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Thread: Baby Roaster mods - remote internal temp, paddle, contact switch, heat guard.

  1. #1
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    Baby Roaster mods - remote internal temp, paddle, contact switch, heat guard.

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hey all,

    Long time reader, first time poster and thought I'd share some mods for the FZ-RR-700 baby roaster. This little roaster does a great job as is and its simplicity is key. I do however roast outdoors on my BBQ side burner and find the temperature control a little difficult (yes I could get a better burner). It's also essential to pick up the roaster regularly and shake it to prevent uneven and burnt beans that remain in contact with the drum too long, even for the motorised version I use. This is no criticism, it's just how the thing works. As you can guess, things get pulled apart and do get hacked regularly at home so modding this little roaster was no exception.

    So, the mods in questions are totally over the top, I admit. They are a little involved but not difficult in practice if you are handy. The end goal for me was to:
    • Have some way of measuring the internal drum temp without hanging wires. I have seen temp probes inserted in the breathing holes, but I didn't quite like that idea,
    • Add a heat guard/shield around the roaster to improve temp control (it can be windy where I am near the coast),
    • Add some kind of paddle inside to avoid picking up shaking the thing every 30s (there are many good threads already for this)
    • Add an auto switch to start/stop the electric motor when the drum is put in place, why not.


    So here is the end result:


    Materials used:
    • Heat guard: one broken stainless steel electric kettle, ours served us well over the years and still does now,
    • Remote temperature sensor: See BBQ section of your nearest and biggest hardware store $19.89 (the only one now that Masters is gone)
    • Electronics and Switch (see your nearest and biggest store):
      • One intrusion switch $4.80,
      • One LM317 regulator wired to produce 3V (2xAA equivalent) to the base unit + resistors, about $2,
      • One small plastic enclosure used to transfer the base unit electronics of Temp sender about $2.50,
      • One standard power panel mount connector, now I can just plug any 12V adapter in, forgot how much, it was cheap,
      • Heat shrink insulation to keep it all neat $1.89 for 1 meter,
      • Some loose wiring, everyone has some lying around to connect it all up.


    Tools - many:
    • Sheet Metal snippers to shape the old kettle and internal paddle
    • Dremel with thin cutting disk
    • Welder if you have one to fix the kettle guard in place (you could screw the thing in I suppose)
    • Soldering iron
    • Some copper tubbing offcuts, I had some from an old A/C job installation to shape a slip ring contact and axle insert, see picture below.
    • Silicon gasket tube, I had some in the garage left from a job on the car. This stuff is good for 265C if you look at the manufacturer's specs, costs about $16 if you need one.


    Total cost: About $40 + a few hours of tinkering.

    Here's a few pics of the builds.

    Paddle, cut and shaped from the old kettle:


    Paddle + Probe in place:


    Temp sensor, one end grounded, other passed through a slot made with the Dremel. Note the copper insert on top for rotation. Also worth noting that the wiring going into the groove is silicon coated (rated beyond 250C), I snipped a bit from another temp sensor I had lying around.

    Switch that acts as actuator to start the electric motor + picks up temp sensors reading off the slip ring:


    Slip ring details + silicon to hold it all in:


    And finally the very first roast ever made from the modded Baby Roaster (Yes it's slightly uneven given the blend I used, but no burnt beans!):


    Anyhow, hope you all have a good laugh and perhaps find some inspiration from this little bit of fun. For me, I can now preempt my FC with accuracy and dial down the heat as needed to maintain the maturation stage at the right stable temp for a few minutes, before finally heating SC and bringing the heat back up.

    Bye.

  2. #2
    Life-long Learner DesigningByCoffee's Avatar
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    Nice work lerebel103
    Looks like some great tinkering to make a great little roaster even more usable and precise!

    Matt

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    There is one interesting thing that I discovered with all this. I used to cut the heat to minimum just as I could hear the signs of FC as to allow the roast to mature for a few minutes until SC. Looking at the temp over several roasts, I discovered the temperature consistently falls back if I do that. On my blend, signs of FC start around 185-190C, then heat to minimum coasts at around 200C, but then would fall back to around 190C.

    Anyhow, this all depends on how much heat your burner puts out on minimum, in practice I now know to bring the heat up a little earlier than I used to during the maturation phase such that it coasts to ~200-205C or so till SC. Results are good.
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  4. #4
    Life-long Learner DesigningByCoffee's Avatar
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    Quote Originally Posted by lerebel103 View Post
    There is one interesting thing that I discovered with all this. I used to cut the heat to minimum just as I could hear the signs of FC as to allow the roast to mature for a few minutes until SC. Looking at the temp over several roasts, I discovered the temperature consistently falls back if I do that. On my blend, signs of FC start around 185-190C, then heat to minimum coasts at around 200C, but then would fall back to around 190C.

