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Topic: Another decent IR2 Profile (3 msgs / 91 lines)
1) From: Ken B
I have played with the IR2 trying to get a profile that matches the 
slope of a USR roaster I watched in action, and came up with this.  In 
~13 - 15 minutes, it produces a roast from FC-Vienna.  Is it 
repeatable?  On my machine, yes.  Your IR2 may (WILL) vary.
First, the basics. 
My thermocouple is accurate to +/- 1 c or ~1.8 f
My scale is accurate to 1 gram
All values are for 148 grams of green beans at Start of Roast
The thermocouple is seated 1/3 of the green bean mass from the bottom of 
the IR2.
There is a 4" dryer vent attached to my IR2.
No loosening and /or removing the chaff screen is required.
For 3 roasts with ambient temperatures of 76, 77 and 78f, here is the chart.
Roast 1 was cut at 446 f.  Roast 2 was cut at 454, and roast 3 at 448 f.
Roasted weight for these in order, is 127 grams, 126 grams and 126 grams
 
Profile in IR2 is:
3 minutes at 320, 4 minutes at 335, 2 minutes at 350, 3 minutes at 365 
and 3 minutes at 390.http://www.onlymysite.net/files/Profile6.xls(I hope this works...it was done in OpenOffice and saved in .xls format)
Please note that dropping stage 5 to 385 will NOT give you the expected 
results, at least on my unit.  I thought it would allow me to use the 
final 1 to 2 minutes of the roast to get to 454.  Instead, it peaked at 
436-438 at 15 minutes...but that is an almost perfect FC, at least how I 
look at it, so it too is a useful profile.
Anyway, I hope this helps some of you who do not have PID's attached and 
still have working smoke alarms in your house. ;-)
Best Regards,
Ken B
PS... If any of you folks who have experience in charting profiles would 
care to comment on the slopetime ranges, etc., I would be very 
interested in hearing your observations.
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2) From: Ken B
Oh, and the 30 second reading was entered to help the chart.  I do not 
start temp readings until the 1 minute mark, so I just entered 200 
degrees for the first 30 second reading.
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3) From: Allon Stern
On Jul 12, 2008, at 1:29 PM, Ken B  wrote:
<Snip>
I'm coming to the conclusion that rate of change is at least as  
important as absolute temperature. If I let the temperature climb too  
fast, the it seems to be hard to slow down the roast later on. I see  
what is meant by the momentum of the roast.
I think using the vent fan helps with this quite a lot -- I can slowly  
edge the speed to slow the rate of change. If I let the temperature  
climb too fast (through inattention or whatever), the crank up the fan  
in an attempt to recover, it just doesn't work. I have to stay on top  
of it, slowly working the airflow up to keep riding the brakes, as it  
were.
Still refining my process, but I'm settling o something like:
5 minutes of warmup, slowly edging from minimum fan to max until I hit
1.5 minute of heat boost. I turn the fan back down to minimum for this  
part, edging speed back up, trying to get 1st crack just started.
Then back to lower heat, and reset the fan back to minimum, sloowly  
edging up again to minimize the rate of change.
Any comments from Mike, Les, Tom, or anyone else with a "real" roaster?
-
allon
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