You can determine the optimum airflow (in the beginning of the roast) with a lighter. Remove the tryer during the roast and keep the flame of the lighter near the hole. If the flame is pulled gently in the hole the airflow is ok, if the flame is heavily sucked in into the roaster, the airflow is to strong, if the flame stays almost upright the flow is to low. When smoke starts to develop during the roast you’ll have to increase the flow of air. My experience is that if the airflow is ok the chaff will be removed from the drum.
I know about the lighter trick. My technique is to just be aware of drum/bean temps and make adjustments if necessary until I’ve learned how a particular roaster handles air-flow. My question was more aimed at Jacob since this is a fairly significant change to the fan RPMs.
Ok. Perhaps missed the point. But it still can be useful to anyone who doesn’t know how to test the optimal airflow.
No worries and I could have been a bit more specific myself. As most of us know that have been roasting for a long time, chaff removal (during the roast) is an important factor. It is very combustible, so we don’t want a roaster fire (which I’ve experienced) or have it otherwise impart any flavors to the roast if it lingers and begins to cook. I do have a squirt-bottle of water always at the ready, but would rather not be doing that into an electric roaster if at all possible. 
My main interest is whether this fan adjustment will still properly remove the chaff even at the new (much lower) RPM levels. Since there aren’t many users (yet) that have implemented this test firmware, that is why I was mainly looking to hear from Jacob. I’d like to hear that he has tested this new firmware with actual roasts and observed whether chaff collection was still working OK at a F1 or F2 level or may have been impaired.
That’s my point, before it was always using the D8 setting I had from roast to roast. With the new firmware even doing back to back drum speed gets reset to D9 every roast.
I did a roast last night with the new firmware and fans calibrated, but without changing any fan settings from the BT-based triggers I had been using. I didn’t notice a difference in how effectively chaff was removed.
I have no idea what fan setting you are using, so our usage could be “apples and oranges”. I use low fan settings that don’t need to go higher than F2 throughout the roast. That is because I have an active variable-speed fan system attached to the roaster that also draws some air through the roaster. So my usage and someone else’s who has a different setup isn’t really useful for comparison. I’m mainly interested in what Jacob has to offer from his engineering understanding off the Bullet and any tests he may have done regarding this change to the fan speeds.
Compared the lines from the “New with CC” and “Old with CC” and made some calculations on the difference between the steps (the triangle, delta). Used only the numbers from F1 to F9 as the two lines are quite linear in this area. Without judging, it is remarkable that the “New + CC” is more linear, has a bigger dynamic range, starts at a much lower number, and the steps are about 25% bigger then the “Old + CC”. Wonder if the bigger (average) stepwidth is beneficial. In my roast environment the optimal airflow is F2. Assuming my bullet is exactly the same as the one from Jacob, this is about F5 in the calibrated airflow. That’s quite a difference.
When I was calculating the differences today, I was comparing the RPM change between the OldCC and the NewCC which are more significant change amounts. The F1 RPMs exhibit the largest change (old vs new with CC) at a 54% reduction in RPM. F2 is 47% lower, F3 is 39% lower and so on up the fan-speed scale.
But yes, you and I arrive at essentially the same conclusion about the possibility of having to up our F2 settings several notches to equal where we used to operate. That narrows the range from my perspective and because the entire range was lowered, I’m not convinced this firmware change would be in my best interest.
It is made to give you more resolution on the lower end but you can still run all the fan you want.
Instead of (almost) nobody using the higher fan settings F7-FA during roasting we are expanding the range so you have greater control by having smaller steps.
An example:
For some people F2 was too little airflow and F3 was too much. But now your old F3 is F5 so you get two extra steps in between.
BUT BUT BUT
The main reason is that everyone will eventually have the same RPM speed so roasts can be more comparable and easier to playback
I cannot see why chaff removal would be different? You would be using a higher fan setting anyway, so your RPM would be the same as you were using before.
I think that’s a great improvement - I saw a few posts in the past cautioning the use of anything beyond F4 as it was detrimental so expanding the useful range is great.
Still would like to know why my drum speed keeps wanting to reset to D9 though…
what is your default drum speed set to in the menu?
Looks like the firmware flash changed it to 9 from the previous set 8. I take it then that previous defaults are overwritten on a firmware update ? Didn’t think to check which may be my mistake …
With certain FW updates your user settings will be reset, yes.
Jacob, I can better understand your thinking with the change. I had no idea that a lot of users were hanging around the lower-end of the fan settings (as I do). But I knew that I had a reason for using lower fan settings due to my active exhaust to remove smoke and odor from collecting in my basement.
I’m glad that you made this change “optional” so that we are not forced to do it. Yes, I can “up” my fan setting from the current F2 to F5 or F6 to compensate for the lower RPMs of the new “option”. But, that doesn’t add range (for me) given my setup and roast qty. My roasts will always be at least 1.5lbs per roast (x2) based upon my own personal usage of coffee. I have that amount of coffee pretty well dialed in at this point in completion time, heat, good chaff collection, etc. So for me, I don’t see a reason to change my fan-speed range today. But, if that changes in the future and I find it necessary the “option” is there. Thanks for answering.
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jacob, you have said a couple of times that “you will still be able to run full speed of the fans,” but then you show a graph that has a line for “new - with chaff collector” and “Old - with chaff collector” on it. The “new - with chaff collector” line is always 300-550 RPM below the old line in the upper range (F7 - FA). They never converge. It does not appear that the new fan settings ever actually run as fast as the old fan settings at any speed? Am I missing something?
Well observed, but I did not include FB and FC. FC will be 100% just like the previous one. I think the FB was 200RPM higher than FA but I can’t remember.
Cheers
When i try to update firmware, it doesn’t allow me to select the beta version. When I click the radio button nothing happens 
Are you on version 2.2.0 of RT?
I was not. I am now and it is updating as I type this. Thanks!
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