    Anyhow, this all depends on how much heat your burner puts out on minimum, in practice I now know to bring the heat up a little earlier than I used to during the maturation phase such that it coasts to ~200-205C or so till SC. Results are good.
    It's certainly informative what a temp probe will tell you.
    Like you've discovered, I used to think you should drop your temperature back before first crack to stop the roast running away to second crack, but often got a substantial stall in the RoR. With a bit more experience under my belt and some data-logging to back it up, I now basically keep the heat on until a little after first crack has just commenced (around 207° on my setup after a 202° first crack) and then drop it down from there in small steps every 5°, to give me a nice even climb to second crack.
    The beans actually suck in a whole heap of heat from first crack to about 5-7° later, then start giving it out again
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    Roast profile

    To illustrate all this and hope this helps other users of this little roaster, here's a roast profile on Columbian beans, single origin. I essentially lower the heat at 195C, then cruise around 205 for 2 mins or so before finally dumping the beans as SC starts (modulating the heat). This is all still very new to me, are there experts would can comment, e.g. without over-analysing, am I anywhere near where I need to be? Relying on senses, it all sounds, looks and tastes ok overall.



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  6. #6
    Mal Dimal's Avatar
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    Excellent work "lerebel103"...

    The roast outcome with its attendant profile above, looks pretty decent to me mate.
    The final arbiter is always the result in the cup, as always and you seem pretty happy with that. How does it compare with some of your favourite pre-roasted coffee? Also a good idea to sample it over the coming few days, every day, to get a handle on when the flavour hits its peak level of goodness...

    Another thing you can do, is to cut a few beans in half (or grind them down using some fine emery paper) and observe whether the degree of roast is the same all the way through. This will give you some guidance on whether the profile gradient is too steep or not. Don't think you have anything to worry about for any other factors though; results in the cup will be your best guide...

    Mal.
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    Life-long Learner DesigningByCoffee's Avatar
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    Quote Originally Posted by Dimal View Post
    Another thing you can do, is to cut a few beans in half (or grind them down using some fine emery paper) and observe whether the degree of roast is the same all the way through. This will give you some guidance on whether the profile gradient is too steep or not.
    Ain't this the truth! I just used a sharp kitchen knife on these (though a box cutter works a treat too).

    Guess which one tasted best!

    DBC-Macro-Kenyan-.jpg DBC-Macro-Tanz-Njiri-Wami.jpg
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    Quote Originally Posted by DesigningByCoffee View Post
    The beans actually suck in a whole heap of heat from first crack to about 5-7° later, then start giving it out again
    I am curious to know what you mean by "suck in heat" after first crack? Do you mean after the first signs of first crack before it starts a rolling first crack? During first crack there is supposed to be an exothermic reaction taking place.
    During rolling first crack I notice a slight hump in my heating rate.

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    Quote Originally Posted by DesigningByCoffee View Post
    Ain't this the truth! I just used a sharp kitchen knife on these (though a box cutter works a treat too).

    Guess which one tasted best!
    Love to know what the different taste profiles were between the two beans.

  10. #10
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    Quote Originally Posted by saeco_user View Post
    I am curious to know what you mean by "suck in heat" after first crack? Do you mean after the first signs of first crack before it starts a rolling first crack? During first crack there is supposed to be an exothermic reaction taking place.
    During rolling first crack I notice a slight hump in my heating rate.
    It seems from my observations, that with a constant temperature input from 160° on, as the beans head towards first crack from around 190° on, the °RoR starts slowly decreasing (ie they are taking in more and more heat). Once first crack begins, normally around 202° on my setup, they go exotermic suddenly in a little spike (hence the cracks!) but they don't seem to go exothermic in a reliable way. It is almost like they wake up, stretch (the cracks) then hit the snooze for a few °C!

    I will often drop the temp a fraction to a certain gun temp at the beginning of first crack (and I have found the profile between first crack - second crack is actually dependent more on ambient conditions rather than the bean origin funnily enough - the actually process is very similar for most beans) but have found that dropping too much will very easily stall the roast. So I keep the heat on longer, even though there may be a little spike in °RoR during rolling FC, and have found from experience that it is often at the end of rolling first crack when the RoR starts climbing again, so I need to start dropping the temp input temperatures slowly from around 207° to the end of the roast…

    Quote Originally Posted by saeco_user View Post
    Love to know what the different taste profiles were between the two beans.
    The Kenyan had an high initial temp a hot and fast roast (by accident - I forgot to change probe positions for a small batch size or some other silly oversight!). From memory, it tasted both underdeveloped (sour) from the too fast roast and over developed (bitter) from the burnt/overcooked insides. Not pleasant.
    This was the profile I think…

    20140325-Kenya-350g.jpg

    The Sidamo was pretty good I imagine!

    Cheers Matt
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    Ahhhhhh, now that's very interesting! Ok, I will cut the beans in half to see how evenly the roast is, got it.
    Many thanks for the pointers...

    @Dimal, results in the cup are ok, mostly I seem to pick up some residual bitterness in the first two days. Past that, it seems to get a little rounder.
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  12. #12
    Mal Dimal's Avatar
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    Behmor Coffee Roaster
    That sounds quite typical l'103...

    During the first couple of days, a lot of CO2 is outgassed and this can create a bit of weirdness on the palate until it settles down. Good to keep notes of the flavour changes each day as that can be an interesting exercise in itself...

    Mal.
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