ROR flick after dry end

Discuss roast levels and profiles for espresso, equipment for roasting coffee.

#1: Post by carlo12 »

Hope someone can help me with this. An RoR flick right after dry end. It happens on every roast. Anyone ever dealt with this/know what causes it? Any help would be appreciated.

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#2: Post by carlo12 (original poster) »

I'm using san franciscan roasting machine SF-25.

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#3: Post by Wbj828 »

I don't know much about that machine, but if the purple curve (D) stands for damper, it looks like the ROR bump is caused by the damper opening. Why not try to set the damper at a fixed value and then leave it for entire roast. Does that do away with the bump in ROR?

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#4: Post by N6GQ »

That's odd, and I can't say I've seen that before. But, as the other person was saying, if the damper is opening and more air is coming in, you could be getting a significant internal heat bump from that. Of course the "flick" usually happens right as FC is happening, so this is much before that, clearly.
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#5: Post by CarefreeBuzzBuzz »

I have seen this on other SF machines. I will ask a friend who has one, but you may want to look on the SF FB users page.
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#6: Post by Almico »

You're carrying way too much heat into dry end and making it worse by opening the damper and pulling all that heat into the roast chamber.

Opening a damper will add environmental heat if the gas is higher and reduce heat if the gas is low.

As coffee beans give off their free water and start to dry out, it takes far less heat to keep the roast going.

carlo12 (original poster)

#7: Post by carlo12 (original poster) »

Yes D stands for Damper. I'm roasting with this machine for almost 1 and half year. I tried different approach to get rid of this flick. I tried using same airflow, not moving the damper, charging in low temperature but still the flick won't go. I don't know if it's has something to do with the sf machine with artisan. It doesn't affect the taste of the coffee in my experience, but I just want to get rid of it. It's always happens right after when the dry end being marked.

carlo12 (original poster)

#8: Post by carlo12 (original poster) »

I've seen someone had posted same problem before but as I read the thread and tried all the advice there still didn't get rid of the flick

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#9: Post by Almico »

I roast on a SF75 and get no such "flick".

I don't speak celsius so it's hard to interpret your profile.

Couple of questions: what size batches are you roasting? What kind or probes and thermometry are you using with artisan to measure? How long are you warming up? From my experience it takes a full 20 minutes to get everything up to temp, ideally longer.

It seems you RoR is dropping to fast and then catching up, but a bit too much.

My SF75 roasts 65# nicely, but it takes every BTU the burners have. I wouldn't dare try 75#. FWIW, the mfgs recommended NG pressure is 6"WC, I'm pulling 8. Don't tell Bill. Based on that, your SF25 would probably prefer 20# or less.

Here is a typical profile. As you can see, my max ET is about 465*F (240C) which occurs about 6:30 into the roast. You are hitting the same temp in 2:25 with much less coffee.

carlo12 (original poster)

#10: Post by carlo12 (original poster) »

Yes I'm roasting 20lbs size batch, 80% of drum capacity.

It's the mfg probe that I'm using and connected via modbus to artisan.

My pre-heat takes 20-30mins maximum.

Also the machine is running through LP.

Does your sf75 comes with afterburner? How you managing it? Do you let it on the entire roast or your just opening it in such time of the roasting?

I'm afraid if I didn't give that much energy during my roast I will not hit my desired DE & FC time. But surely I will give a try and see.