North Coffee 2 kg cast iron? TJ-067 1500 gram profiles?
We get a ton of referrals from Tim at North Coffee re. his various roasters. Kirk asked some very good questions and because I’m basically a very lazy person. I’m posting my email to him as this weeks blog post:
Tim asked me to touch base with you re. 2 kg roasters.
I have roasted extensively on the TJ-067G and E, the TJ-012, and the TJ-072.
With a bunch of work, the TJ-012 can be an excellent performer. We replaced the burner, this was the old one:
installed an ignition system, it came with a push button spark generator like a BBQ grill:
Replaced the drive sprocket to increase the drum speed, ended up reworking the cooling tray and arms completely because I entirely loathed them and the tray was sprung out of round on arrival:
The construction is light sheet metal and tubing. It turned out kind of cute, but it was a lot of work and as you can see, I made my son Alex do most of it:
After a month of work and about $1800 worth of parts, we got it to perform about as well as the TJ-067 or TJ-072 without variable fan speed.
This is why I don’t normally sell them. If you want a winter roaster project, I’ll add one to an order for you. Personally, I won’t rebuild one again.
Meanwhile, the TJ-067 and the TJ-072 are identical save for the addition of one extra burner and a slightly larger drum on the 2 kg version.
Running on propane, I regularly roast back to back 1500 gram charges on the “1kg” TJ-067. As a matter of fact, last weekend I roasted about 100 lbs of coffee over three days of “Big Central” here in Minneapolis. In the wind and the cold, we managed 1500 gram roasts all day Saturday simply because we couldn’t keep up with the requests for samples. -check out Home-Barista (HB Big Central) or my blog at millcityroasters.com (MCR Big Central) for pics.
The North manufactured roasters are ridiculously overbuilt. Solid plate steel construction, 4mm thick stainless drums (between 9 and 8 gauge stainless (I’m from the Midwest: we routinely round down) variable drum and fan speeds and data logging included on everything we offer.
The big deal about cast iron drums is mostly a function of heat output and control. Cast iron holds a lot of heat and releases it relatively slowly. Most of the issues people think they have with stainless is in heating to too high a charge temp to roast a too large charge. The North manufactured machines have several advantages in this scenario.
First, the plate steel construction is a massive thermal battery. These are built more like a Geissen than you’d imagine. They are very thermally stable. Second, they have excellent burners and burner control over their entire range.
You can literally tune the burner down to equal the output of a row of birthday candles or ramp up to a 30F+ degree rate of rise with a maximum charge.
This is what allows us to profile a 1.5 kg charge in a “1 kg” roaster. My profile for a 1500 gram charge is something like:
Drop temp: 320-350F
-fan off and gas at .5 kpa for 1-1.5 minutes.
Drying: 4-5 minutes total, end at 300F
-fan to 30% at 1-1.5 min, gas ramped to 20-30F/ min by end of drying.
Development: decreasing ROR to first crack
-decrease gas pressure every 45 seconds
First crack: 8-10:30
-ROR 10-14F/ min
Drop: 2-3:30 after first crack.
You have your choice of drum speed and potential fan adjustments. I usually ride the roast and tweak those depending on the bean.
I thank you for your interest. I should have addressed most of this on the website long ago, but there’s always a (metaphorical) fire to put out. I’ll post the text of this email in it’s entirety to my MCR blog in the hope that it helps others to either choose a roaster or run one.
Please call me if you have any questions.
Mill City Roasters, LLC
1050 33rd Ave SE
Minneapolis, MN 55414