Another lightweight fiber blanket furnace

Discussion in 'Furnaces and their construction' started by Tobho Mott, Apr 29, 2019.

  1. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    You've all seen Balerion the Black Dread, my big waste oil fired furnace. It was built with having plenty of room grow into for years to come firmly in mind. Lots of room for a much bigger crucible than my #12 in there for when I need it...

    But it's a lot of furnace to heat up, since I'm not using a much bigger crucible. I've been seeing the fast melt times you guys with the ceramic fiber and Satanite furnaces have been boasting, and I'm just not there with the 1" dense castable hot face in this big beast of a furnace.

    Also, the Black Dread is just a little too big to fit into the back of my van, in the event I ever wanted to take it on the road. It's more of a stay at home furnace...

    Time to solve all these problems, for free, in just one Sunday afternoon! Well, ok maybe not quite. Time to do my damnedest to do so, at any rate.

    I've had all the stuff I need gathering dust in my shed ever since I finished building the big furnace.

    An old well water pressure tank that was replaced before we bought the house. I found it in the basement when we moved in. This was actually a candidate for my last furnace build, but I ended up thinking a little bigger.

    (Foot for scale.)

    (Tempting to use this end as the lid and keep the flange for bolting to a non-dome-shaped preheating shelf using those pre-tapped holes...)

    Also had a few 2300F IFB's left over to use for a floor, and some 2600F ceramic fiber blanket.

    leftover blanket.png

    Also had a few scraps of blanket left over. I used that to give the two brick floor some support from below.

    (Plinth for scale. Also for helping determine where to cut off the shell height-wise)

    The remaining length of ceramic fiber blanket was JUST enough to make 2 complete layers around the bore. The lower half in the pic above was just long enough to do the outer layer and the upper half, the inner.

    (Shell has been cut down. The rim of the crucible will actually be inside the domed lid when closed)

    With the remaining scraps of ceramic fiber blanket I had left, I tried to fill in the lid in a few different configurations. Sadly. I'm just a little short on blanket. I'll have to pick up a few more feet, they sell it off a roll at the pottery supply around the corner from work. They don't carry the same 2600F blanket though, just the more standard 2300F type unless I special order. Likely I'll replace the outer layer from the bore with that 2300 stuff to keep it behind a layer of 2600F blanket and use that outer higher temp blanket layer to line the lid instead.

    (Looks ok but the blanket is only an inch thick in the lid here)

    I did end up cutting off the flange on the end of the tank to make the hole wider, when I realized it would end up burning off anyhow - decided to line the edge of the vent with blanket, and the hole in the flange would have gotten too small if I'd kept it...

    All I need now is a bit more blanket and some Satanite. Waiting on an email from the guy at the pottery supply about the blanket, and I have a possible line from another member here about some left over satanite. I'll say more about that if/when it works out, as I'm not wanting to put anyone on the spot. If it doesn't, I found out that high temp tools will indeed ship to Canada, so I've got options. I'd rather not go with the lower rated refractory mortar I can get locally, so looks like in any case I'll have to wait a little bit for the satanite.

    So, not quite a one Sunday afternoon build OR a zero dollar build after all. Hey, I tried... I mean it still needs a tuyere and some legs too after all, but I'm sure that detail stuff is all gonna be fairly simple to set up.

    Considering I spent a while summer and several hundred bucks building the Black Dread, I'm certainly not complaining about the time and cost of this one! Yet.

    Hmmm. It's a worthless steel bucket lined with a few dollars worth of ceramic fiber blanket, it cost me almost nothing to build, and it's that hideous tomato soup red... Think I'll call it the "Red Devil Forge". Umm, I mean furnace... Why on earth would anyone call this a forge?! :rolleyes:

    Here's a shot of the Red Devil sitting on top of the Black Dread, just for scale:


    Hmm, it looks smaller IRL somehow. I have ideas for the flat bracket on the side of the tank too, probably I'll use that to attach hinges for the lid and wheels and a push handle to. More on all that later...

    Douglas Braun likes this.
  2. Petee716

    Petee716 Gold Banner Member

    Nice work Jeff. Keep this handy for when your better half suggests that you may have hoarder tendencies! Nice use of "stored assets". Its great that this road has been so well travelled by other members. Saves a lot of pondering and missteps.

    Tobho Mott likes this.
  3. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Tuyere? What burner and fuel for the roadshow?

  4. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    My Hot Shot can run on propane and/or oil; I'll be building it to fit the same burner. We'll see how well Satanite over 2600F wool holds up vs diesel when the time comes... If it doesn't, I guess this'll be a propane furnace. But I'm hoping it does...

