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AlpenGrill Roaster
AlpenGrill Coffee Roaster

Intro and background:

I?m Rick Waits (aka coffeenut) and have been home-roasting for 7yrs. Putting into words the process and parts I?ve tinkered with over time to build my AlpenGrill coffee roaster was more effort than I had envisioned. I struggled with how much information to include and erred on the larger side. But, I?m glad to do this and am a person that likes to help others at heart, so here goes.

The build of this grill-roaster began in July 2004 and has continued to evolve with modifications I?ve made to date. It began with an old Alpenrost electric roaster that croaked years ago, but I kept the drum from the product. Ron Kyle of RK drums had been sharing his success with Grill Roasting and I was always interested in trying it myself.

The Alpenrost drum had to be modified to be useful in a gas grill roaster. So, I decided that I had nothing to lose if my modification didn?t work and set about converting the Alpenrost drum for use in my BBQ Grill. A fair amount of the parts that I have used for my AlpenGrill Roaster are just things I had around my garage. I hope that this write-up will help you see what you can do, even if you modify another type of drum or make your own. I roast 3lbs each week with this roaster and do either three 1lb roasts or two 1.5lb roasts.

Capacity ? 1.5 lbs or less

Type of heat ? Propane

Type of agitation ? Stainless Steel Drum (10? Long by 5? Diameter). Drum has 5 angular internal stirring vanes (set ~ 30 degrees) with 3? separation between vanes.

Roasting time at Max Load (1.5lbs) = 13-15mins to 1st Crack depending upon bean type/origin
Roaster temp at finish of Max Load = 475F

Building the Roaster:

Basic Components:

(Item, Qty, Unit cost or est Used Value & Where purchased)

1. Sunbeam dual burner grill 44K BTU, 1, $50.00 (used), Home Depot
2. Alpenrost drum, 1, $50.00 (used), Sweet Marias
3. 57 RPM, 115 VAC Inline Gear motorw/starter capacitor, 1, $21.95, Surplus Center
4. 7/16" L-050 Lovejoy Half, 2, $4.38, Surplus Center
5. Lovejoy Buna-N Insert for L-050 NG, 1, $1.40, Surplus Center
6. MDF board, 2, $2.00, Home Depot
7. Bolts for mounting posts, 2, $1.00, Lowes
8. Aluminum Flashing for underneath burners (10?x10? roll), 1, $8.00, Lowes
9. Aluminum Flashing for Grill Lid heat deflection, 1, $(incl above), Lowes
10. Aluminum Flashing for Grill base wind block, 1, $(incl above), Lowes
11. Spit Rod & Collars (taken from an old rotisserie kit) for drum rotation
5/16? W, 37 ?? L, 1, $29.00, Home Depot
12. Steel Lid for Alpenrost drum, 1, $1.00, Lowes
13. Hardware for Alpenrost drum, 1, $2.00 (from my garage)
14. Charbroil Porcelain Heat deflector, 1, $20.64, Lowes
15. Box of Ceramic stones (diamond shaped), 1, $5.99, Home Depot
16. Stainless steel clip, 1, $1.00
17. Teltru Stem Thermometer LT225R (5? stem, 200-1000F), 1, $16.15,
18. Welder?s Gloves, 1, $9.99, Lowes

Total cost estimate = $224.50

Note: The prices above are what I paid at the time, or are the estimated ?used value? and may not reflect the cost or availability today. Wherever possible, I used Stainless Steel, Steel or Aluminum hardware for food safety.
Coffeenut attached the following image:
Prepping the Grill for coffee roasting as a dedicated roaster:

My grill had seen a lot of years as a BBQ Grill, so I didn?t feel any loss in converting the grill to a dedicated coffee roaster. I initially tried using the grill in dual mode (cooking meat and roasting coffee) and just didn?t feel the two were compatible. This BBQ grill came with some of those internal wire grids in the lid that are supposed to be used for warming food. I removed and discarded the wire grids so they would not interfere with the drum movement. I also discarded the grill?s metal cooking grates (they were in need of replacement anyway).

Modification of Grill?s vertical slots that allow use of a rotisserie rod:

My grills vertical openings (that allow you to place a rotisserie rod) were not deep enough and I felt the drum would be too high over the burners. So I removed (cut) some material from these slots on each end to allow the rod to drop down lower in the grill. This also required that I remove and adjust the position of the rod holder on the left side of the grill.
Coffeenut attached the following image:
Alpenrost Drum Modification:

The Alpenrost Drum was originally designed to be rotated by a mechanical gear/cog that engaged the rear outside of the drum. So for grill use, it needed to be modified to accept a standard rotisserie spit rod.

