HomeRoast Digest

Topic: perforated drums (36 msgs / 1080 lines)
1) From: dewardh
The "perforations" allow more circulation of the hot air that actually roasts the beans in and out 
of the drum.
There is a pervasive misconception that it's the drum in a (modern) drum roaster which does the 
heating of the beans, but it's not.  At any given time only a tiny surface area of a small portion 
of the beans is in actual contact with the drum, the overwhelming majority of the bean surface is 
in contact with . . . hot air.  With a solid drum that hot air is either blown through from end to 
end, as in most commercial "drum" roasters, or the air is heated by the necessarily even hotter 
portion of the drum not covered by beans, and in the latter case the overheated drum often burns 
("tips") the part of the bean that does touch it.  With a perforated drum heat (hot air) is applied 
to the roast chamber around the drum, and that hot air both heats the drum and circulates through 
the perforations to heat the beans.  With a (relatively) large heating element (external to the 
drum) there is also the possibility of some radiant heat reaching the beans through the 
perforations, but the effect is (relatively) small.
Put more directly, the "drum" in a drum roaster is not the heating mechanism, it's the stirring 
mechanism.  The less it interferes with the flow of the hot air that does the actual roasting the 
better.  So unless there is end to end (fan driven) airflow in the drum one adds perforations to 
let hot air from the roast chamber into the drum to roast the beans.
You'll find a more thorough discussion of heat transfer during roasting in "Espresso Coffee: The 
Chemistry of Quality", Illy and Viani, pages 92-95 inclusive, and at the Sivetz web site (anyone 
roasting, or especially contemplating building a roaster, should read:http://www.sivetzcoffee.com/newsletter/roasttempDec00.htmat the very least).
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2) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: +perforated drums
Date: Sun, 31 Mar 2002 07:58:33 -0800
Did he mean why don't we use a net (mesh) made with stainless steel wir=
I've been looking for one, but so far aluminum is easy to find but not
stainless steel... (unless I buy something that uses it and break it
to take the part - way too expensive)
The contribution to the roast is determined by the coefficient of heat
transfer and the temperature difference. Even if I ignore the likely
condition that air is cooler than the surface, and assume their temps
be identical, solid-solid conduction has much higher coefficient of
heat transfer. In reality, the surface temp can be higher and there is
a rush of heat at the small area of contact, which can be a
significant part of the roast, as well as it can ruin the roast.
Indeed, radiation from the surface that is not in direct contact with
bean can be a significant part of the roast. The coefficient for
radiation is about a half of forced air flow and double of natural
convection, maybe triple of uncirculated air. People who roast with
direct flamemight get even higher contribution from radiant mode.
If you want to make better use of your energy, you should put another
fan by the heating element to increase the heat transfer from your
heater to the air. Also, regular fans in the similar shape to the
cooling fans become very inefficient (low air flow) as the pressure at
both sides deviate from being equal. So pay attention to the location
of propellers or use turbin-like fans (as in Sunpentown Turbo Oven).
(Incidentally, this is why the computer chassis should have relatively
large openings or even intake fans in order to help the operation of
the exhaust fans - you don't want the internal pressure to be much
lower than outside. Turbin-like fans would be a much better choice but
unfortunately there aren't many used for this purpose.)
So one question is what makes difference between fluid bed and other
roasting techniques? I think the rate of replacing the air with clean
air - if you blow fresh air all the time as in popcorn popper, I think
the coffee becomes too clean -- cups lacking complexity, especially if
roast is dark. If I keep the smoke in the chamber at all time, my cup
tend to have too much bite anything after full city. I don't have
money to try it, but Caffé Rosto can be a good roaster with this
BTW - I have tasted my first batch of Guatemala La Laguna. Compared to
last Fraijanes they offered (I think it was La Montana) or
stereotypical Antigua, this has less interesting flavor, but it is
very soft mild coffee with sweetness. It's almost no chocolate that
Fraijanes had, as well as some "berry minus fruitiness" note.  The
finish is surprisingly good for such a mild clean coffee.  Probably
because I rested for a day, I didn't get any salty flavor Tom's review
mentioned. It's kinda like how I want good Mexicans to be.
BTW again - I'm concerned about el Niño that is appearing this
year... It can be interesting if Sweet Maria's offers totally
different kinds of coffee from this year :-) (that is, those appearing
next year)
