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A few questions for building a new roasting machine

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  • A few questions for building a new roasting machine

    I have never roasted coffee before and will be within the coming weeks using the popcorn machine. I currently go through 1KG of roasted beans in 2 weeks so roasting 500g on a weekend with a popcorn machine is going to get tedious which is why I haven't started for years.

    But I have an idea for a machine, I've had the idea for quite a while but have a few unknowns. The machine will be gas fired but can be electric, I just figured I might get better control with gas. My main two questions are:

    1. What is the ideal temperature to roast, my oven will hold approximately 20-25 litres
    2. At what speed should the drum rotate? Would 30-60 RPM be efficient?

    I've still got to figure out the most effective way to cool my beans once roasted, but I've got a long ways to go to sort out my design first.

    Any opinions are greatly appreciated.

  • #2
    I dont mean to shine the light away from your original question, however have you thought of roasting with a bread maker and a heat gun? The set up is called a Corretto. There is plenty of info on the site to build your own. On top of that there are many people on here to give you advice about it. I manage to roast 450g of beans in one turn. batch takes between 11-16 mins. It cost me under $60 to set it up.

    All that aside i like your idea of building a roaster, i hear there is alot involved. Dont let that stop you though. i think its a great idea and good luck with it.




    • #3
      Thanks Chris, maybe I'm out of my league, but I'd be un-Australian for not trying to build something. If it flops I'll have the satisfaction of knowing I tried

      My idea is based on taking a beer keg, cutting it right down the middle and hinging the top and bottom. A shaft is inserted through the middle to serve as the axel. A couple of gas burners in the bottom with defusers serve as the heat source. I just have to figure out what sort of cage I'm going to use to contain the beans and how I can eject the beans quickly.

      I haven't heard of anyone making a beer keg roaster, though thought it might be a nice place to start.

      If it flops, which is fairly probable I'll crack on (no pun intended) with the bread-machine/heat-gun approach


      • #4
        I like your attitude towards it, why not give it ago!! I believe there are a few people on here trying things like this. So if you can spend the time trawlling through the forum you might find some valuable information that will help you.

        Good luck with it all hope it goes well, at the end of the days its fun trying new things




        • #5
          I am very new to roasting & in the process of building my own mini roaster too.
          From what I understand & have experienced with a popcorn roaster fitted with a thermocouple probe, temperature ideally needs to be controllable from ambient to ~220 degrees.
          For example, gradually increase the temp over x number of minutes to ~180 - 190 degrees to achieve 1st crack, hold that temp for x number of minutes then gradually increase to to ~210 - 220 for 2nd crack.
          I don't yet know the effects of the drum rotation speed, hopefully one of the pro roasters will provide some advise.


          • #6
            Hi Brett
            Certainly do-able - considering many of the variations we've seen come through here! (search for BBQ roaster :-)

            My only real thought is that if you are looking to do 500g a week (which isn't that much - a breakfast bowl of greens), a keg roaster may be overkill. A roaster the size of the keg, which would require a heat source to match, would be more suitable for roasting 10kg+ IMHO. That's a big week of shots!
            I'd concur with Chris. I personally use a Corretto, which is ideal for 300g-600g batches (I do 350g on a weekend for the week) or you could go to a KKTO (Turbo Oven) - handles up to 1kg per batch. These would seem to be the most suitable for your usage.

            And to keep the aussie spirit alive - both of these can be as simple or as pimped as your tinkering/engineering/size of your shed skills allow :-)

            Have fun!


            • #7
              Give it a go. It would be a uniquely australian idea, just like the coretto and the KKTO.

              Plonk the keg on a stable platform. Knock a hole out of the top somehow to let smoke n heat escape. A hole underneath for fresh air.
              Install either electric elements or gas trains inside.
              On the open side, install a door with a window( this window can be also used as a source of fresh air to enter the keg) to view the beans (you're going to have to shine a torch into it to see them beans goin round n round).
              Middle of the door is the shaft linked to the cage and a handle on the outside for the purpose of turning the thing.
              The other side of the keg, knock a hole out and install a device to hold the other side of the cage a la Behmor.
              You will work out a way of pulling the cage to the door, open the door and then remove the cage to dump the beans for cooling.

              Don't forget the right bean cooler for whatever size batch you will be roasting

              Thought i'd give my 1 cents worth. You can then adjust to suit.

              Certainly the coretto and the KKTO is a good option as DIY projects, and these can roast large enough batches for your requirements, but like you said, you would like to create something that,s unique, and i wish you the best.


              • #8
                Sounds like a plan!

                I have just started roasting on my Weber BBQ in a perforated drum (see picture) and i have discovered:

                1. Drum speed needs to be approx 30-40rpm.
                i have roasted at 5-10rpm and find the beans uneven in color. I have roasted at >60rpm and found i couldn't inspect the beans or hear the cracks.

                2. My drum is 300 mm L X 120mm in diameter.
                I can comfortably do 500g in this size, however as sidewayss as mentioned you need to have the right cooler to cool the beans down quickly.
                ( i am currently undergoing modifications)

                3. With the lid down and background noise, it can be difficult to hear first crack.

                I usually roast @250-270 degrees with the rangehood down, i get 1C @ approx 11-14min, and 2C @ 18-21min.

                I still have improvement ideas going through my head on roasting drum designs, but i am happy with the results so far.
                Attached Files


                • #9
                  Can you adjust the speed using that motor?


                  • #10
                    not that i am aware of,

                    Mind you i haven't opened the guts of the unit to peek at what is inside

                    This is my rotisserie motor ( 5-10 rpm).

                    I am trialing a automatic curtain motor 24VDC ( 60 rpm), With a speed controller to get it down to 30-40 rpm.
                    I finally got my shaft coupling from ebay china ($7) and will attempt to mount it all together soon.

                    There is another guy (fatboy1999) who has used an old windscreen wiper motor, for a setup on a larger drum.
                    Check the post titled "To any BBQ Roasters out there" for photos of his setup.


                    • #11
                      A few questions for building a new roasting machine

                      Do you preheat the BBQ?


                      • #12

                        I preheat for 8-10min.

                        Then place the whole drum unit in the BBQ.


                        • #13
                          Hi guys, thanks for the suggestions and I do apologise for being slow, I've been away and only just returned last night.

                          My idea is to have the keg on its side with a hole for the gas burner at the base and a drum rotating along a horizontal axis. Basically I'd like to create a cute mini version of something like this machine: Toper TKMSX Shop roasters - YouTube (Toper TKMSX).

                          At first I thought the drum should have holes, but the more I see the more I think it needs to be a solid cylinder and rely on direct gas burning on the side of the rotating barrel with a fan pushing heated air into the chamber, is this correct? Though what about the fins in this chamber, any idea on the orientation for them?

                          My biggest unknown now is how to replicate that door to get the beans out of the thing. I may need to invert one end of the keg to make it concave to help keep the beans inside maybe?

                          I've done a bit of searching on the interweb to try find what I need to know, I now roll around in bed thinking of how to do this. I'll try and draw something and post what I am thinking on here.


                          • #14
                            Is this similar to what you are building?

                            Mini Coffee Roaster W600 - YouTube



                            • #15
                              Or you could buy my original.