HomeRoast Digest


Topic: Why vary fan speed fluid bed roasting? (33 msgs / 922 lines)
1) From: Mike McGinness
I was thinking about Jim's reply of not varying fan speed (boosting it) for
larger batches while playing with blends etc. Larger batches is one of the
benefits, but not necessarily the main benefit, of controlling fan speed in
addition to heater voltage. Though by boosting fan voltage up to 140v at
start of roast I *can* do 1/2# batches I seldom do. Still do my usual 1/3#
batches most of the time. Varying fan voltage also allows consistent bean
movement, for a given weight, for different greens. The fan velocity needed
for good bean movement can vary greatly from green to green do to their
varying density and moisture content even with the exact same weight batch.
Varying fan voltage also allows controlling bean movement during the same
roast from start to finish. Fixed fan can have just right bean movement when
at start of roast when green but run away bean movement as they dry
requiring much more heater voltage to compensate. Much better control of
roast with both heater and fan controlled IMO.
Just rambling roasting thoughts while sipping a Kona Mountain Peaberry
Americano!
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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2) From: John Abbott
Mike,
Have you made up a profile that includes fan speeds along with temperatures?
I'm hard at work trying to figure out how I can  build a digitally
controlled variac. I know its been done because we used them at Boeing
Aerospace all the time. I just never took the cover off to see how it was
done.  I'm waiting on some parts to arrive and then I think I'll have my 1/2
pound, fully programmable roaster ready to play - except now you have me
interested in the fan speeds.
John - Swilling CRLM like I haven't had anything to drink in a month!

3) From: Mike McGinness
From: "John Abbott" 
<Snip>
temperatures?
<Snip>
1/2
<Snip>
Right now fan speed adjustment is a visual thing with my roasting. The
Rosto's circular bean movement doesn't need (or benefit from IMO) fast bean
movement, just barely moving - maybe 15-30rpm - for extremely even roasts
from drying to finish. Much evenier roasts than my previous rocking
technique. One of the toughest beans for me to get even early in the roast
with my old rockin' technique was PRYS. Roasted a batch to City Friday,
perfectly even every stage of the roast. Even I was impressed:) I haven't
recorded different greens, batch weights, fan voltage requirements etc. What
would be needed for automation, IMO, would be a way to actively monitor the
bean movement and adjust voltage accordingly. A *typical* 1/3# roast Kona
batch might start with fan voltage about 125-130v and end down around 110v.
I just dump in the beans, turn on the fan while watching the beans, adjust
and when movement is right I then turn on the heat and start my timing. PRYS
took higher voltage for early bean movement than many other greens BTW, they
be large dense greens.
Motor controlled variable autotransformers (aka variacs) are commercially
available, for *ouch* prices...
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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4) From: John Abbott
I'm not too sure that the variable fan would add all that much to the drum
roast, but I do know that the HT has the fan on low until just before first
crack and then it picks up speed, goes into a high speed mode at the peak of
first crack until it dumps.  So some speed control is desirable.  I'll go
look at the "ouch" motor controlled variacs and see how large they are,
don't want to add volume to the roaster footprint.
John

5) From: AlChemist John
Sometime around 10:12 2/2/2003, Mike McGinness typed:
<Snip>
I have found that I think I also prefer not to vary my fan speed.  I have 
found the system dynamics nicely "self regulating".  I do not load by 
weight.  I load by bean movement.  What just barely moves the beans at the 
beginning of a roast is how much I use.  As the roast progresses, the beans 
lighten, move more but also allow more heat to escape.  This appears to 
bring me to 1st crack gently, but with sufficient thermal momentum.  At 1st 
cracks the beans noticeably lighten again (or actually increase their 
surface, thus lessen their density) and move even more, air flow increases 
and I usually coast gently into 2nd crack, rarely having to touch my heater 
control.  I think or would hope that a properly "balanced: roasting system 
would naturally self regulate in this fashion, without lots of 
sophisticated digital/electronic or even mental regulation.
I think I am just about at the point where I am fully happy with my fluid 
bed roaster, and do not have active plans to "fiddle and tweak" with it more.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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6) From: Ben Treichel
They are basically a variac with a stepper motor.
John Abbott wrote:
<Snip>
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7) From: John Abbott
Ah - that makes sense - a five volt pulse moves it a single step I guess.
That should be pretty easy to control then. Now my question is if it will
improve the drum roast quality to be able to alter the fan speed.  I'll do
some manual playing before I invest :O)
- john

