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My own D.I.Y. Turbo Oven coffee roaster

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  • My own D.I.Y. Turbo Oven coffee roaster

    Started building this yesterday and finished today at around noon.  However, Ive spent quiet a few hours in planing the execution to suit my particular application.  As you can see, Ive used a terracotta pot as the centre piece for good thermal retention.  Underneath I had fabricated a sub-frame to house the agitator engine, which happens to be an automotive power window motor.  Power supply comes from a battery charger thats been flicked to the 6 volt setting to reduce agitation speed.  The hard part for me was do I put the motor inside the pot to drive the agitator, or do I make an extension to have the motor outside to isolate it from the harsh heat!  The second option was my choice of path, but that meant it needed a long shaft and a means to support the shafts ends to prevent sideways thrust.  

    Luckily I had an old XF Falcon distributor which I was able to locate it inside the pot.  The stainless steel bowl sits on top of the distributor and is fastened to it for stability.  One headache was making a coupling to link the motor to the distributor drive - after about an hour cursing I made a coupling that allowed a little bit of freeplay between the joints to compensate for any possible misalignment - in doing that I minimised any extra loading to the motor which would have otherwise caused an increased current draw.  Fully loaded with 1/2 a kilo of beans the motor draws around 2 amps @ 6 volts.

    Even though I have a temp probe I did not bother to use it on the maiden run as I just wanted get it done.  Anyway, the ovens thermostat was working as it should, cycling the heating lamp on and off at around 210/220c.

    First crack was around 8 mins, and the 2nd was around 12.  The end result is pretty good, but noticed some beans started going dark rather quickly.  Thanks to Andys "starter pack" I roasted the 4 different origin beans, but I suspect that was the reason the roasting was not as even I hope for, but it is what I kind of expected as the beans varied greatly in size.  Next time Ill separate the batches to roast them individually.

    The turbo oven kind of scares me with its UFO bright light effect, and I was worried about blowing up something.  But in the end everything went very well.  I drilled holes into the bowl for some chaff removal, but the chaff that was flying around due to the air circulation was so big that you cannot drill big enough holes to eliminate all of the it without loosing many of the beans.

    When the roasting was done I initially had just the fan of the oven running but was not sure if it was good enough to cool the beans.  So I tossed them into the colander and shook them to cool off.  Next time Ill turn on the compressor  to blow the heat away from them quickly.

    And yes to your question, I did sample them with my Lelit and was pleasantly surprised.  Very smooth tasting with a light coloured crema (not dark as many would prefer).  The beans are now in vented bags.  Thanks to all for contributing to this site and especially to Andy for the quick delivery and for the rustic looking calico bag to hold the green beans.

  • #2
    Re: My own D.I.Y. Turbo Oven coffee roaster

    That is such an awesome setup. Thanks for posting the piccies up. Has given me "ideas" .


    • #3
      Re: My own D.I.Y. Turbo Oven coffee roaster

      Originally posted by 7C5E52525052585F5E310 link=1292121312/0#0 date=1292121312
      I drilled holes into the bowl for some chaff removal, but the chaff that was flying around due to the air circulation
      Nice flowerpot roaster youve got there...

      Try drilling or cutting with a dremel, a ring of holes or slits about 2-3 inches up from the bottom of the pot. If you choose a level above where your beans are sitting, the chaff will get blown out and the beans will stay in.

      Have a look through some of the early pages in the KKTO beta testers thread and you should find some pics showing the chaff slits.


      • #4
        Re: My own D.I.Y. Turbo Oven coffee roaster

        When I removed the bowl I found about a 1/4 of a cup of chaff - much to my surprise.  So I am quite happy with that and will keep it as is for now.  The agitator was quite effective, except some beans decided to go for a ride on top of it (eventually they were knocked off by other beans).  So Ill eventually make a vertical plane agitator as opposed to the current horizontal plane.  

