I’m curious if other roasters have found a BBP that work well for them on the bullet and what it is specifically. I’m currently in Scott Rao’s online course and his BBP for gas machines is:
Turn off Gas
Drop Batch
3:30-4:30 down to bottoming temp
Low gas up to charge temp in no less than 60 and no more than 90 seconds
Charge beans
I can’t seem to accomplish this due to the programming in the bullet wanting the drum to soak longer than 90 seconds before switching into “charge” mode and the fact that the drum heats up very quickly (induction process effect??)
The Bullet is waiting for pre-conditions to be met, principally it’s looking for thermal equilibrium at a user-selected temperature… your Pre-heat setting. Additionally B-Temp must be stable for 1 min after the drum has reached the target temp. The f/w routine is not looking for a specific B-Temp- just stable for a minute after the other conditions have been met.
The Bullet thermal mass is very low compared to a gas fired roaster so it retains less heat from the preceding roast. Being a low drum-mass roaster it’s also very response to power, fan and drum speed changes.
Thanks Bruce! In light of this, do you have a BBP recommendation. I do notice a significant difference (+/- 20-30 seconds of roast time and a 10 degree difference in turning point) in roasting with a warm up process but can’t seem to nail down a BBP for consistency?
Just go to Preheat and let the roaster take care of it.
I use B-Temp to decide when to start the next batch (and that can take over 30-40 min for the 1st batch; patience is needed!). B-Temp will creep up slowly after the first batch. For my 550 gm batch size and 410° preheat temp I wait for B-Temp to recover to about 302°-305°. By the 3rd batch it takes hardly any time at all so I have to be quick getting the cooled beans winnowed then bagged before it’s time to Charge the next batch. By the 4th or 5th batch I have to wait for B-Temp to drop to my charging B-Temp.
Since the B-Temp probe is mounted on the face plate it’s a good indicator of how much heat has been recovered since the preceding roast. Imo the secret is in being consistent; it’s more important than the pre-conditions you choose… without consistency it’s a crap shoot.
But of course there are other views, so YMMV.
Bruce
Edit- I’m doing a heat-soak roast which starts at lower power settings then starts increasing. I didn’t understand what @quartzglen was doing initially and my profile is too slow in applying heat for what he suggested. But it seems to work for my dark roasts so I keep on keeping on.
Also I Preheat to 419° on the first batch then 410° on 2nd & later batches.
Keep in mind Rao writes primarily with a large gas powered commercial roaster in mind. His protocol is aiming to replicate the total system heat so that the roaster is in an identical spot, thermally, at the beginning of each batch.
The bullet has an algorithm to replicate this for the IBTS to try and match conditions, but we have an additional data point - the BT temp. Like Bruce mentioned, if both of these temps don’t match at the beginning of each batch, your roasts are going to start differently.
Typically it’s hardest to nail down the first batches (when the system is at its coolest) I’ll also typically preheat at least +10f hotter than my target temp for 20-30 minutes and then let the roaster cool into my target charge temp.