8) From: Jim Schulman
Hi Mike,
You wrote:
<Snip>
I think you may be right. I'm just tasting a 
number of roasts I did with the fixed fan, 
including some with the same heat profile as when 
I used fan and heat on one Variac together. They 
taste quite different, better in some respects, 
worse in others. 
I can't figure out yet how to systematize the 
difference into a "roasting recipe" like for 
faster/slower = harder/mellower or lighter/darker 
= brighter/bitterer. But since air movement DOES 
make a difference for an otherwise identical 
profile, it is worth controlling and figuring out 
how to best use it to get the taste one wants.
Jim Schulman
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9) From: Tom Gramila
On Sun, 2 Feb 2003, John Abbott wrote:
<Snip>
<Snip>
	I have been considering getting my fan under computer control as 
well.  I have a WBI, and if I run the fan hard enough at the beginning of 
a roast to do my preferred batch size (180g) the beans will get blasted 
out the popper at the end -- if I dont ease off on the fan.  Backing off 
manually on my variac seems to make for irreproducability in my roasts, 
which I would like to avoid.  
	I have found a kit for a voltage controlled dimmer, which claims 
to handle 3.5 A, and which some have claimed to have modified to run 10A 
by changing the output stage.  Seems to have been around for a while, but 
I have not investigated hard enough yet to have determined its suitability 
for running an inductive load (ie. motors).  It's optoisolated. etc.http://www.velleman.be/Product.asp?lan=1&idô89	Seems to be way cheaper than a stepper controlled variac, and 
could be incorporated into the buck/boost transformer approach.	 I'm 
planning to try one out in the next couple of weeks....
Tom G.
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10) From: John Abbott
Tom - Good thought!  I just discovered that I can buy their kits in McAllen
(9 miles) from Rio Radio - and I'm in there about twice a month (ham).  I
might give that a try myself.

