How to Build a Traditional Drum Coffee Roaster

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Introduction: How to Build a Traditional Drum Coffee Roaster

In the Youtube video, you can see the fully functional drum coffee roasting machine which I built in my own garage. This coffee roasting machine is an effort to reconstruct the traditional drum coffee roasting machine using the simplest method and concept. I have pushed the limit of this machine and successfully roasted maximum of 1.2kg of green beans.

The machine can be separated into these components:

  1. Cooling tray
  2. Chaff collector and exhaust
  3. Gas burner
  4. Platform and motor
  5. Thermocouples w Arduino
  6. Inner drum
  7. Main roaster body

Each step will have the shopping list for each components. Details of the construction will be in each photo, and important point will be pointed out as comment inside each photo. Please go through each and everyone of them to make sure you have a full picture of the construction of this coffee roaster.

The tools I used are all very common tools you can find in any garage, only special tool I purchased just for this project is the Dremel 200.

General list of tools I used:

  1. Dremel 200
  2. Glue gun
  3. Sheet metal hand cutter
  4. Plyer
  5. Screw driver
  6. Allen keys (of various size)
  7. Soldering iron (just to make the TC4lite PCB)
  8. Masking tape
  9. Aluminium tape
  10. Kapton tape
  11. Metal saw
  12. Wood saw

The whole project took me roughly 6 months with more hours spent during weekends. This is the third version I made as I need the lessons from the previous 2 to make this a success. I hope you could leverage from my experience and be successful on the first time, but even if you are not, remember this isn't my first either.

Let's begin and all the best!

Step 1: Build the Cooling Tray

The concept is simple, 2 buckets, bottom bucket have an exhaust fan while top bucket have a mesh.

Shopping list:

  1. 2 x buckets
  2. 1 x 250mm round exhaust fan
  3. 1 x mesh strainer 290mm

Additional tools/materials:

  1. Aluminium foil
  2. Aluminium tape
  3. Bicycle inner tube
  4. Few longer screws and nuts
  5. Plenty of masking tape
  6. Glue gun

Step 2: Build the Chaff Collector

There are plenty of different version of the dust collector in the internet, this is my version specifically for coffee chaff. Bottom bucket to collect the chaff, middle traffic cone to create the cyclone effect, top blower to channel air + chaff out from coffee roaster into the cyclone, separate the chaff and continue to channel the smoke out from the garage.

Shopping list:

  1. 1 x Seaflo In Line Bilge Air Blower 130CFM
  2. 1 x PWM 12V DC 3A Motor Speed Controller
  3. 1 x Holman 90 x 75 x 65 x 50 x 40mm Storm Pvc Stepped Adaptor
  4. 1 x traffic cone (small)
  5. 1 x Garden Rain 25mm Female Tank Access Outlet
  6. 2 x small container
  7. 1 x 50mm 6M Long Aluminum Foil Hose Ducting Flexible Pipe
  8. 1 x PVC Round 90deg Bend
  9. 1 x Steel Pipe Clamps
  10. 1 x Power supply 220vac to 12vdc regulator
  11. 50mm PVC pipe

Additional tools/materials:

  1. Aluminium tape
  2. Plenty of masking tape
  3. Glue gun
  4. Few screws

Step 3: Build the Gas Burner

The burner I use is an infrared burner, you do not have to follow my design, any gas stove should do the trick. The 5kpa regulator also is not a conventional one, around 2.5kpa is the usual one in the market. I specifically purchased this one from China market.

Shopping list:

  1. Infrared gas burner (or gas stove of similar type)
  2. 1 x 6 kpa Gauge Pressure meter
  3. 1 x 5 kpa LPG gas regulator
  4. 1 x Needle valve inline control
  5. Few meters long LPG gas tube

Step 4: Build the Platform With Drum Motor

This platform is mainly to position the roaster nicely on the wood plank while the motor stand is fixed behind the platform and aligning nicely to the inner drum shaft. The motor I am using will rotate at 1400r/min because the 220V supply in the country I am in is 50Hz. I purchased the gear box ratio of 1:25 meaning I will be able to achieve 1400/25= 56rpm (max) for my inner drum.

Shopping list:

  1. 1 x AC220V 25W 10-500rpm 4M25GN-C single-phase AC gear motor with speed controller
  2. 1 x 8mm to 8mm CNC Stepper Motor Shaft Coupling Coupler
  3. Few pieces of wood planks

Additional tools/materials:

  1. Screws (to hold the platform together and motor in place)
  2. Metal Mate 12 x 12 x 1.4mm 1m Aluminium Equal Angle

Step 5: Build TC4lite PCB With Arduino UNO

I modified the existing TC4 project to strip it down to the minimum required components and use it together with Artisan coffee roasting software to view the roasting Bean Temperature (BT) and Environment Temperature (ET). I call it the TC4lite. The schematic of TC4lite is in the photo.

You can find out more about the existing TC4 project here:

  1. Artisan coffee roasting supported devices: https://artisan-roasterscope.blogspot.co.uk/2013/0...
  2. TC4 - http://www.mlgp-llc.com/arduino/public/arduino-pc...

To build TC4lite, you need to have the knowledge and understand on schematic drawing and the skill to do PCB soldering; you also need to have knowledge on how to program an Arduino UNO board. Alternatively, you can purchase off-the-shelf solution which can be found in the link above on supported devices.

After building the hardware, the Arduino UNO needs to be programmed with the correct firmware which can be found here: https://github.com/greencardigan/TC4-shield/tree/m...

Shopping list:

  1. 1 x UNO R3 Development Board ATmega328P ATMEGA16U2
  2. All components in the modified schematic of TC4 to build this TC4lite version PCB

Step 6: Build the Inner Drum

The inner drum is the heart of the roaster, alignment is tricky but also the utmost important point in making this machine. Symptom of misalignment:

  1. Hearing the drum hitting the faceplate while turning
  2. Coffee beans escape the inner drum and dropped into the roaster body
  3. Unable to turn the drum totally

* Many fine tunes and trials is required to achieve the perfect position; but if I can make it, I am sure you can do it as well.

* Important note: The 4 x M4 threaded rods need to be installed in the depth of the K-type thermocouple length in mind. Too near and not enough of room will cause the thermocouple to hit the rods and your inner drum won't be able to turn totally.

Shopping list:

  1. 1 x Ikea ordning colander
  2. 1 x M8 threaded rod & nuts
  3. 4 x M4 threaded rod & nuts
  4. 1 x 16mm hallow aluminium tube
  5. Plenty of metal angle brackets
  6. Plenty of M8 washers

Step 7: Build the Roaster Body

The inner drum needs to work hand in hand with the roaster body, both need to align to each other. Similar to inner drum, significant amount of time is spent trying to make sure the inner drum is not hitting the roaster body while it is turning inside the roaster body. My photo of the faceplate have many screws on it, not all are meaningful. As I previously mentioned this is my 3rd version of the built, some holes were mistake from previous version; just ignore them and only concentrate on the one I commented.

Shopping list:

  1. 1 x Ikea SOCKER Bucket
  2. 1 x SOCKER Plant stand on wheels
  3. 1 x 38mm External 35MM dump tube Turbocharger wastegate
  4. 1 x butterfly hinge
  5. 2 x FL08 2 Bolt 8mm Bore Self-aligning Flange Ball Bearing
  6. 2 x 5mm K-type thermocouples
  7. 4 x 29.6cm Metal Mate 12 x 12mm Aluminium Equal Angle
  8. 2 x 42cm Metal Mate 12 x 12mm Aluminium Equal Angle
  9. 1 x 30cm M5 threaded rod with nuts
  10. 1 x aluminium tin can
  11. Plenty of washers

Note: I found out later on if given a choice, it might be better to choose material which is not galvanized.

