Planning your roaster build – For the Inventor

This guide is intended for the inventor-type customer that wants to understand all the finer engineering details required for building a roaster, or if they have their own plans to complete their roaster.  

Note that this area contains more details than with the normal approach.  

You will need much greater handyman skills, and home-engineering skills when following this path. 

If you wish for a more no-nonsense, one-stop-shop approach, please see the “I just need to roast now” guide here.

Choosing a drum\roaster

Choosing a drum size is a common question by many.  We've have a flow chart here for helping understand the process or, cClick one of the items below.

We recommend a 2LB Drum Everything kit for home and hobbyist users that expect very light use and have no intentions of ever roasting for business.  See all 2LB options here.  

 

If you consume large amounts of coffee you may want to opt for the larger 4LB Kits

 

It's quite common for you to begin roasting exceptional coffee, share with family and friends, and in no time people are willing to pay you for fresh coffee.  This has a curious way of turning a hobby into a business.  If you think that could end up being you, then opt for the larger 4LB drum Everything kit.  See all 4LB options here.

If you're on the fence, about going larger, go ahead and get the next size up, as we hear many folks wishing they had gone larger, but never wishing they had bought smaller.

 

 

DRUMIDEAL BATCH SIZEMAX BATCHMAX VOL /HR
2LB Drum2LB2LBup to 6LB per hour
4LB Drum4LB5LBup to 15LB per hour
6LB Drum6LB7.5LBup to 22.5LB per hour
8LB Drum8LB10LBup to 30LB per hour
12LB Drum12LB15LBup to 45LB per hour

IDEAL BATCH SIZE: Guaranteed even roast

MAX BATCH SIZE: Usually achievable with extra heat available, evenness may suffer in some machines, results may vary.

If you're looking to start a business, but you're unsure of yourself, your business plan or your customer base, you might start with smaller business drum.  While we've seen a few people start a business with a 4LB drum, it quickly will result in quite a lot of roasting time.  

At a minimum, we find the 6LB Everything Kit to be the most suitable for entry level business roasting.  

If you are sure of yourself, your business plan or business model, and have access to a substantial customer base, we recommend starting with the 8LB Everything Kit or the 12LB Everything Kit. 

Remember, these drums will roast these volumes 3x and hour.  So the 12LB Everything Kit can roast up to 45LB of coffee per hour when fully loaded, the 8LB,  30LB and so forth.  These volumes are calculated by overloading the drums by 20% 

 

 

DRUMIDEAL BATCH SIZEMAX BATCHMAX VOL /HR
2LB Drum2LB2LBup to 6LB per hour
4LB Drum4LB5LBup to 15LB per hour
6LB Drum6LB7.5LBup to 22.5LB per hour
8LB Drum8LB10LBup to 30LB per hour
12LB Drum12LB15LBup to 45LB per hour

IDEAL BATCH SIZE: Guaranteed even roast

MAX BATCH SIZE: Usually achievable with extra heat available, evenness may suffer in some machines, results may vary.

 

If you are sure of yourself, your business plan or business model, and have access to a substantial customer base, we recommend starting with the 8LB Everything Kit or the 12LB Everything Kit. 

Remember, these drums will roast these volumes 3x and hour.  So the 12LB Everything Kit can roast up to 45LB of coffee per hour when fully loaded, the 8LB,  30LB and so forth.  These volumes are calculated by overloading the drums by 20% 

 

 

DRUMIDEAL BATCH SIZEMAX BATCHMAX VOL /HR
2LB Drum2LB2LBup to 6LB per hour
4LB Drum4LB5LBup to 15LB per hour
6LB Drum6LB7.5LBup to 22.5LB per hour
8LB Drum8LB10LBup to 30LB per hour
12LB Drum12LB15LBup to 45LB per hour

IDEAL BATCH SIZE: Guaranteed even roast

MAX BATCH SIZE: Usually achievable with extra heat available, evenness may suffer in some machines, results may vary.

Choosing a heat source

A propane or natural gas grill is the preferred method for roasting.  Accurate heat control makes the roasting process much easier and quicker.  This is our recommendation.

 

Grills - Grills are the most common and easily accessible method.  Purchase one, or use one that you already have.  There are some requirements.  See below:

Grill Requirements for RK Drums

Understand that NOT ALL grills will work for your roasting application, so picking the correct grill is important. 

