Home Forum Show it off! Cheap Furnace

This topic contains 10 replies, has 1 voice, and was last updated by Profile photo of Shaun Shaun 1 year, 11 months ago.

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  • #2279
    Profile photo of Andrew-MOAMind
    Andrew-MOAMind
    Participant

    This thing has a 50/50 chance of blowing up in my face in some horrible way but it sounds interesting.

    I want to start doing my own castings for aluminium and brass. Primarily because I have buckets of bronze swarf I would eventually like to be able to re-use in other projects.

    The plan is to build a basic furnace following these instructions.
    [media=youtube]vQN7EqGMTuo[/media]

    I have tracked down my supplies.
    100L bag of perlite for $30 from the appropriately names perlite & vermiculite factory
    4L of Sodium Silicate for $8 from the potters market (even cheaper if you bring your own bucket)
    Old steel rubbish bin $FREE

    The only one I havent been able to find is Aluminium Oxide powder which helps with the thermal insulation properties and is also used for the furnace lining

    I havent worked out what ill be using as a burner long term yet. To begin with ill just be using a blow torch.
    Ill upload some photos as I go.

    #2281
    Profile photo of Paul Kelly
    Paul Kelly
    Participant

    Well you COULD do it that way I suppose….

    #2287
    Profile photo of Jacek Gonsalves
    Jacek Gonsalves
    Participant

    Oh furnace building, sound like good fun.
    Check out http://www.mathews.com.au in osborne park. they might have what your looking for?
    Never made anything out of cement, can you point to the website tutorial on how to make up the perlite ,sodium solicate etc?

    Have you thought of just getting a fibre blanket and using that as a foundry? Potters mart sell them…
    I made a small raku pottery kiln out of the blanket and a Ikea bin a few years back.

    #2290
    Profile photo of Paul Kelly
    Paul Kelly
    Participant

    Lots of people (including me) have made propane furnaces. My beef with them is that they are noisy, smelly and expensive to run.
    If you go electric, you can whittle them out of fire brick with a pocket knife and run them in your living room…..


    #2292
    Profile photo of Andrew-MOAMind
    Andrew-MOAMind
    Participant

    Jacek Gonsalves, post: 3128, member: 683 wrote: Oh furnace building, sound like good fun.
    Check out http://www.mathews.com.au in osborne park. they might have what your looking for?
    Never made anything out of cement, can you point to the website tutorial on how to make up the perlite ,sodium solicate etc?

    Have you thought of just getting a fibre blanket and using that as a foundry? Potters mart sell them…
    I made a small raku pottery kiln out of the blanket and a Ikea bin a few years back.

    This is the calculator I wrote up for the ratios. I just blend it all in a big tub and then compact it down.

    I was impressed with what they had at potters mart, although the sodium silicate was $8/L not $8 for the 4L. Still easier to buy than making it myself.

    Mathews is somewhere I have been meaning to check out although they are only open Saturdays by appointment and I wanted to have a practice furnace to experiment with before investing a lot in bricks and quality refectory. Plus sometimes it is more fun to experiment 🙂 They also sell ceramic blankets there, it hink its about $35/m which is pretty cheap I thought.

    Paul Kelly, post: 3131, member: 25 wrote: Lots of people (including me) have made propane furnaces. My beef with them is that they are noisy, smelly and expensive to run.
    If you go electric, you can whittle them out of fire brick with a pocket knife and run them in your living room…..


    My plan is to start with propane but then switch to waste oil burners. About half way down this page.

    Certainly doesn’t solve the odour problem and I wouldn’t be using it in the lounge but it should be the cheapest way to run a furnace if you can scrounge enough waste oil.

    Where did you find your wire? So long as it can do bronze I’ll probably build an electric one if this one fails or I dont end up building a larger waste oil furnace.

    #2295
    Profile photo of Paul Kelly
    Paul Kelly
    Participant

    Andrew-MOAMind, post: 3133, member: 29 wrote: This is the calculator I wrote up for the ratios. I just blend it all in a big tub and then compact it down.

    I was impressed with what they had at potters mart, although the sodium silicate was $8/L not $8 for the 4L. Still easier to buy than making it myself.

    Like I said. You could do it that way… It’s a bit more expensive, doesn’t last as long, and is HEAPS more work…
    But you could do it that way…

    Where did you find your wire? So long as it can do bronze I’ll probably build an electric one if this one fails or I dont end up building a larger waste oil furnace.