Step 8: Put All Together for a Test Ride

This is the moment of truth, but do not rush into charging 1kg of green beans into the roaster just yet, my experience is telling me you will not get it right the first time (unless you are a mechanical engineer and have big boy tools and equipment). Try my testing procedure below to increase the chances of success and avoid unnecessary damage to the roaster while testing it.

Testing the coffee roaster:

  1. Test all components separately before putting them together
  2. Place all components together and test it without the beans and the fire
  3. (Critical test) Test the roaster with the green beans by putting into the drum and let motor turn it. You need to stop the test immediately if any stuck or strange sounds coming from the roaster.
  4. If test 3 all good, move on to test roast a very small batch, like 300g, just to make sure the dynamic did not change with fire comes into the equation
  5. If test 4 all good, you can now pour your heart in and roast 1kg of green beans and start enjoying your amazing coffee roasting machine

All the best!

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    20 Discussions

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    TimB14

    3 months ago

    This is a fantastic project! Congratulations on a great build. I'm going to work on one of these soon and have a question about Step 7. From the picture of the burner hole, it looks like there is a bucket within a bucket and then inside them both, the roasting colander. Is that true? If so, what is the purpose of two buckets--insulation? I'm not sure I understand that particular aspect of the design and would like to. Thank you very much!

    2 replies

    Haha eagle eye indeed! Yes it is double walled. I designed this to roast 1kg of green beans, unfortunately the heat capacity just isn't enough, hence the double layers. It does improve a little but given another chance, I would try to find a reasonably thick stainless steel over the double walled.

    I'm so impressed by your effort and ingenuity. Heat loss was a big issue for my build, which is several generations behind (I converted a toaster oven with a 500g goal). I'm sure you'll get it!

    This is the gauge I got for about $25 (pre-owned) off of eBay: Dwyer Magnehelic 2000-00 (low pressure gauge). Here is an article about its use monitoring airflow in a coffee roaster. https://hankua.wordpress.com/2013/11/23/measuring-air-flow-in-a-coffee-roaster-dwyer-magnehelic/ I believe this can be incorporated into the line between the roaster exhause hose and the chaff collector motor in Thye's design. My blower motor for the chaff collector cyclone is a Dayton model MG0822006171010. It was listed on Amazon.com as a "Dayton 1TDN7 Round Permanent Split Capacitor OEM Specialty Blower" and it had 47 customer reviews with 83% giving it 5-stars. I was able to get one from Amazon Warehouse Deals for $36. The plan is to put this on a dimmer switch for variable speed control.

    Based upon these answers in the Q&A section on Amazon, I believe that this will work with a dimmer switch.

    DaytonDimmerSwitch.png

    Looks like you are doing quite well. Machine taking shape yet?

    I'm finishing up a move to a new house. Once we get things unpacked, I hope to get back on the actual construction/assembly. One other thing I am going to try is to fashion the trier port and the optical window port out of Teflon (PTFE). The teflon is easily drilled/machined and can be mounted over a slightly oversized hole in the stainless lid. The idea is to have a trier (and optical window) hole in the middle of a larger square of teflon and then have 4 smaller mounting holes at each corner of the square. I'm thinking that a trier might be fashioned from a stainless steel cigar case (single cigar).

    Here is a crude drawing of my planned roasting chamber, based upon ChingThye's awesome design. (He provided a lot of answered questions for me already on Facebook.) In place of his galvanized bucket, I'm using a 24 quart stock pot. It comes with a perfectly flat lid, so I will not need to fashion the roaster face plate from something else. It is also wide enough to allow me to cut a big hole in the side and drop a thrift-store-purchased stainless steel sauce pot in for a burner "flue". Just enough clearance, by my measurements. The handle screwed off of the pot that I found, and I think I will reuse the handle to make a bean trier. Photo of the sauce pot that I found is also attached.

    img645.jpgFlueToRoastingChamber.png
    2 replies

    So the first thing I need to do is cut the big hole out of the side of my stock pot (for dropping in my sauce pan to serve as the burner flue - obviously need to cut the bottom off the sauce pan). I realized that I could not just take a circle pattern and bend it around the pot, because the actual hole needs to be slightly elliptical. So how to calculate that ellipse? I was pleased to receive two replies overnight: http://cq.cx/tubejoin.pl and http://www.harderwoods.com/pipetemplate.php?f=dn&u...

