running. Heat gets nowhere near the wheels. i don't see a problem with plastic wheels. My wheels came from my mothers old Zimmer frame.

  2. #42
    Quote Originally Posted by myfordboy View Post
    I can put my hands on the outside of my furnace when it's running. Heat gets nowhere near the wheels. i don't see a problem with plastic wheels. My wheels came from my mothers old Zimmer frame.
    This is good news, I was toying with the idea of fitting mudguards but I think I'll fit these as-is and see how they hold up.

  3. #43
    A little progress today with the lid lifter hardware.



    100 Watt lightbulb in the furnace.


  4. #44
    Only a little progress today. Primed this part as I'm out of argon and it will rust in the humidity here otherwise so I would need to prep before welding either way.



    Question, I have had a bulb inside the furnace body for 36 hours now and it has reached 108 F only. Is this doing any good as part of the refractory curing process?

  5. #45
    Senior Member cactusdreams's Avatar
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    The bulb is only drying it out so you don't have problems when you cure it under fire. The high temp curing makes the refractory change state to a ceramic. But this is a good time to grind and sand off any sharp corners if you choose. Lookin' good so far!
    People who say it cannot be done should not interrupt those who are doing it.

  6. #46
    Quote Originally Posted by negativ3 View Post
    A little progress today, covering one base and the ring support forms with plastic. Just got to let them dry. Struggling to find good firm plastic to form the vertical rings. Best so far is 0.8mm acrylic but it's not flexible enough for the smaller cylinders.
    Late for you I know, but I am sure many folks will read this thread as they plan to build their own furnace. I think I have found good clear plastic for forming. It is 30mil PETG plastic. It looks like this material is widely available in the U.K. In home improvement stores. Not so much here in the US. However I did find a source on eBay 24x48" shipped for 16 dollars.

    http://www.ebay.com/itm/Clear-PETG-p...gAAOSw44BYH1C6

    I got mine today and can say this plastic is crystal clear, nice and rigid yet flexible enough to bend into forms. I think it will be just right for the purpose and will allow inspection while casting to look for voids and areas of inadequate agitation/vibration. It is not prone to cracking in the way that acrylic (Perspex, Plexiglas) is.

    Denis

  7. #47
    Denis,

    Next time I am going to use an old car tyre, piece of wood and an electric motor with an offset weight fitted to the shaft.

    I'm hoping next time will not be so soon

    Good luck with the build and please share your progress.

    Andy

  8. #48
    Not much happening with my build as I'm at work but can anyone comment on minimum advisable clearance between the top of a crucible and the bottom of the lid?
    With a No.10 Crucible I have about an inch gap, which seems ok.

  9. #49
    Senior Member 4cylndrfury's Avatar
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    An inch is not so bad, but its pretty tight. The upside is that the a little turbulence before the flame exits means it will be inside the bore longer, heating the charge more efficiently. The downside is that if its too tight, it could choke the furnace burner, and result in poor heating, so there is a delicate balance there. Also, if your charge sticks out of the top of the crucible too far (like when using bar ingots or larger scrap), you have less space to close the lid, so you could make contact. Ramming a charge into a crucible can be a bad idea if the charge hasnt heated and expanded yet.

  10. #50
    Quote Originally Posted by 4cylndrfury View Post
    An inch is not so bad, but its pretty tight. The upside is that the a little turbulence before the flame exits means it will be inside the bore longer, heating the charge more efficiently. The downside is that if its too tight, it could choke the furnace burner, and result in poor heating, so there is a delicate balance there. Also, if your charge sticks out of the top of the crucible too far (like when using bar ingots or larger scrap), you have less space to close the lid, so you could make contact. Ramming a charge into a crucible can be a bad idea if the charge hasnt heated and expanded yet.
    Thanks 4cylndrfury, all points very well taken.

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