First, I found the center of the back of the drum and removed enough perforated material (approx ??) to allow the spit rod to pass. The resulting hole (shown in the pic below) was too rough for smooth rotation, so I added a SS washer so the spit rod would have a smooth surface to spin against. I first drilled the center hole of the washer out to ??, then drilled (3) 3/16? holes in the washer?s surface (triangular pattern) and affixed the washer to the drum with (3) #6 machine screws and nuts.

Here?s a pic of the drum end after drilling and removing material from the center.
Coffeenut attached the following image:

Edited by Coffeenut on 07/20/2007 5:08 PM
Here?s a pic of the drum end (outside) after drilling and mounting the washer:
Coffeenut attached the following image:

Edited by Coffeenut on 07/20/2007 5:10 PM
Here is a pic of the drum (inside) after mounting the inside washer. Note: I dry-fitted the two washers, machine screws and nuts before attaching them to the drum to see how they looked. When I did this, I noticed the outside edges of the nuts holding the screws were slightly overhanging the washer?s inside hole opening. So I took a small round needle file and slightly filed the edges of the washers down to the inside edges of the hole in the washer hole. This may seem a bit much at first glance, but was really a quick job using a needle file.
Coffeenut attached the following image:
Next, I needed to create a cover for the other end of the drum that could be opened once the drum was removed from the spit rod. This cover would also be made so that it provided pass-through support for the spit rod since that end of the drum was open (original design). I had some 20 gauge sheet steel (not galvanized) left over from another project.

I stood the open end of the drum on top of the sheet metal and used a fine tipped marker to draw an outline of the opening. I also chose to have a small tab that extended from the lid so I could use it as a ?catch? to keep the lid down during roasting. So, then I used a Tin Snip tool to cut out the round lid shape and tab from my outline. I had a small SS hinge on hand that was used to allow the lid to open for dumping the beans. So I mounted the hinge to the lid first and then placed the lid on the drum so I could mark the places where the hinge needed to be affixed to the drum. After marking those places, I drilled them and used a coupe of pop-rivets to mount the lid to the drum.

Once the lid was affixed to the drum, I closed it in place and bent that tab I?d provided down to lay flat against the side of the drum. I needed a small slot in that tab so I could snap it over a clip holder that would add to hold the lid in place. So, I used a small drill bit, drilled 2 inline holes, and then used a small needle file to finish making a small slot in the tab. Then I closed the lid and marked the place on the side of the drum where the tab?s open slot touched the drum. I marked that place on the drum, drilled a small hole and inserted a ?standard cotter pin?. The cotter pin has a round eye on one end that would accept a ?hairpin? cotter pin. I inserted the standard cotter pin through the hole I drilled in the drum and bent the legs of the pin back against the inside wall of the drum. That left just the eye of the pin showing on the outside where I can snap the tab in the lid over that eye and then insert the hairpin cotter to hold the lid closed. Here are a couple drawings of the standard cotter and hairpin cotter pins in case you are not familiar with them:
Coffeenut attached the following image:
With the lid in place (closed and pinned) on the drum, I next needed to cut a small square opening in the center of the lid to allow the spit rod to pass through. That square opening was roughly 5/16? which is just enough to allow the spit rod to pass without any slop. I found the center of the lid, marked the square and drilled the center and used a small needle file to make the edges flat and square.

Here?s a pic of the completed Lid assy:
Coffeenut attached the following image:
Another Lid assy pic:
Coffeenut attached the following image:

Edited by Coffeenut on 07/20/2007 5:17 PM
More Lid Assy:
Coffeenut attached the following image:
Here?s a full view of the Drum on the spit rod:
Coffeenut attached the following image:
If you are not familiar with needle files, they are very inexpensive as a set and I find them perfect for getting into places a large file could not go. Here?s a link to a company I?ve purchased from that sells the set for roughly $13.

Micro Mark

Here?s a pic of the Needle File set from their site:
Coffeenut attached the following image:
Gear Motor build:

A few years ago, Surplus Center had become a popular place to get an electric motor for your grill-roaster and they still are popular. I leave my grill outdoors, so I needed to be able to easily place and remove the motor assy on my grill?s right side table. At first, I was simply clamping the assy to the side table using a couple of those quick-clamps. Later I improved this by mounting some metal pins that mate to a couple holes drilled in the MDF base for the motor.

