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In Memory Of Ginny

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Zen Roaster I
I don't currently roast in this "Zen Roaster" roaster, but I designed and built it a few years back and had a great time. I had a number a goals in building this roaster.

1) Be able to build it with "basic" equipment". Saw, drill, rivets. Nothing fancy.
2) Roast at least a pound
3) Be able to sample beans
4) Be on a 20 amp circuit
5) Have good bean mass temperature measurements
6) Be able to control the profiles
7) Build for under $200.

What fell out was the design you see. It addressed each goal this way.

1) Since I wanted just basic tools, my materials all had to be soft metals like aluminum or thin stainless steel. I did end up using a good jig saw with metal blade, a drill with good metal bits, and rivets. It was also held together with machine screws that I set with self tapping screws (so I didn't have to worry about another tool - a tap).
2) With insulation and the 1600 watts it easily roasts a pound in under 12 minutes
3) I didn't want to fuss with a front plate, tolerances, etc, so I decided to leave the front open. Since the beans needed to stay in, I tilted the drum. The angle of the drum is also based on wanting to look "right down the throat of the roaster".
4) I used four 400 watt heating nichrome coils
5) With the open front, a long stem thermometer slips right in. There is a small hole at the center of the drum to set the thermometer into
6) I was currently anti-variac, so each coil is controlled with an on/off switch. Worked well enough once I got to know the system.
7) Success! About $150

Like many of us, I collected many parts for years "just in case". Many were free so that helped a lot. The following went into the roaster.

2' x 4' of aluminum sheet for the outer shell - free (have had it for years - scavenged somewhere)
3/4" angle aluminum 16' - $16 (for the frame and vanes in the drum)
Rivets - $5.00
Screws - $7.00
Drum (made of a stainless steel chimney cap and section) $36
Thermometer - $15
Aluminum shell - free - graciously made by someone excited by the project .
Switches - <$3.00 surplus grab bag from C&H Supply
Motor - $15 - paint stirring motor via Dan Bollinger
Fan - $3.00
Various electrical connections :$10
Various 120 V lights (which light when their heater is on) $6.00
Metal cutting blades - $12.00
Paint - $4.00
Other various nuts, bolts, connectors, etc. $20

All the photo following are during in process. I don't have any roasting. Just never happened. To roast, I preheat the system to about 350 F, with the drum (which is removable at the end of roast - it connects to a shaft via a hole and set screw) add the beans (via a funnel) and start the motor. The motor rotates at about 40 rpm. The drum rides on a pair of bolts with slip sleeves on them. It is a little metal on metal loud, but cracks are very audible.

At the back of the whole roaster is a small 100 cfm fan. It's use was two fold. It was to keep all the wires and motor cool and to provide a little air flow through the drum. It is a 100 cfm fan, but with very little head, and a very torturous path for the air, so very little made it through the drum (on purpose). It drew air into the roaster, past the fan, through holes (50 or so 1/8" ) in the back/bottom of the roaster shell, around the heating coil ( a little convection here) and through the bottom of the drum past the beans and out. With this gentle air flow, smoke was minimized.

Some random notes: The first time I made the heater coil insulators, I made two mistakes. I used a gypsum based plaster. It calcified pretty quickly and crumbled. After that (which I don't have photos of) I used castable kiln refractory. Built for the heat. The 2nd error was not knowing I had to stretch the coils or they short out. The ones shown were not extended and "blew up" in a huge shower of molten sparks the first time I fired it up. The insulators after that were larger to allow stretching. Also, there is insulation inside the shell now (wired in) and the shell stays pretty cool. There is also insulation layered over the wires to keep the air moving where I want it (past the beans).

How I roast?

At around 1st crack (8-9 minutes) I would turn off the first coil. The 2nd followed at 1st. The third sometimes followed a couple minutes later depending on the roast temp. Final roast times were generally 12 minutes. At the end of the roast, I opened the shell (with gloves), and pulled the drum and dumped the beans to cool via a blow drier.

That's it. Why don't I use it? Mostly, I found I over engineered it. It was heavy, pretty load (metal on metal as the drum rotated) and just not as elegant as I wanted it. But it was a GREAT learning experience.

It is called a Zen roaster as I designed it with balance in mind. Just enough, not too much, everything there for a reason. It lead me to the Zen roaster II (following).
Alchemist attached the following image:
Zen roaster[373].jpg

Edited by ginny on 08/21/2007 12:23 PM
Here's the basic electrical wiring and plans I worked off of. Some of that wiring looks quite heavy, but is actually a high temperature insulation. I was not sure how hot the interior would get so I played it safe.
Alchemist attached the following image:
Here you can see the basic framing. It was all stainless steel angle riveted together. I worked out every one of those angles, lengths and intersections before ever touching a piece of metal. Shock Me? A design freak?

Oh, that that "down the throat" view I mentioned.
Alchemist attached the following image:
Oh, and I guess this shot would have been better first, but oh well. This is a bunch of the raw materials before they started turning into a roaster. It's amazing what you can convert. B)
Alchemist attached the following image:
And a composite photo of casting the insulators, the unfinished insulator and the installed one (before it exploded) - Remember, stretch those electric coils :@
Alchemist attached the following image:
heater insulators[377].jpg
I guess I am just going to go all out of order here. There's some of the drawings, plans and whatnot that I used. When all is said and done, I am very pleased at how well it matched the drawings. Plan 6 times, measure 3 times, build ONCE (except for the heaters ;) )
Alchemist attached the following image:
Oh, and just because I saw the drawing of the motor (above), here is a close up of the motor assembly. I decided on the belt drive for a couple reasons. I wanted to save space, eliminate the possibility of heat conduction to the motor via the shaft and I wanted to be able to try out different motors if need be. I REALLY like how that all went together.