    Andy has confirmed he'll be putting that package of Satanite in the mail for me today, so I guess it's safe to mention him now. What a guy! Swdweeb makes him famous by posting a frame by frame analysis of his exploding bifilm gating glass mold video yesterday, but does it go to his head and make him forget the little guys? No. No, it does not. :D

    Thanks again, OIF!

  5. Me? Satanite? There's some confusion somewhere.

    Anyway I think you'll find it does fine so long as you don't try to melt iron. You fire it up fast and let it cool so the wool doesn't get too hot. If it does the Satanite will stand in the furnace as a hard shell until a piece falls out and you find there's a big gap behind it.:eek: I'd watch for hot spots on the paint.

    What did I just tell you about calling me Mr. Martin now, Jeff?:p
    Tobho Mott likes this.
  6. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    Lol, thanks again sir. :D

  7. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    I added wheels yesterday. They fit so nice I could not resist.

    Got them off one of the kids' old bikes (long since outgrown), so if you only include materials I actually have installed or in hand already, I still have $0 new spending on this build.

    Bit flimsy looking, I know. But lightweight is the the name of the game here, and they do feel sturdier than they look. I have a pretty good feeling about them. The best part is, they only raise the furnace's overall height by about an inch. So now the furnace won't have to balance on its domed bottom end. :D

    I don't expect to be rolling it around very far too often; they'll be acting as legs most of the time, so hopefully they'll hold up.


    Does still need a short foot on the front side of the furnace to level it and add a bit of stability. Also, the pottery supply is all out of fiber blanket, so I will have to wait for that couple more feet I need to arrive before I can complete the lid. They said maybe later this week, I hope so as I am hoping to use this furnace on the 11th and time is growing a bit short...

    Hoping to get a bit more work done on the shell after work today, but it's hard to find much shop time on week days. We'll see...

  8. Wheels do fit in pretty good!

    Very appropriate for your new furnace to have training wheels.:p

    But I'm confused, you said the wheels only add an inch but you then say you're going to add a another foot.

    Did you get them to order 2,600F blanket? It works for 2,300F substitute.
  9. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    Lol, a foot...

    The guy had told me they carry 2300F blanket to sell by the foot and that he'd drop by the shop to set aside what I need. I said great, thinking they'd actually have some and I'd just use that. He didn't get back to me to let me know they were out though, I went around the corner to pick it up yesterday and the lady told me since it wasn't bundled up waiting for me, that meant they'd had to order it. So I guess I'll be getting the 2300 stuff. If he'd gotten back to me I might have asked him to order the 2600 blanket instead, but 2300 is ok, I'll just use that for the outer layer covering the bore behind a layer of the 2600, and take the 2600 blanket that makes up the outer layer now to make the lid with.

  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    3200F fiber blanket? Sounds expensive if true.

  11. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    You got in quick before I could edit that...:oops:
  12. Please get some of the 3200F blanket for me. I can use it.

    Putting the 2,300F behind 2,600F is just right, and 2,300F has better insulating properties anyway.
  13. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    I did not realize the lower rated stuff insulates better. Thanks for the info.

  14. PatJ

    PatJ Silver

    But it doesn't insulate if it melts, and I have done that to ceramic blanket when it gets inadvertently exposed to the oil burner exhaust.

  15. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    Well, that's why I'm hiding it behind the 2600F blanket.

    ...Or was that 6200? o_O


  16. PatJ

    PatJ Silver

    Did you say you were taking this furnace to a show somewhere?

  17. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    No shows, just an inquiry about helping someone out with a casting they want to pour. It's not a sure thing and that's why I didn't go into detail before. If it happens it'll be within a couple of weeks. I got contacted by a local blacksmith, my seal coal guy to be specific. He does some casting on occasion but this project needs a crucible that's a bit too big for his forge. He knows I cast metal, so he reached out to me. I suppose he could come to me, but my shop is a big mess and he has his own sand etc. and was planning on making his own mold. So given that and because I've had already had the idea of building this low mass furnace in the back of my head for a while now... It just felt like the time was right. And it'll actually help me clean up the shop too - I won't have to use up my storage space on the red well tank and the leftover 2600 blanket anymore! :D

  18. I stand corrected. I looked it up to be sure and was surprised that they are the same, both 6# and 8#. And Fiberfrax 2,300 and 2600 both have a 3,000F melting temperature. They offer a 3,000F blanket now too. I had not seen that before.
  19. Tobho Mott

    Tobho Mott Administrator Staff Member Banner Member

    So... Is there any difference at all? What happens to them at 2300 and 2600?

  20. Melting temperature. I'm sure the 2,300 has a lower temperature binder which will cause it to break down.

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