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Thread: My new No.1 Coretto (Mk3)

  1. #1
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    My new No.1 Coretto (Mk3)

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi CSrs,

    Heres the story of my third Corretto.
    Fortunate that a friend updating to a “Behmor” made me the gift of his near new Breville BB400 Corretto, shortly after the electric motor failed on my own low Km, Corretto (No1, Mk2, a modified Sunbeam Cool Touch Bakehouse) so back to my original little old Tiffany Corretto (Mk1) but started planning mods for John’s big new Breville Corretto.
    Finally the new Corretto (No.1 Mk3 Breville BB400) has been commissioned with an initial 833g. of green Ethiopian Kuza and subsequently 1000g. of green Ethiopian Gambella Naturals.
    After observing beans mixing in the bread chamber, I was concerned that mixing may be inadequate, so fitted a new cogwheel to the paddle drive to slow its rate of rotation. This mod required moving the motor position and fitting a longer drive belt. After observation of the mixing I’m now content that mixing is adequate.
    Removed the electronic control circuitry as with Mk1 and 2 but this time I planned to mount some additional features onboard.
    The oven chamber was insulated with fibre glass wool.
    A new lid was constructed from stiff aluminium sheet and heat gun port and windows were cut in it and the window glassed.
    An aluminium half cover was constructed for the bread chamber also incorporating a partition subdividing the bread chamber in half above the stirrer paddle level.
    An exhaust port was cut in the floor of the BMs oven chamber and a salvaged part was adapted as a manifold to carry the displaced hot gasses through the side of the BM (hoped to vent a quantity of chaff with it).
    A simmerstat salvaged from an electric stove was fitted to control the BMs heating element circuit.
    A 12VDC adapter was fitted to supply power to a motor cooling fan salvaged from a computer power supply and lighting for the oven compartment.
    Phillip another friend and electrically credentialed engineer took care of the design and wiring of the electrics.
    The heat supplied by my old Mk1 heat gun (a S’H’ 1600W Craftsman) and assisted by the original Breville element (controlled by the simmerstat).
    The cup and Andy’s TC etc. have assured me that roasting performance is good.
    Chaff dispersal proved to be less than perfect but significant and may be able to be further improved if an effective lid seal can be acquired (early days yet).

    Kind Regards
    Lindsay

    Image1 and 2 illustrates the Corretto assembled for action including TC probe, chimney, observation window, heat gun and fan intake.
    Image3 The detail inside the lid: - TC, lights and heat gun extension tube
    Image4 The exhaust manifold from inside the oven chamber.

    Oops dont know how to improve images








  2. #2
    Mal Dimal's Avatar
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    Re: My new No.1 Coretto (Mk3)

    Just tidied them up a bit for you Lindsay.... :)

    Looking good there mate 8-)... Youll have to post up some photos of your roast outcomes. We all love to see freshly home-roasted beans results ;)

    Mal.

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    Re: My new No.1 Coretto (Mk3)

    Awesome job Lindsay! I am impressed.

    Isnt the chaff landing on the element and burning? How are you getting around that?

    I have also found that the heat from the element heats the shaft of the thermocouple and gives a false reading. Are doing anything to stop that or just living with it?

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    Re: My new No.1 Coretto (Mk3)

    Quote Originally Posted by 6764767672647C050 link=1276428859/2#2 date=1276445858
    Isnt the chaff landing on the element and burning? How are you getting around that?

    I have also found that the heat from the element heats the shaft of the thermocouple and gives a false reading. Are doing anything to stop that or just living with it? *
    Hi Bassway,

    Yes the chaff does land on the element mainly at the exhaust manifold end and spontaneously burns at the high heat setting (the setting I use until first crack) but have detected no problem in the coffee, probable because of the essentially one-way flow of heated air through the Corretto eg.HG in..through..beans then oven chamber..exhaust).
    I do plan an overhead cover for the element in the near future, to shelter it from the falling chaff.
    A significant quantity of chaff lodges on the bread chamber cover and stays put for the remainder of the roast.

    I hadnt focussed on the accuracy of the TC reading but have been in the practice of putting a small aluminium heat dissipater at the probes plastic end. With Corretto Mk 1 and 2 I used temporary shielding around the probe and will get around to that again with Mk3. Apart from that I had hoped that the length of the penetration into the bean mass would be sufficient to minimise TC reading errors.

    Quote Originally Posted by 416C686469050 link=1276428859/1#1 date=1276439784
    Youll have to post up some photos of your roast outcomes. We all love to see freshly home-roasted beans results *
    Hi Mal,

    Yes that’s a good idea but since I have just sealed nearly 50x17gram lots of the 835g. of Ethiopian Gambella next roast will be the 19th/20th at the earliest, will try to post photos.

    Lindsay

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    Re: My new No.1 Coretto (Mk3)

    Hi Bassway,

    Your comments stimulated me into action and had just assembled materials and tools for construction of something to insulate the probe from the elements heat in case that was contributing to TC error, when I come across an "Eclipse" mints metal box (about 75x40x20mm).
    Heated it up to dull red on the gas cook top, gave it a good water wash and scrub, packed it with fibre glass insulation and smacked a hole through it to allow the passage of the probe through into the bread chamber and bean mass.
    Then put together the chaff cover for the element I had in mind (used some aluminium sheet that I had on hand).
    Will use both next roast, hopefully will be for the better.

    Lindsay





  6. #6
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    Re: My new No.1 Coretto (Mk3)

    Hi Mal,
    Here you go this arvos 1000green grams of PNG Wahgi AA became 825g.
    BM heating element on high all the way, with HG (old 1600W Craftsman) on high until first crack then low through to unload as quick as I could get my act together on hearing the first snaps of second crack.
    First Crack at about 13min. at an indicated 204C
    Second crack at about 18min. at an indicated 224C.
    Hoping that Bunnings offers a 2000W HG for Fathers Day then Ill see if I can squeeze any more than 1000gg into a roast.

    Lindsay




  7. #7
    Mal Dimal's Avatar
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    Re: My new No.1 Coretto (Mk3)

    Behmor Coffee Roaster
    Wow!

    Thats a very nice looking batch of beans there Lindsay. Your Roast Profile looks to be close to spot-on too mate. The combination of the BM Heating Element and the 1600W Heatgun seems to be doing a sterling job.

    I guess the next thing wed all like to know ::).... Is what they taste like in the cup. Will be very more-ish I suspect.... 8-)

    Mal.



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