HomeRoast Digest


Topic: Drum rotation > Jimma > PID iRoast (20 msgs / 611 lines)
1) From: miKe mcKoffee
First I'll say I'm not a roaster designer or manufacturer so can't say
exactly how specific drum rotation speeds are chosen for different roasters.
Before his passing Ron did a fair amount of testing for various drums and
drum diameters to determine how fast was too fast for his Q drums. IE at
what speed would the beans not loft but instead have centrifugal force push
them against the wall. IRC the HotTop drum rotation is ~30rpm (checked it
but that was almost 3 years ago so memory fades), USRC 3k ~65rpm, Behmor
very slow ~6rpm. Observation of other commercial drum roasters and their
observed bean loft means using similar speeds to measured (counted) USRC
drum speed. 
A common mistake is thinking the drum itself is the primary heat source for
drum roasted beans. Modern drum roasters convection accounts for about 80%
of the roast energy, air roasters even more. While the specific pre-heat of
the drum and roaster IS VERY important at the beginning of the roast, it's
importance is it's stored energy which is applied primarily via convection
and radiation not conduction. With a bit of understanding of the types of
heat in the roast process and observation of various roasters it becomes
clear constant loft of the beans by the drum is the goal. Convection is the
primary heat transfer in all modern roasters.  (See a good article by Terry
Davis, originally written for Roast Magazine IIRChttp://www.ambexroasters.com/information/read/heat_transfer.html)
If the beans aren't vigorously tumbling convection can't occur for the
majority of the beans stuck in a barely moving mass. This leaves conduction
and radiation as the more predominant roast energies, which is the problem
with the stock Behmor. Radiant energy primarily from the heater and
pre-heated roast chamber primarily affecting the beans on the outside of the
mass and conduction later in the roast bean to bean. At the same time I
split out the heater for variac control Alchemist John put in a faster drum
motor, with marked improved results. (We both had/have first production run
Behmors from Joe) I never got a roast I was satisfied with just by directly
controlling radiant heat, ie the heater. Some "ok" roasts to be sure, but
nothing as good as Caffe Rosto profiled roasts or later CCR HotTop roasts.
Convection or lack thereof was the apparent difference.
IF a faster drum rotation causes problems with the Behmor Alchemist can
chime in since fairly certain he's been using IIRC ~45rpm drum motors for
close to 3 years.
It's easy to turn beans brown, it's a lifetime Journey learning how to make
beans sing. IMO (and that of many others) a huge part of the process is
learning how to effectively control your particular roaster.
Slave to the Bean  miKe mcKoffee
www.CompassCoffeeRoasting.com
URL to Rosto mods, FrankenFormer, some recipes etc:http://www.mckoffee.com/Ultimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/
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2) From: John Borella
My Hottop B drum rotation is 60rpm, sure you are remembering correctly?
John B.

3) From: Robert Yoder
Thanks, MiKe!
 
Happy Roasting,
 
robert yoder
 
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4) From: Robert Yoder
Hi, John,
 
Are the beans lofted at that speed? Is there a Bean Mass Thermocouple?  Where is it mounted?
 
