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Home Made Hot Air Roaster 0.5 - 3kg

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  • Home Made Hot Air Roaster 0.5 - 3kg

    Excuse the repost from homeroasters but in case anyone over here is interested, i though i'd share the roaster i made myself today.

    Its a (up to) 3kg hot air roaster based on RoasterRob (from homeroasters) design, with a few of my own tweaks.

    The roast chamber i've got at the moment is waaaaay too big for what i want. Its probably more of a 3kg+ type of size (150mm square). I'll remake one tomorrow that is more like 100mm square of even smaller.

    I'll try to summarise the info that will be of most help to others:

    - Folded 2mm mild steel construction (probably would use 1.2mm next time)
    - 6mm flanges
    - Ametek 119625 2 stage tangential blower
    - 7kw Primus burner
    - Lathe turned bung to connect the burner through the base plate to a gas line. M8x1.0 male thread one end (for the primus burner), m16 thread on the outside to thread through corresponding m16 hole in base plate and locked off with an m16 nut, and a 1/4" BSP thread on the bottom for the gas connection. This way the burner and burner connection can be fully removed.
    - Cheap triac controlled speed controller (doesn't dim enough though, had to add an intake restrictor)
    - Silverline 0 - 4 bar pressure regulator


    Burner bung (ended up remaking this but didn't take a photo)


    Looking down the roast chamber


    Finished product:


    Beans lofting


    Brown!


    Prices, models and supplier (probably only handy for fellow aussies)


    Solidworks model (and section view)



    Youtube video (literally the first time using the roaster, i'm aware of the multiple electrical hazards )
    Hot Air Coffee Roaster - YouTube

  • #2
    Awesome. That a spouted bed roaster or fully fluidised? I am in the middle of making a much smaller electrically heated and pid controlled prototype of a spouted bed roaster.
    May I ask, is there a reason you didn't go with a circular chamber and what the dogleg in the air feed line is for?

    Comment


    • #3
      Incredibly exciting thread... I'll keep an eye on this one.

      Comment


      • #4
        Originally posted by MrJack View Post
        Awesome. That a spouted bed roaster or fully fluidised? I am in the middle of making a much smaller electrically heated and pid controlled prototype of a spouted bed roaster.
        May I ask, is there a reason you didn't go with a circular chamber and what the dogleg in the air feed line is for?
        I guess its a spouted bed? If you have a look at the video it should make sense. I went with a square design because it was easier to fold up a square section than it was to roll a round section :P I'm thinking of making a circular based one from stainless with a sheet metal roller next.

        The dogleg in the blower supply line is to keep the air feed below the level of the burner (so as to not snuff it out), and to keep the motor above the legs of the roaster. The CAD model is a bit outdated as its still showing when i had it designed for a flow-thru blower.

        A small PID controlled version sounds good, should be easy to setup and allow you to use off-the-shelf pipe sections instead of making them from scratch.

        Comment


        • #5
          Group buy on spun stainless cones?

          Comment


          • #6
            Originally posted by MrJack View Post
            Group buy on spun stainless cones?
            FYI Air forced into a cone at the narrow end travels along the sides of the cone and not in the middle.

            To see this in action light a match and hold the lit portion in the middle of the large side of a funnel and blow in the small side. No matter how hard you blow you can't put the match out.


            Java "Fun with Physics!" phile
            Toys! I must have new toys!!!

            Comment


            • #7
              Originally posted by MrJack View Post
              Group buy on spun stainless cones?
              I'm happy to make a few for fellow roasters.

              Originally posted by Javaphile View Post
              FYI Air forced into a cone at the narrow end travels along the sides of the cone and not in the middle.

              To see this in action light a match and hold the lit portion in the middle of the large side of a funnel and blow in the small side. No matter how hard you blow you can't put the match out.


              Java "Fun with Physics!" phile
              Thats true but in this case its turbulent air coming through any kind of diffuser plate, so it won't behave as if it was unrestricted and non-turbulent airflow.


              Does anyone know where to buy tiny drill bits? I think the jet on the burner is a bit too small, i want to drill it out to 0.3mm or so.