    Waste oil furnaces seem like a great idea. And I guess they are if you have access to a LOT of waste oil. If you don’t then they soon become white elephants because all those 4l containers of engine oil you thought would last forever ran out in 3 melts..

    It costs me about $0.70c to melt 2Kg of Aluminum.

    Elements cost $5 on ebay http://www.ebay.com.au/itm/720mm-x-5-5mm-Forging-Pottery-Kanthal-A1-Heating-Element-Wire-Coil-2-5KW-220VAC-/331221108797?pt=LH_DefaultDomain_15&hash=item4d1e51083d

    The ONLY drawback of electric is that (at 10A draw) it will be slower. Takes 40-50 minutes from cold to melt Al. The gas furnace would do it in 20-30min

    And just forget casting refractories, a fire brick is <<$10 (I paid $6 when I got mine) I used 9 bricks, but I should have built it bigger and used 12 of them.

    #2296
    Profile photo of Andrew-MOAMind
    Andrew-MOAMind
    Participant

    Sometimes the fun is in the making. I work with electronics all the time, this was an opportunity to work with a blow torch for a semi-legitimate reason!

    When I get bored of playing chemist & plasterer and I actually want to get down to the business of casting things then I may build an electric unit. The last price i had from Mathews on fire bricks was around the $5-6 mark. I believe they recommend a refractory/mortar to hold the bricks in place.

    #2297
    Profile photo of Paul Kelly
    Paul Kelly
    Participant

    Andrew-MOAMind, post: 3137, member: 29 wrote: The last price i had from Mathews on fire bricks was around the $5-6 mark. I believe they recommend a refractory/mortar to hold the bricks in place.

    I mitered the edges, wrapped them with wire and rockwool, then shoved the whole lot into the 20L drum.

    #2339
    Profile photo of Andrew-MOAMind
    Andrew-MOAMind
    Participant

    So I am close to finishing this thing off and it has been more than a bit of a PITA. Like all good experiments the fun wore off pretty quickly but it still has been interesting.

    The pearlite & sodium silicate compound works relatively well. It can be formed into shapes easily and once a considerable time has been allowed for curing it is pretty rock solid. Although due to the still large particle size of the pearlite, corners can chip and break relatively easily. It also needs to be applied in layers with time to set, otherwise the inner sections will not harden. Layers of 10cm wrked ok for me.

    I have had a few people warn me about the sodium silicate as a lung irritant, as with all things take precautions but I have not seen any cautions for sodium silicate specifically. Especially not in the liquid form, some things I read about it were to do with sodium silicate powder (?), the pearlite dust is probably more of a hazard.

    As for the aluminium oxide & sodium silicate refractory…. not great. Certainly doesn’t set nicely with heat, instead it bubbles and goes very brittle. hopefully slow air curing is more effective.

    For the crucibles I have ended up machining a series of 100mm dia tubes and welding bases onto them, a 5mm wall thickness should be ok for aluminium & brass. Hopefully it can tollerate the higher temperatures for bronze as well.

    #2350
    Profile photo of Shaun
    Shaun
    Member

    Andrew-MOAMind, post: 3120, member: 29 wrote: This thing has a 50/50 chance of blowing up in my face in some horrible way but it sounds interesting.

    I want to start doing my own castings for aluminium and brass. Primarily because I have buckets of bronze swarf I would eventually like to be able to re-use in other projects.

    The plan is to build a basic furnace following these instructions.
    [media=youtube]vQN7EqGMTuo[/media]

    I have tracked down my supplies.
    100L bag of perlite for $30 from the appropriately names perlite & vermiculite factory
    4L of Sodium Silicate for $8 from the potters market (even cheaper if you bring your own bucket)
    Old steel rubbish bin $FREE

    The only one I havent been able to find is Aluminium Oxide powder which helps with the thermal insulation properties and is also used for the furnace lining

    I havent worked out what ill be using as a burner long term yet. To begin with ill just be using a blow torch.
    Ill upload some photos as I go.

    #2351
    Profile photo of Shaun
    Shaun
    Member

    I have got a small drum furnace up and running.Built my own gas injector and using an old hair drier for the forced air induction.Works very well and have melted about 5kg of brass ,busy with coke cans for the aluminium but a lot of waste with that.Have mixed greensand as well and will soon start with casting.Any good woodworkers out there that could make me wooden frames for the cope and drag? I can run the furnace on charcoal or wood as well.

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