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An attempt at a small drum roaster
Here's the story:
I've been an espresso lover for a while now. (I brew drip and press coffee too!) 3 years ago, I wore out my home department-store espresso machine and after much researching bought a Silvia, broken(not really broken....just neglected) but cheap (relatively). I fixed it, added a matching rocky grinder, PID'd it, and modded some more. A few years of practice and I am able to pull some delightful shots (always improving). This last spring I graduated school in Iowa and matched with a training program out here in the NW. I visited Seattle in April to look for places to live, but had to stop by a few establishments in town(vivace, stumptown) to taste everything I'd read about. I brought some beans back to Iowa and discovered for myself the incredible difference that a fresh (3-day-old) roasted bean can make. I was hooked, but I didn't want to order fresh beans online twice a month. I came across and began to think about building my own roaster. I began collecting parts at thrift/junk stores, and from eBay. In July I moved out here and started work. I'm busy as ever, but when I get a few hours to myself I like to wind down by tinkering in the garage...on my roaster!

My wife is probably sick of hearing me tell her of every little bit of progress that I make, so I thought I'd share it with you all, and hopefully bounce ideas around. My design draws from several ideas I've seen here, but none more than rcwarship's 3/4lb build log. I'd like to tip my hat to Jon and say that I admire his creativity, as well as his building skill (roasters and boats!).
muddyfeet attached the following image:

Edited by muddyfeet on 12/15/2017 11:05 PM
Raw materials: The stainless Ikea kitchen-tool holder, and (2) 400w Watlow elements I found at a surplus store. They were straight, and I bent them 1cm diameter larger then the drum. I have no idea what they were from.
muddyfeet attached the following image:
Once again, I tried to mimic rcwarship in making a chassis. I work better with steel than aluminum, though, so it's 22ga flat sheet. In the absence of a bead roller, the "caveman-pounding-when-clamped-between-two-pieces-of-MDF" technique actually did create a nice flanged edge.
muddyfeet attached the following image:

Edited by muddyfeet on 11/17/2009 12:21 AM
muddyfeet attached the following image:
muddyfeet attached the following image:
I did an early test of the elements, to make sure I had enough power......Outside, in case I caught anything on fire! Even with the gaping open hole in the front and a mild wind, the inside temp climbed to over 500degF in 2 minutes. I think that will do, but I'm a bit unsure as it is only 800 watts... I have kaowool that I'll use for insulation over/ around the steel chamber that you can see here- at least 3/4" thick. I'd like to have a copper/bronze sheet on top of that for the final decorative cover, but I'm not sure if I'll be able to afford it. My second thought was to take a grinder and flapwheel and grind a shiny circular pattern on sheet steel before spraying with a clear-coat to prevent rust. I guess I need to get the roaster working before anything fancy, though!

The plan is to control the elements with a PID control, much like my Silvia. I have two of them, and am trying to decide if I want one for both air temp and "bean-mass-temp". Of course only one controller could drive the elements at any given time, but I thought it would be cool to be able to at least monitor air temp and bean-mass temp simultaneously and be able to switch the element control between the two.
muddyfeet attached the following image:

Edited by muddyfeet on 11/17/2009 12:49 AM
muddyfeet attached the following image:
On to the drum, the quintessential piece for a drum roaster, and the bane of many of us home-builders. I cut the 3/8" holes out of the drum (like Jon did...) and lined it with perforated aluminum I bought at Lowes. That part worked great. I've had trouble with the vanes, though. Initially they were straight across, three pieces of angle-aluminum spaced axially around the drum. My plan for a dump mechanism was to just tilt the entire drum-assembly up and use gravity to empty the perfectly-roasted (im sure...) beans. The plan changed about 3 weeks ago, though, and I wanted a stationary roaster. That meant I had to angle the vanes to dump when the door was opened---much more difficult than I thought. My first throught was to line the drum with a spiral of aluminum rod, much like the hottop roasters. I failed misreably at trying to bend a perfect spiral, though, and the only rod I could find at the time was 1/4"...way too thick. I didn't even take a picture.
muddyfeet attached the following image:
Here's a video of the straight vanes stirring 1lb of beans at 60 RPM. It worked well, but won't dump without a good 20degree tilt.
Edited by muddyfeet on 11/17/2009 12:09 AM
The next idea was to create my own curved vanes, like i've seen in other posts here. I liked the angle-aluminum and wanted to use it again, but the geometry of making the compound-bends required to match the inside of the drum was insane. After several days of trial, error, more trial, slight progress, a few beers, more error, and I finally got some sweet twisting vanes. 3 almost-matching ones. ...and a burn on my thumb from hot aluminum.

