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Frame Design and Construction
I have been working off and on this for a few days. I have come to realize that I can't really teach how I come up with the design and construction order. I have a 40 minute highway drive (each way) to work every day, so I have LOTS of time to think about design and construction. What you see below are my "personal" drawings of how we are going to frame the roasting chamber. No notes really as I know what it means. Currently it is here just for you to see my progress, a vague thought process, and progression. It is NTS. So you are not completely out in left field, the plan is we will be working with 1" x 1/16" aluminum angle, with occasional 1" flats. Red lines generally denote the angle at a right angle to the drawing. In the end, this will be fully to scale with annotation and full dimensions for anyone to build from.
Alchemist attached the following image:
Thanks for the sketches. They will help to get a sense of what I will have to be doing to construct this wonder. ;)

I was cleaning off my outside roasting area and was wondering if the tipping handle on Zen 4.2 could double as a tote handle? Would that take a latch of some kind?
Don't fret about construction. My plan is that you will get some very detailed instructions from me. I have found, after design, this initial framing is quite important, including how it goes together.

As a brief example, when we join two pieces of the frame, you will have two option for aligning it, one of which is a recipe for disaster, but is how I found a lot of people want to put it together. You can either pre-drill each hole in each piece and then put them together and hope you got the alignment right or hand fit them together to the alignment they need and then drill them together. In general, that last way is how we will do it.

With a good machine shop, we could do it the first way, but I found I could NEVER get the alignment I wanted. Doing them together it can't help but work. Occasionally there will be a point you can't pre-drill both hole together. In that case, you will drill the piece you are attaching, align it, mark unambiguously the under portion (I like a sharpie) and then drill it. Same basic effect. I plan on never pre-drilling two holes that have to join unless alignment completely doesn't mater, and I can't off hand think of a place that would be the case.


David wrote:
I was cleaning off my outside roasting area and was wondering if the tipping handle on Zen 4.2 could double as a tote handle? Would that take a latch of some kind?

Nice idea. Yes, I don't think that should be any problem to design in.

Don't let me forget it....
You asked about sheet metal. I checked what I have been working with, what I used in the Zen I and how much we are going to be needing.

First off, what I have been working with is around 28 gauge. Sounds kind of light, and it is, but also rather sturdy once we start bending it, but still bendable with basic tools. Also, the sheet I have is 2' x 8'. Yes, those are feet. It is a piece of roofing sheet metal. In order to make the outer shell we will need something that long. Actually 1' x 6' but close enough. We could look at a little heavier (lower gauge, 26, 24?) if that is what you find, but only for the straight or large pieces. Lighter is going to be cheaper anyway.

Do you want to look online? or see what you can find in a metal supply house? We can go with a mix of metals if you want. The inner shell I want to be mild steel or aluminum. I would like to work in aluminum for the ductwork (which small pieces will work for) and the outer shell and other encasements can be any of those (mild steel or iron, aluminum or galvanized). Mostly, I want to go for the least expensive. We can easily spend way too much on this sheet metal so I want to take our time and find the best prices. A couple sheets 2' x 10' (I have seen this on line) I hope to get for $20 - 30 each. Personally I flinch a little at that price, but it really is quite the roaster we are building and the surface areas add up. Overall, I don't think Home Depot or anywhere like that is good to do us well price wise.

Does that give you somewhere to start?
Yes, that helps a lot.

I will look around locally for some sheet metal in those larger sizes.

I was wondering about thickness measurements. The aluminum angle stock I bought was in fractions of an inch; yet steel seems to be measured by gauge. Is this a good generalization, or have I just had a limited sample? I think I would feel better prepared to shop if I knew what thickness of aluminum I was looking for and what thickness would be right for steel.

You are not the only one confused. I personally don't "get" gauge. Gauge is a measure of thickness, but changes value depending on the material, i.e. 28 gauge steel is thicker than 28 gauge aluminum. From our point of view, the differences are insignificant.

Standard steel at 28 gauge is 0.0149"
Galvanized steel is 0.0187"
Aluminum is 0.0126"

I got those here

As you can see, they are all "about" 0.01" or as my tape measure told me, 1/64". Too small to really be useful, hence the assigned gauge numbers.

