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Double Barrel Blending Roaster
I've discovered the need for a small batch roaster. Doing small (1/4#) batches in my 1# roaster for blends is not very efficient. And changes the roasting dynamics considerably. A single drum would do, but why stop there, why not build a double drum?

Also, we have another 2 months of dark rainy days here in the Northwest. For sanity's sake - I need a project. Here's what I have in mind. (click for larger view)

The two outer shells will be cube shaped with open walls on the bottom (for chaff removal) and the inside (nearest to the nichrome coils). The two sides pivot independently of each other for pinpointing the optimal dump time for a particular bean. A chain drive in the rear powers the drums. I'd like to have the drums rotate in opposite directions to keep the beans as far from the heating coils as possible to prevent scorching. Small 1 to 1 ratio gears can be added to one of the drums to reverse its rotation.

That's the concept so far.

Can't wait to see this build project progress!!! What an awesome concept!
Using a chain as a rack is a novel idea. Here's a suggestion: The motor is located at the point of greatest chain flex, which means it could skip teeth. Instead, direct drive one of the end sprockets with the motor. It will eliminate any skipping, and save you the price of one sprocket.

Traditionally, as you may know, sample roaster drums are driven with a worm and worm gear arrangement, which allows disconnection like the sprockets you have. The advantage for you is that this makes it easy to reverse direction of one drum provided you can find both left and right worms and worm gears. Try

Alternatively, you could direct drive both drums with individual gearmotors in the same way my sample roaster is driven. The cost of these little gearmotors could very well be cheaper than chains and sprockets. The trick will be finding CW and CCW gearmotors since those shaded-pole motors are not reversible.


Merkle Korff offers reversible. I used them for the gearmotor for my 1/2 lb'r. They can custom configure it for you to take up less of a footprint also. Great company!


1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
You are correct. While it might be more fun to engineer a chain drive, It would more than likely be a total headache to implement it. Simpler is usually better. I'll go with a couple of these little DC gearmotors instead. http://www.surplu...e=electric
That simplifies things considerably while also decreasing the size of the base.
As you can see here:

I'll start scrounging around for parts this weekend.

That looks like your best bet. They have plenty of torque. It also has the advantage of supporting the rear of the drum, too.
Hand Towel Dispenser + Bread Pan + Film Canisters + Martini Shakers = Roaster

I wanted to do more of the fabrication myself. Oh well.
Why stop at just two barrels!
You asked for it Dan!

A quad drum roaster!
Is that what you had in mind?

After considering the various problems the design will pose...It's settled, I'll build it.
I like the idea of having an all-in-one roaster that can roast multiple bean varieties individually. Although they'll all have same time/temp profile, having control of the roast level of each particular bean is more important.

Would you like updates? Or just highlights/problems?

For those who have seen this article before on CS.


JMO but the coolest looking sample roaster. If I was going to build a multi barrel sample roaster I would try and build a copy of this Gothot. Also made in 5 barrel format.

VBM Minimax 2gp, 1gp Reneka Techno, 2 gp la Pavoni Pub, la Cimbali M28, SJ Maz, FB 6kg HM roaster and other stuff
Russ, I was imagining four barrels in a row because your design requires them in pairs since they share a heating element.
Rob - What an epic thread! The roaster is a beauty and a beast.
Dan - I considered that as well. It morphed into the current design from there.

Made a full size cardboard mock-up:

I'm happy with the aesthetics. For the shell I'd like to use aluminium sheet that's constructed like cardboard - not sure what it's called. It might be out of my price range though. Otherwise plain aluminium sheet will do.

In the bottom image you can see how the interior is mostly open between the upper and lower shells. Which essentially makes it one chamber instead of four. The trick will be locating the nichrome heating coils for optimal heating of all the drums. I'm guessing two will be located between the upper /lower drums, and another two on the sidewall of the lower shell.

