My days of being dogmatic about roasting are over - Page 6

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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farmroast
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#51: Post by farmroast »

Ken Fox wrote: The aluminum inner pipe will heat up quickly and create a draft going outwards, whereas the current SS Armadillo hose takes forever to heat up, plus has an irregular shape.
This should really help. Fast heat up and easier to keep consistency in the flue temp.
These are considerations used for pellet stoves.
A rule of thumb equation we are using has been adopted by most pellet manufactures. The equation is called the sum of Equivalent Vertical Length (EVL). All of the above mentioned venting restrictions have been assigned EVL values as follows:
Each 45 degree elbow = 3 EVL
Each 90 degree elbow and Tees with cleanout = 5 EVL
Each foot of horizontal run = 1 EVL
Each foot of Vertical run = 0.5 EVL
LMWDP #167 "with coffee we create with wine we celebrate"

Ken Fox (original poster)
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#52: Post by Ken Fox (original poster) »

Thanks, Ed.

One of the risks of buying this level of roasting equipment, as Rob has alluded to also, is that the manufacturers are not used to dealing with the general public, rather they deal with businesses who have people on staff or available to deal with this sort of thing. Collectively, Rob and I have had issues with advice/instructions given regarding gas supply, gas regulation, and ducting. These are not things the average home roaster is used to dealing with.

Unless one is prepared to deal with these and other unexpected problems, one should probably choose a more straightforward and user-friendly type of roaster.

ken
What, me worry?

Alfred E. Neuman, 1955

Ken Fox (original poster)
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#53: Post by Ken Fox (original poster) »

The exhaust from my Diedrich IR-1 roaster was revised last Friday, to produce a less-restrictive exhaust path, allowing easier exhausting of heat from the roaster and better chaff removal. Here are a couple of photos of what the HVAC contractor did:



and



The former tight 180 degree elbow that was present just after the exit from the cyclone has been replaced with a "soft elbow," plus the entire system is now rigid and double walled. In addition, the former standard exhaust cap has been replaced with one that is more or less windproof (not pictured).

I did a roasting session with 1lb batches the day after this was installed and the roaster clearly performed better. Even though I ran the burners at their lowest setting (2" water column) with the damper set to run the air 80% through the drum (for testing purposes on a test batch of junk coffee), the burner did not go out. In addition, chaff removal from the beans was less of an issue than before.

I need to test the roaster with a more standard batch size (I intend to use 2lb as my usual charge weight) before concluding that this modification was successful, but it appears to have been effective.

Using this roaster is very counter intuitive for me at this point. I am not used to having ventilation and heat/burner input control at the same time. With my old 1lb sample roaster, I applied heat gingerly for the first few minutes, then cranked the burner up, then after approaching first crack I turned the burner way down and kept reducing flame height until the end of the roast. With this Diedrich I'm doing more or less the opposite. The roast starts with a fairly low heat input, which is increased a bit once the damper position is changed to have a 50-50 airflow through the drum (in the mid position) after about 4-5 minutes. Once first crack starts you are supposed to shift the damper to increase the flow through the drum up to 80% airflow through the drum until the end of the roast. Each time you increase the airflow, you have to increase the heat input to the burner; this is to compensate for heat loss from the drum as the airflow increases. When I roast a pound of coffee I'm starting out with 2.0 to 2.5" of water column on the burner at first, but at the end of the roast I'm up to 6" of water column or therabouts just to finish the roast in a reasonable time period without stalling the roast.

It goes without saying that there is a real learning curve when going from a smaller roaster to something like this. And, it is easier for me, because I am not making the transition from a consumer roaster, merely from a smaller commercial level sample roaster up to this Diedrich.

ken
What, me worry?

Alfred E. Neuman, 1955

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farmroast
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#54: Post by farmroast »

Ken
That looks great! The gentle curve at the start should really help.
LMWDP #167 "with coffee we create with wine we celebrate"

Ken Fox (original poster)
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#55: Post by Ken Fox (original poster) »

I did a series of 2lb batches today, 4 in total, and found the revised ducting a real improvement to what I had before. What's more, it was quite windy outside, and the wind caused no problems whatsoever with the roaster burner, when this had been a real problem before both as regards heat in the drum and chaff removal while roasting.

