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!
I’ve been experimenting with drum speed. I’ve been working on getting my Agtron scores for whole bean and ground closer together and have had the best results slowing drum speed. I’ve never gone that slow but now I want to try.
Maybe I’m misreading the article but it seems to say that higher the drum speed the more the beans stick to the drum wall. That is at odds with what I would have expected, I can’t explain why a lower drum speed makes the roasts progress faster, if more heat is transferred by conduction.
I didn’t have any close profiles to share, so I made some new batches for comparison. I was really surprised that the timing didn’t change much at all. I was under the impression that lowering the drum speed was speeding things up. I guess it goes to show you how easy it is to make a mistake.
Aside from the brief difference in fan settings, the settings on this next roast were the same except for the drum speed.
I didn’t see any change in roast time overall. I was expecting a bigger difference just based on the drum setting. others have shared in this forum their experiences as well. none of this is new information but I thought this might help the next person that finds this post.
If you look here, you’ll find an example where the drum speeds have little to no difference, which should have been resolved with the firmware update, or that’s just depending on the machine you get. Might be worth checking why you have this problem.
I don’t know which firmware you’re using, but you should update if you haven’t already. Here’s the post where it says how it should be calibrated.
That might have changed with other firmware updates, but if I were you, I’d check mine. Here it says how, but he measured the v1.5 Bullet. Just under that post in that topic, there’s a measurement of v2.
Also, on 1kg batches the difference should be less, but not as much as it shows on your examples. Although, the D9 had a bit more steam coming into the FC and had a higher DT, so it was a little bit faster.
