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Thread: My crematorium
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24th Jul 2020, 10:21 PM #16Most Valued Member
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Thats looking great. Nice job.
So can you just clarify, as well as heat treating (as in hardening, tempering steel etc) you will be able to use it as a foundry as well?
What will be the max temp?
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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25th Jul 2020, 12:26 AM #17Senior Member
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Simon
I calculated my elements to dissipate just over 2W/sqcm that should put the surface temp about the 1200 to 1300 degrees, hopefully. The Kanthal wire melts at about 1500 so want to stay well below that. I don't think i will ever go above 1200 but wont know for sure until it runs. The fancy controller has a 20 step memory so it will be able to do all sorts of ramps and soaks and controlled cool downs. The inside is tall enough to take an A14 crucible and be able to feed it from the front door for melting but i doubt i will ever use that big. I have an A8 for copper alloys and will weld up a bigger diameter and short steel pot for ally.
Glad you like it.
Mike
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25th Jul 2020, 01:23 PM #18Most Valued Member
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Yea that's cool.... I'm mean hot!
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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25th Jul 2020, 05:33 PM #19
I think Baron was referring to what was known as an electric "heat bank" out here about 20-30 years ago. Similar principal to what Baron is explaining, heating elements heating bricks or similar in an insulated enclosure during the night on off peak electricity, then slowly releasing the heat during the day to heat a room. Similar principal to the Russian ovens of old where the wood stove provided cooking but also heated a large mass of material that dissipated the heat to keep the house warm once the fire went out.
Heat banks became popular here for a while but then their popularity started to wain because they had a large amount of asbestos inside for insulation and were caught up in the rejection of asbestos. They had one other intrinsic problem as well, users had to anticipate their needs and turn them on the evening before they wanted the heat so they had time to store the heat during the night, so they weren't overly practical for areas with rapidly changing weather, as you either got heat when you didn't need it , no heat when you did want it, or occasionally heat when you wanted it.I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.
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26th Jul 2020, 07:40 PM #20Senior Member
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Looking good. I’m in process of designing a heat treat kiln myself so I’m interested to see how you go. With respect to elements how many ohms are you looking at? Would you care to share your power calculations?
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26th Jul 2020, 08:19 PM #21Senior Member
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The elements are calculated along the normal power formulae like I=E/R and P=IE but there is another couple that need to be worked out and that is how much surface area does the wire have which leads to how many watts per square cm is it dissipating. Go too high and it will deteriorate fast, i searched looking for those numbers and Sandvic did a graph showing its recommendations. From that you can see my application of heating elements in grooves @1200 degrees Celcius is just over 2.5 w/cm-sq. Kanthal has a slight positive coefficient of temp for its resistance, about 4% i think, which means it should be shorter than the basic calcs suggest. This should be factored in but i will take the basic length and use the temp coeffient as my tuning to dial in the wire temp later.
Kanthal 1.png
The snapsot below shows my calcs. I didnt go smaller than 17g, 1.2mm diameter, as the surface load goes over 2.6 w/cm-sq with very little power. I am waiting for some 1.2mm and 1.4mm wire to come then i will find out if i got the numbers correct
Kanthal.PNG
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30th Jul 2020, 01:55 PM #22Most Valued Member
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Nice work.
I'm enjoying this thread. Thanks.
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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30th Jul 2020, 05:01 PM #23Most Valued Member
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Oh, one other thing,
What mortar or castable refractory mix did you use to bond your fire bricks together?
I notice Bunnings sell a type of "fireplace mortar" which claims to be rated to 1375 Deg C. Wonder if that would be suitable for a similar project?
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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30th Jul 2020, 08:51 PM #24Senior Member
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I used refractory cement from the refractory supplier here. Not cheap at $40 for 5 kg but i feel more comfortable with that than from the hardware shop. I have a bag of castable that i will make some tiles for the floor to protect the softer bricks.
Still no wire but i have a few other projects to play with
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30th Jul 2020, 09:29 PM #25Most Valued Member
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No worries. At $40 for the 5kg I think it actually might be a better deal anyway.
From memory it was about $30 for a 1kg bucket at bunnings!
Simon
Sent from my SM-G970F using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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30th Jul 2020, 09:47 PM #26Senior Member
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31st Jul 2020, 09:39 AM #27Most Valued Member
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Sorry for all the questions,
what size/type of fire bricks did you use?
Did you put the grooves for the wire in the sides or did you buy them already done?
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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31st Jul 2020, 11:09 AM #28Most Valued Member
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Simon, if you're looking to get any bricks/refractory etc I recently got some castable and ceramic blanket from Darley Firebrick in Oakleigh Sth. Prices were reasonable, and they have a decent range of bricks/refractory/clay/blanket etc.
Steve
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31st Jul 2020, 06:26 PM #29Senior Member
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The bricks are mostly all a standard size i think. about 240x70x 50 or thereabouts. The groove was already in them, they come in end type where the groove stops just before the end or the groove goes all the way to make long walls. Of course they come without the grooves if u want. I got mine for so cheap because they had a piece cut out of them and the design changed so they couldn't use them.
When u get them u want the light weight insulating bricks, the heavy ones don't insulate much so take a lot more power to get up to temp and the outside gets bloody hot so needs further insulation to stop that. The heavy bricks are good for rough use furnaces and as a floor for sitting a crucible on but the light ones are fine for a home unit if your a little careful with its operation.
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14th Aug 2020, 11:22 PM #30Senior Member
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The kanthal wire showed up so wound a coil and partially wired the thing up enough to get the coil hot. I left the coil over long and it is not up to full temp so next is short some coils out till i get the colour i like. I can't finish it for a while as am in the middle of the major reorganisation of shed and garage to make way for the lathe etc to come home.
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I have been playing with a few other projects while i waited for the wire to come. Scored a big piece of 25mm plate 1300x1000 and have an electricity pole that was pulled out, 115 OD by 5mm wall, will make my bench nicely. Weight nearly 300KG.
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For something whimsical i have been playing with making damascus hammers after seeing a youtube video. The mate had made a nude statue he made on the 4 axis machine we built so i grabbed that for one of the handles. Also made a couple of lead hammers, mate thinks i have a hammer fetish. Far too much time on my hands i think. Also made the crankcase for a die filer machine to be ready for when i get to the clock.
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Bugger its definitely time for
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