The vanes worked great. So great, in fact, that they piled most of the bean mass against the door and easily pushed it open. I can add more weight to keep the door shut, but the real problem is the crappy thick pile of beans that won't roast evenly at all. The solution, of course, is an interior set of vanes directing the beans toward the BACK of the drum, like the pro-roasters have. After my frusterations with the angled vanes thusfar, I wasn't about to attempt anything too fancy. My solution was to create a short set of interior vanes to direct beans rear-ward, away from the door. I haven't tested it yet, but it should pull beans away from the door and send them back along the drum axis, only to fall to the outside of the drum and once again migrate toward the front. Combined with the drum rotation, this back-and-forth stirring should create an even roast, and allow beans to be dumped from the drum when the door is opened at the end of the roast.
muddyfeet attached the following image:
The motor (my 2nd) is a 115v 60rpm gearmotor ordered from Surplus Center. The first one I tried using was one of those little synchronous clockmotors! I really didn't have a clue about torque! That's why my welding looks so bad back here...I had to cut out the old motor mount and weld in a new one. This motor works great, but I reviewed the specs for it, and it's officially only rated for "intermittant duty". I'm fearful that it's going to meltdown in the middle of a roast sometime, but it works so well I want to keep it running until then! I'm going to keep it as cool as I can.
The drive is pieced together from a few random things. I have an off-center coupling from surplus center that I broke trying to drill-out the diameter a bit larger... I "fixed" it with a piece of 1/4NPT air hose fitting that I cut to size and tapped for a setscrew. It fits the motor shaft well. With a heavier-duty (larger) motor I probably couldn't mount it directly to the axis and would have to transfer power with chain-and-sprockets.
I suppose I could jump to a DC motor for big power in a small package, but we'll have to see.
muddyfeet attached the following image:

Edited by muddyfeet on 11/17/2009 1:37 AM
Last Sunday I spent the entire day in the garage, watching the Green Bay Packer game and making the front of the roaster. It was a cooler day, though, so I left Silvia on and drank lattes all day long. (well, maybe a beer or two)

The front is thicker 18ga steel, with 22ga bent-and-welded into a triangle chute for the hopper. The dump chute on the bottom is 18ga. The door is 22ga steel bent so that glass can be slid in. I sourced the glass from a cheap halogen worklight from a thrift store. It's not ideal that it was a rectangle shape, but It should be able to tolerate the heat. This entire front-assembly bolts onto the chassis so It can be dissassembled to remove the drum if needed. The reason that everything is steel is that If I need extra tabs, mounts, or special-shaped pieces I can just weld them on. I have a few "magic" aluminum brazing rods that I've used to repair various aluminum things before, but I just can't imagine that it's as strong as steel. I'm an amateur welder at best with a small machine, and have nowhere near the skill needed to weld aluminum or stainless.

Along with the light theme, I found a cheap ($7) bare-bones outdoor flood light at Lowes... cutting everything else away, the shroud makes for a perfect Hopper! and it screws on and off too! Here's a video demonstrating the loading and unloading (no heat yet). This video was taken at the time of the the curved-vane-drum(no double-curved vanes yet), so you can see the big bean mass pushed up against the door. I took the handle off my angle grinder and used it to temporarily weight the door and keep it closed.
Edited by muddyfeet on 11/17/2009 2:36 AM
Wow, what a great project, and terrific documentation! Thanks for taking the time to share your project with us. Keep us posted! -bill
Really like your wrap around heating elements! Where did you find them? Should give a more even heating of the drum area.
Ed B.
DreamRoast 1kg roaster, Levers, Hand Mills
doc, I'm really impressed. That is the first really scratch roaster i've seen. I've built several but ususally combinibg modified parts. You made me proud to be an American home roaster.................
When finished send it to China get it mass produced so we can afford one. Great job.
Jim Lyon
Jim's Coffee Beans
I agree with everyone else - nice work! You make it look too easy! :Clap:
Holy moly, kmichaeldoc! Your genius is showing! ThumbsUp

That's a flat-out homerun you knocked out of the park!

How is the motor attached to the back of the drum?

Breathless, speechless,
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
It looks so easy in the pictures. I wish I could do something like that Congrats on your fine roaster. Any chance of your selling them
May the Force be with your cup
Thanks for the comments, I'm glad you approve! Take note though...I have yet to roast any beans, so we'll have to see how everything works out!

The axel at the rear of the drum is a piece of 10-24 threaded rod...yes, I know that any zinc plating can make some bad gas, but I plan to combat that in two ways. 1) Minimize the amount of zinc plated hardware in the roast chamber- it's so useful and readily available at the hardware store, but not oprimal material at tempreature, i know... for that matter, any welding in the interior of the chamber will need to be minimized, as I know that there's some toxic metals in the welding wire. 2) For the few pieces of hardware that I do use, I plan to "pre-roast" any zinc out of them with the MAPP gas torch before the roaster is operational. Do you think that will work? Any way, the amount of zinc plating exposed to beans will be minimal enough where I'm not going to worry about it.

So there's a tee-nut that will be riveted to the back of the drum (is temporarily bolted right now (with zinc-plated bolts)). The threaded axel rod fits in here and can thus be screwed in- or out for length adjustment. It's locked on to the tee-nut with another nut tightened down against it.
muddyfeet attached the following image:

Edited by muddyfeet on 11/18/2009 12:44 AM
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