Here?s the Motor, mounting materials, etc:

Motor = 57 RPM, 115 VAC Inline Gear-motor with starter capacitor included.

The MDF base for the motor (or really any wood of your choice) = 2 pieces screwed together to form one piece.
Coffeenut attached the following image:
This is a pic of the motor mounting plate I made for the motor.
Coffeenut attached the following image:
Here?s a pic of the two posts (mounted on the right side grill table). I simply drop the MDF base (motor mount assy) onto these two posts. The MDF base for the motor has two holes drilled in it that align with these two posts. It positions the motor just right each time so that I can avoid aligning the motor with the spit rod. It?s very easy to just drop the MDF assy onto these posts and the weight keeps the whole assy in place. The two posts are nothing more than a couple of lag bolts with the threaded portion of the bolt cut off with a hacksaw.
Coffeenut attached the following image:
So, what?s inside of that on-off switch box? It?s a simple electrical box that allows you to run the wires inside from the motor to connect to the Starter Capacitor and the on/off switch. Here?s a pic of the electrical switch box, standard 115V AC on/off light switch, starter capacitor (came with the motor) and wiring connections.
Coffeenut attached the following image:
Placement/Assy of Lovejoy Couplings:

This is a pic of the Lovejoy couplers and the Insert that allows connection of the two. One Lovejoy coupler is mounted to the motor shaft ands the other coupler is mounted to the rotisserie rod shaft. The couplings and the insert are very durable and still fit snugly after almost 3yrs of use.
Coffeenut attached the following image:
Rotisserie Rod and Holding the Drum in Place:

The Rotisserie kit comes with the Rod, two spiked meat holders and a motor. The motor was of no use since it turns too slowly for coffee roasting. So, that left the rod and the holders. I broke off the 4 spikes from both of the round collars in which they were mounted. This can easily be done with a pair of pliers (bending the rod back and forth until they snap off) or you could cut them off with a hacksaw. After removing the spikes, you have a nice round collar that has a set screw that is used to hold the collar to the spit rod. Then I did a little smoothing with a metal file where the spikes were removed and you?re done.

Here?s a pic of the collar and how it looks in proximity to the drum when mounted on the rod.
Coffeenut attached the following image:
Here?s a pic of the other end where I have 2 hairpin clips (one holds the drum from moving on the rod and the other hold the lid shut):
Coffeenut attached the following image:
Adding flashing to minimize wind effect that was causing temperature fluctuation:

When the wind was fairly high and blowing toward the rear of the grill, I had difficulty maintaining a steady temperature. The temp would fluctuate as much as 100F at times. So, I added some aluminum flashing in 2 places on the grill to deal with this problem and it has been very effective.

Just recently, I decided to deal with the wind issue that so many grill roasters face and added some aluminum flashing to my grill using pop rivets. The flashing was some leftovers from another project that came from Lowes and is fairly thin. Because the flashing was only 10" wide, I riveted two sections together for the lid piece. I added a piece of copper tubing to the center of the hood to prevent the thin flashing from drooping.

My intent with the 5" tall flashing mounted to the rear of the grill base was to block the wind which easily enters the rear with the lid down. The flashing added to the lid was simply to reduce the headroom between my Alp drum and the top of the lid and hopefully reflect some heat back to the drum. The results have been quite striking. The wind problem has been solved for the most part and I'm able to use much lower settings on my gas control valves to maintain the same amount of heat inside.

I've attached a pic of the finished result:
Coffeenut attached the following image:
Adding flashing to reduce wind effect on bottom of grill:

This is a pic of a sheet of aluminum flashing (looking up from the bottom of the grill) that I added to the under the base of the grill. As you can see, it is discolored from heat, but works just fine. This area was wide open and allowed wind to rush right up into the base of the grill. The base of the grill has these 2 pieces of metal bracing that run the length of the base. I simply cut the sheet aluminum to fit inside of that bracing and it is press-fitted (no rivets, screws, etc).
Coffeenut attached the following image:
Heat deflector:

I've also replaced all that ceramic rock in my roaster with a burner heat deflector (made by Charbroil). The thing I liked about this product was that it was 2 pieces that could slide atop each other to fit a variety of grill interior lengths. We had some discussion over on the Sweet Marias List about leaving/allowing a gap on each end of the burners (outside of whatever heat deflector you used) for better heat circulation. I decided that I had way too much heat absorption with all those ceramic rocks. So, I bought the metal deflector at Home Depot and it fitted perfectly right over my burners.

