Maybe some this for the rotisseries. That might be a good method for me. We have a toaster oven with rotisserie option. I will have to check the dimensions.
Coffee Bean Roaster Rotary Stainless Steel Grilled Cage DIY | eBay
Here is an interesting article by Larry Cotton who I see mentioned quite often when searching for DIY roasters.
My 15-Year Quest to Make the Ultimate DIY Coffee Roaster - Make:
There are a lot more options for those grilled cages on Amazon.
After thinking about that rotary cage in a toaster oven, I was wondering if that would be too much of a fire hazard with the chaff? A friend suggested covering the cage with aluminum foil, but then you couldn’t see how the roast was doing.
My experience is that you really don’t need to see it at all, we go pretty much entirely by hearing and time.
I think you’d want some method of extracting the smoke from the chamber and then you’ve basically got something that looks like the Behmor roasters, so I think it should work.
I went to a place in Edinburgh that specialised in somewhat more experimental coffees and had a couple of naturally processed ones that had been through secondary fermentations. It’s crazy how different again that can be from single origin. Doing that would be an interesting project, for sure.
You can also use the flesh of the coffee cherries to make a tea called cascara. I’ve been meaning to do that with some of the beans we’ve grown, but I bet that could also be fermented into alcohol, too…
Looks like the toaster oven might not get hot enough to work well. Mine only goes to 450f or 230c
Here is an article about it.
Roasting Coffee in a Rotisserie Drum in a Toaster Oven Air Fryer - Sweet Maria’s Coffee Library
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I think the difference there is they’re talking about an air fryer which is basically a convection oven… Lots of people have used convection ovens for roasting, I think you just have to bypass some of the temperature controls and limit the airflow a bit, much the same as you need to do with a popcorn popper.
I’m honestly not even ‘that’ sure how a toaster oven works internally as they’re not really common in NZ as far as I’m aware, but from what I’ve seen of people converting them into reflow ovens, they should perform similarly to the Behmor if they’ve got exposed elements.
The oven in that article looks almost identical to the Behmor housing, so I think they’re probably starting with that design and have modified from there. The differences are the chaff tray, which is no big deal, the exposed quartz elements and reflectors, which would be a pain in the rear, the drum has internal ‘fins’ to stir the beans and then there’s an additional element in the exhaust to fully combust the oils in the smoke to make it less smokey and acrid during roasting.
I think I see what they mean, though, it’s blowing hot air ‘past’ the drum rather than through the bean mass, so it’s not behaving the way the popcorn popper or heat gun + dogbowl approaches are. It’s also not behaving the way a Behmor does because it’s hot air based rather than an IR element.
Oh, and while I remember, the guy who I used to buy my green beans off had built a DIY 1kg fluid bed roaster. He was using sections of ~8-10" OD thin wall stainless steel tube that stacked on top of one another. The middle one had mesh in the bottom to make a kind of basket. The bottom one had legs to become a stand and then the top one was basically just a long chimney. He had screwed handles to each piece. He had an LPG/propane burner at the bottom and a blower fan to provide the airflow. I think he might have had a couple of thermal probes poked in through holes to sit in the bean mass and intake airflow, but I can’t quite remember.
That could be another approach to consider, along with a couple of cheap heat guns and some form of combiner at the bottom.
I was thinking about one of these not a toaster oven. It might be possible to hack the heater controls to regulate it better as well.
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Using the Blackstone the other day, I thought dang would this roast coffee!!! 
If it doesn’t already have on, the rotisserie oven could probably be retrofitted to use the same sort of PID controller commonly used for toaster oven reflow projects, but it might need an additional “channel” if one wanted to control a rotating basket containing the beans.
While I don’t drink coffee, my internal amateur engineer is wondering what the proper sensors would be to detect the stages of roasting. Is it sound? Is it humidity changes (moisture released from the beans then “baked” off)? Is it a simple, predictable temperature profile (similar to solder reflow)?
My understanding is that there are a few reasons to avoid PID controllers, such as the thermal mass changing significantly as the beans heat and lose water weight, also any controller that isn’t fast-switching the element can cause it cycle while you want the temperature of the beans to only ever steadily increase.
The DIY method is to listen for the sounds of the beans (1st and 2nd crack) and profile using that information, element power and time. A common approach might be to run full power for 5 minutes, reduce to 80% power, listen for 1st crack, wait a further 60 seconds and then dump to cool.
The commercial/professional method is pretty much entirely time + temperature based, using element power as the control. Most commercial roasting, at least for specialty coffees, is done in batches in a drum roaster where you’ve got a large drum with a lot of thermal mass getting heated, then the beans getting tossed around within that. Probes give bean mass temperature and drum temperature and you’re working to make those follow a specific path, focusing on hitting the same temperature points with the same ramp rates.
We’re visiting my wife’s brother and I did one roast with the popcorn popper yesterday to show him how easy it was. He’s going to start looking into getting a roaster now. When I get home, I might take the nastalgia popper to see how it can be modified. If I accidentally break it, might prompt me to get a real roaster.
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I took the Nostalgia Air Popper Popcorn Maker partially apart today by taking 6 screws out. 2 slightly longer screws hold the bottom base to the inner part & 4 screws under the rubber feet hold the bottom base to the outside top. The little rubber feet just pried out with my fingernail. I started to disconnect the 2 wires to the switch, but they were not coming out easily & I did not want to accidentally break them. One of the white wires coming through the black base connects to the bottom connector on the white switch. Here are the photos I took. Not sure I want to tackle modifying this. I am leaning towards the flour sifter heat gun method if I go DIY.
I decided to go ahead and order a heat gun & an 8-cup flour sifter yesterday. It will be here Thursday. I will probably just set it up for manual turning to begin with & just make a platform to put the sifter on. I have a lot of V-Slot, so will probably use that for the structure of the platform. I would like to make it a non-destructive build, so I don’t really modify the heat gun or sifter.
Here is what I ordered.
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Parts came today. I have been thinking about how to drive the turning of the handle without dismantling it & am thinking a planetary gear might work if it does not wobble on me. I drew the planetary gear in openscad since there is a very good script to easily do that & I drew up a model of the flour sifter in fusion 360. Think I have some M6 set screws & would use that to tighten the crank knob to one of the planets. Currently I have it at 9mm thick but making it thicker might make it wobble less. It is about a 3.5-hour print like this.
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The 1st test of the planetary gear system for turning the handle worked better than I expected. Here is a video of the 1st test. You might get a little laugh near the end of the video.
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That 1st one is made of alloy steel & not sure how well that would handle the heat over time. I would prefer stainless. That 2nd style was mentioned earlier in the thread but seems a toaster oven I would use it in does not get hot enough to roast coffee.
I am going to go further down my current rabbit hole since I am part way down it already.
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