Thanks, and,
 
Happy Roasting,
 
robert yoder
 
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5) From: miKe mcKoffee
No, that's why I said IIRC and it'd been 3yrs since I checked it. (IIRC = if
I recall correctly) 
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6) From: Archeobob
Robert,
I put mine about 1/2" from the drum - threaded it through a 1/4" 
copper tube through a hole in the side of the bbq grill. Very 
simple to bend the tubing to get good reads. Since my temp gauge 
on the grill shows 600F when my side mount shows 455F, that 
makes a big improvement when shooting for temps.
Swiped the idea from a picture on the RK Drum site.
Bob - Parker CO
--------------------------------------------------
From: "Robert Yoder" 
Sent: Thursday, September 30, 2010 3:06 PM
To: 
Subject: Re: [Homeroast] Drum rotation > Jimma > PID iRoast
Hi, John,
Are the beans lofted at that speed? Is there a Bean Mass 
Thermocouple?  Where is it mounted?
Thanks, and,
Happy Roasting,
robert yoder
<Snip>
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7) From: miKe mcKoffee
Yes, HotTop has good drum bean movement. No, a stock HotTop has no bean mass
monitoring.
miKe
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8) From: raymanowen
No bean mass monitoring?
I've been wondering how to fabricate and install a thermal measuring device
that would Not be affected by the passing hot air that got the little orbs
hot in the first place. Wouldn't they be on the median between the incoming
air and exhaust air temperatures? Something is exactly that hot- I say it's
the beans.
You could be in the market for one of the channel amplifiers of a Leeds &
Northrup multi-point, multi-source chart recorder that plots individual
temperatures, the mode, the median and the mean traces. Relax, it's just
middle-school math. No me but all three kids did it.
Maybe you could find all this stuff on the 'Bay, but all the tubes will be
missing. No such thing as industrial or special purpose tubes or the gas
diodes in the current rare stocks, so Viel Glück.
One more little thing to consider- coffee beans are thermal conductors. The
heat you apply to the outside of a bean travels to the center of the bean
after a while. If the roasting profile is not too radical, the interior will
be roasted exactly the same as the exterior.
If you have to hurry the roast to avoid "baking" the beans, you'll have to
use some rapid temperature excursions to finish the profile trip. The
temperature gradient across the bean would yield an unintended (or not)
"melange" temperature distribution.
If your roaster has a "trier," what's the effect of the time delay of the
first beans into the cooler vs the last beans out the gate?
Cheers, Mabuhay, Prost auf dem besten schmeckenden Tasse Kaffee -RayO, aka
Opa!
When seconds count, the cooler takes mere minutes.
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9) From: Robert Yoder
Ray-O, Ray-O, Reductio-Ray-O,
 =
With all your wonderful competence, why limit your posts to pointing out pr=
oblems?
 =
How about some seriously helpful suggestions, rather than sharp-shooting?  =
We could use your competence, and don't really benefit from bravado.
 =
Happy Roasting,
 =
robert =
 =
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10) From: raymanowen
"How about some seriously helpful suggestions, rather than sharp-shooting?
We could use your competence, and don't really benefit from bravado."
   1. Everything I've ever done started with never having seen or done it
   before so I have to open a new file and file some new notes in the vacuum
   above the shoulders.
   2. I can't start solving problems with the application of random answers
   and formulas  as suggested. It's hard to understand and define a problem if
   you already know the answer. You can't discover or remember anything of
   value by just asking for answers, not questions.
   3. Question everything, not just "what button do I push for..."  If
   someone tells you, that's the only question you'll be able to answer
   yourself.
Every time I tried to violate the laws of Chemistry, Math and Physics, I got
in trouble- or heard that someone else did so themselves. Then my name might
be called- "Hey, Ray, can you come bail us out?"
The least of my favorites were some of the locals whose shop tools consisted
of hammers and pry bars, and the shop itself resembled a Hell-Hole
"No, I can't hurry it up and fix this POS. I don't ever want to see it
again, and besides- if you don't have time now to let me study it and
prevent the pending disasters, when will you ever have time to stop
production and do it right if I miss something like the last hammer mechanic
did that worked on it?"
My only sharp shooting amounts to trouble shooting, where I identify first
causes and likely incipient failures that will only rain on my parade when
I'm 25 or 50 miles away back home. The only time I ever had to make good on
my "It will never fail" warranty, the owners, a husband and wife just looked
at each other as I booked. "You already paid me- keep me posted."
What's all this got to do with coffee? Not much, I guess. At the time, I had
already had the forgettable experience of the Melitta Aroma Roast and I did.
Cheers, Mabuhay, Iechyd da -RayO, aka Opa!
Got Grinder?
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11) From: Martin Maney
On Sun, Oct 03, 2010 at 11:16:04PM -0600, raymanowen wrote:
<Snip>
Non seq.  The difference between the incoming and outgoing air temps
relates to the energy being imparted to the beans and chamber, not to
the temperature of the beans.  Not sayin' there isn't a connection at
all, but it's not as simple as that average.
-- 
On televison everything that happpens is connected;
it's got to be.  In life, marvelously unconnected things
keep happening in the same prime time series.  -- Amanda Cross
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12) From: Allon Stern
On Oct 9, 2010, at 10:39 AM, Martin Maney wrote:
<Snip>
It's an interesting concept. Of course there is more than the beans in the equation - there is the whole roasting chamber as well and it's shedding of heat to the surrounding area.
Airflow has an impact on the roast - note how the 800W Z&D manages as compared to the iRoast's 1400W.
The Z&D uses lower airflow, but doesn't use the air to agitate the beans.
-
allon