And they are all "about" 1/64"; 1/67, 1/53, 1/79 respectively.

And because I just had to know, I found this.


the gauge number is related to the number of drawing operations that must be used to produce a given gauge of wire; very fine wire (for example, 30 gauge) requires far more passes through the drawing dies than does 0 gauge wire.

Note that for gauges 5 through about 14, the wire gauge is effectively the number of bare solid wires that, when placed side by side, span 1 inch. That is, 8 gauge is about 1/8 inches in diameter.

So, aluminum being softer than standard steel will be thinner for the same gauge (number of passes through the die).

So, what it all comes down to, know that you want about 1/64" BUT no one else in the know is going to know that - they are going to want gauge.

Your aluminum angle is a set exact dimension because it is made by running through an extruder of a set thickness. It is not drawn so gauge does not apply.
Edited by Alchemist on 11/09/2007 7:22 AM
Wow! I feel like I'm on my way to earning my Sheet Metal Worker's Belt Buckle! ;)

But as a shopper, will I be looking for 28 gauge in any of the metals that you mentioned: aluminum, mild steel, galvanized? Structurally will they be equally strong in our application? equally cheap/expensive?
David attached the following image:
In general, I am finding galvanized and mild steel about the same price. Sometimes one is cheaper, sometimes the other. Aluminum is generally more expensive, but not terribly so (not like brass or bronze that would look SOOOOO cool on the outside). The two steels will be stronger, but heavier. For our application, I suggest letting price rule where appropriate.
How are you coming with sheet metal sourcing?

I haven't forgot the project. I just got very busy. I would like to nail down the material before I design much more as material dimensions can make a difference in how we will put it together.


Alchemist wrote:How are you coming with sheet metal sourcing?

I haven't forgot the project. I just got very busy. I would like to nail down the material before I design much more as material dimensions can make a difference in how we will put it together.

I have gotten very busy also. This weekend turn out to be an impromptu visit out-of-state (50% coffee-related) to friends and family. I'll be home for two weeks and then travelling again. I'll keep looking when I can. I found some metals places here locally, but I haven't been able to go check them out in person yet.

Galvanized seems the way to go. Brass would definitely be nice, for just a few hundred dollars more!

As for online sources, how do these prices seem to you
Not too bad. These are a bit better over all. That particular aluminum is a good price.

The Hot dipped galvanized is about 1/2 the price.
Edited by Alchemist on 11/19/2007 11:34 AM
Those links I gave were for that Dan also gave.

I really like Express Metal's selection and prices. We could sheath the outside in brass at an affordable (under $100) price. A 1' x 6' piece to cover the main roaster chamber is $84. Not really suggesting we go there, but....
I was not sure where else to put this but this seemed as good as any.

I have been thinking about the glass viewing porthole. In my mind's eye I have been thinking about two pieces of tempered glass with a gap as insulation. The "problem" I keep coming up with is cleaning. It IS going to get dirty inside. If we have it high up, it is going to be difficult to get to without removing the drum, but if it is down low, it may not be of much use.

Thought or ideas?


Alchemist wrote:I have been thinking about the glass viewing porthole.
The "problem" I keep coming up with is cleaning. It IS going to get dirty inside. If we have it high up, it is going to be difficult to get to without removing the drum, but if it is down low, it may not be of much use. Thought or ideas?

I guess it comes down to how often it would need cleaning and how hard it would be to remove the drum, if that is the only access.
We already have a removable trier in mind; how hard would it be to have the glass be removable?
Screw-in, snap-in, slide-in?? :(
It's funny how the idea just forms in one's head. I am going to design it to slip out from the bottom. Nice and simple really. From my own experience with the Zen II, you are going to have to keep it wiped down every couple roasts, although I high burn might also do the trick. But I think simple is better.

So, when the drum is in dump position, you would pull a pin or slide a lever or something and pull the glass out. Clean it down and slip it back in. No muss no fuss.
Kewl! B)
I came across some scrap stainless steel and the price was right.
However, it is 20 gauge. So, I don't really know if I can work with it using the small hand tools that we discussed. It flexes pretty easily, so I'm sure we can bend it to a curve. I am told that it can be cut with snips. I am also told that I can drill it, as long as I have a tungsten or cobalt drill and go very slowly. Too fast and it heats up and becomes "heat-treated" and gets harder and harder.

