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Thread: My new No.1 Coretto (Mk2)

  1. #1
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    My new No.1 Coretto (Mk2)

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

    I was fortunate that a friend acquired for me a bread maker (Sunbeam Cool Touch Bakehouse) with a larger bread pan (than my Mk1).
    I decided to set it up as my new No.1 coffee roaster, according to my current knowledge, practice and preferences,
    Removed the electronic control circuitry and after a good clean, judged it to be in good condition and suited for intended use.
    Wired the heating element and motor directly to standard leads with 3 pin plugs.
    Drilled a few holes in the lid (with a mates help) and constructed an internal cover from aluminium sheet to assist with management of heat flow and venting.
    Dived in at the deep end with a too large 1000 green grams roast, first crack at 13˝minutes and overlooked 2nd crack and finally pulled at 19 minutes, a bit too late.
    Heat supplied by my old Mk1 heat gun (a SH 1600W Craftsman) and original Sunbeam element.
    Roast progress monitoring assisted by my Ebay Turkey thermometer @ $10
    (Andy’s TC and software still on my Xmas list).
    Chaff dispersal by the occasional blast from the blow side of my old Electrolux vacuum cleaner mod 725
    Finished? Well no, but further tuning has now officially begun.
    Exhaust port and chimney Improvements to the structure and detail.
    Insulate lid, space between: metal liner of lid and the exterior plastic (PP) skin.
    Insulate oven chamber and upgrade cooling to stirrer motor.

    Kind Regards
    Lindsay

    Image1 illustrates what it would look like on the way to first crack with beans on board.
    Image2 The detail inside the lid: -heat gun throat, turkey thermometer/TC, chimney and observation window.
    Image3 The elegance of the internal cover, intended to limit hot air loss from element and assist with moving heat into the bean mass etc.
    Image4 The naked bread pan/roast chamber.
    Image5 The hand crafted elegance which is the internal cover, constructed from about 0.6mm aluminium sheet and cut with sturdy scissors.











  2. #2
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    Re: My new No.1 Coretto (Mk2)

    questions

    the 2nd tube (vacuum)
    when you say you blasted it with the vacuum are you blowing down this pipe?
    Or does it just "vent" the chaff as the hot air come out.

    idea !
    if you added a internal elbow pipe above the lid into the vacuum and introduced a stream of "blown" air do you think you could generate a vacuum effect that might assist chaff removal?
    this way you would not be introducing cold air to the roast chamber as much.


    Interesting idea but, I like your nicko pen cutting line, dont want any errors :).... i use the same techniques. I had a laugh

    you going to drink that 1k of coffee you cooked :)
    Leeham

  3. #3
    Senior Member greenman's Avatar
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    Re: My new No.1 Coretto (Mk2)

    Looks good Lindsay, I have just built my Super Corretto from a Breville Big Loaf with twin paddles which I modded for more agitation, Ive built a lid from an aluminium bbq tray and a metal baking dish lid with a hole for heatgun, an inspection window that I keep covered when not using and a vent for chaff, Ive done 4 roasts so far the first 3 were good but the last one was a 3 bean post blend and I bean got a little crisp for my liking, its a work in progress but its looking good. Ive been doing 1.2kg batches which are nice and even, using a Makita 2000w variable temp hg.

  4. #4
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    Re: My new No.1 Coretto (Mk2)

    Hi Leeham,

    "Chaff dispersal by the occasional blast from the blow side of my old Electrolux vacuum cleaner mod 725"
    No not down the chimney, I lift the lid and *carefully give a general blow to cause chaff to exit, close lid and give the heat gun filter, then the general environment a satisfying dechaff.
    *carefully as the air flow from this hose is enough to send beans metres in all directions. Note the Electrolux vacuum cleaner mod 725 is just an ordinary old Electrolux vacuum cleaner pre Westinghouse Email take over like any of their brethren, as now found on roadside hard rubbish collections all over.
    This unit can run 2 hoses simultaneously, one on the suck side of the fan used for standard vacuum cleaning and one on the blow side of the fan, specifically with CSrs in mind for blowing chaff and also useful for running liquid spray guns, leaf blowing and the like.

    idea !
    if you added a internal elbow pipe above the lid into the vacuum and introduced a stream of "blown" air do you think you could generate a vacuum effect that might assist chaff removal?
    this way you would not be introducing cold air to the roast chamber as much.

    Sorry I dont understand your question. Scan me a drawing?

    As my punishment for a less than perfect job, I have been sentenced to drink the whole batch without help (the successes are reserved as an offering to my very rare friends and acquaintances) and I am still enjoying that kilo. There is a lot to be said for old warn out second hand taste buds after all.
    Its a hard afterlife but even here in heaven someone’s got to clean the toilets.

    Kind Regards
    Lindsay

  5. #5
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    Re: My new No.1 Coretto (Mk2)

    idea
    ok you put an elbow in the "out" pipe and blow air in
    might "suck" the chaff out via a vacumm effect ?

    rather than blowing air into the bean mass.

    it still going to suck extra air into the BM via the heat gun a bit i think?


  6. #6
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    Re: My new No.1 Coretto (Mk2)

    Hi Greenman,

    Breville Big Loaf with twin paddles is the direction I am heading but the low fertility of my local roadside hard rubbish collection means I have not yet arrived.
    The inspection window on the Sunbeam is glass, it survived the first roast and my expectation is that it will have a long life.
    Vent for chaff? I had wondered if I could make the glass window able to be opened and closed, but too hard I think.
    I envy your 1.2k batch size, looks like Ill try 0.8k next and see where from there.
    Obviously the dud batch was an anomaly, which is unlikely to be repeated.
    I believe that by nature "the Corretto" is never finished; only our imagination can be finished.
    It looks like our experiences are causing convergence in the evolution of our Correttos and apparently our roast techniques too.
    1.2kg x 3 thats a lot of coffee blend.

    Kind Regards
    Lindsay

  7. #7
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    Re: My new No.1 Coretto (Mk2)

    Hi Leeham,

    Got your great idea now.

    Essentially you would create a low pressure area down chimney from the air injection elbow which would draw air out of the roast oven.

    I had hoped that my design would shed chaff through the chimney but observed very little exiting that path from my one roast.

    Would also be good to be able to balance the heat gun input against the chimney output, be leak neutral and remove chaff, perfection.

    Here is a drawing of another chaff solution,
    or could be integrated together with the chimney as in your suggestion, as I understand it.

    Lindsay



  8. #8
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    Re: My new No.1 Coretto (Mk2)

    Hi CSrs,

    Second roast today in the Mk2 went like a dream.
    If I didnt know myself better, could begin to think I was getting good at this.
    Scaled back to 800gms (Kenyan Gitwe A) reached first crack at 11 min. pulled at 16 min. on the first few cracks of second crack.
    Unloaded and cooled with the vacuum unloader cooler,
    http://coffeesnobs.com.au/YaBB.pl?num=1254874010/0
    making it easily the smoothest, simplest and best ending to any of my roasts. Hoping the cup doesnt contradict this early enthusiasm.
    Kind Regards
    Lindsay



  9. #9
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    Re: My new No.1 Coretto (Mk2)

    Behmor Coffee Roaster
    Looks to be an excellent outcome there Lindsay.... 8-)

    Will be interested to read how it goes down in a few days time ;)

    Mal.



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