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Ambex YM-2 2008 Model: Airflow for roast profiling


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Aug 15, 2016
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I am a new member here and recently purchased a used Ambex YM-2 2008 model. Running great and loving it! I am confused though about the airflow issue with this roaster and am having a hard time finding any solid answers online. If anyone could provide some insight, that would be great!

My question is, on the YM-2 when the air flow flap is open (100% or 50%) for the cooling bin, is it also pulling more air through the drum at the same time or less air? I have been told with some different roasters, such as a Diedrich, when the air flow is going through the cooling bin it means that less air is going through the drum? Just am not sure exactly what is actually happening with this roaster when I adjust airflow for roast profiling?
(Disclaimer) I am not familiar with the airflow through the Ambex YM-2.
I would guess it has a single fan running at a constant speed.
It therefore seems likely that concurrently cooling and roasting would reduce the airflow through the drum.

My roaster only has one fan.
Concurrent roasting and cooling reduces airflow through the drum.
To avoid any roast profile inconsistencies, I do not charge the drum with the next roast until the previous one has finished cooling and I have shut off the airflow to the cooling bin.
This does increase my consecutive roast times by approximately 5 minutes which is a significant percentage when I am doing many back-to-back roasts.
I wish I had a roaster with 2 fans, then I could easily cool one batch while concurrently roasting the next one.
Then again, I wish I had a private island in the tropics.
I'm thinking if you only have one fan then there must always be a small amount of air going through the drum in order to remove the byproducts of burning propane/NG so in this case when you move the lever you are taking air away from the drum and giving it to the cooling bin or vice-versa. This is how a Diedrich works. If you have two fans (one for cooling and one for drum) then both operate completely independently and adjusting the drum lever chokes the air flow through the drum
The function of airflow is in its balance between conduction and convection in the roast process. More air, more moisture leaves the beans. It turns out that you want to slow that process somewhat if you want to impact roast development. How much is totally subjective. What I would do, if I were you, is time your cooling phase with an instant read thermometer. See if it's actually slowing the cooling process when you adjust the damper on the roaster. You should be able to do this without a charge in the drum. If you see no difference on a batch cooling with the air damper wide open vs at 50% or less, then you know you can use air as a roasting control while something is in the cooling tray. I don't know the YM2 at all, but I would remind you that if it has stirring arms, sometimes they will slow the cooling process by moving coffee and allowing air to suck through a gap too easily... when we roast half-size batches on our 5K we stir intermittently and try to make sure the bed of coffee in the tray is more or less level. That dramatically speeds the cooling.

There's a video on the Mill City site, walking through the function of air pressure in the roast process. This was TOTALLY key for me, sort of recognizing the "why" of some of what I was seeing when I roast (only been commercial for 6 months.) I highly recommend you look it up. I know it's there... I showed it to someone else earlier this week. I am not affiliated with them, nor do I use their roasters--though I WOULD if I had started out on my own as opposed to with a group. I think the individual who was teaching in the video works for Cafe Imports, and we're delighted with them as a coffee distributor, FWIW.
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Thank you all for your input, much appreciated! Yes, I also emailed the owner at Ambex and received the same response in that when more air is pulling through the cooling bin it equates to less air going through the drum and vice versa for the YM-2. Now for perhaps the subjective stage of managing air-flow for roast profile development along with charge temp, bottom temp, 1st C, 2nd C and drop temp. Perhaps this is where the opinions vary a great deal, but I have been reading up on air flow as follows: From the start of the roast to about 270 F, minimize air flow through the drum, then from approx 270 F to 365 F perhaps 50/50 airflow, or medium air flow, and then from 365 F on through dump it is 100% air flow through the drum. Thoughts?