Scott Rao - ROR rate of rise "the flick"

[hankua]

Scott Rao's post on Cropster regarding rate of rise issues/defects after the onset of first crack using commercial drum roasters.

https://www.cropster.com/en/news/news-detail/news/detail/News/the-flick/

[SusanJoM]

That is a fascinating article.  (I agree with Marshall Hance's comment that it would have been more enlightening if the before and after profiles had the same smoothing factors.  Rao is certainly sticking to his guns about the absolute nature of the descending ROR, and given how many posts read in various places from people dismissing the flick as irrelevant to their success, he does make a good rebuttal.

Has anyone here with a perforated drum/slow motor  had success yet with losing the flick while maintaining the 20+% roast development? 

[Daave]

That is a fascinating article.  (I agree with Marshall Hance's comment that it would have been more enlightening if the before and after profiles had the same smoothing factors.  Rao is certainly sticking to his guns about the absolute nature of the descending ROR, and given how many posts read in various places from people dismissing the flick as irrelevant to their success, he does make a good rebuttal.

Has anyone here with a perforated drum/slow motor  had success yet with losing the flick while maintaining the 20+% roast development? 

I have had some success with my perforated drum/slow motor. What I've found is that I my ET needs to be rather high compared to my BT, since my BT seems to plateau around 25-30F below my ET. For example, if I want to drop with a BT of ~415, my ET needs to be ~445. To help reduce the possibility of scorching my beans, I've been turning my fan up to 70 on my variac at the onset of 1C, and my burner will be ~0.5-0.75 in order to keep my ET constant (Or just very slowly increasing to my desired ET). I've also been closing the drum at the onset of 1C, which seems to help keep the temperature constant since I'm raising my fan speed to 70.

Here are a few recent roasts I've had.

Honduras:


Kona:

[SusanJoM]

Can you show the ROR/Delta BT so we can see it?

Do you know how to do that?

[Daave]

I know you've recently explained it a few times. I'll look up how to do it on the forums and post some new graphs later tonight.

[thusband]

So is "the flick" more common with the perforated drum?

[SusanJoM]

I know you've recently explained it a few times. I'll look up how to do it on the forums and post some new graphs later tonight.

Excellent.
 
Tools > Extras.
There is a picture in this thread
https://www.hukyforum.com/index.php/topic,420.msg4144/topicseen.html#new

So is "the flick" more common with the perforated drum?

I can't imagine why it would be.

[Daave]

So is "the flick" more common with the perforated drum?

No. The roasting approach between the perforated drum and solid drum are just different. As long as you understand how the drum you're using works with the various variables (Fan speed, open/closed for perforated, and heat), you shouldn't get the flick.

If you use the same approach of ET vs BT with the perforated drum as you would with the solid drum (i.e. aiming to have the BT temp come up to basically exactly the ET temp), you will create a flick since you'll need to add extra energy at the end of the roast to bring the temperature up. I made this mistake my first few roasts and had a nasty flick until I started compensating for this behavior. The approach I'm taking now with my perforated drum (Which I'm still experimenting with - I'd love to hear how others approach the roasting process) is to have my ET be 25-30F above my desired BT, which allows me to avoid any flick at the end of the roast.

My roasting style so far is extremely simple. I keep the fan speed at 52 until 1C, which at that point I bump it up to 70-75. I've also been keeping the heat at 2.0-2.25 until my ET gets close to the desired temperature. Then I gradually bump it down to 0.5-0.75 when I hit my target temperature just to keep it steady. I also close the vent at 1C. I'm still experimenting since I'm still fairly new to the Huky, but I like the simplicity of this approach and the graphs it consistently produces. The beans taste great too

[SusanJoM]

Here's my "flick"

[edtbjon]

Here's my "flick"

The RoR curve looks really good as such, except that you are dangerously close to stalling the roast at the end. But it seems you're getting there. (I would try going into 1C with a bit more energy, giving a more even decline.) Learning how to achieve/place the values of the curve takes a lot of practice and I still feel like practicing after 9 months with the Huky.

[Daave]

Here's my graphs with the deltas enabled (Smooth Deltas=20). I'm not really sure if these are good or not though...

Can someone help me read these?

Honduras:


Kona:

[Daave]

I've re-read the article a few times now. My flick seems pretty horrible on the Kona, but not so bad on the Honduras roast. I'll definitely leave the DeltaBT on for now to start analyzing that data.

Susan - I'm not sure why my ET doesn't drop like yours does during my drop. My fan is at 52, and burner is 2.25. Do I need to turn the burner down or change my fan speed? What are you doing at the start of the roast through the turning point?

[SusanJoM]

I'm charging 350 grams and at a charge temp (BT) over 400. (quite a bit  higher than yours)
The grate is open.  Fan at about 50%.  Gas at 1.5 kPa for the first 5 minutes of warmup or so and then lower until it feels stable (BT, ET, MET all sort of straight lining).  Drum is turning all during warmup.

When I charge, I crank the gas to 3.5 kPa
Then at about 300F I start dropping the gas (you can see that on the profile) in fairly steady increments.
And at 1C I close the grate.

I haven't yet figured out what I'm going to change next.
Although Bjorn suggests it, I'm loathe to add any more gas;  I am more inclined to keep manipulating where in the curve I lower it and perhaps lengthening slightly the intervals to spread the slow down of ROR a bit more.

[Daave]

I think you hit on something key I'm doing wrong. I don't let my charge temp stabilize before dropping the beans in. I'm just heating the Huky until I hit a BT of 300. I'm probably doing some more roasts tonight, so I'll experiment with stabilizing the temps first.

So much to learn. I love it

[SusanJoM]

Keep me posted. 

Here's a profile I did a long time ago of just the warmup