Deft. Coffee Roasters. » roaster

Not the best roast…

Dave — Wed, 28 May 2008 05:22:20 +0000

Bolivia Cup of Excellence: San Ignacio Juana Mamani Huanca.

Not my best effort at the roast. Rushed the warm, and pushed 1rst crack up about 2+ minutes. Shit. And it shows in the cup. Green and tight on the tongue, florals and fruits aren’t well developed. It still has some real nice sweetness that comes out as it cools, but it should be more delicate, balanced than this.

Well, still tweaking the roaster, but damn, wish i’d done this with a coffee that I didn’t have so little of, or that cost so much ($25/lb). Oh well, at least it was only 125g. And I still some.

But, on the bright side of things, I fiddled with the air/fuel ratio on the pinhalense tonight and have a much better flame now, one that has a slight hiss and a good tightly formed flame – not the laziness that it was before. Seems it needed more air (O2). I hope that this means that I’ll be able to mve at least a full load through the times I’m expecting… till now, 300g has been somewhere about a slow 30min. ugh.

Chaff Collection

Dave — Mon, 26 May 2008 17:34:29 +0000

I found where the chaff has been going… just under the cooling vents, and before the entry to the impeller.. that is the hole in on the left side of the floor.”

some images of the new roaster

Dave — Wed, 14 May 2008 17:45:20 +0000

Here’s a little slideshow of the new roaster. I’m planning to take some more details this weekend and will post those as well.

cheers

yep.-)

Dave — Mon, 12 May 2008 21:47:48 +0000

tick… tck… tk…

Dave — Wed, 09 Apr 2008 00:50:54 +0000

Looks like my roaster is shipping tomorrow morning out of Brazil.. I am bouncing off the walls in anticipation.

It’s going to be only a short time now…

Dave — Mon, 31 Mar 2008 04:48:49 +0000

I can hardly stand the slowness that designing and building this roaster is. I know that it is my doing, but that doesn’t make it any easier not being able to really control my roasts. And it’s becoming increasingly painful as I become ever more eager to sink deep into cupping coffee and reaching balance with a roast. I’m not currently exploring as I know I am able… and truly return to my craft.

Well, In fact I couldn’t let this go any longer, and so purchased a sample roaster from Pinhalense.. I just got word at the end of last week that it is essentially ready in the factory as of tomorrow, so all it needs is some crating, an airplane, one long flight from Sao Paulo to Portland. Some gentle customs agents, and a van to get it home. If all goes well, by next weekend, I should be tearing through some junky green that I’ve been stashing away over the past couple months to get it nice and seasoned.

Drawings of the old drum design (sketchup perspectives)

Dave — Wed, 19 Mar 2008 20:20:38 +0000

I was trying to edit a batch of images to Flickr with their batch tool, but the commenting was duplicating anything that I wrote (several times), so I gave up for now and simplified the set I was putting together. I am intending to post all my older designs for the drum—sections, elevations as well as these perspectives—but that will have to wait…

I decided not to go with this design pretty much because I changed my mind about the importance of air control with this batch size. I had convinced myself that at this batch size—80g to 500g—that air flow was less important. but while walking over to a friends home for dinner on night a while back, I re-thought my decision. So I am shifting over to a closed system so that I can adjust air flow much like larger roasters. I am not sure if (or how) I will keep the rest of this design. The dimensions of the chamber itself still feels correct to me, and the vane size and placements as well… I had considered possibly moving to something that agitates the beans in a way to keep them moving off the hot surface of the drum. I am leaning though, toward keeping this setup since I like how it maintains a relatively consistent mass – which my theory (somewhat supported by a scientific article (which I will post a link soon, promise) that the coffee will roast more evenly when it does this. Too much agitation will cause it to roast less evenly. so without much adoo, here are the drawings.

(BTW, notice the new fancy image viewer I found! It’s Pictobrowser a flash plugin written by a couple NYC interaction designers that pulls flickr sets into your site—all contained in this neat little package. The wordpress plugin was written by Kumara Sastry. I altered it a bit to get the original size images to load and so you could zoom them and read the notes… I like it a whole lot. It’s nice)

UPDATE_ I finally got all my drawings from sketchup posted and annotated – well, okay some of the annotations are cut and pasted from other annotations, but whatever… – so they are all in the set now. And if you care, now have a flickr account just for Deft.. you can see what’s there, uhh, here.

Chaff collection box…

Dave — Thu, 17 Jan 2008 00:55:36 +0000

Okay, three last images. They simple show the difference in air flow for low and high air flow. Noticeably more chaff gets around the corner with high air flow.Here they are:

Low air flow:

High air flow:

Comparison of high and low air flow – the magenta overlay shows the difference when the high airflow was done (second):

more airflow thoughts

Dave — Thu, 17 Jan 2008 00:24:09 +0000

I think that I have a bit more figured out and will post when I have a chance to scan a couple drawings… But I think that what I’ve landed on is a relatively simple air path that draws air via two different paths—one entering through the bean chute, through the drum and out the back toward the chaff collection box; the other entering through the bean tray (cooler) and hooking up with the chaff collection box, where both paths meet and out the door…
What is nice about this is I can essentially seal off the chamber where the heat source is located and around the exterior of the drum so that I can make this temperature stable and so controllable and responsive.

