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Drum Roaster Ideas, part 1

25Sep09

Here’s something I knocked up based on looking into a range of drum roaster sizes and styles out there – most of these are from homeroasters.org.

Comparison of drum dimensions of various drum roasters.Refs for these are:

Of course there are other factors to consider in a drum roaster. These include:

  1. Solid or perforated metal on the drum (all of the above are perforated, if I remember correctly);
  2. Heat source(s) and amount of heat available;
  3. Volume of roasting chamber (relative to volume of drum);
  4. Insulation around roasting chamber (and if so, how much?);
  5. Airflow (where and how much?);
  6. Agitation of beans (what kind of vanes in the drum?);

There are no doubt other factors that I haven’t thought of!

Conclusions (ie. what I’ll need for my hypothetical 2kg roaster):

  • Drum volume of around 12 litres – this would be a drum 40cm long and 20cm in diameter;
  • Heating equivalent to around 4000W or 14000 BTUs/hr;
  • A mainly convective heat source (heat gun – 2000W) AND a mainly radiant heat source (IR or halogen @ ~2000W) – these are highly adjustable heat sources;
  • Because of radiant heat source, drum will need to be perforated or (preferably) mesh;
  • Smallish roasting chamber (aim for drum volume to be about 80% of total chamber volume) will be hexagonal or octagonal around cylindrical drum;
  • Heavily insulated roasting chamber so as to conserve all the heat applied;
  • Heat gun also provides an adjustable airflow (some models);
  • Airflow will be directed over/through the beans and chamber, with small exit on opposite side to inlet;
  • Vanes will be fitted on outside of drum to act as an additional fan;
  • Large vanes for maximum agitation – vanes may be used to “scoop” the beans closer to radiant heat source.

A few sketches I worked up:

Octagonal, IR-elements top left, HG-in top rear, air out bottom right.

Hexagonal, halogens bottom right, fins on drum outer, approx bean mass level shown.

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