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Thread: Convection Rotisserie Roaster

  1. #1
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    Convection Rotisserie Roaster

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi All.... Im New to the forum...

    I have read mixed reviews on a few sites regarding putting a drum into a countertop Rotisserie Convection oven.

    I dont think they get hot enough. Could a second heat source be added?

    Any thoughts?

  2. #2
    Super Moderator Javaphile's Avatar
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    Re: Convection Rotisserie Roaster

    Howdy NBR, and welcome to CS.

    I know some people have tried going this route and I seem to recall some convos in here about it. You might try searching the forums for any discussions along these lines.

    Java "A roast a day keeps the DTs away" phile

  3. #3
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    Re: Convection Rotisserie Roaster

    Andy Freeman uses one...modded to run on propane.....the elements didnt cut it.....might be worth having a chat with him about it....


    Chris

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    Re: Convection Rotisserie Roaster

    Thanks for the help. I send him a message.


    Thanks,

    Jason

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    CoffeeSnobs Owner Andy's Avatar
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    Re: Convection Rotisserie Roaster


    I found the original over that I used also suffered from the "not hot enough" and as Chris has mentioned I changed it to (bottle) propane run...

    Dont try this at home kiddies as death might result :)

    http://coffeesnobs.com.au/YaBB.pl?num=1090196434


  6. #6
    Senior Member robusto's Avatar
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    Re: Convection Rotisserie Roaster

    Not enough heat in that small oven -- too much heat in my barbecue. *

    Yesterday the Aldi popper went. Today, the barbecue couldnt stand the heat. *The metal gets soft, and as I lifted the lid to remove the batch of El Salvador *Santa Adelaida, *instead of stopping, it fell right back and ripped off the hinges. *A mounting panel is buckled and so is the rear lip of the lid. *And it aint a cheapie barbecue either.

    The manufacturers did say not to have all burners on the go with the lid shut -- but they were talking about its intended role as a low-heat chicken rotisserie -- not as a coffee roaster.

    It must be the El Salvador beans that are jinxed -- they were also in the popper when the fan fell off.


    Robusto

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    Re: Convection Rotisserie Roaster

    That is a good point. These items are not built for higher temperatures.

    The reason I started looking at these ovens was to get a greater volume from each batch. I would like to roast more than 150 to 200 grams per roast... and I dont think I should have to invest $500 or more to get this.

    The bbq roaster is looking like the best option at this point.

    Thank you all for te input.

  8. #8
    Senior Member robusto's Avatar
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    Re: Convection Rotisserie Roaster

    NewBostonRoaster, it is a barbecue I am talking about. The only way to avoid damaging high temperatures is to roast at a lower heat, in which case it will takes in exces of 20 minutes per batch, or, to roast with the lid open, in which case Id still be out there waiting for that elusive first crack.

    The answer probably involves a metal shroud which retains all the heat from the middle burner, thereby avoiding the need for all the other burners to be on as well.

    However, the shroud needs to be a certain size, and it needs to closer over the rotisserie bar and drum, and it will get very hot, and despite that will have to be removed quickly to access and empty the drum.

    Off to the drawing board.

    Robusto


  9. #9
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    Re: Convection Rotisserie Roaster


    Update:

    The barbecue is ready for action again. Repairs involved dismantling the lid from the hinge and hinge bracket.

    The bracket (which runs along the back of the barbecue) had to be hammered back into shape while trying not to damage the vitrous enamel coating.

    I welded pieces of reinforcement steel into the ends of the bracket so that the bolt holes are no longer a mere 1 mm from the end --- when that 1 mm of of steel heated up, it became soft, and the weight of the lid tore the holes through.

    Some pot belly black heat-resistant paint and were ready to roast again.

    Robusto


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    Re: Convection Rotisserie Roaster

    Hi all,

    Since my last post, I have made some progress with my roaster...

    I got a toaster oven for free, really just for the shell. I added a heat gun to the back, and attached it to a bar to distribute the heat. I have made a convection oven. It is heating to about 260 C in about 12 minutes.