Video of the airflow prototype (version 1.3)

Dave — Thu, 10 Jan 2008 23:34:56 +0000

I am figuring out the design of the air flow—mostly to allow for control of the air flow, but will need to catch the chaff as well. I based what I am doing on what I know of older Gothot sample roaster —why reinvent this? I don’t have one to play with, so am reverse engineering based on my memory and images I have found on the internet.This video is of the easy portion—where the air exits the roaster and enters / moves through a wind tunnel of sorts, separating the chaff from the airflow. you can see where the chaff is caught in the dead zone below the hole it enters through. Still a couple refinements to figure out, but it is working.The Cheesecloth was there cause it is a normal fan and not a n impeller, and I wasn’t sure it would work (well, it didn’t at first, which is why it is version 1.3 -)

AIRFLOW PROTOTYPE: Version 1.3 (the airbox)

Dave — Tue, 08 Jan 2008 00:23:10 +0000

I’ve been making on the fly tweaks to the form of the air box, and have almost nailed down the general design. It is based on older Gothot sample roaster designs that I have seen. I am basically re-creating this from memory and what images I could cull from the interweb. I don’t feel that I need to re-invent this part of the roaster, but am toying with how to build some efficiency into the heating, similiar to how the Kestrel roasters work. That may be phase two though.I need to run through the tests again, but feel that I am fairly close.

Learnings:

Having the air/chaff enter from an overhang (rather than flush with the back wall) creates a nice little dead zone that traps chaff quite well

That if the gap leading to the exist hallway is too large, the fan/impeller will simply pull all the chaff around the corner and out the venting—with lower airflows. The final design will have a slit of a gap.

I may add a fine mesh screen in front of the impeller entrance just to catch any errant flakes, but they could also be caught with t-shaped venting after the impeller (which I should do anyway). A tiny bit of chaff isn’t going to hurt the impeller, after all.

Next I want to repeat this with a larger amount of chaff, and with dry ice (to see what it looks like). and then begin dimensioning this out. I like that it’s really simple and works.After that, I need to add on the air as it comes from the cooling try, which sits on top of the airbox. It’s a bit more tricky, as it will feed both the airbox and the drum—toggling between the two…

AIR-FLOW PROTOTYPE

Dave — Mon, 31 Dec 2007 05:22:22 +0000

Thanksgiving day, Christy drove the girls over to our friends home for dinner while I walked. I was getting a bit squirrelly and the fresh cold air was exactly what I needed. Almost immediately, my mind was engaged with this experimental roaster. I’d been stagnant with any progress since the soapbox derby, and i was really wanting to get back with it. But I was hesitating for some reason.

One of the things that has been nagging at me has been airflow… I had convinced myself that the airflow for roasting 1/2 to 1 pound of coffee wasn’t as important as the drum and bean mass dynamics. Minimal in fact and so I didn’t need to put too much consideration into it… as long as I drew air through the back and out of the front of the drum (the front end was going to be open, like Gothot / Probat and Pinhalenze sample roasters) I believed that I would be able to achieve good control over the roast. But the venting and control that the Gothot has was just sitting there in my mind, picking at my certainty, pointing out that even in small batches, air flow is important.

So I was walking through the neighborhood and re-worked almost everything. Not so much in detail, but mentally re-sketched the entire plan for the roaster. and so now it is more like a grown up roaster, with control over the air flow so that I can control it subtly.

Which brings me to today. I am not trying to re-invent anything, and so built a prototype of the air box based on what I know about the Gothot sample roasters.. an so far just have the chaff collection part built. I should be able to test it in the next couple days and will post images and video of it shortly…

the derby vs. the roaster

Dave — Tue, 31 Jul 2007 01:02:26 +0000

I’m having to admit to myself that being able to build a roaster at the same time as building a derby car is unrealistic. so production is on hold until after August 25th when the Portland Adult Soapbox Derby is being held… or maybe a couple days after that to let us re-coup a little. It at least gives me a little bit of time to accumulate materials.. so I may still make it by the end of September..

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Drum vs. duck roasting.

Dave — Wed, 11 Jul 2007 01:10:19 +0000

Looks like the porcelain enamel I was excited about isn’t all that I thought. Shouldda known. Kinda exactly the opposite of what works for roasting a duck is working against me in the drum design. That and that roasting poultry is a pretty much a linear process in terms of input.. coffee roasting isn’t.

Anyway, I have become (somewhat) initiated into the world of coatings. What’s possible and what’s not. What works well and what doesn’t. Which ones distribute heat, which ones are thermal barriers. Porcelain Enamel, contrary to waht I had read, is a barrier, which is why it works to trap heat (and moisture) in that Le Creuset cast iron dutch oven so well.

So I think I have the right formula for coatings that will distribute the heat efficiently and evenly from the flame to the interior of the drum. It will be a bit tricky to make sure that the ambient temperature around the drum stays stable and responsive to the flame, but I think that with a combination of insulation and coated drum material, I will be in really good shape. So that means I am ready to begin building the drum and the housing. Aluminum and mild steel. I never thought that I would end up with a drum that didn’t have stainless steel as the inner surface of the drum, but here I am, with a design for a solid aluminum drum. Well, it’ll be coated of course but the aluminum will transfer the heat from the heat source to the roast chamber extremely well. Extremely quickly. And because of the coatings, it should be extremely even. Now, all I need to do is build the working prototype.

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PORCELAIN ENAMEL…

Dave — Sat, 30 Jun 2007 01:21:17 +0000

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.)

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