    Will do the job for you. I used the first link and got the following as a PDF that I could print to Ledger Paper. You could print on smaller paper and use some scotch tape also. Cut out the circle and trace that outline on the side of pot (covered with Painters Tape). I'm hoping that a jigsaw and this blade will do the job (pilot hole to get started). Bosch T118EHM1. I found it at a local home improvement store, but you can also order them online: https://www.google.com/search?q=Bosch+T118EHM1&rlz...

    StockPotHole.png

    I like your drawing, I have 2 whiteboards full of the drawing for the above design too, only difference is I am the only one who can understand it haha

    Some of my parts have come in, and so I wanted to share a bit more on my proposed build of ChingThye Gan's design. I'm moving this month, so won't get to finish this until closer to spring, but I wanted to put this out there for anyone else looking to build. Firstly, I went with a relatively inexpensive 24 qt. stock pot. It is wider (12-1/2" I.D.) than it is tall (approx. 10" inside). I liked it for that reason, and also because it comes with a perfectly FLAT lid (perimeter is raised about 1/4", but otherwise flat) - see photo. Photos attached also show the relative sizes of the Stock Pot, the Ikea colander, and the sauce pot I plan on using as the burner flue. I've also attached a screenshot I took of a technique for grinding off the spot welds (needed to remove the handles on the Ikea colander and the handle on the stock pot lid).

    PS... the stock pot that I purchased is sold under different brand names. Mine was found on eBay under the brand ExcelSteel for $49, shipped. Note the flat lid and the style of the handles when looking to see if the one you found is the same one (or similar). The model number (for all brands) was #513. I believe the Thunder Group SLSPS024 is the same pot also.

    24qtRoaster1.JPG24qtRoaster2.JPGlid-24qt.JPGGrindOutSpotWelds.png

    Thank you for this superb instructable, ChingThye Gan! I will be sharing my build, as well, based upon your design. One of my goals will be to eliminate all galvanized metal. For example, my roasting chamber will be a 24 quart stainless steel stock pot. It has a totally flat lid (one I cut off the handle) so I will use it for the roaster face. I am wondering about whether a flame arrest mesh (or plate) would be helpful between the flames & the drum (similar to Khaldi Fortis. Thoughts?

    2 replies

    You are welcome! My only issue is I don't have the ability and tools to cut stainless steel and perform stainless steel wielding. I am planning send some of my next design to a CNC shop and get them CNC out or lazer cut. I don't really know much about Khaldi Fortis but if you have a mesh between flames and drum, might be useful in catching chaff dropping down.

    I have never done it before, but there is an excellent 7 minute video on YouTube by Wayne Canning entitled "Drilling and Cutting Stainless Steel" with good tips.

    Superbly done! I would go stainless steel as cheekygeek suggests, and, I can also see traffic cones mysteriously disappearing from road works all over the country....

    2 replies

    Yes that is why I am already planning my next build. All stainless steel, but I might keep my current traffic cone, looks cool!

    I'm sure you are jesting, but traffic cones are relatively inexpensive at any hardware/home improvement store.

    I also believe that I will eventually be going with the Phidgets VINT solution for connecting to either the Roastmaster app or Artisan on a laptop. Kudos to ChingThye for showing his TC4Lite solution (I just lack the necessary skills to build it). For anyone interested in a great article on the use of thermocouples in coffee roasting, check out Rob Hoos' article in Roast Magazine entitled "Our World through a Keyhole" and subtitled "Understanding the Limitations of Thermocouple Readings". It is available as a PDF online if you Google it.

    1 reply

    Yeah there are plenty of solution, Phidgets is indeed a very good alternative.