Comments on: Field Trip Notes – Cortez Coffee

By: Joe Johnston

Joe Johnston — Thu, 25 Feb 2010 22:57:01 +0000

Thanks for the comments, Steve. He did show us the Behmor and did say that it was his favorite. My only issue was that it does not seem to be scalable into a commercial size.
I agree about airflow being critical, as well as uniform roasting. Ability to control convective heat transfer by both airflow and burner inputs will be important in the design. The whole tipping and charring defect is related to one of the two general types of conduction: metal-to-bean. Bean-to-bean is important, too, but will not create the defect you spoke of. An over heated drum (upon load) and catch points on stirring vanes, faceplates, etc. all contribute to tipping/charring.

By: Steve Belt

Steve Belt — Thu, 25 Feb 2010 01:31:41 +0000

Joe, you didn’t mention Ron’s Behmor roaster. I’m sure Ron must have told you it’s his favorite roaster of all of the roasters he owns.

Anyway, I thought I’d throw a design nugget for you to comment on: Airflow is an important element in the roaster design, and I’ve noticed you’ve brought it up to some degree or another several times. And maybe this is why you focus on air, but for me, agitation of the beans during the roast is a critical and fundamental design element (thus the drum design’s prevalence).

I suppose they go together, but I’ll explain what I mean: Roasting of coffee requires heat be applied to a mass of small individual beans in such a way that each of the small beans within the large mass is evenly roasted. Airflow is certainly a component of that, but I think the motion of the beans during the roast is also a critical component. That is, unless no motion is required, because the beans aren’t in a mass and somehow aren’t touching anything, there needs to be a way to ensure that every bean within the mass receives a roughly equal amount of heat over the roasting time period.

When I think of the drum design itself, and how some beans will have burnt edges, or some beans may get caught in the drum and under or over roast, I think about the failure of the drum design to produce even roasting. I’m curious about your thoughts on that.

By: Joe Johnston

Joe Johnston — Tue, 23 Feb 2010 16:39:58 +0000

Thanks, Mitch, for your comment. I enjoyed the link to Mazda. When you have a blank sheet of paper, you might as well try many possible solutions. You may end up with the conventional solution, but at least you’ll know why.

By: Mitch Eiler

Mitch Eiler — Tue, 23 Feb 2010 05:06:24 +0000

Hey Joe,

Im a friend and coworker of Mark Miller. He talks about your blog often enough I decided to check it out. At the end of your post you expressed a desire to use a different shaped bin if at all possible. It made me remember some research I did for a church campaign back in Indiana called re:invention. Most of my design inspiration came to me via Mazda and the invention of their ‘Renisis’ engine design which has a unique(and critical) keystone shape. Results ended up producing some of the best scores ever in power/weight ratio, efficiency, and emissions ever produced for a naturally aspirated combustion engine. I know your not building an engine, however the storied success of this design, and the history of the keystone shape within design was more than enough to get my brain out of the box, so maybe it can be for you too. Good luck in your search!
http://www.youtube.com/watch?v=6BCgl2uumlI

By: Joe Johnston

Joe Johnston — Sun, 21 Feb 2010 21:19:51 +0000

Thanks, Adam, for your comments. I hope you enjoy learning more about coffee and roasting. It is a fascinating topic. The aim of my blog is really to look at the design process and it just happens to be applied to this particular piece of industrial art: the coffee roaster. Please feel free to ask any question you would like or to comment.

By: Joe Johnston

Joe Johnston — Sun, 21 Feb 2010 21:17:09 +0000

Michael, thanks for your comments and for participating in the blog. You are quite right that the vast majority of roasters are drum roasters. There are also quite a few fluidized bed roasters based upon the M. Sivitez patent, as well. Precedent exists for bowl roasters. Probat currently builds the Saturn Series which operates on basically the same principle.

I am certainly willing to end up at a drum as the geometry, but it must be proven that it is superior in performance. It is possible that drums are common due to manufacturability, economy of construction, and other reasons unrelated to performance. We shall see. As a designer, I would like to look at the alternatives prior to returning to the conventional methodology.

Thanks, again. I would certainly like to meet you next time I am in Tucson. I’ve heard lots of good things about Caffé Luce. Please continue to comment.

By: Michael Foster

Michael Foster — Sun, 21 Feb 2010 20:59:32 +0000

Joe,
I’ve been following your posts with great curiosity…quite the undertaking. I just wanted to note that although I understand the desire to break the mold on roaster design, do not dismiss the simple fact that drum roasters have and continue to be used by 99% of the worlds coffee companies; it’s because they work. Many have tried other designs and for the most part failed miserably; simple physics dictate the rules here. You are obviously putting a great deal of time and money into your project, we all want to see it succeed!
Best wishes….
Michael

By: Adam Bamford

Adam Bamford — Sun, 21 Feb 2010 04:59:35 +0000

Great stuff, Joe!

Even though I have virtually zero knowledge of coffee roasting, I’m following with interest as your design progresses. Funnily, we must have just missed you at Cartel today! Tara and I ventured there for our first time this afternoon, and we sat at the table that is practically attached to the San Franciscan… I sipped my superb latte while admiring that spectacle of a machine:-]

Cheers.