Oh, my aching head. I'm so confused! I don't have time to pull up the
schematic just now (still have it though), but I didn't recall that you were
DC'ing the fan. It takes DC? Good grief, I don't even remember -- are there
some diodes on the back end of that motor? I'd thought it was an AC! Geez,
I'm REALLY out of it. ;-)
I run line into a 140 boost Variac (a low wattage unit I've had for 20
years) for the blower, and let the heater run through a short extension cord
to cool it just a bit. With a Corning 3" bread tube and generous tilt, I'm
able to "flow" (I won't call it "loft" per se) a superb circulation of 10
oz. (sometimes more) if the beans are small, 8 oz. for typical dense beans.
Monsooned Malabar is insanely light; in theory I could do more than 8
easily, but in practice the flow is darned weird when I go much taller.
There's a proportion of tube width to height that makes a definite
difference. Also, when I say "small" beans, I do NOT mean peaberry; the form
of a peaberry bean presents serious challenges to the way this is working
for me. The hemisphere morphology of a typical bean makes for far better
agitation of a bean mass, IMO. I have to do smaller batches of peaberry
than of normally shaped beans of the same size.
On Wednesday nights I do six to eight 8-ounce batches in the Pumper.
The operational profile consists of preheating to 350 or so with the fan on
full (boost to 140), charging the column with 8 ounces, and waiting till the
bean mass is at 350 before lowering the Variac boost. Depending on ambient
air temperature, just how and when I do this varies. It also depends on
whether I'm doing a light roast or a dark roast. In any case, I shoot for 12
to 16 minutes.
I also use a Salamander IR emitter alongside the tube, which has an
interesting way of "autopiloting" the last few minutes of roast, once the
beans have expanded enough that the mass is high enough in the tube to
absorb the heat well. The effect is to smooth out any adjustments I make to
the blower during the last few minutes of the roast. I haven't thought of
that as the system "being less responsive" so much as the system "being less
vulnerable to my random idiocies with that Variac knob." ;-)
I also have my "flow impeder" in play, which takes a lot of pressure off the
beans that are below the tube, down where the action is. I suspect that's
very much responsible for the amount of beans I can do. Also, it helps me
when I haven't weighed a batch and I'm just "winging it," because as I pour
beans into the tube the point at which they begin to fail to circulate well
is more of a range than a point; they don't just STOP. Operationally, when
doing this I always leave the boost at about 135 just as a safety; when the
flow slows I stop charging and boost back up to 140.
What kind of "loft" are you after? A "spouting up the center" kind of thing?
I'd think not, if you're tilting.
On 10/2/06, Douglas Strait wrote: