I’m very interested in trying this pre-soak method as I’ve noted baked notes in many of my roasts and this could be why. Would you mind sharing a representative roast profile to help solidify in at least my mind how your adjustments through that first stage are being done? I was going to go search through the online profiles, but last time I checked one has to scroll through hundreds of profiles to find the user of interest.
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I’m curious what version roaster you have? I’ve the V2 and there is a very definitive change in every level of drum speed selection.
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I’ve noticed the same change in drum speed as noted by Tony.
I’m curious regarding Charge temps as per Quartzglen. If a higher Charge temperature than 330f is desired, why not just start at your target of 370f?
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I was able to upgrade from a V1 power board to a V2 power board at the end of June. With that change I can now control drum speed for the first time in 1.5 years. I’m like a kid with a new toy and can’t seem to leave drum speed alone! 
Bruce
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Bruce have you noticed that your tryer is less effective at catching beans with lower drum speeds? Using D6 with a 450g batch I had trouble getting more than 2 or 3 beans into the tryer in say 10 seconds.
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Now that I have working drum speed control I have so far been increasing drum speed as the roast progresses. By the time I think to use the tryer it’s higher than D6 and I have been able to catch a few beans ok. I picture the beans falling away from the upper rotation path earlier since there’s lower centrifugal force at lower drum rotation speeds. I’ll try to pay attention to that next time out, but what you describe makes sense to me.
Bruce
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Well isn’t that a pain in the butt! At D3 thru D6 not a single bean caught by the tryer. Needs higher rotation speed to throw the beans far enough to reach it. Not useful till I’ve increased drum speed to D7/D8 toward the end of the roast.
Bruce
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@bab, I just found the same that I can’t catch beans without a higher drum speed.
There is some worthy summaries and reading over at Coffee Roasting Navigated on drum speed: Roasting coffee basics - CoffeeNavigated.net
One part discusses centrifugal force potentially having the potential to increase wall sticking above D8. I don’t think that is a major issue, but there could be some small percentage of beans that spend time stuck in a corner or low agitation point.
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Thank you for that link… interesting analysis. Apparently the poster is in Europe… ?? Lots to read there. I have the impression they are working with a Bullet but some of the images are Probat. Need to dig into it tomorrow and answer my own questions! Bottom line, though, is that the tryer will only be useful at D8/D9.
Thanks again!
Bruce
On the recent Rob Hoos online class he shared an anecdote from roasting at a bigger shop where they had cleaned down a Probat and when reassembling, had reversed the gears driving the drum, the net result being it spun way too quick. They didn’t notice the error until they loaded the beans and instead of hearing them tumble, nothing, silence. When they opened the bean drop chute and looked in they saw their mistake. All the beans were stuck to the outside of the drum like carnival riders on the Wall of Death 
I don’t think the Bullet has anytning approaching that speed…
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Ah yes… the Wall of Death. Been there; done that; never again! Taught me all I’ll ever want to know about personally experiencing centrifugal force. That 360 seconds (or whatever it was) seemed to last hours!! I’m fairly certain you’re right that the Bullet won’t reach those speeds.
Bruce
I was trying to remember the name of that carnival ride just the other day…didn’t have to do with roasting, but now you have me thinking of each bean as a carnival rider!
Careful… that could be the stuff of nightmares!
Bruce
Tilt-a-whirl!
Yeah I don’t think the bullet drum speed can get that so high as to create that effect for all the beans. Even at 9 it seems like the bean pile is pretty stable and settling in the bottom left side of the drum. I was hoping that there would be a little more loft in the rotation.
An ImageJ analysis on the size of the bean pile for a 500g green bean batch at variable drum speeds would be interesting. Have anyone seen such an image analysis?
Some people have measured D9 around 77 RPM. Rao generally recommends 70-80 RPM for a 1-2 kg roaster. Lower RPM for larger roasters (ie. 60-70 RPM for 5-7kg & down to 50-54 RPM for 15k kg roasters).
BRADM and I were discussing drum-speeds a while back and found significant differences in the speed settings of our Bullets.
My D6 (Bullet V1.5) was 80rpm, having no issues with tipping or any other roasting defects and he had a way lower RPM at his D6 setting.
I think there is a significant variance in drum speed settings at least between the V1.5 and V2.0.
Maybe Brad can chime in and shine some light on his adjustments.
Cheers
It’s funny you should say that because after I upgraded my power board to V2, it seemed the drum speeds were quieter or slower or both. I put it down to the newer spring motor pulley but as I never made note of the original drum speeds, I can’t say for sure…
@jacob - are we imagining things ?
Mark the drum axle and count the revs.
I did it several times with 1lb. (453.6g) about
5 min. into the roast and the result was always 80rpm at D6.
Again my Bullet is a V1.5 (#001569) with about 200 roasts on the clock.
The drum speeds on my V2, measured cold and empty, are:
| Drum Speed | RPM |
|---|---|
| D1 | 42 |
| D2 | 45 |
| D3 | 48 |
| D4 | 52 |
| D5 | 55 |
| D6 | 60 |
| D7 | 64 |
| D8 | 68 |
| D9 | 74 |
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Gravitron. That was the ride.
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Raising this thread from the dead. I am starting out with a bullet and very interested to continue expanding on this conversation.
Does anyone have some profiles to share of a pre-soak? I am having a hard time bringing this concept to realization.
Thanks for any help!
-Thunderbolt