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renatoa
03/29/2024 1:55 AM
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03/25/2024 12:38 PM
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Dan's Direct-Flame Roaster
coffeeroastersclub

Quote

Dan wrote:
Here's a link to a QuickTime video of the roaster in action. The flame wants to blow out, probably from drafts. You hear how noisy the chain drive is and how jerky the mechanism is, too. Next time it will be direct drive.

http://claycritte...aster1.mov


Dan,

Even though the drum is a bit jerky does it ever fall off the sprocket? If not it should be ok wouldn't you think?

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
Dan
Len, Yes, it has jumped its tracks quite a bit. But, tweaking the chain and sprocket alignment, as well as the position of the rear bearing makes it more trustworthy. The weight of the beans help, too. It behaved nicely on that last roast. The noise is obnoxious, though, but I can hear the cracks OK.
 
Dan
Did another roast today with much better results. I turned down the regulated pressure and that made the flame more stable. It only flamed out twice. I think I'll make a hurricane shield for the burner so it never flames out. I finished a 3#, FC+ roast in 14 minutes. I finally feel more in control of the process now.
 
seedlings
Nice work Dan! Will the hurricane shield be a cylindrical metal tube or something more intricate?

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Dan
Yes, a perforated cylndrical shield. The perfs are important. They should open up about 1/3 of the area to disrupte breezes. I'll mount it to a circular baffle attached to the burner head halfway between the intake holes and flame exhaust. I think that will help block air blowing out the flame.

I'm surprised at how low I need to turn the flame down to. I thought flame roasters were supposed to be inefficient.
 
JETROASTER
Great project! How's the coffee? -Scott
 
Dan
I'm not sure yet! Only the last batch had a reasonable profile, and it is just two days old. It went a little darker than I would have liked. But, I took some of it into work today and let someone brew a pot with it. People were commenting about its aroma and taste, and people who I don't think of as regular coffee drinkers were asking for a cup. I suspect part of it is that they aren't used to fresh roasted coffee and even this mediocre cup tasted good in comparison. I hope to have my grind setting dialed in tomorrow morning and hope to learn more about it after three days of rest.

ADDED the NEXT DAY: It's been three days, so here's my tasting notes. Like I mentioned earlier, the roast is pretty dark and it continues to darken with age a little. The beans were glossy this morning. I'm not a fan of dark roasted coffee, so it isn't pleasant tasting to me. The cup is balanced, not bitter or acidic. There are tangy wood notes, followed by a little bit of apricot, and a hint of cardomon. It improves as it cools. This weekend I'll roast some more and work to control the final temperature better.
Edited by Dan on 10/05/2011 8:48 AM
 
Dan
Another roast today, and this one is spectacular. 2.5# of Mexican Organic DP Nayarit Rustico. I'm getting a better feel for the profiling. I begin at about 6kBTU until just after 1st crack began at 11:00 minutes and then reduce the heat to about 4kBTU for the duration of the roast until the first few cracks of 2nd crack at 17:40 minutes. I looked for defects and found one divoted bean.
Edited by Dan on 10/10/2011 1:16 PM
 
JETROASTER
Very nice. :Clap:
How would you compare the control of this machine vs. your other drum? -Scott
 
Dan
Scott, If I compare to my sample roaster using its manual control (0-100 % percentage timer dial), then it is a similar "driving" experience. With the percentage timer I turn the dial for more heat, and then monitor the thermocouple temperature that lags a moment later. For the flame roaster, I turn the dial and monitor the size and sound of the burner flame. They are both seat-of-the-pants control. On the other hand, there is no comparison between the flame roaster's control and using my sample roaster with the ramp profile PID. That's a set it and forget it unit.
 
Dan
I roasted five batches this weekend. I'm roasting for the winter. Everything will go into the freezer. I'm really getting the hang of it. One roast I almost stalled, but recovered. I reduced the batch size to 2.5 pounds, but that's just because its a multiple of the 5, 10, and 20 pounds I order. Once I feel more confident I'll try a 5 pound batch.
 
JETROASTER
:Clap:
 
seedlings
A roaster that can go from 2.5# to 5# is very versatile. Great work Dan!