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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3) From: dewardh
transfer and the temperature difference.
And, most important in this case, the surface area exposed.  In the case of a batch of beans 
tumbling in a drum more than 99% of the surface is exposed to air, not to the drum, so the air 
contribution swamps the drum contribution, even if direct conduction is more "efficient".  This 
effect is compounded by the low thermal conductivity of the bean itself, which concentrates the 
conductive heat at the (small) point of contact and contributes to the "tipping" (burning) effect.
roasting techniques? I think the rate of replacing the air with clean
That may well have some effect, but nothing prevents recirculating the roast air (and smoke) in a 
fluid bed machine (although most home roasters are not designed for high inlet air temperatures). 
 The Caffe Rosto does in fact recirculate some of the hot air internally.  But trapping all the 
smoke just coats the beans with burnt oils (including rancid "seasoning" oils from the surface of 
the drum or roast chamber) . . . it gives them, as you say, "too much bite".  You might as well 
spray them with "liquid smoke" from your barbecue kit . . .
The big difference, I think, is roast duration.  In order to avoid burning the beans drum roasters 
with limited air circulation are run relatively cool, producing a long roast time, and an even 
roast.  Hot air machines, whether they be fluid bed or drum agitated, permit much faster (very 
even) roasts, and that can effect roast "character".  Nothing but economics, however, prevents 
longer roast times in an air roaster (and control of the "roast profile" is easier).  If you 
programmed a hot air machine to match the roast duration and profile of an old fashioned drum 
roaster you'd be hard put to tell a difference between the products.  Comparing modern high airflow 
drum agitated and fluid bed hot air machines taken to the same end temperature in the same time I 
doubt that you'd find any difference at all.
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4) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: RE: +perforated drums
Date: Sun, 31 Mar 2002 10:42:48 -0800
I don't think so. Not much of the smoke is adsorbed by the bean unless
you are roasting extreme amount of bean in a small roaster or
something one wouldn't normally do.
THis is very different from my result.
It is possible to prolong the roasting time with hot air blow in my
popcorn popper by decreasing the rate of temperature increase during
the roast. I did this by increased continual airflow and intermittent
operation of the heater.  The coffee smells great during the roast,
yet the cup is dull! I finally put them back to more typical profile
to roast in 6 to 8 minutes. (But I don't use it any more)
When I roast with radiation and natural convection of the hot air, I
can roast for 15 min to make full city- and it has developed great
flavor as well as better aroma than seeds cooked in popcorn popper for
the same duration for the same roast.
One reason I like about Sunpentown Turbo Oven is that it makes good
circular airflow inside the chamber and the air is mostly enclosed
inside the chamber but a small portion is ejected unless I block the
exhaust hole. I usually block this thing until first crack becomes
rapid. Yet I can control the roast profile rather easily by turning
the thermostat while watching the timer, bean color and the air temp
inside the chamber. I can roast 10 min to get light full city- out of
central americans like Nicaragua, and I prefer it to the same roast
came out of popcorn popper in 6 minutes.
After all, I would use a mesh or a perforated sheet to make roaster
drum too. I have been thinking about rotating drum combined with this
Turbo Oven unit might make a very good roaster for about a pound batch
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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5) From: Simpson
On 3-25-02, Steve Ackman posted this in alt.coffee, when we were discussing
roast volatiles in drum vs air roasting and the question was whether or not
the drum trapped these constituents and if this is what made for the
different roast tastes:
"  I don't know if this is a factor.  The Diedrich 12k, for
instance, has a 320 cfm blower (IIRC).  If the drum is ~2.5 
cubic feet, and the damper directs 70% of the air flow 
through it, then you have some 90 air changes per minute, 
or a complete air change in the drum about every 670 msec.
 Are the volatiles hanging around significantly longer than
with an air roaster? "
As to perforated drums in small batch roasters, I'm still not sure I see
it... I was under the impression that the small cupping roasters had solid
drums, and doesn't the 1lb san Franciscan have a solid drum? Hmm, just
checked Jim P's refurb pics of a 1 lb sf, and it IS perfed in the back of
the drum:http://makeashorterlink.com/?T26512C9Does it have active air circulation or is the perforation there to allow
passively circulating hot air to make its way into the drum? I ask because