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13) From: Edward Bourgeois
Pro roaster design has been tweaked for many years. Much effort, r&d,
$$$ has gone into fin/vane design and adjusting to the proper speed
for the design. I'm very happy with my hybrid homebuilt but got a
Behmor (thank you John) early after it's release to play around with.
There's much to like about it. But as most 1st models it has some
design issues that can be improved upon. Drum speed it certainly one.
Agitation is very important for quality of roast along with
efficiency. Increasing drum speed has allowed for improvements in both
these areas(I'm running 50rpm but also have a 30rpm I could try and
compare). I still haven't had a chance to really test the chaff issue
Tom mentioned but in the few roasts I've done it didn't start a chaff
issue that was bad enough for me to notice. I've thought about trying
to lower the floor a bit  and redesign the chaff tray but just haven't
gotten around to it. For anyone who didn't see my recent mod. post you
can check out my blog below.
On Thu, Sep 30, 2010 at 12:20 PM, miKe mcKoffee  wrote:
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-- =
Ed Bourgeois aka farmroast
Amherst MA.http://coffee-roasting.blogspot.com/Homeroast mailing list
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14) From: Edward Bourgeois
One thing that has baffled me is why all the profiles end with a 100%
power. This goes against what the beans need after 1st crack and adds
to the chaff singeing issue.
On Sat, Oct 9, 2010 at 11:19 AM, Edward Bourgeois  w=
rote:
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-- =
Ed Bourgeois aka farmroast
Amherst MA.http://coffee-roasting.blogspot.com/Homeroast mailing list
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15) From: ricky carter
I completely agree with the comment about all profiles ending in 100% power,
it's the biggest hurdle for me with the behmor, P2 is an alternative, but
getting the cutback timed just right is a challenge.  a user initiated low
medium and high heat setting would make the Behmor a very nice roaster.
Of course it can be done by modding the roaster, but it would be nice if it
was built in.
On Sat, Oct 9, 2010 at 11:33 AM, Edward Bourgeois wrote:
<Snip>
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16) From: Ira
At 08:33 AM 10/9/2010, you wrote:
<Snip>
If I was guessing it's because of the short arbitrary limited roast 
time. Full power at the end tries to insure that it the roast was too 
short it can actually finish roasting the beans even if it's not the 
optimal profile.
Ira
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17) From: Martin Maney
On Sat, Oct 09, 2010 at 10:57:55AM -0400, Allon Stern wrote:
<Snip>
It's less than that, actually.  Total load is around 800 watts
(actually a bit less once it's warmed up IIRC), but that includes the
motor (probably not a big factor) and the "catalytic" heater, which is
something between 200 and 300 watts, I believe.  Wait a sec, that's
easy to check...
Nope, it's more than that.  Motor plus cat heater is around 350 watts. 
So the comparison of the bean heater is 500W to 1400W, more or less.
-- 
Self-pity can make one weep, as can onions.  -- Fodor
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18) From: michael kaericher
It's also not all that hard to crack the door open periodically after 1C st=
arts.  I tend to do about 3 seconds of every 15.
Overall I do agree about more control at the end though.  Most important =
for me would be some way to bypass the end time.  Like a "don't end now b=
utton".  To prevent a user from  letting the roast run way to long, the=
 button could be one that has to be held in as long as the user wants the r=
oast to continue, or it could extend the roast for small periods (30 second=
s) and need to be pressed in the last 10 seconds of the roast.
I sent similar feedback to to Behmor already.  Joe Behm contacted me and =
noted that this is a feature that he is trying to figure out how to work in=
.  He would like to work it in in such a way that existing users can take=
 advantage of it. (Though I noted that I am not averse to buying and instal=
ling a replacement control panel if it would offer additional control)
I'll send another reply to this with my email chain with Joe Behm.
-Mike
--- On Sat, 10/9/10, ricky carter  wrote:
From: ricky carter 
Subject: Re: [Homeroast] Drum rotation > Jimma > PID iRoast
To: "A list to discuss home coffee roasting. There are rules for this list,=
 available athttp://www.sweetmarias.com/maillistinfo.html"
Date: Saturday, October 9, 2010, 11:30 AM
I completely agree with the comment about all profiles ending in 100% power,
it's the biggest hurdle for me with the behmor, P2 is an alternative, but
getting the cutback timed just right is a challenge.  a user initiated low
medium and high heat setting would make the Behmor a very nice roaster.
Of course it can be done by modding the roaster, but it would be nice if it
was built in.
On Sat, Oct 9, 2010 at 11:33 AM, Edward Bourgeois wr=
ote:
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19) From: Allon Stern
On Oct 11, 2010, at 10:37 AM, michael kaericher wrote:
<Snip>
Again, this works into the "fully-manual SLR versus point and shoot with 12 modes" argument.
-
allon
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20) From: michael kaericher
Point and shoot anything with really high heat is dangerous.
-Mike
--- On Mon, 10/11/10, Allon Stern  wrote:
From: Allon Stern 
Subject: Re: [Homeroast] Drum rotation > Jimma > PID iRoast
To: "A list to discuss home coffee roasting. There are rules for this list,=
 available athttp://www.sweetmarias.com/maillistinfo.html"
Date: Monday, October 11, 2010, 9:42 AM
On Oct 11, 2010, at 10:37 AM, michael kaericher wrote:
<Snip>
starts.  I tend to do about 3 seconds of every 15.
<Snip>
<Snip>
t for me would be some way to bypass the end time.  Like a "don't end now=
 button".  To prevent a user from  letting the roast run way to long, t=
he button could be one that has to be held in as long as the user wants the=
 roast to continue, or it could extend the roast for small periods (30 seco=
nds) and need to be pressed in the last 10 seconds of the roast.
Again, this works into the "fully-manual SLR versus point and shoot with 12=
 modes" argument.
-
allon
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