11) From: Rick Farris
John wrote:
<Snip>
I roasted up some CRLM and some La Berliner in the Alp Thursday and I'm much
more pleased with the La Berliner.  Have you tried any since you got the HT?
As to a digitally controlled variac, it's pretty simple.  Attach a stepping
motor to the variac shaft, figure out how many steps each direction to the
end, build a calibration table for voltage vs. number-of-steps, and you're
in.  If you're anal, worry about limit switches and such.
Personally, though, I'd get Mike McKona to scour his surplus stores for a
used prebuilt motorized variac.  Much neater.
-- Rick
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12) From: john kangas
<Snip>
I've been around the Portland surplus shops lately, and have only seen one 
old (no motor) variac. Just got back from Wacky Willy's, no variacs, one 
analog-dial tempurature controller for $50, (too much) and the pile of 
heating elements they had last week are completely gone! Piles of assorted 
motors, however, including a few dozen 25rpm gearheads that look like a 
rotisserie drum wouldn't bother them a bit.
DaLode has the variac, been there for months, if that tells you anything. A 
while back they did have a 110v to 50,000v transformer, there's a roasting 
method that hasn't come up yet!
Haven't been by R3D5 yet, maybe they'd have something. They're more of a ham 
and vacuum tube oriented shop, from what I've heard.
John Kangas
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13) From: Mike McGinness
From: "Jim Schulman" 
<Snip>
That's the hard part. And to make matters worse it'll vary from bean to
bean. And just when you finally dial in the perfect time/heat/fan profile
for a given bean it'll be out of stock! Just what was needed, another roast
variable:)
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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14) From: John Ross
on 2/2/03 5:40 PM, AlChemist John  wrote:
<Snip>
<Snip>
John:
I'm with you.
I find that using wooden spoons as first pop gets
rolling to agitate the beans slows the progress of
the roast-- probably by absorbing heat more than
by moving the beans. the timing of applying the
spoons (I use four) and still leaving enough time
to allow the thermometer to ramp up to the dump
and cool is the most complicated part of the
procedure.
Actually, I find I can add two minutes to a dark
full city--early in 2nd or right as second begins
(depending on the bean) is easy at less than 60
degrees ambient --an 8:30 becoming a 10 to 11+
minute roast and as soon as I can acquire more
spoons I may add more (I play a game with myself
when I go to thrift stores--the spoons have to
be dense hardwood, have little bowl to the spoon
and be less than 50 cents)
The simplicity and artfulness of this procedure
appeals to me, even as it means I roast early
in the morning or late in the evening during
the summer.
Course, I roast outdoors with poppers (and one
HWG with the lid off) the chaff blows harmlessly
out over my backyard flower beds most of the time.
John Ross
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15) From: John Wanninger
I've been using dual variac control on my West Bend Poppery I for about 6
weeks now, and the ability to provide separate airflow and temperature
control is nothing short of liberating, particularly when  trying to roast
in a 10degF garage. I use a 0-180V 20 amp motorized variac to run the
heating coils and to source a separate 0-140V, 10A variac for the fan(no
auto control-yet).  First of all, setting the fan variac down slightly helps
to warmup the roaster in cold temperatures.  I monitor temperature just
before inlet to chamber with a thermocouple/temp controller, which I also
use to cycle heat on/off for an initial conditioning while outlet/bean temp
is via Weber grill thermometer in chimmney/chaff collector. 
My most recent profile:
After 2 minutes of 250F conditioning, I then move temperature setpoint way
up out of the way (>470F), and use the variacs to set the inlet temperature.
I genenerally try to ramp from 330F to 410F in about 4-1/2 minutes at which
time 1st crack starts. As the beans are swelling in size, I decrease
airflow, which increases temperature. After 1st crack starts, I usually aim
for about 3 minutes more of roasting, and I aim for an ending inlet temp of
about 440F, although I end the roast based on smell, sound, sight, and
outlet temperature too.      
What I'm finally getting to: 
After first crack starts, it takes much less air to maintain the fluidized
bed. I'm quite concerned that excessive air movement past the beans might
unnecesarily erode oils and other volatile flavor components near the
surface of the bean, which may be the reason that a 15 minutes works out for
drum roasts and not for air roasts. So if one wants to prolong a roast for
flavor development/modification or to 'even it out', might it make sense to
use just enough airflow to provide good mixing?  
John
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16) From: Ed Needham
That makes a lot of sense, John.
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
****************************************
**********************************************

17) From: Mike McGinness
From: "Ed Needham" 
<Snip>
I almost agree but don't. Different beans start with a different weight both
because of different density and moisture content. What works *ideally* for
one bean may not be the *ideal* profile for another, may not even be ideal
for same bean different week of processing. (though admittedly usually very
very close) Why else would multi-thousand dollar roasters be designed to
regulate both heat & air flow, both drum and fluid bed designs... The hope
of natural self regulating coffee roasting might be like hoping a rib-eye
steak will cook itself miraculously to 135░f thrown on the same grill any
time of year for the same time period... at least somewhat similar. The only
truly *self regulating* roasters I know of use extensive feedback and are
computer controlled, not set the temp and air flow at the beginning of the
roast and let it go unchanged...
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
<Snip>
have
<Snip>
the
<Snip>
beans
<Snip>
1st
<Snip>
increases
<Snip>
heater
<Snip>
system
<Snip>
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18) From: AlChemist John
Sometime around 20:29 2/4/2003, Ed Needham typed:
<Snip>
I have found that it seems a lot of "natural" processes work well if you 
let them work and not try and over control them.  Often it is a matter of 
just finding why something is not behaving well, and nudge it gently into 
control instead of using a sledge hammer.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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19) From: AlChemist John
Sometime around 22:26 2/4/2003, Mike McGinness typed:
<Snip>
Augh!! I am crushed, Oh, that's what we do here :-)
<Snip>
True, although I did note that I do not load according to wight.  I load 
the system so that it is starting at the same process point each time, i.e.=
 
beans just moving.
<Snip>
Because they are using a lot of coffee.  I have no feel for loading a drum=
 
roaster to "just" the right point but I expect I could load a fluid roaster=
 
if it had the same dynamics as mine.
<Snip>
 
<Snip>
Ah, but I do "hope" that works IF the grill is fully up to temperature, 
stable (known system parameters) and the ribeye is always the same 
thickness (but not weight necessarily) and the same starting temp.  For a 
given time, I expect a given temp (and usually get it mind you)
<Snip>
In this case, the extensive feedback is my brain at the beginning during 
loading and progress checks (look, don't usually touch) through out the 
roast and of course end point.  My main point is that once started MY 
system for ME does not really need adjustment to roast.  It took getting it=
 
to that point though with hacking .
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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20) From: Ed Needham
I've posted before that I like to be able to control the air, but the
description John put forth made quite a bit of sense.  Even in light of his
observation, it would be a good thing to be able to tweak the air to further
refine the roast.
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
****************************************
**********************************************

