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Thread: Scavengers new furnace build!!!

  1. #141
    I used this saw blade to cut the same fire bricks. I ripped 12 bricks, mitered them, and then carved out the inside of them similar to kcoffield's build. The blade held up fine. The amount of dust was monumental. Buy a good mask.

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

  2. #142
    Hey steelguy. The bricks are soft insulating fire brick. I did not even change the wood cutting blade in my table saw to cut them. It did not even dull the blade. You can practically cut these brick with your finger nail they are so soft.

    Plus on on Mach's suggestion on the dust mask!

    Justin
    I got tired of being told what I can't do...

  3. #143
    I thought I would update my thread with the latest modification to the furnace. While making a pour before Christmas, I opened the furnace to skim and add silicon. Basically I was at the end of the melt with molds made and a crucible full of iron. Everything was going just like normal when mechanical failure reared its head! The lid, which weighs over 160 pounds and is about 2900f FELL OFF THE LIFTING MECHANISM! No injuries; so that is a plus.



    I had to scramble to salvage the melt which meant I did not get to skim as well as I wanted nor did the silicon get as much opportunity to mix into the melt. It was still a successful pour, though I did have some slag get into the mold, and the iron had just a small amount of chill in them. The parts drilled and I was able to fill the slag voids with cast iron rod.

    So, as with any failure I decided to rebuild bigger and better. The prior design was something that has been modified to 3 different furnaces and was never intended to run as long as it did. The bearings were from a transmission and were never meant to be exposed to direct heat. Couple the heating cycle with blowing rain and they rusted very quickly. On more than one occasion I had to oil the bearings and force the mechanism to free up. Also bearings were never meant to be welded on. In all, from an engineering standpoint the design was a complete failure. It was made with what I had laying around at the time.



    Above is a picture of the old design. You can see the lift is completely rigid. Meaning there is no allowance for the lid to set down on anything but a completely even plane. This is fine for sporadic use. One of the failures I have noticed in my furnaces seems to be the point where the lid meets the furnace. Flames begin leaking out. Eventually at hotter temperatures fluxing starts to blow out with the flames and it eats up the lid and body. I managed this with refractory blanket. The refractory blanket only lasts if it is compressed. I noticed as slag built up on the furnace lid/body it would act as a spacer. The "spacer" would prevent the lid and body from closing completely because the lid is mounted "rigidly." The fiber blanket would just blow out leading to heat loss and further fluxing of the furnace and lid.

    So. Taking what I have observed I came up with a new design. Simpler and much more robust.

    I began by cutting off all the old lifting mechanism. I kept the foot pedal and the main support post. I took a cylinder I have had laying around from a fire suppression system and discharged it in a fun yet uneventful manor. My connection is slow otherwise I would upload the video of the cylinder discharge.

    I chucked the empty cylinder in the lathe and parted off the top cap.



    I reversed the cylinder in the lathe and drilled though the end cap. I found the cylinder wall was about 3/16" thick ( to be expected...) The end cap was over an inch thick! I thought my drill was slipping into my chuck.



    Next I took some 1" round stock and turned it 45 deg with the compound. The other end was turned down to fit into the drill rod I used as the support post. The part was driven in with a hammer. No precision needed here!



    The cylinder was dropped over the modified lifting mechanism. The idea is the 45 degree part contacts the hole in the end of the cylinder. There is very little contact except on the shoulder. This design will never rust of seize!





    Two angle iron arms were welded to the cylinder and chains were used to attach the lid lifting mechanism to the lid. I used 3 points of lift so as to prevent the lid from rotating. The lid has hooks on it with the chains looped through. All I have to do is block up the lid and I can easily unhook the chains from the lid for when I need to service the lid. Before with the old design I could not service the lid without some major hammer time beating the rusted components apart.



    Now I can use the weight of the lid to my advantage. The weight of the lid compresses the fiber blanket making it last longer and sealing off the furnace. I am so happy with this improvement. My melt times due to better sealing have actually come down and the wear on the furnace is also considerably less. The fiber blanket lasts 2- 3 melts whereas I was constantly having to replace the blanket 2-3 times each melt. (Which is not easy to do when you have 3000 degree flames shooting out at you!)

    Click on the picture below for a short video demonstrating how the weight of the lid is allowed to compress the blanket. No leaks!!!



    And so the furnace lives on.
    I got tired of being told what I can't do...

  4. #144
    That looks like a great improvement Justin. May I ask approximately how much oil you use (per hour if your know) and iron you melt in a typical melt?

    Best,
    Kelly

  5. #145
    Hi Kelly, I was just looking at your build. I have missed it until now. Wow.....

    After doing hundreds of melts I can say it does vary. The quality of the oil seems to be the biggest factor. Good clean oil burns hotter obviously. Thick oils are harder to burn. I find that diesel and oil diluted with diesel also do not burn as hot as straight oil. Gasoline mixed with oil actually burns cold. Humidity, always a factor in southeast Texas also plays a role. Wet air is harder to heat up than dry air.

    With good clean oil, the initial heat takes about 6 gallons of oil and each heat thereafter takes about 4.5 gallons. I have gotten the first heat done on as little as 3 gallons in perfect conditions. I have taken as much as 10 gallons of oil to produce barely usable cast iron. My initial heat will take anywhere from 50 minutes to 1 hour 30 minutes. I figure I use about 5 gallons per hour. My average time is about 1 hour and 10 minutes and about 6 gallons per melt.

    Also it helps to put it in perspective. My furnace has a huge thermal mass which I did intentionally for longevity, and I am blasting an a-40 crucible rated for 90 pounds full of iron. A smaller furnace will use less oil.

    One day if and when I have a little time I will perform some efficiency tests. I did try to hone in on efficiency early on but looking back I was making many mistakes and not getting the maximum potential out of the burner/furnace.
    I got tired of being told what I can't do...

  6. #146
    Thanks for that Justin. I started a thread in the burner section and was thinking of you when I said Monster burner and was figuring you were North of 500kbtu/hr. Hard to say how much based upon the variables you cited, but probably somewhere between 500kbtu/hr and 1mbtu/hr if my info and assumptions are correct. In any case, it's serious heat.

    Best,
    Kelly

  7. #147
    Well I hope you are taking the day off to be pampered, seeing as its your birthday and all
    The only time You're not following your nose is when your going backward!.......Andy (ME) .
    Have you filed in "Who do you think you are?" "War Grade Report" " My photo's"

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