The deflector has sort of a "W" shape to it that includes two slots that run the length of the metal deflector between the peaks of the W shape. Those slots would allow some flame to still reach toward the drum. So, I took a few of those diamond ceramic stones and placed them into the valleys of those slots to block the flame (only under the area where the drum sets). The diamond shapes fit perfectly into those V shaped valleys and block any flame. So, now what I have is a mostly metal deflector with a few ceramic stones to block any flame. I've attached a pic for those who have interest.

To make a long story short, this new deflector allows a lot more heat to reach the drum and it is still manageable for roasting. Using the flashing really allowed me to use less heat than before, and this new heat deflector has allowed me to reduce heat settings on the grill even more. I can do my roasts at just about the lowest settings of my grill as a result of both of these mods. In case anyone is interested, my grill is an old dual burner Sunbeam 44k BTU. I'd like to have gas controls that have less "play" in them, but that?s possibly a future project.

Here?s a pic of the Charbroil product as it comes from the package:
Coffeenut attached the following image:
Here?s a pic of the deflector inside my grill with a few diamond ceramic stones. The stones are added to deflect flame under the area where the drum sets.
Coffeenut attached the following image:
Wind and Heat Deflector (Lid & Base):
Coffeenut attached the following image:
Basic Process of Roasting with this Roaster:

1. Preheat grill to 450F
2. Pour beans into drum (cold drum for first batch, warm to hot drum for successive batches)
3. Close drum lid and insert with hairpin cotter pin
4. Run the spit rod through the hole in the closed end of the drum, out through the square hole in the drum?s lid until the drum meets the fixed collar on the spit rod.
5. Insert the other cotter-pin through the spit rod to hold the drum in place.
6. Mount the drum and spit rod into the grill and push into the Lovejoy connector on the motor shaft.
7. Set the handle (using the set screw) such that it holds the spit rod firmly against the Lovejoy,
8. Close the lid and flip the switch to start the motor.
9. Start a count-up timer to keep track of time.
10. Burner controls on Low to prevent too fast a ramp in the first few minutes.
11. The grill will start off about 370F because the lid has been opened to load the drum.
12. For the first 3-4 minutes, temps will gradually climb up to the 420 to 470F areas.
13. I like to keep temps below 450F during the first 7mins and then allow them to climb no higher than 480 until 1st Crack is reached.
14. 1st Crack varies with beans, but in general it occurs around 13mins.
15. It will last 3 to 3.5mins and then 2nd Crack will begin.
16. Open the grill lid, remove the spit rod and set the drum across the resting area (lined with ceramic rock) to the left.
17. With a pair of pliers, pull out both cotter pins, pop open the drum lid and pour the beans into the bean cooler.
18. Before loading the next batch of beans into the drum, I like to quickly blow out the chaff that fell through the drum onto the grill?s heat deflector. I do this so that I?m not continuing to burn that chaff and introduce any smoky flavor from it into the next roast. Maybe not necessary, but only takes a few seconds.
Roast Log I use for recording roasts & profiles:

Here?s something else I?ve found useful?a roast log. I began logging results of my roasts back in 2000 when I first started roasting as a learning tool and I still do it today. My log has gone through many versions (and roasters) to evolve to what I?m sharing below.

This log allows me to record 4 different roasts on one 8.5 by 11? piece of paper. I print the log front and back on a single sheet of paper, so I get 8 roast recordings from each sheet. Portions of the log have to do with bean(s) used, blend data, etc. Other portions of the log have to do with recording my gas valve settings, temps by the minute, 1st Crack and 2nd Crack times, and other info.

The small white circles with line markers are representative of my gas control valve and match the marks I have added around my valves as reference points. I can easily note on the log where I had my valves set and what changes I decided to make as the roast progressed. Above each white circle is a block where the temp can be manually recorded for each minute as the roast progresses. I use a thermocouple probe for my temp readings. The thermocouple is ~ ?? from the drum and about center mass of where the beans are located in the drum.

I also have a Notes area where I can jot a few pertinent ideas about the roast that may be useful for future reference. This log was created in an Excel file for ease of managing row/column data and formatting same.
Coffeenut attached the following image:

Edited by Coffeenut on 07/20/2007 5:40 PM
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