I think that goal for back to back roasts should be to keep temperature of the drum as high as possible (next batch of beans is about to be added to cool it down) , and that we need to cool drum motor and electronics back to safe temperatures to start the next roast.
I have extra thermoprobes on drum motor and electronics area, and my cooling routine for back to back roasts is below, picked up from my post on another forum:
I installed manual fan switch, with slight modification: in manual mode fan is connected to external power source. This adds more wires, but it gives me more room for play as it's completely independent circuit.
I changed my roasting routine:
1. Roast
2. Eject
3. Fan on manual, take the filter out
4. Take the beans to external cooler
(At this point temperatures of both drum motor and electronics are shooting up as selenoid keeps the bean eject door on the back wall open, and heat easily leaks behind the backwall).
4. Press POWER on HT display as soon as it shows up - power the HT off.
(Temperature of the motor now changes at rate of -4C per minute, which allows for 7 minutes cool down to bring the motor under 60C)
5. Prepare the HT for the next session: vacuum the chaff, save log, load template for the next roast
6. 7 minutes after end of previous roast, set fan to auto and start new roast.
13 minutes roasting and 7 minutes cooling allow almost 3 roasts per hour.
My goal is close to 4 roasts per hour.
Miroslav