I would like to make a small drum roaster and would love to avoid the whole
fan thing if at all possible.
Oh, another data point. What about the BBQ rotisserie 'drums'. They are
perfed (actually they are often heavy screen) butt there is no fan forced
airflow. Is it needed?
*********** REPLY SEPARATOR  ***********
On 3/31/2002 at 12:42 PM Ryuji Suzuki -- JF7WEX wrote:
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6) From: dewardh
Perhaps I'm not following what you're saying very well . . . in your last post you said "If I keep 
the smoke in the chamber at all time, my cup tend to have too much bite".  In the very next post 
you say "Not much of the smoke is adsorbed by the bean".  How then is the smoke "flavor" 
influencing the coffee flavor?
popcorn popper by decreasing the rate of temperature increase during
the roast. I did this by increased continual airflow and intermittent
operation of the heater.
It does not surprise me that jolting the beans with alternating blasts of hot and cool air would 
not have the same effect as a steady roast in moderately hot air (and I think it a weakness of the 
HWP that it pulses the air temperature by pulsing air flow, btw).
Turbo Oven unit might make a very good roaster
It might.  It does clearly relegate the drum to its only useful function . . . stirring the beans.
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7) From: Ryuji Suzuki -- JF7WEX
From: Simpson 
Subject: Re: +perforated drums
Date: Sun, 31 Mar 2002 14:48:31 -0500
As I said in my previous posts, even if there is no forced air flow
there, the drum may radiate heat and bean may be roasted because of
this heat. If you do this, the drum must be quite a bit hotter than
your roast temperature, and you need to pay a bit attention so that
the conduction heat does not ruin the roast.
If you can drill two holes on the side of the glass bowl and put a
small drum inside, you can make a small drum roaster inside Sunpentown
Turbo Oven. If you don't mind rotating handle for several minutes, it
could be done well under $100. THis is what I'm thinking about now.
Someone posted that idea here before. They suggested the heater isn't
strong enough. I suggested to take the heater+fan assembly from
Sunpentown and put it on the rotisserie unit. No one responded to that
idea so far.
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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8) From: Ryuji Suzuki -- JF7WEX
From: dewardh 
Subject: RE: +perforated drums
Date: Sun, 31 Mar 2002 12:15:58 -0800
It may inhibit further release of volatile substance from the coffee
bean. You know how SWP decaf process is supposed to work? The same
idea, but just in gas instead of aqueous solution.
In Turbo Oven where air temp is pretty close to the bean temp and
chaff burning is very rare, I don't get as much smoke as from other
methods... though this can be just an inaccuracy of visual observation.
If you do this quickly the effect is probably insignificant because
the heater assembly has some heat capacity. But I would rather avoid
doing this, of course. In Turbo Oven, thermostat on-off while the air
is still running, but the air is mostly enclosed so the temperature is
rather stable.
Indeed, I'm rocking the unit a few times every one minute, and that's
pretty much all I need for agitation. The agitation doesn't even have
to be continual if the tray/drum temperature is comparable to the air
temperature. But many drum roasters have drum temp higher than
air/bean temp so they have to keep rotating. This even makes me think
I don't need a motor to rotate drum if combined with this heater
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
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9) From: Angelo
I was thinking that you might try to find a Stir Crazy popcorn popper in a 
thrift shop(not sure if they are still produced) and use the bottom half in 
your Turbo roaster. I'm not sure of the dimensions but, if it fits, you 
could remove the heating element and just use the stirrers and the plate. 
You might even just take out the stirring motor and attach it to a plate 
that does fit. The agitation would be sufficient and the plate would get 
heated from the blowing heat....just a thought. If you let me know the 
interior diameter of the Turbo, I can measure the diameter of the Stir 
Crazy(I have one, of course.. :-))  and let you know if it would fit...
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10) From: Ed Needham
There is another heat type that you didn't factor into the equation, and
that is radiant heat from the drum itself, without actually making contact
with the drum.  Without having detailed temperature measurements on which to
base my assertion, I have no idea what percentage of heat comes from
airflow, drum contact or radiant heat from the drum mass itself, but my
guess is that radiant heat is a significant factor in the roasting process.
The roaster I am building is a fluid bed roaster, using a high BTU gas flame
and a squirrel cage blower. The heat it puts out is significant, and I am
currently building the roast chamber, thus, my question about perforation
Ed Needham

