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Old 12-23-2017, 01:56 PM
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Dave Hilty Dave Hilty is offline
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Small Successes

Had an interesting day yesterday. I turned down my 80# Moly to 1750F last Wednesday and didn't return to the studio until yesterday at 7am to find that the furnace temp was down at 250F. The problem was the Bussmann fuse, protecting the SCR. Fortunately I had a spare in the drawer. We had a group of 10-12 folks scheduled last night to make ornaments. I really hated to call and cancel as they had really been looking forward to this event as part of their family Christmas with some folks in from Montana etc.

I never would have tried to return the furnace to blowing temps in less than 12 hours or imagined that the power package could push it back up that fast.
What I had in the shop was a secret weapon. We converted a Home Depot weed burner to a mega torch at the bench for those times when larger pieces require it or won't fit back in the glory after pushing the size.
I figured that even if the crucible cracked as I went crazy fast through the danger quartz inversion zone, I might be able to dig out glass enough for the planned evening event. (the crucible was in need of replacement anyway so the risk was worth it)

The torch saved my ass. And with the early morning reading of 250, this was probably well below the remaining 1/3 pot of glass temp. Crazy to see my moly with the door open enough for the torch. Are there other reasons to consider a dual fuel furnace? The btu's put out by that thing really mimic a larger gas burner.

Long story short, I got back up to 1950 in less than 12 hours, no new cracks in the crucible and a nice event was had by all.
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Old 12-23-2017, 02:55 PM
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Pete VanderLaan Pete VanderLaan is offline
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I have made dual burner furnaces and the issue which has to be considered if one is going to be gas and one electric is that the gas opening will try to turn into a flue and you do need a flue for such a setup.

I have certainly kept furnaces at temp during power outages with a burner in the cleanout. It might be the place to consider designing in a secondary unit.
But it still needs a flue.
I think Steve has told me that Moly elements don't really perform well in other fuel environments but I don't recall the reason.

I am glad to hear that it worked... so far.
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Old 12-23-2017, 05:08 PM
Josh Bernbaum Josh Bernbaum is offline
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My idea of a perfect furnace (for me anyway) would have a gas burner for doing melts so plenty of BTU's for that and then the moly would take over for the rest of the time. And some sort of "cap" to seal the flue vent when burner is off. I don't know if the logistics would ever work out but in my mind I've been liking the idea of something like this.
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Old 12-23-2017, 05:13 PM
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You are spot on with the flue. If I pushed the throttle even half way the flames wrapped right back out the door. Thought about opening the drain port and placing the torch head there but didn't want to hit the crucible with direct flame. Should have taken the time to open that port as an exit flue. I'd really like to know what gas combustion does to the molly elements. I'll try to track that down.
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Old 01-02-2018, 02:28 PM
Steve Stadelman Steve Stadelman is offline
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Under 2550f molys work in a reduction atmosphere. The Kanthal Super handbook is available as a PDF online.
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Old 01-02-2018, 03:19 PM
Eben Horton Eben Horton is offline
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Quote:
Originally Posted by Josh Bernbaum View Post
My idea of a perfect furnace (for me anyway) would have a gas burner for doing melts so plenty of BTU's for that and then the moly would take over for the rest of the time. And some sort of "cap" to seal the flue vent when burner is off. I don't know if the logistics would ever work out but in my mind I've been liking the idea of something like this.
If my memory serves me correctly, Pratt fine art in Seattle has a furnace like this.
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Old 01-02-2018, 04:35 PM
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Pete VanderLaan Pete VanderLaan is offline
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Quote:
Originally Posted by Steve Stadelman View Post
Under 2550f molys work in a reduction atmosphere. The Kanthal Super handbook is available as a PDF online.
****
that, considering all of the issues would be a perfect system. I think that GAS has the horsepower that Moly does not have. Melt the stuff, back off, switch and go to sleep.
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Old 01-02-2018, 06:11 PM
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Franklin Sankar Franklin Sankar is offline
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I missed something . If moly works in a reduction atmosphere does it mean it can also work in normal air. </2550.
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Old 01-02-2018, 06:47 PM
Jordan Kube Jordan Kube is offline
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Quote:
Originally Posted by Eben Horton View Post
If my memory serves me correctly, Pratt fine art in Seattle has a furnace like this.
They have a gas furnace by Wet Dog.
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Old 01-02-2018, 08:38 PM
Eben Horton Eben Horton is offline
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They have a gas furnace by Wet Dog.
How about 10 years ago?
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Old 01-03-2018, 12:18 AM
Jordan Kube Jordan Kube is offline
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I'm pretty sure that's a no.
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Old 01-04-2018, 05:59 AM
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Franklin Sankar Franklin Sankar is offline
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The new kanthal super handbook is the best . Thanks Steve it has some great illustrations/ examples.
Franklin
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