Loading ...
Sorry, an error occurred while loading the content.
 

Re: [multimachine] Furnace Size Question

Expand Messages
  • David G. LeVine
    ... I am NOT a furnace guru! I am just an amateur. First of all, it sounds like you are not going to like the result. With that thin a wall, the casing will
    Message 1 of 9 , Dec 26, 2011
      On 12/26/2011 03:46 PM, jcrous wrote:
      I am now about to start making a furnace with a propane tank to cast parts out of aluminum.
      The tank is 295 mm diameter (inside about 11 1/2 inches).
      I am going to make a 100 X 200 mm (4 X 8 inch) crucible with 20 mm (3/4 inch)handles on the side.
      I am going to use a gas powered burner and cast-able refractory.
      If I make the the hollowed chamber 160 mm in dia ( about 6 1/2 inches), the walls of the refractory will be 65 mm (2 1/2 inches) thick.
      
      Questions:
      
      1. Will the clearance around the crucible, 30 mm (about 1 1/4 inch) be enough for the gas flames to surround it and warm it up? [The clearance will be enough to lift the crucible in and out without problems].
      
      2. Will a wall thickness of the refractory of 65 mm (2 1/2 inches) be thick enough?
      
      I only have this propane bottle available. It is a 22 kg (very long but thin.
      This furnace will compare about to the two buck furnace I guess. The cast-able
      refractory is very hard (and brittle)and can withstand a heat of 1550 degrees of
      C (2800 degrees of F). This is quite durable with regard to wear. I also use
      this for pizza ovens. Can last forever if you look after it, but is prone to
      shattering if you drop it.
      
      I wanted to do this for years but have never started it yet. Now I am building a milling machine (Engine Mill) and need to do some castings for pulleys and handles, etc.
      Thereafter I would like to make parts for my lathe like a dividing attachment and also the Gingery Shaper.
      
      I don't want to waste this forums time by asking stupid questions but these two questions is still a bit unclear to me after spending hours and hours on the Internet.
      
      Regards,
      Johan
      

      I am NOT a furnace guru!  I am just an amateur.

      First of all, it sounds like you are not going to like the result.

      With that thin a wall, the casing will be very hot and the fuel consumption will be high.  Consider a 1 1/2" insulating wall and a 1" hot face.  Hot face is what you appear to be using for all the refractory, it is REALLY good for a hot surface, but as insulation it is pretty poor, IIRC.  Insulating refractory will NEVER be able to take the dings hot face refractory will.

      Insulating refractories tend to be cast-able refractory, grog (broken up firebrick) and an air entrapment medium.  Often Pearlite or sawdust is used, sawdust needs a LONG curing/bakeout cycle to get the sawdust to release all the gasses, Pearlite has temperature limits and can melt when casting some alloys, aluminum should be okay, but IF it melts, no big deal, the holes will still work well.

      The best furnace liner is silica wool (Kaowool, for one name brand) with rigidizer, but it makes for a fragile hot face.  It will do a great job of insulating and will make the furnace much lighter.  It can also be used with "real" hot face, which is a good compromise for some.

      Some rock wool works, some doesn't!  If the melting/slumping temperature is too low, it will not work.

      If the refractory mix is not a good enough insulator, the furnace walls will get VERY hot and a guard will be needed.

      So there is my advise, it is worth what you paid for it  =-O but not much more.  I suggest you get a copy of Mike Porter's book on burners, it is a goldmine of information.  That one is worth MORE than you will pay for it  O:-) I do not have any connection with Mike other than being on some groups with him and being a satisfied reader.

      Dave  8{)

      --
      "Political Correctness is a doctrine, fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."
      (quoted from http://www.wattflyer.com/forums/showthread.php?t=30060)

      NOTE TO ALL:

      When forwarding emails, please use only "Blind Carbon Copy" or "Bcc" for all recipients. Please "delete" or "highlight & cut" any forwarding history which includes my email address! It is a courtesy to me and others who may not wish to have their email addresses sent all over the world! Erasing the history helps prevent Spammers from mining addresses and viruses from being propagated.

      THANK YOU!
    • David G. LeVine
      ... Another point, the furnace can be almost any container! Waste baskets (especially the mesh kind) seem popular, pop corn tins (but please paint over the
      Message 2 of 9 , Dec 26, 2011
        On 12/26/2011 03:46 PM, jcrous wrote:
        I am now about to start making a furnace with a propane tank to cast parts out of aluminum.
        

