Form and Function: Conceptual Drawing of the Roaster #2

2010 June 3
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I’ve been wanting to sketch the form of the roaster for some time now. It is said that “form follows function”. I believe that to some degree, however many of my favorite industrial designs break the rule or at least go a bit further.

For instance, one of my favorite designs of all times is the Vespa scooter. The form does start by following function. The basic idea is to create two-wheeled transportation that is economical, simple to operate and that a lady wearing a dress can ride. This leads to a step-though design (unlike a motorcycle) and a leg shield, both of which are iconic Vespa features. The body encloses the mechanicals, so that clothes cannot get soiled. The controls are simple bicycle-like affairs that make learning to ride very easy. However, the designers went to the additional step of infusing a measure of beauty into the scooter. They added flowing lines, grace in the curve of the headlight enclosure, and many smaller details that make it a work of art. While there are other “functional” scooters from the same era, none are as beloved and timeless as the Vespa.

I take a similar approach to design. Function is very important: beauty, pattern and presence are also very important. Here’s how I came up with the drawing shown below, which is a possible form of the roaster.

First, I consider function. A roaster needs (1) a place for the green, unroasted coffee to be held, (2) a roasting chamber, (3) a cooling chamber, and (4) areas where burners, blowers, ductwork and motors needed to operate are housed. Since I am currently focused on using a bowl as the roasting vessel, it makes sense for me to house the bowl in a round form. The form could be spherical our cylindrical: I chose spherical due to my fascination with the Automium. Furthermore, the green coffee hold may include preheating of the beans to drive off moisture and set a uniform starting condition for the roasting vessel. This means that it has a similar function to the roasting vessel: heating and mixing the beans. The cooling chamber is essentially the inverse of the roasting chamber: removing heat and mixing the beans. Since all three functions are closely related, it makes it possible for the form of each  be similar, hence the three spheres.

This plays nicely into two design features I enjoy: pattern and odd numbers. The repeating spheres and the number being three looks good to my eye. I have added the connecting chutes for the beans and the necessary ductwork for the roasting vessel (this still needs refinement). The bases for the roasting sphere and the cooling sphere contain the drive motors to run bowls or mixing arms (the cooler?) for each. The various blowers, burners, gas controls, and ductwork are in a housing behind the spheres. Each sphere has a window so that one may observe the activity going on inside the sphere.

The design is simply an initial idea. I will be refining the basic idea and adding more detail. On the other hand, I may just toss this design out, if a better one comes to mind.

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7 Responses
  1. Michael permalink
    June 4, 2010

    It’s good to see an aesthetic design element in a roaster. It would be elegant if you were able to pivot at center bowl so that the greens or cooling bowl could be brought up & down to an easy working height.

    I was wondering where a tryer might fit in? I suppose you could drop beans out the bottom (awkward) or expel them from the bowl centrifugally through a discharge port (gee whiz). But probably a conventional tryer beside the window to sample from the dropping beans would be best?

    • June 9, 2010

      Thanks, Michael, for your comments. I agree with you about the need for ease of working by making sure the height and dimensions of the bowl fit the human scale.

      The tryer is a bit of a conundrum in a shop roaster based upon a bowl. My current thought is that it would be longer than a traditional tryer, so that it can extend into the path of the agitating beans. I like your alternate ideas. I’ve thought of several complex ways of doing it, but I think the most simple solution is usually the best.

      If you think of other methods, as the design develops, please tell me!

  2. June 9, 2010

    I hope you do not toss this design. It is extremely interesting. The first sphere offers a solution for many problems associated to some exotic and coveted green coffee or also to some just plain dirty coffee. Because this coffees are processed mainly by hand and sometimes not treated by a dry mill (polished), causing to have some of the dry silver skin still on them, makes them produce an enormous amount of chaff. Also coffees that are too fresh present high chaff volumes. All this makes them a high risk for roaster fires. Most of you know, you are not a real roaster until you have a real fire. To get extremely clean coffees from many African nations is sometimes problematic.

    I have always been a fan of a lower temperature first roasting stage and a more aggressive final roasting stage that is also easy to visualize in the triple sphere design.

    Finally the finishing sphere (cooling) answers directly the question of how fast can i chill my finished roasted beans. I think the sooner the better so imagine a cool air vent directly from an air conditioning source will make that being a super cooler (from 450 F to room temperature in 30 seconds).
    I already dream about this machine humming away and producing even more caramels out of any coffee or handling smoke contamination so efficiently that makes yirgacheffe taste like coffee with rose water. Great job.

    • June 17, 2010

      Ron, thank you for the affirmation. I do like the basic design. It does solve quite a few problems, but introduces a few of its own such as: where to put the tryer. Thanks for your input and feel free to make suggestions!

  3. July 19, 2010

    Just started following….what a great project.
    A really good looking air roaster would be refreshing. I built my 5 lb. Frankenroast about 10 yrs ago. It works great….but yours is going to be sexy.
    I could see this working without the need for mechanical agitation, but I’m no engineer. Looking forward to the updates -Scott

    • July 21, 2010

      Thanks, Scott! I don’t really consider the bowl roaster an air roaster, although as in most roasters hot air (convection) will be the predominant heat transfer medium. Regarding agitation, I wanted to decouple air flow from having to do the agitating so that I can overcome some of the issues with fully fluidized bed roasters. Mechanical agitation allows me then to vary airflow and heat input from convection more independently. Please feel free to comment at any time!

  4. Dean Richardson permalink
    July 29, 2010

    Depending on heat source the intensity can be managed by varying the amount of heat added, fire or current. Forced air convection is VERY effective at minimizing hot spots and assures an even roast. It also adds the benefit of being able to carry away chafe to a settling area in a closed loop convection system. Forced convection also allows you to minimize on the number of heat sources and just use valving to economize on the number of thermal and agitation devices. Here is what I love most about air agitation. Only one moving part. Which means only one part to replace.

    I love the design though. It looks great and says Joe Johnston all over it. Nice art!

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