Huge Jump in Drum Speed going from D8 to D9

Hey everyone,

I’ve been taking a closer look at how drum speed affects my roasts and today before roasting I was cycling from D6-D8 and noticed only modest increases in speed of rotation. However when I hit D9 I was shocked at just how much more quickly it started spinning. So I counted:

At D8 I got approximately 54 RPMs. D9 was a whopping 73! A 19 RPM increase. Is that normal for everyone else here ?



About 35% increase in speed. I don’t think it’s normal but it’s about the same thing I see. Beans completely miss the tryer and BT-RoR jumps since the beans are pinned against the drum and receive much more heat per revolution.

I’ve used D4 thru D8 since the beginning (I don’t use D1 - D3). I replaced the small PCB that the motor connects to when I replaced the drive motor 3 (?) yrs ago. More recently I replaced that same PCB (only) as part of the V1.5 → V2 upgrade. I presume (always dangerous!) the non-linearity in drum speed started at one of those 2 part replacements. I don’t believe not having usable D9 drum speed has been limiting.


Hi Bruce, thanks for sharing your experience with this. Through Aillio Customer Service they revealed what the drum speeds are calibrated to for the V2:

D1 = 39 RPM
D2 = 43
D3 = 45
D4 = 48
D5 = 52
D6 = 56
D7 = 60
D8 = 63
D9 = 75

Interesting that my D8 is the official D5.5 (54 rpm) lol. I guess the lesson is, especially when exchanging roast profiles, everyone should probably take 10 minutes and count their drum speeds just so you know what you’re dealing with!

I wonder if D9 is truly even fast enough to pin the beans to the sides? Maybe it being tough to catch beans in the tryer does reveal that to be the case? Frustrating at the least.

I found an article online here:

They discuss a formula for optimal drum speed from an old engineering article that states (based on the bullets radius) that bean exposure through hot air as it rises up and away from the drum and then falling is maximized at 76.9 RPM. They gave a range and this is at the lowest end. The highest I think is around 90 which certainly feels too fast even if we could achieve that!

So much to ponder.

Cheers Bruce, pleasure to meet you.