Coffee

Turbo Oven Drum Roaster.. Quick Release Edition

The newest version of my turbo oven-powered drum roaster has had a few batches under its shiny aluminum belt and has been working pretty great!

My goal with this version was to make inserting/removing the drum as easy as possible. The previous one had me skewering the roaster and drum with the 1/4″ rod which was hard to remove in a hurry at 2C.

Here are some photos of the finished product:

Here are some build photos:

A rundown of parts:

  • Motor – 14W, 30RPM gear motor from eBay. It has a 6mm output shaft.
  • Shaft adapter – 6mm x 1/4″ flexible adapter from eBay
  • Drum – 14cm diameter x 18cm long drum from eBay. It has 1/4″ square holes on its center axis
  • Rod – 1/4″ stainless square rod purchased at Home Depot
  • Bushing – 3/8″ ID x 1/2″ OD x 1″ long bronze bushing from bronzebushings.com

I don’t have any eBay links because they go invalid so fast – but if you search for those terms you’ll find the same stuff very easily.

The Drivetrain
The 1/4″ bolt and 7/16″ socket are really the only the complicated aspect of this roaster. Recall that 1/4″ shaft diameter bolts have 7/16″ heads, hence the 7/16″ socket. The socket has enough slop around the bolt head to allow it to be tilted and pulled off fairly easily – that is the magic that lets the drum be quickly pulled out of the roaster. The roaster wall holds a bronze bushing – this acts as a smooth bearing surface for the bolt. So the order of parts is:

  • Motor
    • Motor
    • Shaft adapter
    • 1/4″ bolt secured into the 1/4″ side of the adapter. This was a longer bolt trimmed to an appropriate length.
  • Drum
    • 1/4″ square rod
    • 7/16″ socket fitted onto the 1/4″ square drive rod.

At first I had the socket J.B.-welded onto the rod, and this lasted for 6 months before the epoxy failed. I think that the heating/cooling cycles of two dissimilar metals caused it to give way.

So I then used a 1/8″ tension pin to hold the socket onto the drive shaft. The flat you see ground onto one side of the socket allowed me to cross-drill the socket without the drill bit wandering all over.

The Drum
The square rod is a permanent part of the drum, it’s locked into place using the drum’s locking screws. The end of the shaft that rides in the hook had a flat spot turned down on my lathe. The little hook is just a piece of flat aluminum bar.

I realize that this is not a “build” and is lacking many details of how exactly I made this thing. This is partially because I am lazy and don’t want to write all that, but also DIY coffee roasters work with the materials on hand so it’s unlikely anyone will ever make one just like this – use it for inspiration!

8 thoughts on “Turbo Oven Drum Roaster.. Quick Release Edition

  1. Hi – Great stuff for a newbie, wanna-be roaster. Can you help me understand your roaster progression? Is it even a progression or just a journey? Is this one the “best,” as in you’ve improved on the way from BM/HG to Stir Crazy to this Turbo Drum? Or maybe this is just the most interesting project to date? I’d love to see some kind of matrix of maybe worst-to-best, easiest-to-hardest (to build), and easiest-to hardest/least-to-most efficient (to roast), to see if I can figure out the sweet spot of effort/quality for me. Or else maybe I’ll just fire up a heat gun, flour sifter, drill unit, and call it good!

    Regardless, thanks for sharing your projects. There’s tons of useful, and appreciated, info here.

    1. Hi Tim, thanks for writing! Here’s a matrix for ya.

      Over the last 10 years my roaster progression has been:

      Heat Gun / Bread Machine
      O.G. Behmor
      Stir Crazy Turbo Oven
      Turbo Oven Drum Roaster

      With each move I’ve tried to increase power output, usability, and roast evenness. So far this drum roaster setup is pretty awesome – I get cheap, off the shelf power from the proven Turbo Oven along with the obvious roast evenness of a drum. Its biggest negative is the difficulty in constructing/finding the enclosure. I suspect that a rotisserie oven of the right size (and insulation) would work pretty well. I looked at a few at the thrift stores and they were pretty big and not insulated. My aim is the minimize the interior volume in order to maximize heat efficiency.

      A basic BM/HG setup is pretty easy to build, and with a good heat gun would likely last a long time. I however, remember it being really loud – the greens rattle around in the pan something fierce.

      The SCTO only works well if you’re able to perfect the stir arm agitation. Otherwise your center beans will crack faster than the edges. But it’s pretty darn easy to build.

      For me 3/4 of the fun in home roasting is building stuff and solving problems. I had it worked out in a spreadsheet – it would be cheaper for me to just buy coffee instead of roasting it myself. I’d highly encourage you to try out your own machine!

      -Dave

      1. Thanks for this reply. I didn’t see it when you first commented! I’ll try to let you know where/when I start!

  2. Hi, I really like your set up. It seems like a large amount of effort went into creating the insulated chamber for the drum. Do you think it would be possible to convert an old crock pot or other ceramic pot for this purpose and still use the turbo oven for heat?

    1. Repurposing a pot would be a heck of a lot easier! My friend Dominick tried this and wound up with excessively long roast times due to heat loss. His experiment inspired my drum roaster and my attempt to make a well insulated body.

      Perhaps one could wrap a stock pot with insulation?

      1. I was thinking of using a ceramic pot like those in a slow cooker. Maybe it would be possible to drill through it with the right drill press and bit.

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