        But the total cost has come under $50 including the turbo oven as the pot, battery charger and distributor I already had.  The power window motor was to be thrown out by my mechanic friend, so that was free.  The bowl was 4 dollars and sits just inside the T.Os metal ring.  The laminated particle board off cuts were $4 as well.

        Some further improvements will be made, but for now its looking good from my end.  Its not flash or shiny as some of the others, but I think it has the edge with thermal insulation and efficiency helped by the terracotta pot and the wide bowl which goes out to the full edges of the glass lid, maximising the TOs swirl effect


        • #5
          Re: My own D.I.Y. Turbo Oven coffee roaster

          Superb Moccacino.... [smiley=thumbsup.gif]



          • #6
            Re: My own D.I.Y. Turbo Oven coffee roaster

            Heres the page with the slits pic....



            • #7
              Re: My own D.I.Y. Turbo Oven coffee roaster

              Thanks Borat (and also to those for the kind comments) - after seeing the pics Ive just twigged at the slits you were talking about.  Good idea as theyve long enough to allow largish sized chaff to slither through, but tight enough to prevent whole beans through.  I would place the slits higher on my bowl where the curvature begins as that is where stiffness is at its most.  If I were to elongate the existing holes I think the bowl would weaken considerably as its quite thin.

              The bowl is a Durmaz brand purchased at a Southland 2 dollar shop.  The  terracotta pot is from Bunnings.

              Heres some pics to help anyone wanting to get the same key parts, as sourcing the right sized bowl is not easy.


              • #8
                Re: My own D.I.Y. Turbo Oven coffee roaster

                Very nice Moccacino, I saw exactly the same terracotta pot yesterday at the local hardware store and thought ‘that would make a good roaster’, and here is one!
                Does the TO move about on top of the pot at all?
                How hot does the outside of the pot get?
                Did you pre-heat, and if so how hot?
                That Pot would be about 10 litres, which would be about ideal volume.
                I especially like your battery charger connection terminals, simple and reliable.
                I’d love to see how the distributor fits into the drive mechanism.

                Good work,  BB.


                • #9
                  Re: My own D.I.Y. Turbo Oven coffee roaster

                  Thanks BB. The idea of the terracotta pot came from someone else on this site who used one to reduce heat loss within the stainless steel pots.  Like you, I saw the pot and thought "roasting coffee"!  Only this time it was at my gfs house and she said "just take it".

                  Theres no preheat time - I put the beans in from cold and just turned it on.  The terracotta pot got very warm, but cool enough to pick it up straight after roasting to pour the beans into the colander.

                  The TO lid sits on the perimeter of the pot - not in and not out.  The bowl sits in and a little low in the pots perimeter, but sits inside the TO lid.  By sitting on the distributor, the bowl protrudes above from the pot about 3 mm but is a little wobbly as its so thin.  But once the TO lid is on the pot the bowl gets pressed into alignment.  The end result is a good seal without any silicone tubing.

                  The base of the terracotta pot has a large hole that only needed minor filing to allow the distributor to fit through.  The distributor sits on top of (and screwed to) a piece of the particle board to get the height right.  I then drilled 2 holes in the base of the pot to screw and fasten the inner and out particle boards together

                  The distributor is from a Falcon, but now Im not sure which model - It could be anything from an unleaded XF, all the way to an EL (but not an EF as they had a coil pack instead).  Ill take some detailed pics to help get you over the little hurdles that stumped me when they popped up.  I had to drill and tap a thread into the top of the distributor to fit the Allen bolt.  But you can just drill a hole through the side of the shaft to fit screw and nut to clamp the agitator.


                  • #10
                    Re: My own D.I.Y. Turbo Oven coffee roaster

                    I successfully pulled a good shot with my first roast by tampering a little harder - to me it looks pretty good, and it flowed out of the portafilter beautifully thick and rich.  The flavour after less than a day from roast is very smooth, full and with absolutely no bitterness, but maybe on the mild side.  But for me its very satisfying and look forward to see how it improves over the incoming days.