Building a Drum Home Coffee Roaster

So you are going to build your own drum home ? You’re nuts, but you already know that… and in fact, a is a very simple machine. Hey, if this guy can do it, why can’t you?

Also, see our pictures of the Jabez Burns Sample Roaster

Perforated Sheet Metals Used in Home Coffee Roasters

Here’s some information to those interested in building their own home coffee roasters, especially drum-type roasters to be installed in gas Barbeque grills, what hole-sizes and patterns are used in the currently available coffee roastingThe application of heat to green coffee seeds (beans) to create palatable material for brewing a great cup!: Coffee roasting is a chemical process induced by heat, by... appliances. Here are some images, and all should be at the same scale, although they are not “actual size”:

1. The Alpenrost Drum is unique among these samples: it is the only one designed to allow to fall through it while roasting! Notice the percent of open space to metal … this is highly perforated. The holes measure just a hair over 3/16 inch. It corresponds somewhat to McNichols 3/16″, 1/4″ staggered centers, 18 holes PSI, 50% open area (although it looks even more open than this, more like samples with 60-65% open area)

2. The bottom of the Hearthware Precision Roast Chamber has 2 hole sizes. The smaller hole is 5/32 ” and the larger is 3/16, same as the Alpenrost. This is a little surprising since the function of this roast chamber is not to allow chaff to pass down through the roast chamber and fall down into the base. But with such a positive airflow upward, this is not much of a risk.

3. This is the ring from the interior of a well-used Hearthware Precision Chaff Collector. This hols size and pattern is identical to the Zach & Dani’s coffee roaster’s roast chamber bottom, but I couldn’t get a good photo of that. The function here would be to hold back chaff, but allow airflow. It is approximately 1/16″ holes and corresponds to McNichols 1/16″, 7/64″ staggered centers, 98 holes PSI, 30% open area

4. This is an image of the Coffee Kinetics 1 Lb roaster’s roast chamber bottom. This roast chamber is like any of the smaller air roaster chambers (Freshroast, etc) in that a strong airflow comes up from the base … so the function is to hold the coffee and resist letting chaff drop-down (although airflow prevents this too). These are 1/8″ holes and corresponds to McNichols 1/8″, 3/16″ staggered centers, 33 holes PSI, 40% open area

5. This is the Freshroast roast chamber bottom, and they appear to be 5/32″ holes with a much greater open area than the Coffee Kinetics (But the CK roast chamber diameter is about 8-9″ compared to about 3″ on the tiny Freshroast). This material corresponds with McNichols 5/32″, 3/16″ staggered centers, 33 holes PSI, 63% open area

6. This is not perforated metal, it is a screen, and its from the top of the coffee kinetics. All manufacturers are using screen for places where they want air to pass, but all chaff to be trapped. Freshroast Plus has the coarsest screen, HWP is very fine, and the Zach & Dani’s, in the top piece, has an extremely fine screen.

I hope this helps a bit! Happy roaster building, and remember to visit the best BBQ roaster construction sites:

Thehomeroaster.com is a great site created by Ed Needham, with detailed articles on the construction of a rotisserie drum roaster, and some neat articles about Maui Moka, Kopi Luwak, Etc.
Jim Gundlach has a great page with details on his home-built barbeque rotisserie roaster. The drum construction uses a perforated sheet with a standard heat duct for end caps. Check it out at http://www.auburn.edu/~gundljh/BBQ.html

-Tom 2/14/03