If this works, there may be room in the budget for that brass that you covet. Grin
If not, then we'll get some thinner stuff.
That is quite some find. We will see how we can work it in. I fear it is going to be a bit heavy. From the Metalexpress website, that much stainless is going to weigh in at about 4 lbs for the size we need for the outer shell. On that note, I have been finally able to run through some numbers. Here is an overview of what we will need (NOT set in stone) and approximate sizes. Don't go having metal cut at these sizes just yet. We will need some margins.

Upper Outer shell: Any choice of material that can be worked, bent, drilled etc.. 14" x 42"

Lower Outer shell: Any choice of material. No bends needed. Either one piece 12" x 56" or more likely four pieces. (2) 12" x 16" and (2) 12" x 12".

Base and center divider: Any material. (2) 16" x 14"

Inner roaster walls: Food safe metal. Aluminum or mild steel. 12" x 30" (sides and top) (2) 12" x 12" (front and back walls)

Roaster inside chaff tray holder : Food safe. 18" x 18"
Chaff tray 18" x 18"

Front and back outside walls. Choice of material except ferrous. Need non-magnetic due to the removable trier. 18" x 18"

Cooling tray - outside. Choice of material. 12"x 60" would be nice. We can work with 12" x 48" and 12 x 16" if needed.

Cooling tray bottom and top. Choice of material. (2) 18" x 18"

I think that is everything major, and there are extra margins included. It's easy enough math if you want to see what the approximate square footage is we will need. Otherwise, I will put that together also grouped by metal.

Overall long (6 feet) "working" pieces 18" wide would do us well. Laying it all out first to conserve and plan cuts would be best.
Here's a grouping and rough layout of the 3 pieces. I think the file might be a little wide. I will edit it down if need be.
Alchemist attached the following image:

Edited by Alchemist on 12/26/2007 12:11 PM
Nice work! s:2 s:1

I'll see if I can fit that into the sheets that I have.

Nonferrous for front and back, eh?
Does that mean that we might have to use brass?? B) c:2
Well, the front could be brass, but just aluminum would work fine. And the back actually doesn't matter. I guess I just grouped them together. Back can be anything.

Based on that list, do you have enough for the cooler?
I have playing with the layout of these parts on the 4 four pieces of stainless steel that I have. The pieces are 14x72, 24x72, 24x48 and 24x48. I got all of the pieces arranged so that they could be cut out, with three exceptions.
I'm thinking that I'd like to go with aluminum for the chaff tray [#8 & #9] and use brass for the front [#10].

Here is what I have come up with:
David attached the following image:
Hey, it looks like we are finally starting to get somewhere. Nice layout.

Commentary now.

Making the dividers out of SS (3 & 4) is a bit overkill, but since you have the material I don't have any real problem with it.

Brass will be sharp looking for the front and should be easy to work.

OTOH, using this SS for the inner roasting chamber (5, 6 & 7) I think is just asking for trouble. We need to do a bit of fussy exacting cuts and joins and I worry the stainless is just not going to allow that with the basic tools we have. Personally I would prefer aluminum or mild steel. And just as a gut feeling, I would prefer the entire chamber be one material, and the bottom you have opted for aluminum, so that would be my choice. Leave the pretty stainless for where it will show.

On a flip side, if you want to give it a go, it was free material and maybe it won't be as bad as I expect.

At this point it looks like you have enough for the cooling tray portion and we can test SS there.

Are you ready to give it a go?
Well, I have been thinking about this stainless steel that I have. It would look so nice as an outer skin and yet a PITA to try to build some of the more complex stuff with. If I just used it to skin the roaster, I could have enough for two roasters: one for me and one, umm, for you!

I laid out the pieces that I thought we'd need to do the outer parts and there is just barely enough [see diagram]. We might be" forced" to use the brass for the front and there would be areas that we would probably want to paint. The top surface of the cooler would be one and the back of the roaster top would be another.

We could use mild steel for all the parts that weren't stainless.

Whaddaya think?
David attached the following image:
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