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Thread: Gas forge - external temp?
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25th Jan 2016, 10:50 PM #1Senior Member
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Gas forge - external temp?
G'day all
Just fired up a long term project, a small gas forge based of course on a propane cylinder, this one was 5kg I think - a little smaller overall than a 9.
I have 1" of ceramic wool with itc100 coating.
The burner is a mikey style, 3/4" tube.
The problem is the outside gets a lot hotter than I expected. Barely touchable after 3 or 4 mins, which was enough time to heat a 3/8 rod to bright red.
Normal? Not enough insulation? More itc100?
All advice appreciated..
Russ
-Russell
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26th Jan 2016, 01:23 PM #2Senior Member
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G'day Russell,
sounds like a great project.
I'd suggest at least another layer of Kaowool; see https://www.youtube.com/watch?v=1DyeESQpac0
for what you can achieve with (4 inches of?) the stuff- a tin can that can melt cast iron!
good luck,
AndrewOC'Waratah' spring hammer by Hands & Scott c.1911- 20, 'Duffy, Todd & Williams' spring hammer c.1920, Premo lathe- 1953, Premo filing machine.
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26th Jan 2016, 07:35 PM #3
The rule of thumb that I have seen is that the wall insulation should be about one-quarter of the total diameter thick - so that's 25% insulation, 50% furnace area, 25% insulation.
See this for the best introduction to the entire 'make things hot enough to melt' topic I've found to date (pdf file)
The Hobbyist's Guide to Casting Metal--2nd Edition (print).pdf
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27th Jan 2016, 02:58 PM #4Senior Member
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I posted a reply yesterday but it seems to have got lost in the ether.
I guess I'll have to add a second layer with another coat of itc100.
I was just surprised by how hot it did get so quickly.
Ps, thanks for the link to the casting book... Very informative.
-Russell
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27th Jan 2016, 04:02 PM #5Member: Blue and white apron brigade
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- Feb 2006
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- Perth
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The shell of my mains powered gas forge is 12" in diameter.
It has a 2" layer of insulation so it has a 8" diameter cavity.
This is what happens after an hour or so with one torch operating at full flow.
I can put my hand on the outside of the back of the forge for about the first 15 minutes or so of operations.
I generally don't run it for longer than an hour.
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27th Jan 2016, 05:51 PM #6
The guys that I know of all use 2" of Isowool, The isowool by the way comes in 3 heat rating as well as 1" and 2" thicnesses.
Then rigidiser and a layer of castable ceramic. to seal the wool.
I just fitted the isowool to mine today but haven't tracked down any itc100 or castable yet.…..Live a Quiet Life & Work with your Hands
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28th Jan 2016, 12:30 PM #7
Just use satanite Dale. My "little pig" is 6" od with 1" of wool and the hard face, yes it gets hot to touch but it also keeps welding heat no problems without using much gas. No amount of insulation is going to be able to maintain a difference of 1200 degrees for long without so.e kind of active cooling.
1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.
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28th Jan 2016, 01:21 PM #8
Ewan is Satanite a castable refractory cement
…..Live a Quiet Life & Work with your Hands
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28th Jan 2016, 03:36 PM #9
Yes and you can also use it to clay blades for quenching to create hamons.
1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.
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28th Jan 2016, 04:36 PM #10
Nice
…..Live a Quiet Life & Work with your Hands
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