Quest M6 First Attempts + Curves!

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
cjhacker23

#1: Post by cjhacker23 »

Hello Fellow Roasters!

So I only have about a half-dozen roasts under my belt with my new roaster, the Quest M6, but I thought I'd share a few curves and ask for the community's collective wisdom before burning though any more beans (so to speak).

I have been trying to internalize Rao, and the Quest Handbook, and think I have a handle on my general goals (adequate heat to start, declining RoR, development @ 20-25 percent of total roast time), but am having a bit of trouble with execution. Let me start with a few graphs. From Roastmaster:





Charge was the same for each (453g) with the same bean (SM Nicaragua Wet Process). I began with the roaster idling at 400 (BT) and 550 (MET) with power at 600w and fan @ 8. About 30 seconds before charging, I cranked to full power (1155w) and set fan to 0 (which is dead stop on my roaster).

Here are my observations/concerns: turnaround dips quite low (131, 155, 171). I tried correcting for this by upping the charge temp on successive roasts (416, 434, 492). I worry that charging any higher than this will lead to scorching. Is this so? Do others have experience charging in the 500+ range? Also, MET climbs quite high--to 723 at its highest point. Is this okay/normal? For MET, I placed EricS recommended probe in the recommended location, through a specially drilled screw near the top right of the drum. Do others get MET readings this high? And finally, my RoR seems to stall at the 5 minute mark and doesn't decline again until FC, on all three roasts. At dry end, I start raising the fan, thinking that this will slow the roast, but it doesn't seem to have much effect. My concern is that if I cut the heat during the browning stage, I'll drag out the roast too long. Hence the idea of raising my charge temp. Seems like I might need to raise it to as high as 550 to get everything in line, and to give me enough room to cut the heat a bit during browning. Does this seem like a good idea?

I would sure appreciate any wisdom anyone would be willing to share about what I'm doing wrong or what I could be doing better.

Thanks!

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Nunas
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#2: Post by Nunas »

Here are my observations/concerns: turnaround dips quite low (131, 155, 171). I tried correcting for this by upping the charge temp on successive roasts (416, 434, 492). I worry that charging any higher than this will lead to scorching. Is this so? Do others have experience charging in the 500+ range?
There's not really any such thing as turnaround, although you do see what looks like it. The beans start at ambient and rise in temperature. The so called turnaround is simply the BT probe having been heated to ET and being impacted by the cool beans, losing heat. So, my advice is to ignore it totally.

In the Quest roasters, there's no point in trying to build up heat in the drum, like on big commercial roasters. The drum has very little mass and cannot store much energy. On the M3 one can build a little energy, as the mass of the drum compared to the mass of the beans is a bit larger than on the M6.
Also, MET climbs quite high--to 723 at its highest point. Is this okay/normal? For MET, I placed EricS recommended probe in the recommended location, through a specially drilled screw near the top right of the drum. Do others get MET readings this high?
Yes, the versions of the Quest roaster that have total blower cutoff during warmup, such as the M6, can develop very high MET. I was uncomfortable with this, being used to my M3-Mk2, which has no blower-off position. I posted two solutions. One is to install a trimpot on the blower control and adjust it so the fan barely turns at setting zero. The other is to add a PID. In any case, this is only a warm-up issue on the M6. During the roast, the MET drops. The heaters on the M6 are a bit small for the stated maximum capacity. (The M3 is actually a more powerful roaster). It's nearly impossible to overheat it, unless you roast tiny batches. All this said, I've no idea if the really high METs we see on the M6 are a safety issue.
And finally, my RoR seems to stall at the 5 minute mark and doesn't decline again until FC, on all three roasts. At dry end, I start raising the fan, thinking that this will slow the roast, but it doesn't seem to have much effect. My concern is that if I cut the heat during the browning stage, I'll drag out the roast too long. Hence the idea of raising my charge temp. Seems like I might need to raise it to as high as 550 to get everything in line, and to give me enough room to cut the heat a bit during browning. Does this seem like a good idea?
The fan has an odd effect when the speed is changed. I still have not totally got my mind around it. One would assume that increasing the fan would decrease the ROR, since one is removing heat from the roaster. I've noted that at first the reverse is true. It seems that the heaters and outer case must store some heat. Turning the fan up moves this to the beans. But, if left like this for a short while, due to the small mass of the roaster, it begins to reverse and act as one would expect.

cjhacker23 (original poster)

#3: Post by cjhacker23 (original poster) »

In the Quest roasters, there's no point in trying to build up heat in the drum
I'm not sure what you mean. My idea is to charge at a higher temp, say at 525 or 550, so that the so-called "turnaround" happens at a higher temp. Is that not a good idea?