One of the most common questions we get is "Will this or that grill work?"  Determining if your grill will work is quite easy!  Please click the size of drum you have purchased or want to purchase below to see the requirements.

2LB Grill Requirements

4LB Grill Requirements

6LB Grill Requirements

8LB Grill Requirements

12LB Grill Requirements

While we don't recommend grills specifically, as of 2019, the following brands at Home Depot seem to work well for anything up to 12LB, and can be had or $180 or less.

NEXGRILL
DYNAGLO

SPECIAL NOTE:
If you are planning on buying a grill anyway, go ahead and buy a grill that will fit a 12LB Drum, this way, since all of our kits are cross-compatible you can just swap the drum out if you wish to upgrade later on.  

 

volume

The easiest way is to choose one of our kits that has most or everything you need.  Select a roast volume below to see the kits.

  • 2LB Roasters - Roasting for the family or for the professional sample roaster.  ¼LB-6LB per hour volumes.
  • 4LB Roasters - Entry level hobbyist or business roaster.  ¼LB-15LB per hour volumes.
  • 6LB Roasters - Mid-level hobbyist or business roaster.  ¼LB-23.5LB per hour volumes.
  • 8LB Roasters - Large volume business roaster.  ½LB-30LB per hour volumes.
  • 12LB Roasters - Largest volume business roaster.  ½LB-45LB per hour volumes.
  • Need bigger?  We have custom drums up to 150LB/hr.  Call us. 470-798-9464 or Skype Logosm  NAME: rkdrums

5.  Not sure what you need?  Check out the roaster flowchart here to help you decide.

selector tool mini

Grill Requirements for RK Drums

Understand that NOT ALL grills will work for your roasting application, so picking the correct grill is important. 

One of the most common questions we get is "Will this or that grill work?"  Determining if your grill will work is quite easy!  Please click the size of drum you have purchased or want to purchase below to see the requirements.

2LB Grill Requirements

4LB Grill Requirements

6LB Grill Requirements

8LB Grill Requirements

12LB Grill Requirements

While we don't recommend grills specifically, as of 2019, the following brands at Home Depot seem to work well for anything up to 12LB, and can be had or $180 or less.

NEXGRILL
DYNAGLO

SPECIAL NOTE:
If you are planning on buying a grill anyway, go ahead and buy a grill that will fit a 12LB Drum, this way, since all of our kits are cross-compatible you can just swap the drum out if you wish to upgrade later on.  

While we don't recommend grills specifically, as of 2019, simply because it's a major task to keep track of all of them, and most of them will work in any case.  The following brands at Home Depot seem to work well for anything up to 12LB, and can be had or $180 or less.  Please, double check these brands against the below requirements. anyway with a tape measure.  Nothing worse than dragging your grill home, only to find out it won't work.

NEXGRILL
DYNAGLO

 

SPECIAL NOTE:
If you are planning on buying a grill anyway, go ahead and buy a grill that will fit a 12LB Drum, this way, since all of our kits are cross-compatible you can just swap the drum out if you wish to upgrade later on.  

One of the most common questions we get is "Will this or that grill work?"  Determining if your grill will work is quite easy!  Please click the size of drum you have purchased or want to purchase below to see the requirements.

2LB Grill Requirements

4LB Grill Requirements

6LB Grill Requirements

8LB Grill Requirements

12LB Grill Requirements

 

It will probably work for one drum or another, you'll need to make sure that the BTU and size requirements are met, see the requirements question above.

Most likely it will work on one of our drums, see the requirements above.

NO!  Do not feel the need to buy an expensive grill for the coffee's sake.  If you want it for your own reasons, knock yourself out.

Charcoal or wood fired grills can be used if desired.  Some people, approximately 5-10% of the people we talk to (in 2019) are interested in doing this kind of coffee because it provides a more artisan, and perhaps niche method for producing coffee.  

The upside here is that you will be able to impart a charcoal\natural wood\smoked flavor to your coffee which some people may find attractive.

The downside is that heat control is more difficult and will require good air flow management to increase or decrease the heat.  Keeping your roast timed correctly is important, so some experimentation may be necessary, and sometimes you just may not have quite as much control.  Nevertheless, if you're in to this kind of thing, there's nothing wrong with it.