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
JETROASTER
It would seem to me that this heat transfer method requires less physical space than a drum that is mostly conductive.
In fact, since the beans fall over the flame, the convective heat transfer is likely more effective as well? -Scott
 
Coffee makes the world goround
Hey folks :)
i was in Hamburg this weekend , in Speicherstadt kaffer?sterrei
they Roast in the caffe (big roaster)and have one of these as decoration (different color )

www.coffeebeanintl.com/sites/all/files/u3/Whitmee%20Blog%20Photo%20%234.JPG

i did use the camera of a friend . so i dont have the photos i took at the moment

But i took photos of the inside Grin
When i get copys of them i will post them
 
seedlings

Quote

Coffee makes the world goround wrote:
Hey folks :)
i was in Hamburg this weekend , in Speicherstadt kaffer?sterrei
they Roast in the caffe (big roaster)and have one of these as decoration (different color )

www.coffeebeanintl.com/sites/all/files/u3/Whitmee%20Blog%20Photo%20%234.JPG

i did use the camera of a friend . so i dont have the photos i took at the moment

But i took photos of the inside Grin
When i get copys of them i will post them


Is that a direct-flame roaster?

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Dan
Yup, that's a Whitmee direct-flame roaster. They have the tri-lobal cover and the specially designed, novel chute. When it is time to dump the load it reaches into the drum, catches the falling beans, and conveys them out to the cooling bin. I hope you post those pix!

Quote

In fact, since the beans fall over the flame, the convective heat transfer is likely more effective as well? -Scott


There's probably a good radiation heat output from the flame since it is incandescent. But, when you consider that a flame is just super-heated air, the convection component must be very high, like you say. We know that heat transfers faster (more BTUs/minute) when the temperature differential is higher. A 2000? flame temperature is pretty high compared to a 72? bean.

I'm enjoying a City roasted Kenyan Auction Lot right now. Very bright, citrus and cola flavors. It reminds me of the Kenyans I used to roast in my hot air machine, not the tamer Kenyans from my sample roaster.
 
Dan
I'm liking this roaster more and more, so I've decided to build a better one based on what I've learned from this proof-of-concept model. To begin, I bought a 28 rpm gearmotor with sufficient torque. I'll use this to direct-drive the drum.

Originallly, I planned on using bogey wheels to support the drum. But now I don't think I'll need to. I noticed that the gearmotor's specs say it can handle a 50 pound shaft load on its 1" long shaft. A 5 pound roast at the end of a 10" shaft (to center of drum) is 50 pounds, too. This means I can cantilever the drum, making it quieter and simpler. :) Worse case scenario is that I'll have to install bogies later on.
Edited by Dan on 11/05/2011 11:13 AM
 
JETROASTER
Same capacity? -Scott
 
Dan
Yeh, same size. I'll even buy two, new SS bowls of the same size from Sam's.
 
allenb
So I'm assuming with that low of an rpm you won't be dropping beans through the flame path as in the Whitmee roaster?

It would be great to hear results of coffee roasted in a roaster that would emulate two of the attributes of the Whitmee. 1. beans fall through flame. 2. Lower temp flame (yellow color) but without sooting.

I have no idea how one would accomplish this low of a temperature combustion without emitting soot and maybe the soot wouldn't necessarily cause a big problem with sufficient exhaust.

I was looking at a table showing flame temperatures using various fuels and it looks like a lab bunsen burner using natural gas at a yellow color is between 1600 and 2700 F. Propane runs from 2200 to 3100 F.

To fabricate one capable of this would unfortunately complicate things a lot.

I'm excited to hear you're getting good results from your present setup which means there is merit in the direct flame method.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Dan
The roaster I'm using now is 28 rpm. I started at about double that, but it was too fast. I slowed it down to get a nicely formed cascade of beans. The trick to good cascading is from deep vanes with a lilpped edge. My 15" diameter drum has 2" wide vanes with a 1/2" wide lip bent upward so the vanes act as scoops, lifting more beans higher before letting them drop. On my new roaster I'll use the same vanes, but install four instead of three.

The Sievert burner I'm using now has a wide range of adjustment. I have the burner turned down to about 1/4 of its rated BTU, which of course means the flame temperature is lower, too. I suspect that I could get by with a smaller burner than the one I have.

I hope to do some side-by-side taste tests in the future, hopefully blind tests using people with cupping skills in order to see if the coffee does taste different or better.

I believe bunsen burners only work when the flame is shooting up vertically, so couldn't be used here. From what I know, how they work is that the gas mixture is buring outside the burner head, not inside like in venturi burners.
 
allenb
Yeah, I was only mentioning the bunsen for a temperature reference and you're right, the bunsen would not be a candidate at all for the application. From what I've been able to glean from different sources on the Whitmee is they either used a pipe burner down the length (inside the drum) or a single large burner operating near the front end of the drum where the largest portion of the beans fall across it.

I now understand how you're able to toss the beans far with a slower rpm using large vanes. Good thinking!

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Dan
"Toss" might be the wrong verb here. The beans cascade down like a waterfall with a pleasant swoosh, swoosh, swoosh sound.
 
allenb
So the beans are not carrying over in air and dropping through the flame path. If this is the case then it's not really a direct flame to bean as Whitmee does it but direct flame /convection would be a better description.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
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