        Another point, the furnace can be almost any container!  Waste baskets (especially the mesh kind) seem popular, pop corn tins (but please paint over the poker playing dogs), pots, even 55 gallon drums have been used.  The smallest I have seen is a coffee can sized unit, the largest was over 5' in diameter.  They all worked to some degree.

        Actually, ask local blacksmiths about their forges, propane ones are not uncommon and and are similar to furnaces.

        Dave  8{)

        --
        "Political Correctness is a doctrine, fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."
        (quoted from http://www.wattflyer.com/forums/showthread.php?t=30060)

        NOTE TO ALL:

        When forwarding emails, please use only "Blind Carbon Copy" or "Bcc" for all recipients. Please "delete" or "highlight & cut" any forwarding history which includes my email address! It is a courtesy to me and others who may not wish to have their email addresses sent all over the world! Erasing the history helps prevent Spammers from mining addresses and viruses from being propagated.

        THANK YOU!
      • costasv
        Hi I have not well understoud.You ant to make a squar crucible to be used in a round fournace? Anyway 2 1/2 of rarefactory wals are OK. About the clearance
        Message 3 of 9 , Dec 26, 2011
          Hi
          I have not well understoud.You ant to make a squar crucible to be used in a round fournace?
          Anyway 2 1/2 " of rarefactory wals are OK.
          About the clearance around the crucible is OK, if combustion gas are circulating around the crucible's surface.To do this, the gas burner must some how be located as possible tangencial to the fournace inner diameter.If the clearance around the crucible is larger than that, you must make a smaller lid opening since all the hot combustion gas,will escape from there .
          Costas

          --- In multimachine@yahoogroups.com, "jcrous" <jcrous1@...> wrote:
          >
          > I am now about to start making a furnace with a propane tank to cast parts out of aluminum.
          > The tank is 295 mm diameter (inside about 11 1/2 inches).
          > I am going to make a 100 X 200 mm (4 X 8 inch) crucible with 20 mm (3/4 inch)handles on the side.
          > I am going to use a gas powered burner and cast-able refractory.
          > If I make the the hollowed chamber 160 mm in dia ( about 6 1/2 inches), the walls of the refractory will be 65 mm (2 1/2 inches) thick.
          >
          > Questions:
          >
          > 1. Will the clearance around the crucible, 30 mm (about 1 1/4 inch) be enough for the gas flames to surround it and warm it up? [The clearance will be enough to lift the crucible in and out without problems].
          >
          > 2. Will a wall thickness of the refractory of 65 mm (2 1/2 inches) be thick enough?
          >
          > I only have this propane bottle available. It is a 22 kg (very long but thin.
          > This furnace will compare about to the two buck furnace I guess. The cast-able
          > refractory is very hard (and brittle)and can withstand a heat of 1550 degrees of
          > C (2800 degrees of F). This is quite durable with regard to wear. I also use
          > this for pizza ovens. Can last forever if you look after it, but is prone to
          > shattering if you drop it.
          >
          > I wanted to do this for years but have never started it yet. Now I am building a milling machine (Engine Mill) and need to do some castings for pulleys and handles, etc.
          > Thereafter I would like to make parts for my lathe like a dividing attachment and also the Gingery Shaper.
          >
          > I don't want to waste this forums time by asking stupid questions but these two questions is still a bit unclear to me after spending hours and hours on the Internet.
          >
          > Regards,
          > Johan
          >
        • jcrous
          No, the crucible will be made from a round, thick walled steel pipe of 100 mm diameter (4 ) and 200 mm long (8 ). This is the size recommended by someone else
          Message 4 of 9 , Dec 27, 2011
            No, the crucible will be made from a round, thick walled steel pipe of 100 mm diameter (4") and 200 mm long (8").
            This is the size recommended by someone else for use for the Gingery Shaper castings. It is big enough.

