Fan Speed... Increase or Decrease as the roast goes on

I got advice from an “Expert” on the bullet when I bought mine… and was given a rule of thumb on decreasing fan speed during a roast, leaving the drum speed alone etc… now that I have read Scott Rao’s book, and asked other people… I am not sure either of these are correct… as a rule of thumb… anyone??? I had to roast without a computer for about a month… and that changed the whole game for me, so my last 3 roasts I did plug it back in… The taste at the end of the day has been flipping EPIC! so maybe I leave well enough alone, or keep hunting for that something else? LOL!!! Such the journey!

As you know, during the roast, as you progress, there will be smoke and chaff, and something needs to blow all of it out, so decreasing is not ideal. Either leave it be or increase, never decrease. What I mean by that is that you could start and end the roast at f4, f5, f6, or whatever you want, and leave it there for the duration of the roast. Of course, you’ll need to control the roast just with heat adjustments in that case. Or you could start at f2, f3 and finish with f5, f6. Depends how much smoke and chaff there is. For example, if you start at f6 and finish at f1, you won’t be able to get rid of all the chaff, since that forms around FC, and for naturals already at yellowing. So, decreasing as chaff increases is not the way to go.

Interesting to say the least, I think on my next roast of the same Brazil, I am going to try increasing the fan speed along the way. Thank you for the advice!

My 2cents: fan speed also controls the conduction vs. convection of heat. If I recall correctly Rob Hoos mentions this in his book.

My 1kg profiles start with F1 and ends around F4 or F5. Drum speed starts with D7 and then stays constant at D8.

If you roast dark you definitely want to get the smoke and chaff out of the drum as braca mentioned.

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cool and thank you! I for sure roast a bit darker, as I am really only roasting for espresso.

You have arrived, you like the brew you roast.

Fan speed is a bit weird on the Aillio, well, with roasting in general. Changing the airflow is changing a lot. It would be interesting if Aillio could add “.5” adjustments to the fans and power settings. The fan is kind of used in a F2-F4 range by most people, so you have 2 steps to play with? not elegant, so you have to have a strategy for the stepping. Same with the Power settings, you get 9steps, so every power setting is a 11% jump. Of course, there is the decay time of the heating, but if you want to hit a target, you can’t always find that one power setting that will take you there, and there is stepping through out the roast. It works, but perhaps not the ideal.

in my experience using a lower drum speed with the bullet means going a bit faster during roasting . What are your thoughts on this?

right?!?!!?? and its getting better now :slight_smile: its amazing when a friend shows up and drinks a cup, and has the balls to give an honest opinion.

I haven’t given that point much thought actually since I don’t go lower than D7 on my 1kg and even then it’s for a short time (during heat soaking).

What’s your batch size when you see this happening and how slow is your drum speed?

Maybe others who have played with drum speed more than I have can opine on this point you observed. :slight_smile:

Edit: You can skip reading this and move on to where the misinformation is corrected.

That is correct. Slowing down the drum will prolong the contact of beans with the hot surface leading to faster roasts. More conductive heating, which is what we’re talking about, will also raise the risk of scorching because of prolonged exposure of the bean to the hot surface of the drum. If you’re going slower with the drum, you should decrease your PH temp. In the end, you should end up at the same point, because decreasing PH will lenghten your roast, and nobody likes scorched beans. In my opinion, this would only be necessary if you’re struggling to reach FC with larger batches. On smaller batches you will most certainly scorch the beans if you don’t adjust other parameters accordingly.

This made me smile. I worry sometime that despite my asking for that honest opinion, the friends that I give coffee to are too polite to tell me that there’s something that they don’t like with the flavor.

That said, I generally like what I roast very much, so I don’t get that worried :smiley:

Happy to make a smile :slight_smile: I have those friends as well… but somehow I can just tell when the are being polite… And I agree as long as you like what your roasting, who cares!!!

Actually it is the other way round. Faster drum speed will roast faster and shorten roast time due to greater convective heat transfer with the hot air. Just try repeating your exact same roast recipe but only change your D7 to D9 and see for yourself :blush:

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Yeah, I had a blunder. Let’s put it this way. If you slow down your drum in the beginning and then put it back, it will go faster. If you keep it slow all the way through, it will be slower. It’s my fault for writing without thinking. I’ve never touched the drum speed. I’m always at 9 and never thought about changing. Never had any problems, never needed more power or anything, even with 1kg batches, so not really my field. Well, everyone makes mistakes, the important thing is admitting. :smiley:

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For me personally the best compliment are the friends and colleagues who liked it so much that they ask “can I pay you to send me your beans?” Those are the ones that appreciate it and like it :slight_smile:

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Yeah that is a good one to have happen as well :slight_smile:

Bless you @braca19452f9m, when it comes to “mistakes”, I take the prize. I stuck my finger where the impeller fan is while it was running and was lucky I didn’t cut it off. One moment of lapse of concentration and nearly one thumb less. :grin: