peterz Senior Member Joined: 24 Apr 2006 Posts: 3 Location: arizona Expertise: I live coffee
Posted Mon Apr 24, 2006, 10:30pm Subject: Re: Radiant roasting, part II
SCOTT!!! Congratulations on your success! Your project is amazing! Now you just need a larger thermal carafe :) Of course 8 oz is a just fine accomplishment. I had problems with that red hi temp rtv getting gummy and releasing after a year or so with my PGR, but you may have better stuff. I liked the spring set up you had on your first roaster.
I have seen 12 cup Vacuum Carafs at thrift stores in town.. now I have to try this. How about those 2 qt vacuum pumper pots? Maybe the neck is too narrow.. and they are glass..
They have old slide projectors there also, for a few bucks.. I bet the lamp set up in those will work.
Awesome! I suppose the caraf could be clamped or glued to a record player turntable.... I love that it stays cool on the outside! Now I have to think smaller, like yours is, so I can take it camping :)
PressedCup Senior Member Joined: 20 Feb 2006 Posts: 27 Location: North Carolina Expertise: Just starting
Espresso: None Grinder: Doseless Rocky Vac Pot: French Press Drip: Presto Roaster: Cast Iron Pot.....Plus
Posted Tue Apr 25, 2006, 6:40am Subject: Re: Radiant roasting, part II
That,s very impressive to get an 8oz roast in that time with low wattage. Your rig is obviously breeze proof. I have been shielding my "Cast Iron Pot....Plus" from back porch breezes with a large piece of cardboard and have been thinking of surrounding the whole thing with a short piece of insulated (or not) sheet metal pipe. Your rig definitely shows the power of effective insulation.
I contacted some Chinese (they make all this stuff) and they really want to make a big one for me. If I had the bucks, it'd be fun to set that up. Here's the problem: they'd want me to design it. Well, duh. But the moment I think about that, I realize that I have no idea how I'd want it to be. It's one thing to successfully adapt something else, like a vacuum carafe. It's another altogether to contrive an ideal set of specs: "If you could have it be any way you'd like, what would you do?" It really implies more experimentation with more versatile mock-ups and such. Good grief.
peterz Said:
They have old slide projectors there also, for a few bucks.. I bet the lamp set up in those will work.
Well think about this -- and I'm dead serious -- the low required wattage and the availability of 12 volt halogens means you COULD run something like this from a cigarette lighter. If you want 240 watts, that's only 20 Amps. If the cigarette lighter fuse is too low, use jumper cables. ;-)
PressedCup Said:
That,s very impressive to get an 8oz roast in that time with low wattage. Sounds like you're having a lot of fun.
Yeah. One thing I'm thinking is this: that 1300 watts of power my popper was using for heat (another 120 for fan)? With that and this I could do over a kilo, in a bigger form factor.
peterz Senior Member Joined: 24 Apr 2006 Posts: 3 Location: arizona Expertise: I live coffee
Posted Tue Apr 25, 2006, 10:31am Subject: Re: Radiant roasting, part II
The proof is in the tasting ;) How does the coffee taste? or is it still too soon to tell? :)
I suspect you can use a larger chamber but not have it a vacuum wall setup.
If you got the right size (pick a size) SS cylinder and found a suitable larger size one to surround it, you could fill the gap between them with suitable furnace insulation. Those inexpensive sets of ss stockpots come to mind. They nest nicely :) I doubt that spray in foam (great stuff) would stand up, but a blanket type sure would. My PGR stays cool to the touch on the outside, and It is just insulated with fiberglass ; but I have a large heat loss where the turbo oven sits.
I agree, if you want to roast 8 oz or more at a time, it is easier to just go outside and roast. With your set up, weather (coldness) should not be a problem, for the roast anyway.
Chaff is removed during cooling, here in Lake Havasu City.
I used a fairly nondescript Colombian that I've found good only after 4 or 5 days rest. But to my surprise, it tasted good a half hour after I cooled it. BTW, I brewed it in an Aero with a metal mesh -- something I hadn't done in a while. Given what I didn't like about the unrested bean, I suspect the metal filter would have exacerbated the bean's weak points, so this definitely raised my eyebrows. However, I also roasted the bean further this time, than I have on other occasions. Maybe I just found its sweet spot. :-)
I suspect you can use a larger chamber but not have it a vacuum wall setup.
Depends on what kind of deal I can cut with these Chinese. ;-)
If I can swing a deal and anyone else is interested, it might be practical to manufacture some. It'd be expensive though, for small quantities. At any rate, anyone interested would want to be in on specifying a design. That's a big issue.
If you got the right size (pick a size) SS cylinder and found a suitable larger size one to surround it, you could fill the gap between them with suitable furnace insulation.
True enough. This process is energy-efficient enough that less-efficient insulation (than a vacuum) wouldn't be much of a problem. I suspect this is a good answer to the "if you're going to design a bigger vacuum flask, you have to prototype it somehow" issue. And it might be good to tinker with a hemisphered design that's flanged for disassembly of the thing across its midpart. Dunno.
peterz Senior Member Joined: 24 Apr 2006 Posts: 3 Location: arizona Expertise: I live coffee
Posted Tue Apr 25, 2006, 12:31pm Subject: Re: Radiant roasting, part II
Glad to hear that the beans taste good :) My experience has been, when I added an additional heating coil below the shield on a Turbo Oven, the beans did not roast right. What I suspected was that the heater coil needs to be behind a shield or you get the burnt/baked taste. Your experiments seem to disprove this theory.
Or maybe Halogen lamps heat differently than resistive heaters designed for ovens. Maybe because you also shield it in the test tube?
Why would Halogen lamps radiate differently than heater coils? The heater coil does not even get to red heat, whereas the Halogen lamp is at white heat...
Jasonian Senior Member Joined: 8 Aug 2005 Posts: 3,846 Location: Lubbock, TX Expertise: Professional
Posted Tue Apr 25, 2006, 1:02pm Subject: Re: Radiant roasting, part II
peterz Said:
Glad to hear that the beans taste good :) My experience has been, when I added an additional heating coil below the shield on a Turbo Oven, the beans did not roast right. What I suspected was that the heater coil needs to be behind a shield or you get the burnt/baked taste. Your experiments seem to disprove this theory.
Or maybe Halogen lamps heat differently than resistive heaters designed for ovens. Maybe because you also shield it in the test tube?
Why would Halogen lamps radiate differently than heater coils? The heater coil does not even get to red heat, whereas the Halogen lamp is at white heat...
The white glow in a halogen lamp comes from the fact that there is no oxygen in the bulb (it's a vaccum), thus making combustion impossible.. in turn allowing the filament to glow without damage. I'd imagine it works quite differently than what you are suggesting.
Posted Tue Apr 25, 2006, 4:19pm Subject: Re: Radiant roasting, part II
peterz Said:
Glad to hear that the beans taste good :) My experience has been, when I added an additional heating coil below the shield on a Turbo Oven, the beans did not roast right. What I suspected was that the heater coil needs to be behind a shield or you get the burnt/baked taste. Your experiments seem to disprove this theory.
Or maybe Halogen lamps heat differently than resistive heaters designed for ovens. Maybe because you also shield it in the test tube?
Why would Halogen lamps radiate differently than heater coils? The heater coil does not even get to red heat, whereas the Halogen lamp is at white heat...
I suspect the beans are more tolerant in my setup because they're agitating faster. Not as fast as I'd like, but faster. They tumble and flow and get buried and come up somehwere else in the mass pretty rambunctiously, you might say. They just don't expose themselves in one orientiation to the radiant heat for very long, so this probably results in more even heating.
IMO, a VERY aggressive agitation -- little different from a conventional drum -- would be good. But what I have just now isn't bad.
I'm awfully pleasantly surprised by this. It's enough of a milestone for me that tonight I'm going to clean up a month's accumulation of experimental junk that I've scattered about. TIme to breath a satisfied sigh and enjoy another cup of this stuff. ;-)
Posted Tue Apr 25, 2006, 4:27pm Subject: Re: Radiant roasting, part II
Jasonian Said:
The white glow in a halogen lamp comes from the fact that there is no oxygen in the bulb (it's a vaccum), thus making combustion impossible.. in turn allowing the filament to glow without damage. I'd imagine it works quite differently than what you are suggesting.
Tungsten redeposition is the halogen lamp's raison d'etre. Something to consider is that this process depends on enough heat, so dimming halogens can shorten their life a bit. However, using a dimmer to turn them on slowly to full power will actually lengthen their life a bit; it stresses the filament less to bring it up slow.
Look for new lamps with carbon filaments to be all over the place in the market soon. They last half as long as halogens, but compared with the halogen's 87% energy-to-heat transfer, the carbon ones are about 93% -- and they're not bright at all. That makes it a LOT easier to work with them without going blind.
In all honesty, I think this 300 watt sucker I'm using could be dangerous to vision if one wasn't careful. It'd be weird if I had to wear welding goggles to roast coffee. ;-)
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