At this point I am not able to exactly replicate roast profiles from batch to batch, however at least with the 2lb batches I am able to get more or less the same overall roast times and essentially the same post roast weight loss each batch (~16%) which is what I shoot for and what I used to get on my old 1lb sample roaster. I am not able to comment yet on the relative improvement or lack of improvement in my roast product, although today's roast session may help in forming an opinion.

As to trying to replicate the slow start/fast finish roast profile(s) preferred by Stephen Diedrich, I'm not at all sure they are possible on my roaster as currently configured. The only ways I can think of to get a slow start (with first crack starting at 11-13 minutes) are to decrease the flame height/heat input and to increase the airflow. Doing so will result in not enough heat going into first crack to be able to finish the roast in 2-3 minutes if the goal is to get to, or close to, the onset of 2nd crack. This assumes one would use full on gas flow (7" WC natural gas at the roaster gauge) plus full on air flow. The full on air flow is necessary to evacuate the chaff and is in fact how the roaster is supposed to be operated after the onset of first crack. One is supposed to use full on air flow for a total of 1-2 minutes before the onset of first crack, to help evacuate the chaff as soon as it becomes visible through the viewing window into the roast drum (typically around 4-5 or 6 minutes into the roast).

I can draw out the build up to first crack to 11-13 minutes if I want to, but I see no way to finish as quickly as Stephen prescribes, short of reducing air flow which I think would be a mistake.

What I've ended up with so far is an amalgam of my prior roasting profiles with my sample roaster and what Stephen Diedrich recommends. I'm hitting first crack at 10 to 11 minutes and taking about 4 minutes to reach onset of 2nd, which is where I'm ending the roasts, at least for now. The result is ~16% weight loss and the beans appear to be roasted to FC to FC+ on visual inspection, about what they looked like before coming out of my sample roaster.

I think the results will be good, but I won't know for sure until I taste them over the next week.

ken
What, me worry?

Alfred E. Neuman, 1955

godshot
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#56: Post by godshot »

Ken Fox wrote: The former tight 180 degree elbow that was present just after the exit from the cyclone has been replaced with a "soft elbow," plus the entire system is now rigid and double walled.
You mean 90 degree elbow, I presume. 180 degrees is more of a switchback than an elbow.

Ken Fox (original poster)
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#57: Post by Ken Fox (original poster) replying to godshot »

Yeah. What's 90 degrees among friends?

ken
:mrgreen:
What, me worry?

Alfred E. Neuman, 1955

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Carneiro
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#58: Post by Carneiro »

Ken, what was the temperature reading when you finished these last roasts you are describing?

Márcio.

Ken Fox (original poster)
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#59: Post by Ken Fox (original poster) replying to Carneiro »

Marcio,

In degrees F, it was 421-422. This is in the same general area as the finishing temperatures on my 1lb batches, which might be a degree or 2 F lower to hit the same level of roast (FC to FC+; ~16% weight loss during roast; no visible bean oiling at the time of bean dump; very start of 2nd crack or just before).

This is supposed to be a "bean temp" measurement, however I would not attempt to transfer it to any other roaster, regardless of where the "bean temperature" probe is located. On my 1lb sample roaster, the end of roast temperature for reaching the same level of roast is around 435 to 436.5F. On my M3 Quest it is around 428 to 430F (225g batch size). All of these temperatures are obtained from TC probes located in the middle of the swirling bean mass, and hence represent "BT" of one sort or another. Different batch sizes and roast profiles on any of these roasters would be expected to change the final (measured) temperatures in a "non-trivial way."

ken
What, me worry?

Alfred E. Neuman, 1955

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Carneiro
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#60: Post by Carneiro »

Ah, yes, as the probe measure the bean+air mass around it, for sure it will vary from roaster to roast as long as from bach size to another.

I was curious as I've roasted some batches on a Diedrich IR-12 (1200 g batches). But in general, at the IR-12 or now at my Quest M3, I hardly go over 207C, 2:30 to 3:30 from 1C to the end, but in general I get 16% loss too.

I think the way Steve advocates his roaster can be used to lighter roasts, finishing below 210C in a short time. Of course it depends a lot on the batch and coffee (I'm always talking about Brazilian as I can't roast another bean!).

Márcio.