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Jborks 2kg drum roaster build
Build a 2kg drum roaster with basic tools, readily accessible materials, and at a low(ish) cost.

Hi All!
Long term reader of this forum and first time poster.
I started off roasting coffee in a home-brew turbo oven design that was only able to roast half a pound of coffee. My goal was to build something that could roast >1kg of coffee and after reading this forum for a few years I settled on a drum roaster design.
Specifically, one based on UmMerkur build located here: https://homeroasters.org/forum/viewthread.php?thread_id=6720

In general, I love tinkering with things and working with my hands. It is a good escape from my day job and instant gratification. Having said that, I didn’t want to buy fancy equipment or source expensive materials. This is a hobby after all……. My goal was to build a coffee roaster with parts available at Menards or homedepot and use tools that I had on hand. This ended up working for the most part, other than ordering a number of specialty items off amazon.

A few caveats:
First, I have zero previous welding experience and this made me nervous before starting. However, I found it easy to join metal. The hard part was making it look nice. Please go easy on me if you are a proficient welder! My welds are complete garbage, but functional.
I settled on a flux core welder that was $100 off amazon – YESWELDER 135Amp.
It worked great.
Second, I was limited by sheet metal sizes and gauges available at a big box store. That impacted some of the design (specifically the drum liner) and made for interesting fabrication.

General Design
------------ Drum ------------
-- Harbor Freight 5 gallon air tank
-- Cut to 9” x 11”
-- Volume = 11.47 liters
-- 1/6 rule: 11.47 / 6 = 1.9KG pounds of coffee
-- 5/8" drum shaft
-- "shell" around the outside to deflect heat
-- perforated back to allow air in
------------ Burner ------------
-- 60,000 BTU castiron burner
-- https://www.amazo...ct_details
-- The shape is not ideal but it’s the best I could find
------------ Motor ------------
-- 60RPM 120W 30:1 gear motor
-- 20nm torque
-- https://www.ebay....6621786710
------------ Air Handler ------------
-- Harbor Freight Cyclone Dust Separator
-- https://www.harbo...57194.html
-- I'm really hoping plastic will be OK.
-- There will be some distance for the air to cool as it reaches the cyclone.
------------ Control ------------
-- RaspberryPi
-- Bean Mass thermocouple
-- Air Temp thermocouple
-- homebrew python logging script

Main Tools:
-- YESWELDER 135Amp flux welder
-- Angle Grinder with cutoff wheel and Flap Disc
-- Bench clamp
-- Tin Snips – cutting 22G metal
-- Hand Drill – various bits
-- Jig Saw with metal cutting blades

-- attach thermocouplers
-- Connect burner
-- Connect motor
-- Cooling Tray
-- configure Cyclone Filter
-- Outer shell with insulation

Attached are a few images of the progress so far.
I'll be including the build process in additional posts.

Comments are welcome and appreciated.
Thanks for looking!
jborks attached the following images:
img_8420_small.jpg img_8423.jpg img_8422_jpg.jpg

Edited by renatoa on 01/19/2024 11:54 AM
Frame Construction

The frame was pretty straight forward.
It needs to be long and wide enough to for the drum plus ~2" in the back for air flow into the perforated drum back.
I also allowed ~2" around the top and sides to allow for insulation.

Here is a picture of the mock-up
jborks attached the following image:

First I cut the harbor freight air tank to size and used a flap disk to sand off the paint.
I then proceeded to weld on small tabs which would allow a small gap between the drum and the shell.
The shell is intended to deflect heat and scolding of the beans.
Unfortunately, the big box store did not have a long enough piece so I had to weld two sections together around the drum.
It wasnt pretty... bit I think it should work.
jborks attached the following images:
img_7755.jpg img_7753_1.jpg
Drum Vanes

This was probably the most difficult part.
I settled on a 20 degree angle after reading numerous threads.
The hard part was tracing that angle onto the drum and cutting vanes to match the curvature.
Imagine a half pipe and cutting a vane to fit the curvature; then add a perpendicular twist at 20 degrees.
Rather than use fancy math I simply created a 20 degree template and used a laser to trace it into the drum.
Then I painstakingly cut a vane template until it fit properly and duplicated that shape 8 times.
4 - pushing vanes
4 - returning vanes
1.5" in height
jborks attached the following images:
img_8314_1.png img_8315_1.png img_8389_png.jpg img_8390_jpg.jpg

Edited by jborks on 01/19/2024 12:50 PM
Next up was fabricating the front plate and the various add-ons.
-- Eyesight from a 20W Halogen light bulb
-- Bean Sampler with wooden handle
-- Door locking mechanism. I opted against the typical Ball lever approach.
-- Bean hopper and Exhaust Exit manifold

That is all I have been able to complete to date.
Its been months and months of work.
I'm hoping to finish things off in the next month and get a test batch running.
I'll keep this thread posted!
jborks attached the following images:
img_8422_jpg_1.jpg img_8420_small_1.jpg
Hi and welcome to HRO! Looks like you have been bitten by the roaster build bug! Looking good. I think you will have a nice functional roaster soon and it's great that you have acquired the tools and skills to bring it all together.

Keep us posted and have fun!woohoo
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
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