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RK Drum Temps?
I am excited to be a new member of and learn what other folks have done to make great coffee. I have been roasting on a 4lb RK drum for over 10 years and have always been happy with the results. (Nobody I gave my coffee to, has ever spewed it across the room). But I am certain that I will learn new techniques from everyone on how to make my coffee even better. We typically roast Sumatra/Sulawesi beans for drip use.

My setup is a dual burner BBQ grill with the RK drum mounted to a gear motor. Since the original clasp failed fairly early, i now use paper clips.



My methods are simple and relatively non-scientific. I preheat the grill to my desired temperature, load with beans, put the drum in, and set a timer. I know where my setting needs to be get a temperature of 500 which is where i usually roast batches of 3 1/2 lbs. I come back in 20 minutes when 1st crack usually starts, then listen for second crack, and set the timer for 1 minute after 2nd crack is well under way. Then pull the drum and dump them in my fancy-dancy cooler.


So my initial question is about temperatures. I have been doing a little reading and it seems like folks roast at a higher temperature than i do. I can probably get to 525 with my setup. If so, how will higher temperatures improve my roast?
chipsnchunks attached the following image:

Edited by JackH on 12/05/2014 2:59 PM
Home roaster using an RK drum. La Pavoni PDH Espresso, Technivorm Moccamaster
The thing about temps is that everyone is different, so your 525 could be another's 450 just because of the position and type of temp device. People are endlessly discussing the best way to read temps for this reason. The approximate time to 1c and 2c is a better indication of the relative heat being applied to the beans. If no one responds here, then I would read other peoples' bbq threads to see where they are landing.

Read the forum for more info, but to get you started, the most popular "rules" people like to follow to varying degrees seem to be,

1) Bean temp should hit 300f in the 4-5 minute range.
2) First crack should come 4-5 minutes after 300f.
3) Time to first crack should represent 75-80% of the total roast time.
4) Too long of a roast typically equates to "baked" flavors regardless of how it looks.
5) Bean temps should be continually increasing during the roast.
6) The bean temp rate of rise should be continually declining during the roast.

Consider that your large volume will probably affect the 4-5 minute times indicated above, but I can't speak to it cuz I'm small potatoes. To achieve their "rules", most people typically do some sort of ramping of their heat temps. If it is taking you 20 minutes to complete a roast and you are close to max temps already, then I would experiment with smaller batches, e.g. 1/2 lb, because the beans will heat faster and give you more flexibility. Also, this will save you from wasting 3.5 lbs o.f beans on a bad experiment.

I'm sure better advice to follow, good luck :-)
Thanks onions ... what technique do people use to measure bean temperature in a rotating BBQ drum?
Home roaster using an RK drum. La Pavoni PDH Espresso, Technivorm Moccamaster
Very good question, unfortunately, I can't answer it completely :-( Even though I use a bbq thermometer for the my bean temps, I have a fluid bed roaster, and while there are general principles shared between roasting methods, there are some definite nuances that are different, one including probe placement. I would start by reading the bbq/drum threads.

Couple things in general. It is a good for your probes to be locked down so they don't move from one roast to another. Slight changes in the position of the probe can make a big difference in the consistency of the readings. Based upon my experience, I don't recommend drilling a hole and inserting each time you roast.

Also, you want to use something that will average out the temps, so an exposed thermocouple connected to a multimeter with no averaging function will give wildly fluctuating readings due to their high sensitivity. A high temp thermometer or something with a casing around the thermocouple like this will generally work better.

Finally, you don't want the probe to average the temps of what you are trying to read with something else like air or the metal housing of your roaster. So make sure your bean probe is not touching air and some people will isolate the probes from the housing using pure silicone caulking or equivalent, depending on their setup.

It does take a little effort to get it all sorted, but it adds a whole other level to your roasting. Apart from getting better coffee, it lets you actively participate in the process, as opposed to just waiting for it to go off. For me, it makes roasting something I look forward to, as opposed to something I have to get done.
OK, I assume by bean temperature, you are talking about the temperature inside my chamber? (as opposed to doing some kind of ir check of the beans themselves?