You can also see all those holes I mentioned into the shell for air to flow through.
Alchemist attached the following image:
The final thing I will leave you with is the label design.

'nuff said.
Alchemist attached the following image:

Edited by Alchemist on 07/31/2007 1:15 PM
Nice, Alchemist. I first saw this unit in a picture linked from a Sweet Marias get together... I can't remember much more about how I got to the picture, just that I liked the looks. It was on a table next to a modified popper and a few other roasters...

You say you don't use this one any more... why is that?

Thanks for the entry. I remember when you were working on it.
Such a classic!
Thanks for posting this, John


David wrote:
Such a classic!
Thanks for posting this, John

Classic in what sense?

I remember YEARS before I started home roasting I saw a drum roaster with an inclined drum like this. Never have figured out what that was but it was the best coffee I had ever had.
Thank you for the praise!

It is a head scratcher isn't it. Over designed is the key. And heck, I am my number one critic. Lots of little things. The panels are too heavy, I missed designing in the thickness of the metal on the shell hinge, it is every so slightly out of alignment and squeaks. There is more heat lost out the snout than I would like. In general, it is cool, but fussy for an every day roaster. I could build it way better a 2nd time.

I currently have two more designs in my head. I really want just one, but I can't get that 2nd one out of there. I don't NEED two, let alone three, working roasters. er, make that four - I still have my modified P1.
John, Like Ed, I followed this design as you built it. It raised the bar on homeroasters that's just now being reached by other homebuilt machines. Congrats, Dan
Actually, the view in the Zen I is better than in Zen II, if for nothing else there is no glass reflection. Look at the mock up of the roaster third picture down. The view of the beans looks a bit like Dan's icon.

Lately thoughts of flitted across the gray matter about turning the Zen I into a propane roaster. I have never played with gas and that is how I learn most of what I currently do. Research it then build it. So, who knows about making a properly balanced propane burner? Seems it needs to be more than just a tube with a dozen holes drilled into it.


Alchemist wrote:


David wrote:
Such a classic!
Thanks for posting this, John

Classic in what sense?

I remember YEARS before I started home roasting I saw a drum roaster with an inclined drum like this. Never have figured out what that was but it was the best coffee I had ever had.

Dan said it best: "It raised the bar on homeroasters that's just now being reached by other homebuilt machines." That's the kid of classic that I meant.

I didn't realize how large and heavy (and over-engineered) it was from pictures I had seen earlier. I had thought of trying to build one like it (the tilted bed feature, mostly) but now I realize that it is well beyond what I would be able to pull off. I will have to content myself with appreciating the ideas embodied in it. Such a classic!!

I appreciate the time and effort you put in to posting it here for us.

Wow, I had not realized people actually took notice of this roaster. I feel rather honored.

As for what you can do, I bet you can do it. I don't consider myself that great at building, and I don't have all that many tools. Part of the design that was critical was what I could do myself with a limited number of "simple" tools. Consider the following:

Material: Aluminum where possible. Very soft and workable with virtually any hand tool. Moderate drill, no drill press, jigsaw with metal blades. No lathe or other special equipment. The only stainless was the drum, and I was able to baby my tools to get the holes I needed in them. Slow and lots of oil.

Attachments. Rivets, nuts and bolts and self tapping machine screws. Again, easy to use. No tap and dies.

Oh, the welds on the aluminum case are beyond me BUT it was done by someone else. I had it all planned out with flat plates and aluminum angle.

What could you not pull off? I recall thinking the same thing of some of Dan's work. Lathe work that was beyond me. I had to go off the shelf or simple.

Some of the over-engineering is just the weight of the metal. I have learned to use much lighter sheet metal because it creates it's own stiffness as you bend it and put it together. Oh, and I soldered all the electrical connections. That was ignorance. I should have used and now use quick connect tabs.

Oh, on the bending. All by hand either in a vice or just held in place on a bench top and hammered with a hammer through a 2x4 (so not to mare the surface). No fancy metal roller.

Thanks again. {blush}

OK, that helps with the intimidation factor.

If I were to scale it own a bit in weight and still go for a .5 to 1.0 kilo capacity, how would I do it?

Would you help me with the step-by-step?

(Maybe we can turn this into the article that you didn't have time to do for the contest. OK?)



David wrote:
OK, that helps with the intimidation factor.

If I were to scale it own a bit in weight and still go for a .5 to 1.0 kilo capacity, how would I do it?

Would you help me with the step-by-step?

(Maybe we can turn this into the article that you didn't have time to do for the contest. OK?)


I would be happy to run through how I would design it. I have to toss in a couple, what?, caveats? What about this roaster do you like? If I was going to build this again, I would take it into a different direction. Do you like the tilted drum? The looks in general? With the open snouted design, on 15 amps electric, 1 kilo is tough with heat loose. I am not even sure I have tried a kilo in it. I doubt it. Do you want to stick to electric or is gas ok?

In general, since it was the Zen II that I didn't have as much time and documentation for, and had the generally better response, but for the writeup, how do you feel about a step by step of that one? Or maybe a hybrid of the two?

Sure, regardless, let's talk.
I really like this roaster. Time is very short today but I will try to put my thoughts together
so I can add my 89 cents...

very nice design, love the elevated front of the roaster...


gotta s:8s:8s:8
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