Wobble Disk Coffee Roaster Gets The Beans Just Right

Coffee roasting is an art or a science, depending on who you talk to. Both camps will however agree that attention to detail is key. Many diehard beanheads, as they’re known, will go so far as to create their own roasting hardware to get the job done just right. [Larry Cotton] is one such builder, who has created an elegant roaster to get his brew just right.

The build is based around a wobble disk design. This consists of a round plate fixed at a 45-degree angle to a rotating shaft. As the shaft spins, the disk gently sweeps and agitates the roast, allowing the batch to heat up evenly without burning the beans. It’s a two-part design, with heat gun parts in the base to generate the hot air for the roasting process. The bean basket sits on top, held in place by magnets that also act as a conduit for the wobble disk motor’s power supply.

It’s a tidy build, which allows for accurate roasting and easy dumping of the beans once finished. If you’re a serious beanhead yourself with a few hacks up your sleeve, be sure to let us know! Video after the break.

16 thoughts on “Wobble Disk Coffee Roaster Gets The Beans Just Right

  1. Didn’t the wise man say never to waste counter space on a single purpose device? ? ? …. so can we have a version that does popcorn and hot air reflow too?

        1. Or peanuts, cashews, chickpeas, almonds… and of course acorns, to be prepared for the kind of apocalypse where there’s no coffee, but you inexplicably have ample electricity to heat things with.

  2. Aside from the sourcing of raw beans this is the best way to shorten the time to a week or so between roast and grind-brew. time. I do the daily grind but on shelf whole bean coffee. If this can be marketable coffee will benefit, imagine the aroma.

  3. I like the whole idea, but I have never heard a quiet heat gun. I can’t imagine being in the same room with this thing for 15 minutes while it’s running. It needs a quiet blower…

    1. The process of roasting coffee also involves a heck of a lot of smoke, it doesn’t smell particularly pleasant (think “burning grass clippings”), and there have been studies suggesting it may also cause cancer.

      This isn’t something you’re going to be doing in your kitchen without dedicated ventilation. The noise is the least of your problems.

      There is however and advantage to running the machine a little quieter, which is that you can hear the sounds being made during roasting which turns out to be pretty helpful. A while back I wrote some machine learning tools that can characterize those sounds but I don’t know that it would work very well with a lot of background noise. More details on that here: https://www.home-barista.com/home-roasting/roastlearner-for-artisan-give-artisan-ears-t43169.html

      1. Correct that roasting coffee doesn’t smell like brewing coffee at all. It’s not bad; just different. However, City roast can be accomplished in about 12 minutes with very little smoke; let it go to City+ and you get smoke. Ignore it and you just wasted a bunch o’ beans! Home roasting does require constant monitoring.

  4. I use to roast for a few years. Fresh roasted beans lose their magic flavor after a few days. They are still better that what you buy at any grocery store for a week. A timer is handy, but it’s really the sound of the beans crackling, that signals when to stop the roast. It’s not precisely the same for every batch. Timer just gives you a heads up, to pay attention. I like a dark roast, just a little into the second wave of crackling. I’ve only got it just right a few times, but the beans can come out, with almost a sweetness to them. I just drink black coffee, strong, full-bodied, no added sugar or creme. Usually Columbian or Costa Rican beans.

    Roasting, is definitely an outdoor activity. I don’t mind the smoke, though I wouldn’t want to fill up the house. It’s mostly water anyway. The worst part, is a thin membrane that covers each bean. The beans expand, the membrane splits, and flies off, and everywhere.

    The price of green beans really jumped up, and when my roaster died, I never built another. Think about it occasionally, really liked the coffee, but it got a little expensive, and cutting into some of my other hobbies.

    1. there are some good comments here. i like to think of roasting coffee as very similar to grilling. dedicated appliances, done outdoors, monitored carefully. that’s really all there is to it, except the roasted beans need to be cooled immediately or the little suckers will continue to roast a bit past where you want them.

  5. How closely does the diameter of the disc have to match the diameter of the screen bowl? And does the shaft have be mounted at a precise height above the screen to enable precise contact between the disc and screen or is it not important?

    1. good questions there’s at least 1/8″ gap between the wobble disk and the sifter screen. beans tend to push each other around, so you don’t need close tolerances. sorry for the late reply!

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