We recommend propane/gas for ease of use and roast control however.

Charcoal Grill Requirements for RK Drums

Understand that NOT ALL grills will work for your roasting application, so picking the correct grill is important. 

Dyna-glo Heavy-Duty Compact Charcoal Grill, Size: 568, Black

Make sure that your charcoal grill meets the dimensional requirements below.  You'll still need the equivalent BTU heat output to roast well however, but usually this means "more charcoal".

2LB Grill Requirements

4LB Grill Requirements

6LB Grill Requirements

8LB Grill Requirements

12LB Grill Requirements

Yes.  You can do this either on a gas or charcoal grill.  

You can smoke the green coffee beforehand and then roast, much like a pork butt, or other meat, or smoke during the roast process.   Your results may vary.  We are hearing more and more of this, particularly from folks looking for a roasted coffee niche.

Check our Youtube channel for a demo of this:

https://www.rkdrums.com/roast-videos/

Charcoal presents a more challenging platform for roasting in that it is more difficult to add and remove heat precisely, quickly.  If your charcoal grill has a way of managing heat well, this may be less of an issue.   In coffee roasting, timing is everything, and we use heat to speed up the roast or take away heat to slow down the roast.  

Check out the recommended roast profiles for target times and suggested temperatures here.

In this way, you may find dialing in the correct time for the roast for each given volume more challenging.   For this reason , we recommend gas\propane as you can control the heat with the turn of a knob.

 

Once you understand the amount of airflow required to adjust heating for your particular roast volume, then you may find that heat control is less of an issue.

 

Some people, however, interpret the charcoal as imparting unique flavors to the coffee and it may represent a niche, business advantage, or simply a more interesting cup of coffee.

 

 

Some people use Brick Ovens, Pizza ovens,  Plantain ovens, or chicken rotisserie ovens to roast in.  We make special drums for these ovens that have a special Lateral Door.   Determining how to make our kits work on these types of ovens is beyond our scope, but many people do it with a pinch of creativity.

The BK Industries BK10 rotisserie oven has been retrofitted in the past for cacao operations and requires shipment to our machine shop in Georgia for customization.

This lateral door is best used when removing the drum to remove the product is not an option or inconvenient.  The door uses 2 latches instead of 1 latch, so it's one more thing to do during the unloading process.  So if in doubt, only choose this kind of drum if you have one of these ovens or otherwise have determined you need it. 

lateral door rk drums roaster

The quick answer is no.

We won't tell you it's impossible, but we're yet to see someone successfully do it.  We definitely recommend roasting outside since it can generate a good deal of smoke.   A vent hood to evacuate smoke would be highly recommended.

Getting a motor mounted to these ovens would also require some creativity.  

 

Yes.  This is the ancestral method of coffee roasting and has been done for centuries.  There's at least one of our customers that roasts as a cowboy over a fire pit with a hand crank.  Western style.  It's part of a show, but it's still really cool.

Electrical System

Within the Do-It-Yourself path or the Inventor path, we don't supply the electrical system, as this is considered common hardware store components.  

You will need to supply at the very minimum your own power cord, which is nothing more than a 2 prong standard power cord (see image).  

standard 2 prong power cord

This is extremely simple to do, simply wiring one wire to one side of the motor and the other wire to the other side.  In this scenario you would:

a) Unplug\replug your cord to turn your roaster on and off

b) Use the power switch on the surge protector to turn your roaster on and off.  

You can do other sorts of things such as incorporating power switches and the like, it's really up to you how you want to build it.  See the electrical section of our assembly guide for how we accomplish this.  You can model yours in the same way with a nice attractive power switch which attaches to your motor mounting plates.

Our Everything Kits, supply the entire electrical switching system if you'd prefer that approach.  See the "I just need to roast now" path for this.

In the United States and Canada, we simply use 110V AC electrical equipment.  Common hardware store household electrical works fine.  

 

Other countries such as Australia use 220V and we have a 220V motor option for Australians and in other countries.  

 

While it's possible to use 220V in areas that commonly use 110V (Such as the United States), if you have this most likely you know who you are.  If you don't know, most likely you have standard 110V and you probably don't need to give it much more thought.  Consult an electrician if you have any particular concerns.


Within the Do-It-Yourself path we provide you a standard 110V motor, so 220V won't be of concern here.

Choosing a rotisserie

1.  A rotisserie rod to mount the drum on is required.    See our rotisseries here.  Note the rotisserie rod must be 5/16" and square.  Fortunately, this is the most common rod found in stores.   Please do not try to use hexagonal, or split rods, or 3/8" rods.

buzzy note0.1 rot0.1

It might, but it needs to be 5/16" and square.  The reason for this is that the square rod acts as an interface to the drum.  This functions a bit like a square peg in a square hole and it prevents the drum from ever slipping on the rod.

buzzy note0.1 rot0.1

Note that you cannot use:

  • A 3/8" rod
  • A rod with a hinge or a split in the middle unless it is less than
  • 5/16"
  • A hexagonal rod.

Should you decide you need a rotisserie rod   See our rotisseries here.  Note that we include a rotisserie in the Everything Kits, and you might opt at this point to choose one of these kits.

Yes we do!  If that's your thing, we have them here.

Choosing a motor\hand crank.

You will need some method to turn your coffee over the fire.  Either choose our motor and mount assemblies, supply one yourself, or use a hand crank.

Our Do-It-Yourself kits and our Everything kits both come with motors and mounts

Our motor of course!!  It comes with a 1 year warranty.  You should easily expect 5-8 years of solid service and I'd guess the majority are still in service after 15 years.

All of our kits come with the motor assembly.

Some folks have used other types of motors.  We've seen people hook up car windshield wiper motors to car batteries to setup their own portable rig.  

Really, as long as you're turning 20-60RPM and with enough power that the motor doesn't burn out, you should be in good shape.

No, you don't need our plates necessarily.  It makes life quite a bit easier since we have created mounting plates that permits the vertical and horizontal position adjustment of the motor.  

Some folks however have made their own plates from wood or some other method.  

We recommend a motor with 15in-lb of torque minimum.  Our motors utilize 25in-lb of torque.  Recommended speed is 20-60RPM.  Our motors currently feature 26RPM.  Older motors between 2017 and 2008 utilized 52 RPMS.  

There is negligible difference between the different speeds.

Maybe...

Back before 2010, you could easily find these kit rotisserie motors running at 6RPM.  Somewhere around then, it seems most rotisserie motors went to 1.2RPM's.  

If your motor spins at 6RPM (spins 6 times in 1 minute) then you can use this with decent results up to about the 4LB drum.  

The 1.2RPM motor has universally been shown to produce unevenly roasted coffee.

rotisserie motor

Anything you want!  It just needs to be able to turn the weight.  It needs to ideally spin at 20-60 RPM.  Some people have used a corded drill as a motor.  These can be found cheaply.  Others have gotten very creative and used car windshield wiper motors attached to a 12Volt battery for portable operations.  

One fella attached his to a bicycle and pedals his roast every day.  

You can certainly use a variable speed motor, but we do not currently support this.  From a technical support standpoint, it introduces added variables that complicates roast troubleshooting.  

In our experimentation with various speeds, we see negligible difference between RPM ranges 20 and 60RPM.  Considering added cost of a variable setup, we prefer to keep it simple.

Temperature sensing

We strongly recommend using a quality thermometer from a company that specializes in making quality temperature sensing devices.  The reason for this is that the repeatability and predicatability of your roasts from one roast to the next depends on accuracy of your thermometer.

Our Everything Kits ship with a Tel-Tru brand of analog thermometer.  If you need to recalibrate your Tel-Tru brand of thermometer, click here for instructions.

We have found that the thermometers used in grills are completely unreliable for the most part.

The most challenging concept to understand when roasting with your thermometer, outside of the coffee bean mass is the relativity of your thermometer.  Read here for more on this point.

Installing a thermocouple or temperature probe inside the drum or inside the bean mass has been done by some individuals.  

In short it requires drilling a hole on the side of the end cap near the outer circumference of the drum and inserting a thermocouple or probe so that it touches the beans when in rotation.  This wire would then travel down the length of the rotisserie towards the rotisserie handle where it connects to a wireless transmitter.

This then transmits to a wireless receiver.  At this time we do not provide guides on how to do this.  See our Facebook page for examples of people doing this. 

This however is not required for accurate roasting.  See this article here.