            --- In multimachine@yahoogroups.com, "costasv" <cvgoodphones317@...> wrote:
            >
            > Hi
            > I have not well understoud.You ant to make a squar crucible to be used in a round fournace?
            > Anyway 2 1/2 " of rarefactory wals are OK.
            > About the clearance around the crucible is OK, if combustion gas are circulating around the crucible's surface.To do this, the gas burner must some how be located as possible tangencial to the fournace inner diameter.If the clearance around the crucible is larger than that, you must make a smaller lid opening since all the hot combustion gas,will escape from there .
            > Costas
            >
            > --- In multimachine@yahoogroups.com, "jcrous" <jcrous1@> wrote:
            > >
            > > I am now about to start making a furnace with a propane tank to cast parts out of aluminum.
            > > The tank is 295 mm diameter (inside about 11 1/2 inches).
            > > I am going to make a 100 X 200 mm (4 X 8 inch) crucible with 20 mm (3/4 inch)handles on the side.
            > > I am going to use a gas powered burner and cast-able refractory.
            > > If I make the the hollowed chamber 160 mm in dia ( about 6 1/2 inches), the walls of the refractory will be 65 mm (2 1/2 inches) thick.
            > >
            > > Questions:
            > >
            > > 1. Will the clearance around the crucible, 30 mm (about 1 1/4 inch) be enough for the gas flames to surround it and warm it up? [The clearance will be enough to lift the crucible in and out without problems].
            > >
            > > 2. Will a wall thickness of the refractory of 65 mm (2 1/2 inches) be thick enough?
            > >
            > > I only have this propane bottle available. It is a 22 kg (very long but thin.
            > > This furnace will compare about to the two buck furnace I guess. The cast-able
            > > refractory is very hard (and brittle)and can withstand a heat of 1550 degrees of
            > > C (2800 degrees of F). This is quite durable with regard to wear. I also use
            > > this for pizza ovens. Can last forever if you look after it, but is prone to
            > > shattering if you drop it.
            > >
            > > I wanted to do this for years but have never started it yet. Now I am building a milling machine (Engine Mill) and need to do some castings for pulleys and handles, etc.
            > > Thereafter I would like to make parts for my lathe like a dividing attachment and also the Gingery Shaper.
            > >
            > > I don't want to waste this forums time by asking stupid questions but these two questions is still a bit unclear to me after spending hours and hours on the Internet.
            > >
            > > Regards,
            > > Johan
            > >
            >
          • jcrous
            No, the walls will be about 65 mm thick (2.5 ) For the propane bottle that I have to my disposal, I have only 11 1/2 inches (295 mm space to my disposal. If
            Message 5 of 9 , Dec 27, 2011
              No, the walls will be about 65 mm thick (2.5 ")

              For the propane bottle that I have to my disposal, I have only 11 1/2 inches (295 mm space to my disposal. If I want to use this bottle, I can only make use of refractory concrete, and not a layer of insulation as well. (This is concrete, not the softer heat resistant insulation - It can take heat of up to 2800 degrees F). I can increase the thickness of the walls to 3 inches, but then I will only have 20 mm (3/4") clearance on both sides of the crucible.

              I can decrease the thickness of the concrete if you suggest I do that, to about one and a half inch thick and a thin layer of vermiculite / cement mixture as I use for pizza ovens.

              Maybe I must rather get a bigger container?

              --- In multimachine@yahoogroups.com, "David G. LeVine" <dlevine@...> wrote:
              >
              > On 12/26/2011 03:46 PM, jcrous wrote:
              > > I am now about to start making a furnace with a propane tank to cast parts out of aluminum.
              > > The tank is 295 mm diameter (inside about 11 1/2 inches).
              > > I am going to make a 100 X 200 mm (4 X 8 inch) crucible with 20 mm (3/4 inch)handles on the side.
              > > I am going to use a gas powered burner and cast-able refractory.
              > > If I make the the hollowed chamber 160 mm in dia ( about 6 1/2 inches), the walls of the refractory will be 65 mm (2 1/2 inches) thick.
              > >
              > > Questions:
              > >
              > > 1. Will the clearance around the crucible, 30 mm (about 1 1/4 inch) be enough for the gas flames to surround it and warm it up? [The clearance will be enough to lift the crucible in and out without problems].
              > >
              > > 2. Will a wall thickness of the refractory of 65 mm (2 1/2 inches) be thick enough?
              > >
              > > I only have this propane bottle available. It is a 22 kg (very long but thin.
              > > This furnace will compare about to the two buck furnace I guess. The cast-able
              > > refractory is very hard (and brittle)and can withstand a heat of 1550 degrees of
              > > C (2800 degrees of F). This is quite durable with regard to wear. I also use
              > > this for pizza ovens. Can last forever if you look after it, but is prone to
              > > shattering if you drop it.
              > >
              > > I wanted to do this for years but have never started it yet. Now I am building a milling machine (Engine Mill) and need to do some castings for pulleys and handles, etc.
              > > Thereafter I would like to make parts for my lathe like a dividing attachment and also the Gingery Shaper.
              > >
              > > I don't want to waste this forums time by asking stupid questions but these two questions is still a bit unclear to me after spending hours and hours on the Internet.
              > >
              > > Regards,
              > > Johan
              >
              > I am NOT a furnace guru! I am just an amateur.
              >
              > First of all, it sounds like you are not going to like the result.
              >
              > With that thin a wall, the casing will be very hot and the fuel
              > consumption will be high. Consider a 1 1/2" insulating wall and a 1"
              > hot face. Hot face is what you appear to be using for all the
              > refractory, it is REALLY good for a hot surface, but as insulation it is
              > pretty poor, IIRC. Insulating refractory will NEVER be able to take the
              > dings hot face refractory will.
              >
              > Insulating refractories tend to be cast-able refractory, grog (broken up
              > firebrick) and an air entrapment medium. Often Pearlite or sawdust is
              > used, sawdust needs a LONG curing/bakeout cycle to get the sawdust to
              > release all the gasses, Pearlite has temperature limits and can melt
              > when casting some alloys, aluminum should be okay, but IF it melts, no
              > big deal, the holes will still work well.
              >
              > The best furnace liner is silica wool (Kaowool, for one name brand) with
              > rigidizer, but it makes for a fragile hot face. It will do a great job
              > of insulating and will make the furnace much lighter. It can also be
              > used with "real" hot face, which is a good compromise for some.
              >
              > Some rock wool works, some doesn't! If the melting/slumping temperature
              > is too low, it will not work.
              >
              > If the refractory mix is not a good enough insulator, the furnace walls
              > will get VERY hot and a guard will be needed.
              >
              > So there is my advise, it is worth what you paid for it =-O but not much
              > more. I suggest you get a copy of Mike Porter's book on burners, it is
              > a goldmine of information. That one is worth MORE than you will pay for
              > it O:-) I do not have any connection with Mike other than being on some
              > groups with him and being a satisfied reader.
              >
              > Dave 8{)
              >
              > --
              > /"Political Correctness is a doctrine, fostered by a delusional,
              > illogical minority and rabidly promoted by an unscrupulous mainstream
              > media, which holds forth the proposition that it is entirely possible to
              > pick up a turd by the clean end."/
              > (quoted from http://www.wattflyer.com/forums/showthread.php?t=30060)
              >
              > NOTE TO ALL:
              >
              >
              > When forwarding emails, please use only "Blind Carbon Copy" or "Bcc" for
              > all recipients. Please "delete" or "highlight & cut" any forwarding
              > history which includes my email address! It is a courtesy to me and
              > others who may not wish to have their email addresses sent all over the
              > world! Erasing the history helps prevent Spammers from mining addresses
              > and viruses from being propagated.
              >
              > THANK YOU!
              >
            • jcrous
              I have access to paint drums but they are very thin walled. i would like to use something that will be durable, on which I can arc weld my feet or fittings.
              Message 6 of 9 , Dec 27, 2011
                I have access to paint drums but they are very thin walled. i would like to use something that will be durable, on which I can arc weld my feet or fittings. Paint drums are so flimsy.

                --- In multimachine@yahoogroups.com, "David G. LeVine" <dlevine@...> wrote:
                >
                > On 12/26/2011 03:46 PM, jcrous wrote:
                > > I am now about to start making a furnace with a propane tank to cast parts out of aluminum.
                >
                > Another point, the furnace can be almost any container! Waste baskets
                > (especially the mesh kind) seem popular, pop corn tins (but please paint
                > over the poker playing dogs), pots, even 55 gallon drums have been
                > used. The smallest I have seen is a coffee can sized unit, the largest
                > was over 5' in diameter. They all worked to some degree.
                >
                > Actually, ask local blacksmiths about their forges, propane ones are not
                > uncommon and and are similar to furnaces.
                >
                > Dave 8{)
                >
                > --
                > /"Political Correctness is a doctrine, fostered by a delusional,
                > illogical minority and rabidly promoted by an unscrupulous mainstream
                > media, which holds forth the proposition that it is entirely possible to
                > pick up a turd by the clean end."/
                > (quoted from http://www.wattflyer.com/forums/showthread.php?t=30060)
                >
                > NOTE TO ALL:
                >
                >
                > When forwarding emails, please use only "Blind Carbon Copy" or "Bcc" for
                > all recipients. Please "delete" or "highlight & cut" any forwarding
                > history which includes my email address! It is a courtesy to me and
                > others who may not wish to have their email addresses sent all over the
                > world! Erasing the history helps prevent Spammers from mining addresses
                > and viruses from being propagated.
                >
                > THANK YOU!
                >
              • David G. LeVine
                ... Your choice, but I was suggesting two kinds of concrete, a hot face of refractory concrete and a layer of concrete plus some air entraining material, like
                Message 7 of 9 , Dec 27, 2011
                  On 12/27/2011 05:07 AM, jcrous wrote:
                  No, the walls will be  about 65 mm thick (2.5 ")
                  
