A couple of tidbits that I just came across… kinda makes me giddy since it may simplify the construction of this drum extensively!
THERMAL CONDUCTIVITY
Porcelain enamel is not a thermal insulator, but it is a relatively good heat conductor when applied in thin coats. Its emissivity characteristics are particularly good. Normally, porcelain enamels are applied so thin there is only a very small temperature gradient through them.
and
Enamel is a relatively good heat conductor when applied in thin coats, however it is not a thermal insulator or diffuser.
Not too worried that doesn’t diffuse heat, that is what the aluminum will be for…
oh, and it’s recyclable (not that ss/aluminum wasn’t, but good to know this is too.)
The past few weeks has been a lesson in the dynamics of falling beans.
I built a couple prototypes for testing how beans will move in the lab sample roaster… This way, I can test, at least visually, how the movement of the beans in the roast chamber will occur. In future iterations of the lab sample roaster, I will be able to exchange barrels out and test different drum configurations and their effect on the development of flavor… But I shouldn’t get ahead of myself… anyway… It’s a beautiful thing.
This is about 0.25 lb of green coffee. As you can see, the vanes are opposing, and in parallel, which will folds the coffee back and forth towards the center of the drum. Three vanes ended up splitting small loads in half which is obviously not a good thing.This is about 1.25 lb of green coffee. To be honest, I liked the way it fell in another test where there were three vanes, but given the problems that were coming up with minimum loads, I think that this is acceptable. The beans stay together well, and though it doesn’t show in this test, the beans integrate/mix within about 45 sec. (That is why there are black beans spread throughout. I painted about 0.25 lb of the beans with black spray paint and laid them in the drum on top of the other beans and timed how fast they integrated. I didn’t think it was necessary to separate them back out…) Anyway, I feel that I have figured out, pretty much as well as I can until I am running real sample roasts what this will look like. It is nice to have the certainty of having seen how the beans will fall. How well they keep together and so on. It’s obviously not a precise science—if it were, roasting wouldn’t be an art—but having gone through this prototyping is giving me both confidence that what I am building will be quality and a much better sense of what is happening inside the drum.This week is my week to draw the mechanicals for this and spec materials… I still need to decide on the construction method. I have a couple options. To slip a stainless steel sleeve inside an aluminum or copper tube, or to press fit machined cooking pots together. I like the latter, but getting pots without the handles, in a reasonable amount of time is my concern. That may actually be a second drum.
As a short bit of follow up to The Best of Panama auction dissparity, I am pretty pleased to see that the auction prices in the Nicaragua Cup of Excellence are generally higher, and more evenly spread across the entire auction.
It is great to see that many farms receiving more well more than $5/lb.
It’s not dripping from a naked portafilter, and I’m pretty sure it’s not that old Papua New Guinea Sigri AA, at it’s height, roasted just so, but here are some beautiful images of sweet milk breaking the surface of some sexy gauzy coffee. All shot at hi-speed. Very pretty.
I posted this on the Roaster’s Guild Public forums as well as here… I am just looking for insight as to why there is such a large gap—one that seems to be widening—between the winning auction lot of high scoring coffees and the #2. Even when the cup scores are quite close. I say in in the cross post below, but I’ll mention it again. My questions are based on the cup scores, the auction price and a little on the cupping notes. I didn’t sample any of the coffees, and so I wanted to steer clear of commenting about the actual quality of the coffees.
The full post after the more>:
UPDATE: a link to a discussion of this on coffeed.com, including several of the purchasers and at least one of the judges. And another thread where Tom Owens (of sweetmarias) posted a letter from the Cup of Excellence board that addresses the main concern I have (that the gap between 1rst and 2nd auction prices is huge) by changing the price structure of the next CoE auction in Nicaragua.
UPDATE 2: I am searching for a list of the international judges in the Best of Panama 2007 auction.. cause I just noticed that at least one was part of the winning group (?).. A point that I’m not sure what it means—though it probably just meant that those that knew what they were purchasing bid for it… Willoughby’s states on their website although I don’t know who it was. (Note that they have the cupping score for Mama Cata (MCGC), the #2 coffee, different from the official auction results—I don’t know which one is correct, but assume the auction results are the correct score).
I am working my way though the drum dimensions… I figured that it would be easier to build a prototype of the drum than try to envision how the beans are going to fall over the vanes, how many there are, etc… so I built this. My friend Brian (who is helping me build this) squeaked out a little jig that I could put two tire hubs on it—it’s suuper crude, but it works well enough that I can see what is happening inside the drum. The image is just the PVC tubing that I got to simulate the roaster drum before I put in vanes and sealed the back end….
What did I learn? That the depth of the drum is going to be a different ratio to the diameter than I had originally thought—slightly shorter. I need to do more testing around the vanes… I realized (duh) that they need to have a ratio to the depth of the coffee. If the coffee is going to fold correctly, keeping a bean mass, but constantly rotating the position of the coffee beans from being in (brief) contact with the drum wall to positioning it away from the drum wall, I didn’t get it right this time around, but that’s what prototypes are for…