11) From: Ed Needham
Two comments...
In spite of the HWP's cycling air flow (and heater coil BTW), the heat curve
is surprisingly consistent.  Refer to these actual plots:http://www.anywhy.com/graphs.htmlThe plot looks like it wiggles a bit on the roast portion, but it also
wiggles the same amount on the cool cycle where the fan and the heat does
not cycle at all.
The other thing is that the drum is also useful as a radiant heat source and
thermal mass heat sink to aid in retaining heat and transferring it to the
beans through direct contact and radiation.
Ed Needham

12) From: Ryuji Suzuki -- JF7WEX
Good idea! The diameter of the top element is a small fraction of an
inch larger than 12" but because the stir crazy doesn't look like it
has a lot of air volume, Turbo Oven might be a little overpowered.
Did you say you can roast a full pound in stir crazy? At least if the
unit can stir one pound in a uniformly random way, then it should be
really an easy job for this combo.
Ryuji Suzuki
"I can't believe I'm here.
People always say that I'm a long way from normal."
(Bob Dylan, Normal, Illinois, 13 February 1999)
From: Angelo 
Subject: Re: +perforated drums
Date: Sun, 31 Mar 2002 17:54:34 -0500
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13) From: dewardh
that is radiant heat from the drum itself
There is radiant heat transfer in any roaster . . . from the walls of a fluid bed machine 
(themselves heated by the air), for example, and from bean to bean.  The amount of transfer depends 
on the emissivity of the radiating surface (the reason a Thermos bottle is Silvered) and its 
temperature . . . at the temperatures involved in a roaster the contribution, though perhaps not 
negligible, is small compared to convection and conduction.  At higher temperatures (as where the 
heat source begins to visibly glow) radiant transfer becomes quite significant.  But a radiant 
source still heats only the surface on which it shines (your back remains cold while facing the 
campfire),  where hot air, especially in a "fluidized" machine, can reach all the surface of all 
the beans all the time.
and a squirrel cage blower. The heat it puts out is significant
You'll need to carefully balance heat output, bean mass, and air temperature.  If the air 
temperature is too high the beans will roast too fast, too low and the roast stalls.  If you are 
providing more heat (BTUs) than needed to heat the quantity of beans being roasted the excess heat 
just goes up the chimney wasted, too little and the roast takes too long.  Gas is relatively easy 
to control in a linear fashion, although the motorized valves needed are not inexpensive if you 
want to automate temperature control, but be prepared for problems lighting and keeping the flame 
lit in a high velocity air stream, and providing automatic shutoff in the case of blowout or fan 
failure/blockage.  If you have access to one you might want to look at  the igniter, burner and 
safety features in a Polaris (forced draft) water heater.  The whole Polaris burner assembly, 
including its (squirrel cage) draft fan, might be directly convertible to a (large) roaster.
You might want simply to measure the smallest dimension of the smallest bean you might roast and 
use perforations 1/2 to 1/3 of that.  Note that with the Alpenrost, for example, the problem is not 
so much with the beans falling through the perforations (they'd just end up harmlessly wasted in 
the chaff tray) but with them getting stuck in the perforations and burning (radiant heat from the 
wrap around heating element? ).  The perforations need to be enough smaller than the bean to 
avoid that.
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14) From: dewardh
I have not noted any cycling of the HWP heater . . . next time I use mine I'll put an Amprobe on it 
and see if I see any . . . (I'll get back to you on that )
It would certainly be a lot nicer if there was some indication of what was being measured, and 
where . . . (thermal lag in the probe, sample frequency etc.)
Addressed in previous post . . .
Depends on the drum, of course, but the sheet metal drum of the Alpenrost, for example, is light 
compared to either the bean mass or the body of the roaster, so its contribution to heat retention 
would be trivial.  And high heat retention in the drum would be a disadvantage if one intends to 
cool the beans in the roast chamber . . .
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15) From: Todd Smith
The Alpenrost has 3/16" holes in the drum.