21) From: David Westebbe
<Snip>
<Snip>
I had an experience which was the same, but opposite.  I opened up the air
vents on my WEPP in order to increase airflow and to roast larger batches.
It worked.
But I developed a problem, in that the airflow was too great at the end of
the roast, and the temp stalled prior to second crack.  The only way I could
get the airflow down, and consequently the temp to go up, was to manually
block the top of the roaster with some object (usually my heavy gloves).
Before I increased the airflow I had no problem getting the temp high
enough.  But with the increased flow, the stasis temperature was only around
350 or so.
I had to do something.  Maybe I could have experimented with more and more
beans, so that the airflow would be restricted sufficiently even at the end
of the roast.  But that would have required fussy stirring near the
beginning, which was too much of a PITA for me.
So I installed a transformer and dimmer to turn down the fan near the end of
the roast.  It works great now.  I can easily do 3/4 cup of dense
aerodynamic beans, like current-crop peaberries, and up to 1 1/4 cups of
puffy light beans, like monsooned malabar.  No initial stirring is needed,
and when the temp reaches stasis, I just turn down the fan slightly.
I find that this has an added benefit in that if I screw up and don't pay
attention, the beans won't go into thermal runaway because the temp is
insufficient to reach first crack.  I could conceivably leave them in for an
hour and they wouldn't get hotter than around 350.
I used to try to do the biggest loads that I could, but now I do convenient
sized loads which need no stirring at the beginning, and which allow me to
precisely profile.
So my hacking screwed me up at first, but now allows precise control.
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22) From: John Wanninger
I've been using dual variac control on my West Bend Poppery I for about 6
weeks now, and the ability to provide separate airflow and temperature
control is nothing short of liberating, particularly when  trying to roast
in a 10degF garage. I use a 0-180V 20 amp motorized variac to run the
heating coils and to source a separate 0-140V, 10A variac for the fan(no
auto control-yet).  First of all, setting the fan variac down slightly helps
to warmup the roaster in cold temperatures.  I monitor temperature just
before inlet to chamber with a thermocouple/temp controller, which I also
use to cycle heat on/off for an initial conditioning while outlet/bean temp
is via Weber grill thermometer in chimmney/chaff collector. 
My most recent profile:
After 2 minutes of 250F conditioning, I then move temperature setpoint way
up out of the way (>470F), and use the variacs to set the inlet temperature.
I genenerally try to ramp from 330F to 410F in about 4-1/2 minutes at which
time 1st crack starts. As the beans are swelling in size, I decrease
airflow, which increases temperature. After 1st crack starts, I usually aim
for about 3 minutes more of roasting, and I aim for an ending inlet temp of
about 440F, although I end the roast based on smell, sound, sight, and
outlet temperature too.      
What I'm finally getting to: 
After first crack starts, it takes much less air to maintain the fluidized
bed. I'm quite concerned that excessive air movement past the beans might
unnecesarily erode oils and other volatile flavor components near the
surface of the bean, which may be the reason that a 15 minutes works out for
drum roasts and not for air roasts. So if one wants to prolong a roast for
flavor development/modification or to 'even it out', might it make sense to
use just enough airflow to provide good mixing?  
John   
(I apologize if this comes as a repost - Re-Sent Wed 02/05/2003 4:22 PM CST,
originally Sent Tues 02/04/2003 5:14CST, AFAIK original post never came
thru)
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23) From: AlChemist John
Sometime around 09:23 2/5/2003, David Westebbe typed:
<Snip>
Snip
<Snip>
This got me thinking that you are actually in the same position I was in, 
but took a different route to a solution.  In general, the reason we all 
hack our various roasters is that they do not perform as we desire them to, 
be it because they are meant to only pop popcorn or simply because we want 
to roast more than the roaster was designed for.
We often try to find the "sweet spot" for a particular bean.  In hacking, 
we are conscience or unconsciously trying to find a  roasters sweet 
spot.  Immediate hacks to a popcorn popper basically "shows" it does come 
with a  coffee roasting sweet spot.  They usually have to much heater 
output, causing fast roasts and/or do small of a batch size.  What do we 
