[Homeroast] RK drum learning curve troubles

John Nordling john.nordling at gmail.com
Wed Feb 4 16:13:29 CST 2015


Okay . . . after a couple phone calls, a lot of reading and listening to
what you all have had to say on the topic, here's my plan:

1) Suck it up, admit defeat, and order the right motor and gearing (the
first and third parts of this are done.  I still think I could make it
work, so I can't bring myself to admit defeat).  In the end, losing several
pounds of quality beans because of slow rotation and a motor of
questionable quality is not going to be worth the heartache it will
ultimately cause.

2) Run the temperature higher OR run a smaller load for a few tries to dial
in the roast profile, then use RK's guidance on how to relate larger loads
to temperature adjustments.  For whatever reason, I'm not getting enough
energy into the beans fast enough.  It may be the low ambient temperature,
it may be the placement of my thermometer (I'm going to thread my digital
thermocouple in somewhere before I roast again), or it may be that because
of the low ambient, I'm not vaporizing propane fast enough to drive the
chemistry that happens in the beans at an acceptable rate.

Someone asked about the distance from my drum to my burners - it's several
inches, but I haven't measured it.  I have also placed a stainless plate
across my burners to diffuse heat better.  So, while I'm effectively
heating the air around my drum, I think I'm not pumping enough energy into
the drum, even with my vents baffled way down.

Thanks for the feedback.  I might try a 1 lb load tomorrow night out of
impatience with the USPS, but most likely I'll hang tight until my new
motor gets here.

-John

~~
"Can't believe how strange it is to be anything at all."   Neutral Milk
Hotel, *In the Aeroplane Over the Sea*

Email:  john.nordling at gmail.com

On Wed, Feb 4, 2015 at 11:41 AM, Andy Thomas <adt0611 at yahoo.com> wrote:

> "motor is geared down to between 4 and 5 rpm"
> John, I think this is your problem; your motor is way too slow. I am not a
> drum roaster, but it is my understanding that it must rotate in the 40-60
> rpm range to avoid scorching the coffee. For example, the motor recommended
> on the RK site <
> http://www.rkdrums.com/index.php/en/products/misc/rk-commercialhome-motor>
> rotates at 52 rpm.
>
>       From: John Nordling <john.nordling at gmail.com>
>  To: Homeroast Coffee <homeroast at lists.sweetmariascoffee.com>
>  Sent: Tuesday, February 3, 2015 7:36 PM
>  Subject: [Homeroast] RK drum learning curve troubles
>
> I did my first couple roasts tonight on my new RK drum roaster build  - 2
> lbs each in a 4 lb drum.
>
> In the first, they came out black (blackest beans I've ever seen), hitting
> first crack at over 25 Minutes. I was going for second, but pulled them at
> 30. I think that was a good move - I must have been seconds from ignition.
> The grill temp was held around 525 the whole time (preheated, then brought
> back up as quickly as possible after loading, and monitored/tweaked
> throughout the entire roast).  I was roasting blind, because I didn't want
> to drop temp. (Also, I have always roasted by smell/sound on my Whirley.) I
> bought a thermometer from RK, and it seems accurate, though I haven't done
> a boiling water check.
>
> The second roast took close to 15-20 minutes to hit 1st crack, which never
> really took off. (I wrote down the exact time, but my log is in the
> garage). I dumped it on the cooling fan at 25 minutes. I started this one
> trying to maintain 550, but after 10-12 minutes, I bumped up to 575 because
> I figured I was under heating. I also suffered heat loss in this
> batch because I pulled bean samples at a couple points, trying to
> understand what was happening. Since it was about 20 out, that caused
> significant cooling. Finally, toward the end, my propane tank was getting
> too cold (I think-or its almost empty, though I haven't run for that long
> on it yet), so I was having trouble keeping my temp above 550 (when
> starting, I was hitting 600 at 1/4 gas.  This was at wide open). That may
> have also been a factor.
>
> Also weird-very little to no smoke during the roast (except at the very end
> of the first batch, but that was coffee oils considering ignition.)
>
> Any suggestions?  I suspect I'm not giving it enough btu's in the early
> part of the roast, but I wanted to bounce this off you all before I blow
> through another two lbs of my sacrificial beans. (I get three more tries
> before I have to either try on my good stuff, or buy more cheapos).
>
> Finally, my surplus store motor is geared down to between 4 and 5 rpm. I
> think that's ok for now, but some day I'll be ordering a faster one.
>
> Thanks for any advice you can give.
>
> John
>
>
>
> --
> ~~
> "Can't believe how strange it is to be anything at all."  Neutral Milk
> Hotel, *In the Aeroplane Over the Sea*
>
> Email:  john.nordling at gmail.com
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