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.
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 -)
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…