16) From: Ed Needham
You brought up a number of problems already addressed in my design.  The gas
will be controlled manually, based on temperature at the roast chamber.  The
blower is controlled with a variac unit and also with a damper above the
bean roast chamber.  The flame is actually out of the air flow and inside a
thick, (and expensive) 6" diameter x 14", vertically positioned stainless
steel cylinder.  The heat doesn't meet the rapidly moving air until it is at
the top of the heat chamber.  The air also absorbs radiant heat from the
sides of the SS heat cylinder as it circulates around it and upwards toward
the roast chamber.  The Igniter and thermocouple safety shutoff are already
in place.  The initial design is pretty much all manual, as far as the roast
temps and air, but after the shakedown I plan on outfitting it with a triple
input PID unit to monitor air into the roast chamber, roast chamber
temperature and a safety temperature sensor (to detect overly high
temperatures--fire) above the roast chamber.
Finding time to work on it has been a problem lately, but little by little
it's coming together.
Ed Needham

17) From: Ed Needham
These graphs used to be on a web site where all the measurement specs were
described.  He also had pictures of his measuring setup.  If I recall
correctly, he had a FLUKE datalogger and a probe inserted into the heat
chamber at bean level.  I have not measured amperage draw to determine if
the heater cycles, but I can see the lights dim a bit and hear the fan slow
slightly as it cycles.  All three of the units I've had do this, so I think
it's safe to say the heater cycles, as does the fan speed.
Ed Needham

18) From: Ed Needham
Thanks Todd.  I may make the holes just a tiny bit smaller than the Alp to
keep it from grabbing those smaller beans. The hole to solid space ratio is
more important to me than hole size alone.
Ed Needham
---- Original Message -----
From: "Todd Smith" 
Sent: Monday, April 01, 2002 3:46 PM
Subject: Re: +perforated drums
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19) From: dewardh
sides of the SS heat cylinder as it circulates around it
You'd best add some turbulence enhancers to the airstream . . . air does not absorb radiant heat 
(it is almost completely transparent to IR) so it will only be heated by direct contact with the 
heat exchanger wall.
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20) From: John - wandering Texas
Ummm - wouldn't that make a panel heater inoperable?  One can SEE the
effects of radiant heat on the surface of a road.  So now I'm a bit confused
(not something new).
John - glad to be home!

21) From: dewardh
effects of radiant heat on the surface of a road.
No, and uh, yes .  "Radiant" heat warms an absorbing *surface*.  It does not warm the air 
*between* the radiant source and the absorbing surface.  What you "SEE" on a road "surface" (apart 
from melting asphalt ) is the air immediately above the road being heated by the road surface, 
not by the "radiant heat" itself.  The turbulance and "shimmering" you see above the heated road is 
caused by the density gradient (and motion) of hot air rising from the hot surface into the cooler 
(unheated) air above.  If air were "radiantly heated" it would be the first thing to warm up when 
the Sun rises on a cold day . . . it's not, of course.
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22) From: Henry C. Davis
You usually have to have a rather high level of dust, moisture or other
debris in the air to absorb much radiant heat, and even then, the air isn't
getting heated, the stuff mixed in in is. Check the difference between a
clear winter night temp change vs one with low clouds/fog/heavy snow after
the earth turns from the sun for a good comparison of the other end of the
process where radiant heat stored by the earth during the day is trying to
leave. One of the misperceptions humans have about this is how hot THEY get
out in the sun when exposed to radiant heat from the sun and reflected
energy from light bouncing objects (dirt, rocks, pavement, boat decks,

23) From: Ed Needham
The heat absorbed as it circulates around the stainless steel cylinder will
be very minimal, with the bulk of the heat coming out the top, just above
the top of the flame.  This is by design.  Whatever is absorbed from the
sides of the heat cylinder is just a plus.  The roast is shielded from the
direct flame by a 1/4" steel plate, but the direct heat mixes with the
circulating air at that point and creates quite an effective forced air heat
source.  I will try to get a few pictures up on a web page.  It will be more
easily understood in pictures.
Ed Needham

24) From: Ed Needham
As is said in a previous post, I am not trying to get much heat transfer
from the heat cylinder, but it will radiate heat, as it will have a
170,000BTU flame inside it and as the air circulates around it, the air will
absorb much of the heat.  I know this for a fact, since the outside wall of
the heat chamber is cool to the touch, whereas the heat cylinder is red hot.
There is an approximate space of 4" between the two where the 365CFM blower
circulates air around it and up through the top into the roast chamber.
Remember, the bulk of the roasting heat though is from the 'top' of the heat
cylinder where the flame is directly below.  This heat blends with the
circulating air to provide quite hot forced roasting air.  I'll post some
pictures to make it easier to visualize.   I was not going to post them
until it was completed, but hey, plans change .
Ed Needham

