Here is the air flow diagram of a typical solid-drum, single-pass roaster.
AFAIK, BT (
blue) and ET (
red) probes are usually installed at the marked positions. A manometer (
grey) can also be installed on the exhaust hose.
Replying the previous PM last month reminded me the noise issue of my roaster when drum is not fully warmed-up. I sent Frank (the owner) an email regarding this issue and Frank immediately answered my question. This was due to the drum rubbing the faceplate. He suspected the extreme temperature fluctuation being the culprit, and suggested adjusting the distance between the drum and the faceplate to fix it.
It took me three minutes reading and understanding his instruction, and one more minute to fix. I fund the loosen adjustment screw and used my bare hand to tighten it. Job well done?
No. My BT and ET readings went hay wired. I immediately realized that I pulled the drum too far (
green) and substantial hot air flowing through a gap had thrown off the readings (
orange). Actually it’s not really an observable “gapâ€, because the drum was still tightly fitted on the faceplate like a sleeve. I adjusted the drum in the opposite direction, but this time with my glove on. Finally problem fixed! There is no noise during the warming up or in the working temperature range.
On the user’s manual, it specifies that the adjustment has to be done when the drum is hot, and doesn’t recommend the user doing this adjustment. Now I understand. I won’t want to touch the drum alignment nor the main frame since it has been carefully calibrated by the manufacture.
In the past year I had [airflow vs. roasting flavor] discussions on other forums, and I received mixed opinions from users of different roasters. Now I got it. Not all roasters were built the same. And some other roasters may not been calibrated to the same degree as KapoK when leaving the factory. Various internal airflow paths may cause unpredictable effects on BT & ET readings and it couldn’t be distinguished by the manometer.
Ps. I use 1-second sampling rate and over sampling in Artisan, via Bluetooth connection. No spikes in Artisan as of now. I’ve seen people using longer sampling time (3, or even 15 seconds of sampling time) to circumvent the spike issue. My complaining about the spike issue may sound like bragging to others.