Look okay?
Russ, I think you are trying too hard to make a universal machine. I'm concerned that you will have problem with getting enough heat up to the top three barrels. And, dumping the large barrel is going to take more effort because of the weight of the extra barrels on top. Here's an idea based on my prediction that you won't be using all four barrels at once. Why not make a convertible machine?

Keep the lower heating chamber and controls just the same. Then, make up two roasting "tops" for it. One has the large barrel and will be a lot like my one pound sample roaster. When you want to try some blends using smaller batches, take off the large barrel and drop on the three little barrels.
Appreciate your input Dan. A more modular design sounds neat.
I share your concern about the upper barrels not getting enough heat.

As a remedy I considered having two separate sets of 1200w nichrome coils. One for the main barrel, and another directly underneath the smaller ones. Which wouldn't be run simultaneously. The controls would be all the same except the SSR output line would have a switch to toggle between the upper/lower coils. Creating two machines in one. Essentially what you suggest, except keeping the current design intact.

As you can tell - I'm a little attached to my current design.

In the end...I concede. Your modular idea is better. Two individual tops sharing a common base makes a lot of sense. They can be optimized better that way.

Back to the drawing board.
I think we're on to something here. Dan's "convertible" roaster idea is a brilliant one.
It makes for a multi-purpose platform that's not only useful for roasting, but also food dehydration, sausage fermenting (another hobby of mine), Etc, All one needs to do is fabricate another "top" for that particular function.

I think we're at version 4.0 of the design now:

The two "tops" can be attached/hinged by a simple sliding latches on the front face.
There will be plug-in sockets for the motors on the side of the base. One each for A/C + D/C power supply for the motors, with a DPST switch to control both. The sockets can be two different types to prevent any mix-ups.

I'm excited!
Are we talking about running any two drums simultaneously? Wouldrequire a lot of skill. What if 1 drum hits a stall? But not the other and they share the same heat?
Bad coffee prevails when good coffee roasters stand by and do nothing.
Three drums. In my experience with "pre-blends" the beans follow roughly the same profile from drying phase all the way to 2nd crack. Some may take a little longer than others, but usually finish within 1 or 2 minutes of the rest. The goal with this roaster is to have control over the final roast level of each bean variety. Independent profile control would be nice, but it's not practical at this point.

Did more material scavenging:
Found the 3rd and final martini shaker at the local goodwill store. Also got a great deal on 16ga galv. sheet. It's a bit heavy, but what the heck, It'll be much more robust than my current roaster, which is a little too flimsy for my liking.

While imagining the final look when sheathed in galvanised steel - This came to mind:

We may have to get creative to conceal the "concrete blockyness" of it.
I like the constructivist look!

Running multiple sample roaster barrels is common practice in cupping rooms and some have more than 3 barrels. Sure it will keep you hopping, but it shouldn't be a problem. My experience with my sample roaster is that I rarely have a stall and it usually because I'm not paying attention during a manual roast. With a PID profile roast it never stalls.
Construction begins!

Managed to cut, bend, and weld the bottom section. Had to reinforce my cheapo bending brake to handle the 16ga sheet.
The base was twisted on the diagonal by about 1/4".

I tried standing on it, then bear hugging and wrestling with it. No go. Then made this little jig:

After a couple of overshoots it ended up true and square.
Probably caused by welding warp. Nice pan, it looks just like the two pans on my sample roaster, one for controls, the other for the heater.
Thought you'd recognise it. ;)

Hope you don't mind. It's simply the best way to go about it. My current roaster has double walled aluminium with fibreglass insulation between to isolate the heat in the roasting chamber from the electronics. After a couple of roasts the wall of the electronics cabinet is too hot to touch. Your design creates a nice air gap between the two boxes. I'd like to take it a step further and use 1/2" stand-offs between the two. Something like this:

The upper tray will be double walled and insulated as well. I'd like to install a slide out drawer on the bottom to help remove chaff. The nichrome coils will be suspended towards the top of that section.

Metalworking is fun!
It's starting to look like a roaster.
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