Huky and Airflow - Let's Continue the Discussion

[thusband]

Wow this comes as a surprise because that's never happened to me using the method in the guide or any other approach that includes a lot of fan in later stages of the roast. Have you got that baffle in the J tube all the way open?

Yes, the baffle is wide open.  I think it's the poor sealing around the vent bowl.  There's hardly any pull at 25%.

I should clarify.  The fan at 100% at the end of first crack does pull chaff but by then so much has fallen down into the stove there's not much for the screen to catch.

[Taekwondodo]

I really don't understand the role the airflow plays in the roast. I'm not able to intuitively alter the fan mid roast to achieve a certain result. So far my use of the fan has only been following instructions to "Change fan to X at Y point in the roast". Is there a somewhat in depth explanation of this anywhere?

[Gregr]

I don't have an in-depth discussion to point you to but I'll list some of what I think the fan can do to help you along.
A small amount of fan throughout most of the roasting process helps to evenly distribute the heat to all the beans, generally yielding roasted beans that look very uniform in terms of color.
A small amount of fan (approximately 15-35%) will give a boost to the temp inside the drum.
A burst of very high fan (over 50%) can remove heat from the drum- watch the MET and ET drop shortly after you crank the fan up high.
High fan for long periods can effectively slow the roast a great deal. I like to use the fan at high settings to temper the flick that occurs around the last phase of the roast.
No fan at all during the drying phase, or at least part of the drying phase, can help gently bring the beans up to roasting temps and help them retain some moisture.
A burst of high-ish fan (50-75%) at the end of the drying phase can help remove moisture from the drum and give a boost to the bean temp as it moves into the ramp phase.

[hankua]

Thanks, hankua, what were your old measurements?  I guessed at percentages on my Variac but with gaps in the pieces maybe my 50% is more like 25% and 25% is nil. 

I can't quite picture your gasket set up with two holes.  I thought a thin ring cut out of a silicon sheet might work.  Not sure where I'd get the sheet though. 

I also thought when I put the J-pipe in the funnel if I pressed down hard on the wood sleeve before I tightened the screw it might make a better seal.

edit: silicone not silicon.

I'll have to take a picture of the gasket. I traced the outline/ring of the top plate for the gasket and cut it with a box knife. Placement was: stove body, grill, top plate w/fasteners. Inexpensive silpad is a good idea for a gasket.

Just for fun I tried measuring the air flow from the empty roaster, drum rotating without the J-pipe. I could feel some air flow, would not register with the anomemeter; but the lighter flame flowed upwards verifying a small amount.

My first attempt measuring air with all the exhaust connected, was over the chaff funnel opening which fit the anomometer. I was a little surprised the readings with the J-pipe were as close, just a loose seal between the funnel and pipe end.

Here's the first set of readings chaff funnel/no J-pipe. Starting out at 120v and moving lower, I'll have to do another set of measurements from low to high. Something went wonky at 25v, it might be a case of inconsistent reliability at that voltage. Using the dimmer made low fan easier, going from high to low with the slide bar and built in detent; but could only manage two other settings afterwards before 100%.

New Huky Air Flow Measurements - Funnel Top
(Measurement taken from the exhaust fan funnel top, with all hoses connected)

120v-17.7m/s-100%
100v-17m/s-96%
90v-16m/s-96%
80v-15m/s-84%
70v-13.8m/s-77%
60v-11.5m/s-64%
50v-9.2m/s-52%
40v-6.4m/s-36%
30v-3.8m/s-21%
25v-1.1m/s???

[thusband]

Yes, I'd love to see a photo as I still can't get my head around it.  Thanks!

I forgot about using a flame in front of the trier hole to judge fan pull.  I'll give that a try today and see if 25% has any pull.

[hankua]

Just did the bean cooler fan.

[hankua]

Two more photos.

[thusband]

Got it.  Many thanks, hankua.

[SusanJoM]

So the mailing cardboard is just the pattern, right? 
That makes sense. 

And the silpat compresses with almost no weight so it closes up the gaps?
Excellent.

I had used high temp tape, but that makes taking it apart for cleaning a sticky mess.

[hankua]

Yeah, the mailing cardboard was on the thin side, and handy. There's still a tiny gap on a couple of sides, gluing the paper gasket to the top ring would eliminate that issue I think. If one thickness of silpad didn't work, it could be doubled up. Does this make any difference? Not sure, but it's easy to do and Huky owners love to experiment.

[thusband]

I did some flame in front of the trier hole tests and at 25% there was no pull at all.  In fact it was slightly blowing out!  Going from 25% to 50% there was still no pull but if I went up to 75% quickly, built up some RPM's and then down to 50% it pulled like, I guess, it should.  I read about doing that in one of the threads here.

There are a lot of gaps between the flat metal ring and fan body cause by the grill.  I removed the grill which closed that gap and the pull is now better.  I think if I cut out some gaskets like hankua did it'll be even better.

[hankua]

That's a good idea, I'll have to try removing the grill. My measured airflow went down instead of up, sealing the gap underneath the top plate.

I really don't subscribe to the match/tryer airflow measurement, reason being the back of the drum is ventilated and roaster is designed to be operated with the tryer in place. If you can feel any airflow with your hand, exhaust is working. Smoke is going be seeping out the fan/bowl assembly if the airflow is 0 as well.

Every setup is different, and using a constant speed blower and better damper is also a consistant way to manage air. The Yang-Chia line of roaster has precision dampers with evenly graduated air settings and very quiet blowers.

 I like the idea of a 3" exhaust with a blower, connected to a box under the Huky fan. The blower could provide a negative air pressure, while the Variac controls the actual air flow during roasting. That way we could stick to 3" exhaust piping, without the 2 1/2" headache.