    All I have left to do is add a rotisserie. Take a look, tell me what you think...




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    Re: Convection Rotisserie Roaster

    I should have also mentioned, I am not using the toaster ovens heat source at all.

  12. #12
    Senior Member robusto's Avatar
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    Re: Convection Rotisserie Roaster

    Looks clever and adventurous, NBR. And the inbuilt timer will come in handy.

    Be careful the heatgun doesnt overheat, though.

    Robusto

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    Re: Convection Rotisserie Roaster

    Love the idea, but I would echo Robustos comments about the heatgun. They are not designed to sustain operation with a back pressure. They are designed for 100% unloaded operation, and you may find, unless you have an exhaust hole, that youll significantly reduce the working life of the heat gun.

    How are you going to attach a rotisserrie? Ive been thinking of something very similar and am keen to see the results of you trials. Keep us posted. ;)

    Boris

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    Re: Convection Rotisserie Roaster

    I had considered that may be a problem. I did some math....

    Size of opening on gun = 0.785 sq. inches.

    Size of holes in pipe = 0.012 sq. inches.

    0.785 / 0.012 = 65 holes.

    The toaster oven itself has so many holes in it, I didnt figure it would be a problem. Does this cover your concerns? Should I put a small vent near the front of the heat gun?

  15. #15
    Senior Member robusto's Avatar
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    Re: Convection Rotisserie Roaster

    My concern is that irrespective of how many holes through which the generated heat exits the gun, the surrounding air into which that heat is meant to dissipate will be very hot. More than 200 C.

    Normally, a heatgun is designed to deliver very hot air into a relatively cool atmosphere.

    Perhaps the gun specifications mention operating temperature range.

    Robusto

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    Re: Convection Rotisserie Roaster

    very good point... I will check on the specs that came with the gun...

    and I will get you all an update as to how well this works!

  17. #17
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    Re: Convection Rotisserie Roaster

    Hi nBR,

    Great idea by the way [smiley=thumbsup.gif].

    Something that might be worth considering.... instead of fitting the HG into the distribution manifold youve made, would it be possible to construct and fit a simple air-flow deflection system that would ensure adequate distribution around the oven? This would significantly reduce the back-pressure issue with the HG, but probably not completely eliminate long-term high temperature exposure issues for the HG nozzle. This may or may not be an issue though as heavier duty HGs can be left running all day long while in use and suffer no ill effects.

    Food for thought though, for sure :)

    Cheers,
    Mal.

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    Re: Convection Rotisserie Roaster

    Mal,

    Thanks for the feedback. Do you think a small opening around the tip of the gun would work, maybe 2cm space before the manifold?

    Also, after seeing all these discussions, I think Ill preheat the oven with the regular toaster oven, then roast with the heatgun, reducing the time the heatgun is on.

  19. #19
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    Re: Convection Rotisserie Roaster

    Gday nBR,

    Hmmm, Id say it would depend on the amount of resistance to free air-flow into the oven..... too much and most of the HG output would probably just deflect around the nozzle/input manifold with very little actual heated air entering the oven.

    With heaters like HeatGuns, they are not designed to deliver heated air under pressure as has already been mentioned, and it is this design limitation that you need to consider when using one in an enclosed/pressurised space.

    To work effectively, the oven would have to facilitate exhausting air at the same rate that heated air was entering it, taking into consideration convection flow characteristics of the oven itself. You could probably ensure this by drilling a few extra holes in judiciously appropriate locations around the base of the oven... somewhere low down in the roasting chamber anyway.

    I think all of this can be easily overcome with a bit of ingenuity, and the usual trialnerror ;), and you certainly seem to have plenty of the former nBR :). I suppose you wont really know whether youll need to use the ovens own elements until you try a couple of roasts and it may just come down to using them to preheat the oven as you you say. Id reckon with a bit of experimenting, tweaking here and there and youll have a roaster that will prove very capable 8-). All the best,

    Mal.