25) From: Steven Dover

26) From: dewardh
That's really Ed's question to answer, but . . . Illy and Viani, in "Espresso Coffee: the Chemistry 
of Quality", estimate that roasting coffee requires between 1000 and 1500 kJ/kg  (430-645 Btu/lb). 
 Assuming no heat recovery from the waste air and overall efficiency in the low tens percent, and a 
target roast time of around ten minutes, a 170,000 Btu/hr burner would be sufficient for around a 
10-15 lb batch size.  With a carefully engineered heat recovery system and modestly longer roast 
time it might do for up to 50-60 lbs.  A bit big for the average home roaster, but not unreasonable 
for a small commercial shop.  I'd guess, though, that Ed's intending no heat recovery (and no 
particular concern about thermal efficiency, which would be unimportant for occasional use) and to 
run the burner at substantially less than maximum output for a batch size of a few pounds.  That 
would make it a pretty reasonable garage size project . . .
All estimates with a *large* margin of error, of course . . .
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27) From: Ed Needham
I'm hoping it will do a max of 2 pounds at a time.  The heat can be
controlled to get the optimum roast temperature / air CFM ratio.  Had a
significant breakthrough today and found a deal on the perforated stainless
for the bottom of the roast chamber.  In the process, I was able to grab a
bunch of sheet stainless from a scrap bin at this stainless manufacturing
shop.  Wooo Hoooo!
Ed Needham

28) From: Ed Needham
The burner is a simple propane burner from a 'turkey roaster'.  It is quite
spectacular at full blast, shooting flame to the top of a 14" heat cylinder.
With the garage door open, blower on and burner on full, it worked really
well as a garage heater .  My guess is that I will only use the burner at
a low setting, but with the 365 or so CFM blower, it may take more heat than
I think to bring that volume of air to roast temperature.  No recirculation
is designed into this roaster.  Efficiency is not a hallmark of most fluid
bed roasters.  I think the Ambex has a well designed recirc system, and I
can't think of a Sivetz that I've seen that recirculates heated air.  Maybe
that can be a 'phase 2' project.
Ed Needham