                  For the propane bottle that I have to my disposal, I have only 11 1/2 inches (295 mm space to my disposal. If I want to use this bottle, I can only make use of refractory concrete, and not a layer of insulation as well. (This is concrete, not the softer heat resistant insulation - It can take heat of up to 2800 degrees F). I can increase the thickness of the walls to 3 inches, but then I will only have 20 mm (3/4") clearance on both sides of the crucible.
                  
                  I can decrease the thickness of the concrete if you suggest I do that, to about one and a half inch thick and a thin layer of vermiculite / cement mixture as I use for pizza ovens.
                  
                  Maybe I must rather get a bigger container?

                  Your choice, but I was suggesting two kinds of concrete, a hot face of refractory concrete and a layer of concrete plus some air entraining material, like Pearlite.  Do NOT use Vermiculite, it is hygroscopic and can cause spalling problems (or worse!)

                  You just made a good point, the same technology you use in Pizza ovens is probably a good choice, but beware of anything which will trap water in the set-up cement.  Steam pressures will get high when the water comes out and vitrified cement is not porous.

                  A bigger container will allow more insulation, but will take more fuel to heat (the hot face and insulation have mass and must be heated, but the heat loss once at heat is lower.)  It is all a tradeoff.  The container does not need to be very strong, in fact, a plastic container with a metal mesh lining should be fine, just cut the plastic off before use.  The metal mesh it for your protection in case of accidents.

                  Dave  8{)

                  --
                  "Political Correctness is a doctrine, fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."
                  (quoted from http://www.wattflyer.com/forums/showthread.php?t=30060)

                  NOTE TO ALL:

                  When forwarding emails, please use only "Blind Carbon Copy" or "Bcc" for all recipients. Please "delete" or "highlight & cut" any forwarding history which includes my email address! It is a courtesy to me and others who may not wish to have their email addresses sent all over the world! Erasing the history helps prevent Spammers from mining addresses and viruses from being propagated.

                  THANK YOU!
                • David G. LeVine
                  ... The drum is flimsy, but the lining is not. Inserted objects (like steel bolts, threads out and protected with Vaseline) tend to be remarkably robust. The
                  Message 8 of 9 , Dec 27, 2011
                    On 12/27/2011 05:09 AM, jcrous wrote:
                    I have access to paint drums but they are very thin walled. i would like to use something that will be durable, on which I can arc weld my feet or fittings. Paint drums are so flimsy.

                    The drum is flimsy, but the lining is not.  Inserted objects (like steel bolts, threads out and protected with Vaseline) tend to be remarkably robust.  The drum is a protective element (in case of lining failures), not a strength element.

                    Better than bolts are steel hoops (circumferential rings of thicker steel) embedded in the concrete with wax bolts (to provide a place to put the real bolts later), the rings transfer the load to the refractory, the crinkly can is just for when things go wrong (to hold the refractory together long enough for you to get away.)

                    A 1/4" thick ring embedded in refractory will take a LOT of load, even if it is flush with the refractory surface.  The rings do not need to be continuous, a ring with a butt joint a few mm wide is fine, if it is heavy enough.

                    Dave  8{)

                    --
                    "Political Correctness is a doctrine, fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."
                    (quoted from http://www.wattflyer.com/forums/showthread.php?t=30060)

                    NOTE TO ALL:

                    When forwarding emails, please use only "Blind Carbon Copy" or "Bcc" for all recipients. Please "delete" or "highlight & cut" any forwarding history which includes my email address! It is a courtesy to me and others who may not wish to have their email addresses sent all over the world! Erasing the history helps prevent Spammers from mining addresses and viruses from being propagated.

                    THANK YOU!
                  Your message has been successfully submitted and would be delivered to recipients shortly.