If the latter I am using a good quality Tel tru BQ300 Bi-metal themometer. it is fixed.
Home roaster using an RK drum. La Pavoni PDH Espresso, Technivorm Moccamaster
I roast in a 4 pound RK drum in a Weber 36000 BTU gas grill - 3 burners.
I think 20 minutes is too long to get to 1st crack - I shoot for something closer to 10 minutes and then 3 to 4 till second crack if you want to go that far. Also, I don't want to get there too fast so I try to maintain lower temps till I get to a bean temp around 325.
I typically roast only 2 pounds at a time to help get these temps.
Also, as you know, getting a bean temp is hard in an RK drum, but I use a technique I saw on a thread somewhere quite a long time ago. I use the digital themometer with K type thermocouple that Sweet Maria's sells - they currently sell for $29.90.
I tape the thermometer to the grill handle with, you guessed it, Duck Tape. Then I wrap the wire around and around the spit and then thread the end through one of the holes in the drum. I position the sensor end so that it's close to, but not touching, one of the stirring vanes - fairly deep in and on the side that the coffee beans will fall on as the drum rotates. This requires you to be in attendance while the roast progresses. As the thermometer rotates, you can read the temperature. I use a data sheet to post my temperatures each minute. (you may not like this if you are used to being away from the roaster for 20 minutes.) I like to use all my senses, time is of course important, but with this rig, I can usually count on 1st crack - which I listen for - around 410 degrees BT and somewhere between 9 and 11 minutes. For a 2 pound roast, I typically will use a environmental temp of around 400 degrees until the BT reaches 325 then I increase the heat to 525 until 1st crack then I back off the heat to about 470 - otherwise the bean temp increases too fast.
I dont mean to hijack the thread, but wondering about the thermocouple setup that bean2friends uses. Is one pound of beans enough to cover the sensor or do you need more to cover it and get a more accurate reading?
I'm new to Homeroasters and I enjoyed this post because I'd like to find others with the same setup I have to fine tune my roasts.

I too have an RK drum on a two burner Char-Broil grill that I'm pretty sure is the same one seen in the RK videos. I've had the drum for about 7 or 8 years and there is zero wear and tear on it. I use a thermocoupler centered on bean mass during roasts which have helped quite a bit. I also use a large steel baking sheet to diffuse the heat.

I also used some thin metal sheeting to cover the rear vents on the grill which helps to control temperature.

For tasting I've used a variety of methods including old fashioned drip to siphon to french press to moka pot and now I have an Aeropress which I really enjoy for drinking and tasting my coffee.

The all important grinder isn't high end but a really nice economical Capresso Infinity conical burr grinder. I don't do espresso any longer so this grinder has worked beautifully for my needs over the years.

Overall, I've really enjoyed my entire setup.


* I heat up the grill to 500 degrees and keep it there until I know my grill is truly heated up so it doesn't become a heat sink

* I pre-heat with the drum inside the grill.

* I do not take out the drum to load the beans...I open the door on top and quickly funnel the beans into the drum

* I control the re-ramp of my grill temp keeping an eye on the thermocoupler temp...I essentially get to 480 to 500 (NEVER over that temp) 6 to 8 minutes.

* I BRIEFLY lift the lid after rolling 1C...

* I never roast long because I typically roast 1.32 pounds of green beans to get 1 pound of beans hit 1C consistently between 8 and 11 minutes...with a nice pause between 1C and 2C...with roasts always ending in roughly 13-15 minutes.

* My cooling method is to dump my beans into a 14" reinforced flour sieve on top of a cheap elevated floor fan (elevated on saw horses)...I stir occasionally to blow chaff like a charm every time in all types of weather.


* IN GENERAL, the coffee I roast is usually very balanced...even while using different beans from around the world...but this has taken time to learn without the sense of sight involved.

* I have NEVER had an uneven roast...never...I think this is due to the incredible agitation (high RPMs from the motor) and the use of the cheap, steel baking sheet to diffuse the heat.

* Heat control is very responsive...almost too responsive given the rather basic controls of the grill itself...the use of the thermocoupler on bean mass has been a huge help in this regard.

* Set up and take down is amazingly quick...with a small footprint in my garage...(makes the wife happy).


* I think this setup would be perfect for roasters who want to continually mass roast the same bean type over and over...i.e. a small commercial roaster who buy and sell the same bean over and's less perfect for those of us who like to try different types of beans. It took me quite some time to develop my roasting skills with different beans with this roaster. Even so, I still don't always hit the roast that I want due to...

* ...You can't SEE the beans develop through the someone without sight you do develop your other senses...but...I'd really like to see the roast given that I like to roast a variety of beans

* To some degree I have to factor into my roasting times the time it takes to remove the drum and dump the beans...over the years this has become less and less of a is a factor in every roast.


* In general, the drum/grill requires a tremendous learning curve with each variable needing to remain exactly the same over short, don't mess around too much with the variables.

* I would recommend this type of roaster with reservations which would be true for all roasters

* I AM looking around to build another type of roaster where I can SEE the beans

** The all important taste of the coffee is general are typically high quality even when I miss the roast level. The drum method tends to give you more body in the cup. I hesitate to talk more about this because you also have to match your brewing variables with the type of coffee you GENERAL...I get a great product to work with from my drum/grill setup.

That was a long introductory post...I look forward to refining my roasting skills from trolling these forums over time...roasting coffee is like golf...easy on the front end...but takes a lifetime to master.
Edited by tenacean on 01/01/2015 10:05 AM
Yea, someone else with an RK Drum! What is your thermocouple setup? Are you monitoring temps inside the drum? My set up is the kit including RK's thermometer so I can only monitor interior temp of the bbq itself. I am having pretty good luck, still learning the best temp profiles etc.
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