29) From: Tom & Maria
I was trying to hunt down the thread where someone (Jim G.?) was 
talking about a source for pre-perforated steel for making the metal 
drum for a  BBQ roaster. Any recollections of what that source was?
T.I.A. -Tom
                   "Great coffee comes from tiny roasters"
            Sweet Maria's Home Coffee Roasting  -  Tom & Maria
		1455 64th Street Emeryville CA 94608
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30) From: jim gundlach
The material I used was perforated brass and I got it at McMaster-Carr   
They have several kinds of perforated sheets at a wide range of prices.  
  Their URL is:
        http://www.mcmaster.comThey seem to have done some recent changes in Java because I can't get  
their pages to work.
    Jim Gundlach
On Monday, February 3, 2003, at 08:46 PM, Tom & Maria wrote:
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31) From: John Abbott
Jim, They seem to work just fine in Linux :O)  
Here's the page with the actual perforated materialshttp://www.mchttp://www.mchttp://www.mcmaster.com/asp/loadpagerange.asp?begin401&end402&qi=master.com/asp/loadpagerange.asp?begin401&end402&qi=http://www.mcmaster.com/asp/loadpagerange.asp?begin401&end402&qi=master.com/asp/loadpagerange.asp?begin401&end402&qi=On Mon, 2003-02-03 at 21:28, jim gundlach wrote:">http://www.mchttp://www.mcmaster.com/asp/loadpagerange.asp?begin401&end402&qi=master.com/asp/loadpagerange.asp?begin401&end402&qi=http://www.mcmaster.com/asp/loadpagerange.asp?begin401&end402&qi=master.com/asp/loadpagerange.asp?begin401&end402&qi=">http://www.mchttp://www.mchttp://www.mcmaster.com/asp/loadpagerange.asp?begin401&end402&qi=master.com/asp/loadpagerange.asp?begin401&end402&qi=http://www.mcmaster.com/asp/loadpagerange.asp?begin401&end402&qi=master.com/asp/loadpagerange.asp?begin401&end402&qi=On Mon, 2003-02-03 at 21:28, jim gundlach wrote:
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32) From: floyd burton
Tom I believe it was me-the first drum I made was constructed of 18 gauge
cold rolled steel.  Really cheap-a 23" x 34" rolled sheet and a 12" x 34"
rolled sheet and 2 ea 14" x 14" flat pieces with the larger pieces rolled
into a drum shape cost $45. What I would recommend is 16 gauge cold rolled
steel with pre drilled or perforated with 1/8" holes.  Hot rolled would work
but it tends to be kinda nasty and ugly while cr has a cleaner finish. Oh
after fabricating-you need to scrub them with hot water and detergent-got
all kinds of nasty oil to protect the steel sheet-after scrubbing and
rinsing-stick it in the oven at 350 till all the water evaporates.
The 16 gauge cr perforated steel sheet is a common stock item with metal fab
houses.  Am going to build another drum from the 16 gauge cr perforated
steel.  Let me know if u have a hard time finding the stuff-I know the area
around you and there are metal fab houses everywhere screaming for business.
If however you can't find someone willing to convert the stuff-let me know.
The supplier I use has a roll that will let you make a 10" diameter drum
fairly easily.  I just used a nylon hold down strap to pull the already bent
steel sheet into the drum size I wanted and then clamped it with a couple of
metal clamps-modified vise grips and then started drilling and screwing it
together.  U could use rivets but I like using nuts/bolts cause you can take
it apart very quickly.
Only roasted two different batches with my drum-works very well - only
problem was getting the drum warm in 15F weather-guess you don't have that
temp in the city by the bay. If u want a motor source or anything else, let
me know.
Oh I ordered Ukers book and a couple of 2# lots of beans for samples.  My
drum is 10" x 23" so I tend to roast in 1# increments-tested it cold with
10# of beans and it appears it would work.

33) From: Dan Bollinger
Tom,  Jim and I both mentioned McMaster-Carr as sources in earlier posts:http://www.mcmaster.com/ the are a good, but expensive, source for small
pieces. For entire sheets -- and even cut sheets -- or for large quantity go
to "The Hole Story", McNichols sheet metal supply.  They are now online and
have a shopping cart, too.
Here is an example of one of the dozens of sizes they make:  Gauge may be a
little light:
3/16" round hole
1/4" hole center
20 gauge
36" X 96" SHEET
50.0% opening
0.75 pounds per square foot
You submit a quote online for the price.  If you need help, let me know, Dan

34) From: floyd burton
One additional consideration maybe the amount of time/effort it takes to
turn a flat sheet into a drum.  Maybe easy but it could be a wildcat also.
My drum is 18 gauge-sucker takes time to heat up in really cold ambient
temps-that is a definate disadvantage.  The pro drums seem to be fairly
heavy-the Hothow has a cast drum.  Ed and others have been very successful
with very light gauge SS drums and some are using wire mesh material for
their drums and getting good results.  Maybe there are lots of ways to skin
a wildcat.

35) From: Tom & Maria
Thanks folks. I have a feeling McMasters is the main source. I was 
looking at their web site last night after I posted to the list. ... 
lots of options! And there is a warehouse/store 20 minutes south of 
us in Hayward. I also had a printed catalog of perforated steel that 
I was trying to find. For all I know, it was all McMaster. I actually 
wanted to get some to keep flat (for our green cleaning equipment) 
and some to play with for a drum. I agree that rolling a thicker 
gauge into a drum without the right equipment might end up a bit 
lopsided! I actually have thought of drilling a non-perforated drum I 
have. Of all things, its from a butterer, a food service device to 
butter toast etc. Its amazing what you can find at a good used 
restaurant equipment store...
                   "Great coffee comes from tiny roasters"
            Sweet Maria's Home Coffee Roasting  -  Tom & Maria
		1455 64th Street Emeryville CA 94608
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36) From: jim gundlach
I dropped them a line.  They said they were having some problems and  
that they are fixed now.
      Jim Gundlach
On Monday, February 3, 2003, at 09:49 PM, John Abbott wrote:
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