A DIY coffee roaster with part callouts.

Follow The Red Ball Wobble Disk Roaster To Coffee Excellence

If you’ve never considered roasting your own coffee at home, you may be surprised to learn that it can be done in a few minutes with a regular popcorn popper and not much else. After all, you only really need two things to roast coffee: heat, and constant agitation to distribute that heat evenly. While the popcorn popper provides both, it’s easy to end up with semi-uneven roasts, probably because the beans are mostly just spinning around and not being tossed as well as they could be. Eventually, one might want a more advanced machine, and that’s where something like [Larry Cotton]’s latest wobble disk roaster can step in.

For starters, this machine roasts more beans than the average popcorn popper in a single throw — the maximum is 350g, or just over three-quarters of a full pound, which is way more than the average popcorn machine will hold. It essentially consists of a heat gun pointed upwards at a sieve full of green coffee beans that are being constantly pushed around by a motorized wobbling disk. As the heat blows, the large metal disk does figure eights through the beans, keeping the heat nice and even. So where does the red ball come in? It’s at the bottom, keeping the flying bean skins (chaff) from entering the heat gun’s fan motor.

Toward the end of the short video after the break, you’ll see a diagram showing all the parts of this roaster. If that’s not enough for you, here’s a build guide for a previous wobble disk roaster (PDF) that should be quite helpful in building either version.

If you want to see some of Larry’s previous machines, we’ve got ’em. And then you can let Hackaday Editor-in-Chief [Elliot Williams] tell you all about roasting at home.

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Wobble Disk Coffee Roaster Looks Good In Wood

If you love coffee, you probably make it yourself at home most of the time using beans from some hipster coffee shop where the employees have full-sleeve tattoos and strong opinions. Maybe you even buy whole beans and grind them right before you use them. If you want to go all the way, you gotta roast those beans yourself. There are various ways to go about it, like repurposing a hot air corn popper. If you’re [Larry Cotton], you buy heaps of green beans and keep building wobble disk roasters until you’ve achieved DIY perfection.

[Larry]’s latest roaster boasts all-wood construction with no metal brackets or housings in the structural parts. This is good because you’re less likely to burn yourself on anything, and you aren’t sinking heat away from the beans. Nothing should get hot except the sifter, the beans, and the stiff triangle of wire that holds the heat gun nozzle in place. Once the roasting cycle is complete, [Larry] just shakes out the beans onto an adjacent screen that’s situated over a fan so they can cool off.

Unlike some of [Larry]’s previous designs, this one uses an 8-cup flour sifter situated over a heat gun. A battery-powered screwdriver drives the wobbling disk that churns the beans and helps them roast evenly, and a wooden arm holds down the power button. We love the simplicity of this machine, and think wobble disk roasters are mesmerizing to watch. Check out the video after the break to see it in action and learn how to build your own.

There’s more than one way to roast beans, and one of them is even officially sanctioned by Hackaday editor [Elliot Williams].

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How To Cobble A Wobble Disk Roaster Together

As with anything else, once your knowledge of coffee expands, the more attractive it becomes to control as much of the process as possible. Buying whole beans and grinding them at home is one thing, but you’re not a real coffee geek unless you’re buying big bags of green beans and roasting them yourself in small batches.

[Larry Cotton] has made an even more portable version of the wobble disk roaster we saw last summer. Beneath the housing made of aluminium flashing is the guts of a $15 Harbor Freight heat gun pointing upward at a metal strainer. A large metal disk mounted at a 45-degree angle to the spinning axis tosses and turns the beans as they get blasted with heat from below. [Larry] used a 12 VDC motor to run the wobble disk, and an an adapter to change the heat gun from 120 VAC to 12 VDC. This baby roasts 1½ cups of beans to city plus (medium) level in 12-15 minutes. Grab a cup of coffee and check it out after the break.

Roasting beans isn’t rocket science. Even so, there are some things you would benefit from knowing first, so here’s our own [Elliot Williams] on the subject of building DIY roasters.

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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.

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