do?  Add a variac or switch to control the heat or something else 
(transformer, different fan blades etc) to boost the air flow to help 
"balance" the system.
I think that balance is a particular set of ratios of bean mass, air flow, 
heater output and roast time.  Some "roasters" don't have overlapping 
condition sets, so no "sweet spot" exists until we move the conditions sets 
around.  Sometimes our own decisions move the sets (i.e., ok, I want to 
roast more beans, or want a  longer profile).  For me, it is about finding 
that balance (Zen roasting?).
David, in your case, instead of installing the transformer and dimmer I 
would have tried either adding sightly more beans to naturally block the 
air flow or blocked the inlet air a little.  By not reaching 2nd crack, 
your heater output/airflow ratio sets are moving apart.  To each his own.
I like having a system in balance that needs little attention.  I can see 
the convenience of a fan controller, just like not having to use one.
--
John Nanci 
AlChemist at large
"Zen" Roasting and Blending by Gestalt
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24) From: David Westebbe
<Snip>
Yep.  My initial goal was to increase batch size.  I did it simply by
enlarging the air holes at the bottom of the chamber.  But that had
unforeseen consequences.
<Snip>
Interesting concepts.
<Snip>
I liked the idea of hardware hacking.  Not only that, but my roaster is more
versatile now.  I can do different sized loads, different beans, and
different profiles.  I could,  for example, load it with a tiny load, turn
down the fan considerably, and get them cracking in almost no time.
Alternatively, I can do a big load, and stretch it out to reach second crack
in 25 minutes.  Or anything in between.
<Snip>
Personally, I like twiddling dials and flipping switches.  :)
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25) From: AlChemist John
Sometime around 10:35 2/6/2003, David Westebbe typed:
<Snip>
Which roaster did you hack?  What were the unforeseen consequences.  I have 
thought of increasing (actually adding) holes to my WBI to increase air 
flow to its maximum.
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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26) From: David Westebbe
<Snip>
I hacked a Wearever Popcorn Pumper, 1250 watt model, no switch.
The unforeseen consequence was that the airflow was too fast (once the beans
lost moisture) to get it hot enough temp to crack the beans.
So I could do a bigger batch, but if I were to do a batch big enough to slow
the air at the end, I would have to stir at the beginning.  The unencumbered
full-flow temperature was only around 350 or so.
I increased the airflow by enlarging the existing holes in the aluminum bean
cup.  It worked great to increase the airflow.
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27) From: Jim Schulman
On 4 Feb 2003 at 17:14, John Wanninger wrote:
<Snip>
Afaik, drum roasters take long to get to 350F, 
after that they're about as fast as airroasters. 
You can check the webpages with roasting profiles 
to see.
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28) From: floyd burton

29) From: Jim Schulman
On 7 Feb 2003 at 15:02, floyd burton wrote:
<Snip>
Oops, I wasn't clear. I meant the bean 
temperature. Never met a commercial roaster who 
didn't preheat their drums (out of business, I 
guess)
Jim
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30) From: Oaxaca Charlie
<Snip>
Floyd, I've been wondering...do you leave your drum out in the
cold weather? Seems like if you started heating it at household
temp it shouldn't take so darn long to warm up in that monster
grill.
Charlie
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31) From: floyd burton

32) From: Ed Needham
Way back when, when I was using the Melitta AromaRoast coffee roaster, that
is exactly what I would do.  it had an air control that would let you
increase or decrease the air flow on the fly.  I would put the beans in and
as they became lighter and lighter throughout the roast, I would slow the
airflow more and more.  In the Aromaroast, that worked really well, because
it allowed higher air temps.  The AromaRoast was underpowered in both the
heat and the air flow departments, so any way to increase either was welcome.
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
****************************************
**********************************************

33) From: Mike McGinness
From: "John Wanninger" 
 What I'm finally getting to:
<Snip>
for
<Snip>
to
<Snip>
Works for me too!
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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