Nunas
Supporter ♡

#4: Post by Nunas » replying to cjhacker23 »

No, that's not a good idea IMHO. Sorry, but I know what I wish to say, but I'm not sure I can describe it to you in a more understandable manner, but I'll try. At the risk of becoming pedantic, forget about the turnaround temperature, it's meaningless. The temperature you're seeing before "turnaround" isn't real BT. The drop you're seeing isn't really a drop. There's no valid reason I can think of for raising the turnaround point on the curve. OTOH, there may be a reason for for a particular profile to to get to yellow/dry (arbitrarily 300C) more quickly. If you start from a higher charge temperature on a big roaster this will happen. Indeed, some roasters have so much drum mass that some operators lower or cut the gas for a while right after charging to avoid getting there too soon. However, on the Quest, the difference in time won't be very much, due to the low mass of the drum. It can only store so much heat. When you charge the roaster, what little heat the drum has stored will quickly transfer to the beans, but the BT won't go up by much. Perhaps the thing to do would be for you to run a few roasts at various charge temperatures, as you've already done, and watch the time to dry. On the Quest M6, you won't find the time will move much. Moreover, as you pointed out, at very high charge temperature, you risk scorching the exteriour of the beans.
Edit: Doh, what was I smoking! yellow/dry is 150C, not 300C, which is the same temp in F)

cjhacker23 (original poster)

#5: Post by cjhacker23 (original poster) »

there may be a reason for for a particular profile to to get to yellow/dry (arbitrarily 300C) more quickly.
First of all, thank you for the explanation. I understand what you are saying now. And yes, this is my goal, to get to dry more quickly, as I will have more wiggle room to achieve a declining RoR. The other thought is, maybe adjust the charge to 400g or 350g? That would get me to dry more quickly, wouldn't it?

Lastly, what do you think of the RoR curve on these roasts? Is that flat RoR from minutes 5-10 something that need fixing? Or is that okay? The way Rao talks about it, it seems like a no-no.

[EDIT/UPDATE]: Hold on, something just clicked--getting to 300 more quickly by raising my starting temp (and thereby limiting the initial dip) will NOT make it easier to achieve a declining RoR later because it doesn't take into account the delta. The problem is that the RoR is kind of sluggish to begin with. Compare it to any example of an "ideal" curve (I know, no such thing!) and the "ideal" curve has a dramatic initial rise that gradually tapers off. This is what I am trying to achieve with the Quest, and just raising the charge temp isn't going to get me there. But maybe lowering the charge amount? Or...? Some way to get the roast to take off faster. Your point is well taken about the roaster drum not retaining much heat. Perhaps painting it black, the way some early users of the M3 did? Plus insulation around the exterior? Or will this create more problems than it will solve?

Nunas
Supporter ♡

#6: Post by Nunas »

Yes, you've grasped it! Lowering the charge will have a much greater effect on getting to dry sooner than a higher charge temperature.

cjhacker23 (original poster)

#7: Post by cjhacker23 (original poster) »

:-) Thanks for bearing with me!

I just ordered some fabric insulation with which to wrap the outside of the roaster. I'm hopeful that this and/or a slightly lower charge (400g) will yield a sharper initial rise.

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Jonk

#8: Post by Jonk »

I'm by no means an expert on this but here are my thoughts.
cjhacker23 wrote:About 30 seconds before charging, I cranked to full power (1155w) and set fan to 0 (which is dead stop on my roaster)
I think you can have a more efficient transfer of that heat you're now accumulating outside the drum if you keep the fan at a low setting instead. On my ADM3s I set it on a 1½-2, but it'll be individual for each Quest I think. This way you'll avoid excessive MET as well.

I do think it's a good idea to charge fairly high on the Quest due to the limited heaters - 460F or so and lower it if you get problems with scorching.

Then instead of increasing the fan when you want to make RoR decline you can decrease heat some instead. That will always have the intended result, just don't decrease it too much or the roast might stall.

Estimated temperatures because your probes and roaster are different from mine..
I usually start decreasing power at the latest around 320F, some more around 340F and little bit after that I'll increase the fan to 3 (IIRC Rao recommends increased airflow somewhere around this point).

The approach to FC through to dropping the beans is the most difficult part for me. I will often try to push the roast so RoR doesn't crash after FC. That will mean anticipating the right time to increase heat before FC so there's some extra energy stored outside the drum. Heavily dependent on the beans and at what temperature they start FC, but say around 365F I'd probably try full power again in your case. Then full fan 30s later and when FC starts either drop power by half, completely or not at all - it depends on the specific bean behaviour..

If RoR starts rising before my intended drop temperature I'll drop anyway, but I like light roasts, YMMV. I don't care much for DTR and if you read Rao's instagram he seems to think there's been too much focus on DTR, even though he's partly responsible. I think the most important thing is to not exceed ~20-25% or so.

If a roast doesn't go to plan, I'll try to salvage it a little but I think it's difficult to remedy mistakes on an electric drum roaster. At least a failed roast will give ideas for what adjustments to aim for next time. That is another reason you might want to start with smaller batches.

cjhacker23 (original poster)

#9: Post by cjhacker23 (original poster) »

Thanks for your insights!

Regarding keeping the fan on low, Maurice has suggested this as well, especially on the M6 where MET gets very high. And I was just watching an interview with Rob Hoos, who was talking about how when he roasts on a sample roaster, he tends to keep moderate constant airflow throughout the roast, just to eliminate it as a variable.

I am a weekend roaster, and all this technique talk has me chomping at the bit to fire up the Quest... sadly, it's only Wednesday. :cry: