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Part 6 - Cooling tray
Here is another one I found - 12" x 4". Solid bottom, but cutting or drilling the bottom should not be too bad.
Edited by Alchemist on 10/11/2007 8:49 AM
I have been finding more options also.

For example, I found out that the perforated bottom insert that we have been looking for may be one of these pieces of pizza equipment: a "Pizza Screen" or a "Perforated Disk"
Wow, sorry about the delay there. I like the openness of the Pizza screen, not to mention the price. Thinking out loud - if we go with that, we would have to support the stirring vane shaft, but that is no big deal.

Tentatively, I say we go with the 12" x 4" solid bottom cake pan and cut the bottom out, plus the matching Pizza screen. Did the source you found for cake pans have any larger? Our design (roaster 16" wide minus 1.5-2" edge support) would accommodate up to a 14" one, although 12" is fine, and the pizza screens go up to 14" (although, I would go for a "shelf" and get a 14" cake pan, and 13" screen so we have no chance of binding).

I am going to attempt to get an outline sketch up today.
OK, here is the first "official" drawing. I say it that way in that it is how I start. It is to scale, but there are no dimensions. It is the concept drawing. What you see is a top view and front view. The red is 3/4" aluminum angle. What I will flesh out will be the exact dimension, and a lot more detail.

What we will be doing is taking a piece of 3/4" aluminum angle and bending it (with a jig assisted technique I will detail) in the shape of the top view edge. It's mirror image will be built for the base. Will will join them by aluminum angle as shown (the red L's) to give it the appropriate height. A couple other supports will be present for the blower and stirring motor. Then it will have a sheet metal shell bent (with the same jib technique) and fastened on the outside surfaces. Inside surfaces will be sealed with aluminum duct tape.

Let's start with the basic's. Do you understand the drawing and what it is conveying? Can you "see" it in 3-D in your head?
Alchemist attached the following image:
OK David, you ready? Here's the first real bit of working information.

We are going to be taking a piece (length to be determined below) 3/4" aluminum angle 1/16" thick, and bending it into the top and bottom frame shape we desire. From the roaster design section, we know the roaster is 16" wide (8" drum, 2" clearance (per side), 2" insulation (per side)). That gives us an outer (half) circumference of the frame of:

16 x 3.1415 x 0.5 = 25.13"

In order to make this bend nice and easy, we are simple going to notch the aluminum at intervals. I played around with a few numbers and 1 per inch should go very nicely. This is verified by seeing what the inner 1/2 circumference needs to be, i.e.

(16 - (3/4 x 2 ) ) x 3.1415 x 0.5 = 22.78"

25.13 - 22.78 = 2.36"

With the cuts we need to remove 2.36 inches of material.

2.36 / 25 = 0.0942" or virtually exactly 3/32" or the width of a standard blade cut.

As for the total length, we have

25.13" + 8 (side) + 16 (back) + 8(side) = 57.13" or just shy of a 6 foot piece.

A few other notes that are floating in my head.

The two ends of the construction start at the back left (where you need to make a 45 degree cut for fit).

You come down 8" and start cuts 1" apart for 25 inches. You then start at the other end, go 16", make a V cut, another 8" from the center of the V and you would be within 0.13" of that last cut of the 25.

This will be given structural stability from the sheet metal shell. Rivet holes will be pre-drilled before all the 25 notches for the sake of strength (this is be a little wobbly until fastened together).

Two of these will be made and riveted together via aluminum angle uprights.

Personally, this is enough information for me to cut this out and know how I will put it together (but NOT put it together - we don't have the rest of the frame designed).

Input please. Is this enough for you? If not, where do I need to expound?
Alchemist attached the following image:

Edited by Alchemist on 10/18/2007 12:39 PM


Alchemist wrote:Tentatively, I say we go with the 12" x 4" solid bottom cake pan and cut the bottom out, plus the matching Pizza screen.

I ordered the 12" pizza screen from [I have had good service form them before.]

When it arrives, I will test fit it in the 12" cheesecake pan I already have.
If the fit is OK, then I'll get a 12x4 pan. If the fit is too snug, I'll go for the 13" pan.
I like your drawings, and I think I have the picture in 3D.

It looks like the aluminum frame is a box with one edge missing in order to accommodate the cooling tray. Is that right? If not, then I'll need a simple line drawing of just the aluminum frame -- just the parts that you put in RED in the first of the two drawings immediately above.
OK, a little more explanation. All you have in the above picture is one piece of aluminum angle. In red is the horizontal part that all the cuts will go in, black is the angle going "down".

The lower "thing" is the piece of aluminum after you cut it, but before it is bent up.

Oh, and check the dimensions. The 12" cooling tray is not going to touch this piece at all. This is the top and bottom outer frame. Once we know the exact dimensions of the cooling tray two more pieces of metal will go in to give support under the sheet metal. I will edit up the above image to show those proposed pieces in blue. No dimensions because we don't know them yet.

And because it is part of my goal here (is it yours?), did the math and HOW I came up with the above make sense? We will do the same thing for the frame of the main part of the roaster.
Edited by Alchemist on 10/18/2007 12:41 PM
I think I get it now. The drawing is just the outer skin.
The cooling tray itself is "hanging in mid-air" for the time being.

The directions for cutting the perimeter angle aluminum is very clear.
I will look for the 3/4" size. If it's not available in the quantity we need, I'll get the 1" and ask for new cutting directions.
Good job on finding the 3/4" angle.

I looked at the motor Dan sent and it's length including the shaft is just over 4". I have a tentative plan the base will be 8" thick, so if you can find a 3" deep cake pan, that should work out nice. 4" deep won't quite give us working room.

I don't think it matters if the pan is bottomless or with a bottom. It will cut like butter. Go for availability and price.


Alchemist wrote: if you can find a 3" deep cake pan, that should work out nice.

Roger that.
Since we have that height nailed down, I am going to run through a few other calculations and verify 8" will work for the rest of the roaster. After than I will get the rest of the drawings done and we can start fabrication.

While you are looking around, scope out the thin gauge sheet metal you want. Galvanized is ok in this application as no beans will be in contact. Thin aluminum sheet is fine too.

Also, for the bending jig (that I have basically only hinted at) you are going to need a few feet of wooden 2 x 4 and a piece of plywood around 2' square. Oh, and a few wood screws.
Hey, sorry about the long intermission here. Life and sickness got in the way.

I am going to see about figuring out how much sheet metal we need for both the cooler here and the roaster in general.

Do you want to buy it all at once or a couple pieces at a time?

Remind me where you are with the tray itself? I like the link to the flour sifter you found. Did you find out if it had a support rod?
Edited by Alchemist on 12/07/2007 4:14 PM
I have been away also. I went to Texas to see family and to Phoenix for a conference. It took a day to get caught up on sleep!
I want to buy the metal all at once, if possible.
I may have a chance for a one-time deal on some scrap sheet metal. It is probably thicker than what you suggested. One sheet is galvanized and the other is stainless! I know you like your Zen II in part because it is lighter than Zen I.

The price may be more than right and I love the idea of having a stainless steel roaster. BUT, I will have to see it to decide if it is something that I can work with using low-tech home tools. I'll know next week on that one.

I like the looks of the flour sifter, but I strongly suspect that they all need that support rod. A friend of mine has a big sifter and it has the support rod. The screen is pretty flimsy. I also share your concern about the air flow through the fine screen.

Best mix of strength and airflow would seem to be the pizza screen. I think I'll go with that unless we can source some stainless steel mesh, a bit finer than what we have in the George Foreman wire mesh basket. That would be the best of all, IMHO, unless it would also need some kind of support. Any ideas along that route?
The price was right! I now have the stainless steel. c:2

I'm going to continue this post in the Frame Design and Construction thread.
Here we go!

The Cooler Prototype Test

I rounded up a 14' cheesecake pan and a couple of different pizza screen and set out to test our concept with the Mini Leaf Blower.

I carved a 14" hole in a cardboard box and inserted the cheesecake pan into it. I attached the Mini Leaf Blower to the side of the box and tested it. It backed it self out immediately (coolus interruptus?).
David attached the following image:
With its mandatory seatbelt now in place, the first actual test was to check its power against the solid disk which served as the pan's removable bottom. It lifted it almost an inch.
David attached the following image:
Next was the pizza "Mega" screen, a perforated disk the same size as the original bottom. It didn't lift up, but neither did it pass very much air though.
David attached the following image:
Finally, the pizza screen itself. You can see by the size of the openimgs that the wires do not block much of the air, mmm, maybe 20% or so. There was a half-inch space between the outer edge of the 13" pizza screen and the 14" cheesecake pan. I thought it might be a "dead" space that the stirring mechanism would have to deal with.
David attached the following image:
2 lbs. 8 oz. of Brazil Monte Carlo were roasted to Full City and poured into the cooler on top of the waiting thermocouple. I turned on the timer, the blower, and my camera. I didn't get a readable shot of the initial temperature.

However, as the pictures show, the temperature was down to 163F after a mere 47 seconds. And, at a full minute the temperature was down to 142F [blurry picture available on request] and I found that I was able to stir the beans with my bare fingers. There were some warmer beans around the outer edges where the air could not flow through, but they were not "hot."
David attached the following image:
The temperature was down to 90F after 2 minutes.
It hit 79F by the third minute and 75F at the four minute mark.
David attached the following image:
The final weight of the cooled beans was 2 lbs. 2.25 oz. I think that's about an ounce shy of a full kilo.

So, my conclusion is that the arrangement as tested is quite sufficient to cool at least a kilogram of roasted beans for the Zen 4.2 roaster.
David attached the following image:
BTW and FWIW --

After weighing the beans I poured them into the 12"x2" cheesecake pan that we had initially thought we could use. The picture shows the comparison 12x2 to 14x3. I think we did well to go with both the increased depth and increased diameter.

Your comments?
David attached the following image:
Comments - GREAT!

BTW - to those entered in the cooler competition, THIS kind of time vs temp style data would be great (hint hint hint says one of the judges ;) )

You are very right - I am very glad we moved to the 14" x 3" pan and pizza tray.

Would you verify something for me please? The cake pan is nominally 14". Is that inner or outer diameter? Either way, can you give me the outer diameter (circumference / 3.14159) to say 1/16"? Likewise, is the depth exactly 3"? And while you have that tape measure out, what is the depth from bottom to the bottom of the edge curl?
Ah, yes, the measurements.

I had noticed earlier that the disk had plenty of room at the top, but snugged up as it went to the bottom. Clearly there was a taper, but didn't actually measure it.

So, 14" is the OD at the bottom.
14 3/16th is the ID at the top and the metal is about 1 mm thick.

From the bottom of the pan it is 3 3/4" to the bottom of the curl.
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