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    Re: Convection Rotisserie Roaster

    So... this roaster is finally finished and roasting well. Im sure everyone was waiting for an update :)

    I am using the heatgun at full blast from the back of the oven. Additional heat, to get the 1st crack in less than 14 minutes, comes from the ovens toaster function. I turn it on every 2 minutes, for 1 minute. I get to first crack in 8 to 9 minutes.

    The power for the rotisserre motor is wired into the toaster wiring. The heatgun is plugged in separate.

    I also put in a separate switch for the motor.

    I had a lot of help making the rotating drum... thanks Mike!


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    Re: Convection Rotisserie Roaster

    For nBR and others that may be interested, my experiments with a portable rotisserie oven can be found in this thread.
    http://coffeesnobs.com.au/YaBB.pl?num=1150630717/0#8
    basically it proved to be cheap and effective to do and required no modifications of the oven.

    Cheers
    David

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    Re: Convection Rotisserie Roaster

    I appreciate the response... but I am looking for more of the long-time roasters experience.

    Do the times sound good? Does the method sound solid?

    Thanks for the responses.

  23. #23
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    Re: Convection Rotisserie Roaster

    Gday nBR,

    Just to help us out a bit, what are the timing milestones for the overall roast profile, i.e. Time that 1st Crack stops, Time to the start of 2nd Crack, Time to the start of Rolling 2nd Crack, Time to when the roast was pulled and the beans cooled. Once we have that info, well be able to help you out a bit more,

    Cheers,
    Mal.

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    Re: Convection Rotisserie Roaster

    One example... Kenya Peaberry:

    1st Crack Start: 8:23
    1st Crack Finish: 9:40
    2nd Crack Start: 11:45
    2nd Crack Rolling: approximately 12:15 (I have not kept this record, but I will now)
    Unload: 12:30
    Cool: Cracking stopped approximately 13:15, reached ambient temperature around 16:00. Again, I havent kept accurate records of this, but will start.
    When you say "Cool" how much do the beans need to cool to stop the roast? Do they need to reach ambient temperature or just stop cracking? What are the results of slow cooling?

    Thanks for the advise!

  25. #25
    Mal Dimal's Avatar
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    Re: Convection Rotisserie Roaster

    Hi again nBR,

    These timings look pretty good to me. How do the brews taste? The only thing I would try to improve upon would be the cool-down time. How cool is cool? I couldnt find much reference to this but in my case, I try to cool the roast down to less than 65deg C ASAP and usually consider the batch to be cool enough when tepid just prior to bagging.

    Maybe one of our Pros could chip in with something more concrete and considered to be an Industry Standard :),

    Cheers,
    Mal.

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    Re: Convection Rotisserie Roaster

    Thanks for the feedback. I feel pretty good about the roast times.

    The coffee has been great since I got down to these times.

    The hardest part about this roaster design is getting the beans out of that hot drum. Something to consider when building the next one.

    One other newbie question... Is a "profile" about the amount of heat, the timing of the heat or a combination of both? When would you slow the roast, or speed it up?


    Thanks,

    nbr

  27. #27
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    Re: Convection Rotisserie Roaster

    Quote Originally Posted by newBostonRoaster link=1142808662/15#25 date=1151365988
    One other newbie question... Is a "profile" about the amount of heat, the timing of the heat or a combination of both? When would you slow the roast, or speed it up?


    Thanks,

    nbr
    Howdy nBR and welcome to the wonderful world of home roasting.

    A profile is how much heat is applied at different times during a roast. To bring out the best a varietal/blend has to offer different profiles are needed depending on the beans used.

    In general the lower the altitude the bean was grown at the lower the heat during the initial roasting or drying phase.

    Java "Still working on his profiles" phile

  28. #28
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    Re: Convection Rotisserie Roaster

    Behmor Coffee Roaster
    Very good info, thanks for the response!

    Does anyone have examples or profiles they have used on different beans?



    Thank you all!



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