              Comment


              • #8
                Originally posted by Mischa View Post
                Does anyone know where to buy tiny drill bits? I think the jet on the burner is a bit too small, i want to drill it out to 0.3mm or so.
                Element14 have 0.3mm search on their site for Twist / Jobber Drills, 0.3 is then in the "filters"

                Comment


                • #9
                  Originally posted by Javaphile View Post
                  FYI Air forced into a cone at the narrow end travels along the sides of the cone and not in the middle.

                  To see this in action light a match and hold the lit portion in the middle of the large side of a funnel and blow in the small side. No matter how hard you blow you can't put the match out.


                  Java "Fun with Physics!" phile
                  A fun phenomenon resulting from low flow and a very short duct (the pingpong ball experiment is fun too).
                  Add a section of straight piping onto the outlet, increase the upstream pressure/flowrate, use a flow straightener or even just fill it with small objects (i.e. beans) and the behaviour will likely be somewhat different.

                  Comment


                  • #10
                    Originally posted by Mischa View Post
                    I'm happy to make a few for fellow roasters.



                    Thats true but in this case its turbulent air coming through any kind of diffuser plate, so it won't behave as if it was unrestricted and non-turbulent airflow.


                    Does anyone know where to buy tiny drill bits? I think the jet on the burner is a bit too small, i want to drill it out to 0.3mm or so.
                    Could you use carburettor jets instead perhaps?

                    Comment


                    • #11
                      Originally posted by MrJack View Post
                      Could you use carburettor jets instead perhaps?
                      possibly, but when i've searched for them they don't seem to give you the actual size of the jet? it seems to be all manufacturer specific sizing. I also thought about using a MIG contact tip but the smallest they go down to is 0.6mm probably in the future i'd be better off just using a sievert burner as they seem to have the greatest range of burners.

                      Comment


                      • #12
                        They work on flowrate from memory.
                        You could probably confirm with the manufacturer or perhaps just measure some at a motorcycle shop?

                        Comment


                        • #13
                          Originally posted by MrJack View Post
                          ...or even just fill it with small objects (i.e. beans) and the behaviour will likely be somewhat different.
                          Yeah, I'm looking forward to seeing what kind of a movement pattern will emerge in a 3kg capable cone. I'm thinking maybe a cycle with the beans moving up in the center and down next to the cone.

                          We may never find out though as Mischa said he was thinking of making circular ones, not conical shaped ones.


                          Java "New toys are so much fun!" phile
                          Toys! I must have new toys!!!

                          Comment


                          • #14
                            Could you use carburettor jets instead perhaps?
                            Originally posted by Mischa View Post
                            possibly, but when i've searched for them they don't seem to give you the actual size of the jet? it seems to be all manufacturer specific sizing....
                            Most carby jets ( Delorto, Mikuni, etc) are calibrated in "numbers" ..EG: .# 50, #85, #105, etc.
                            But those numbers are actually hundredths of a millimeter.
                            so a # 50, is actually 0.50 mm diameter.
                            A good carby specialist should be able to sort you a #30 ..but good carby specialists are hard to find !
                            The threaded fitting may be a bit different to gas fittings though ?
                            Tip.. the common Honda 6.5 hp industrial 4 stroke uses a #28 main jet !

                            PS.. nice project,
                            Is there an optimized design for a 1kg version ?

                            Comment


                            • #15
                              Originally posted by blend52 View Post
                              Most carby jets ( Delorto, Mikuni, etc) are calibrated in "numbers" ..EG: .# 50, #85, #105, etc.
                              But those numbers are actually hundredths of a millimeter.
                              so a # 50, is actually 0.50 mm diameter.
                              A good carby specialist should be able to sort you a #30 ..but good carby specialists are hard to find !
                              The threaded fitting may be a bit different to gas fittings though ?
                              Tip.. the common Honda 6.5 hp industrial 4 stroke uses a #28 main jet !

                              PS.. nice project,
                              Is there an optimized design for a 1kg version ?
                              Thanks for the info!

                              The two sections just sit on top of each other, so i can take this roast chamber off and plonk one on thats a different size. I roasted 1kg in this roast chamber yesterday, however it is on the large size for that amount of coffee. I'm thinking that 80 or 100mm square would be better for 1kg, I'm planning to make one of that size tomorrow probably.

                              Comment

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