Lately I have been roasting 1kg batches on my R1v2 120v. The beans are pretty dense, they need a lot of heat throughout the whole roast to prevent crashing. I usually aim for about 2:30-3:00 development time, finishing before second crack. Just for more context, weight loss is 16-17%. First crack happens between 9:30 and 9:45. I call it a medium-dark ish roast.
To reach those targets on my machine I have to preheat to 310c, and start power p9, fan F1 or f2, and a very low drum speed, D2. I didn’t notice a big difference between D2 and D3, but at D4 and up the roasts start to get longer and also less tasty (in my opinion). At D9 it adds almost 2 minutes to the roast.
I make progressive adjustments to the settings so that I’m going I to first crack at p7 f2 D4 and near the end of the roast I’m around p3 f3 d6. I am really just experimenting with the settings so that I can reach my targets. I bump up the drum speed throughout the roast, mostly out of fear of scorching the beans, but also because it slows down the rate of rise a bit. I noticed if I go higher than d6 is has a dramatic effect on the roast curve, like what happens when you go to f5 or f6.
I think the lower drum speed has helped me in a couple ways - first it speeds up the roast time. Second, I find it smooths out the power and fan changes and makes them easier to control. When I was roasting batches at D9, I found that the power and fan changes made a much bigger impact, but especially the fan changes. I thought maybe it’s because the beans are agitated more at higher drum speeds. Maybe too much, for these particular beans?
Just browsing the forum, I don’t see a lot of profiles that use very low drum speeds, and I’m wondering if it’s something that people have experimented with and discarded for any reason. Do you use different drum settings for different beans? I saw some old posts discussing RPMs and setting a drum speed and leaving it, but haven’t seen a lot about changes in drum speed throughout the roast. I know it’s introducing another variable and complicating things, but Aillio gave us control over drum speed and I feel like it should be used!
Edit: this post is what inspired me to try this: How coffee beans move within a revolving drum. (Also: Why you should be anticipating a revolution in the coffee industry.) | by Aillio | Medium. I thought it was interesting but how to apply it wasn’t clear and still confuses me.