Our first prototype EB cooker
was an EB‑42T. The goal was to build a relatively large cooker that was
capable of cooking faster than many other panel cookers. The 42 inch diameter
EB‑42T was chosen because it is the largest EB cooker that can be cut from a single piece of 48 inch wide material. Figure 1 shows the first almost completed prototype.
The reflector portion of theEB42T looks a bit like a parabola, but is safer than a parabola because it does not
have a point focus. It is a triple angle cone consisting of three cone sections
and a circular disk.
Figure 2 is a drawing of the triple cone reflector with the target (pot) represented as a sphere. Figure 3 is a drawing of the reflector viewed from the rear. Figure
4 shows a cross section view of right half of the cooker, with the spherical target appearing as a circle. Note that the dashed blue lines that are tangent to the circle represent the reflections of vertical (on
axis) suns rays that are reflected from the edges of each cone section. This
shows that the cone sections are designed to insure that when the cone is pointed directly at the sun all of the reflected
energy will hit the target sphere. In practice, the cooking pot will replace
the target sphere. The orientation of the pot relative to the reflector cone will vary, as the cooker is oriented for different
sun elevation angles. However, if the smallest dimension of the pot is equal
to the diameter of the sphere all of the reflected energy will hit the pot for all sun elevation angles. We recommend using a pot with smallest dimension larger than the sphere diameter to insure that all of
the reflected energy will hit the pot even when the cooker is pointed a few degrees from the sun.
Figure 1
First Almost Finished EB‑42T
Prototype
Figure 2
View of Triple Cone
Figure 3 Rear View of Triple Cone
Figure 4
Cross Section of EB‑42T
Cooker with Spherical Target
Figure 5 shows how the three
cone sections laid out and ready to be cut from a single piece of 48 inch wide material.
We have experimented with different ways of drawing the large circles. Unless
you have a very large compass, you may need to be a little creative when drawing the circles.
One method that works is to use a small strip of wood or metal that is a little longer than the radius of the largest
circle (A yard stick or a meter stick will work). Put a small nail in one end
for the center point, and then drill a small hole at the radius of the circle. Then
use the stick as a guide for drawing the circle. First, drive the nail through
the stick into the material where you want the center of the circle. Then insert
a pencil through the hole in the stick and rotate the stick about the center point to draw the circle.
Figure 5
Layout of Cone Sections
In addition to the three
cone sections shown on Figure 5, you will also need to cut a 6 inch diameter disc from the material used for the cone sections.
Joining the cone sections
The three cone sections and
the center disk are assembled to construct the triple cone cooker. We have used
two ways to join the ends of segments as well as different cone segments. The
first, which works well for thicker materials, uses bendable straps with fasteners.
Figure 6 shows how straps are used to join cone sections. Holes are drilled
through the ends of the straps and at selected locations on the cone sections. Then fasteners are placed through the holes
and tightened. Often cone segment materials require that a reflective coating be applied.
Sometimes the cone material is itself reflective on one surface. The second method, which works well for thin cone
section material are the tabs made by leaving a section of material at selected sites on the cone segment. Often the smaller
radius edge of the cone segment is selected so when two cone segments are joined the tab is on the outside of the lower cone
segment. Holes are drilled so fasteners can be inserted with the flattest surface of the fastener on the reflective side of
the cone surface. Each method has its advantages with the straps method providing butt joints between cone segment edges.
Stand for EB42T
The EB42T cooker requires
a stand to support the cooker. We have built two different frames for this cooker.
Sawhorse Type Stand
The first Stand we built
was an A Frame sawhorse style structure. This frame is shown in Figure 6. It also can be seen in Figure 1, which also shows the pot and pot holder. This frame
consists of the two A Frame ends with reinforcing strips between the legs. The
pot holder is made from 3/8 inch diameter re-bar and bent to extend through the mid point section of the upper cone segment.
The ends of the pot holder attach to the solar cooker frame through bearing blocks.
Figure 6
Cooker on Sawhorse Stand and Straps Joining Cone Sections
New Portable Stand
The Sawhorse type frame was very strong and stable even on windy days. However it proved to be cumbersome to move from place to place. Therefore we replaced it with a lightweight portable frame similar to the one that had been used with the
EB800. For a more detailed description see the section on the EB800D. This frame is not as stable as the sawhorse stand in windy conditions.
However, we have used it on windy days buy placed a toolbox or other weight on the base. Figure 6a shows the new frame before the reflector and potholder were added. Figure 6b shows the EB42T on the new stand.
Figure 6b
EB42T on Portable Stand
Scaling the EB-42T to make different size cookers
In the following table can
be found dimensions for building a selection of triple cone EB style cookers. There
are many options and currently EB suggests for all except the smallest sized
cookers the triple cone segment is better.
| Dimensions
of Cone Sections for EB Triple Cone Cookers |
|
|
|
|
|
|
|
|
|
|
|
|
|
EB-24T |
EB-30T |
EB-36T |
EB-42T |
EB-48T |
EB-54T |
Cutout |
| Cooker
Diameter |
(inch) |
24 |
30 |
36 |
42 |
48 |
54 |
Angle |
| |
|
(cm) |
61.0 |
76.2 |
91.4 |
106.7 |
121.9 |
137.2 |
(deg) |
| Outer Cone Sect |
Outside Radius |
(inch) |
16.97 |
21.21 |
25.45 |
29.69 |
33.93 |
38.17 |
105.4 |
|
|
(cm) |
43.1 |
53.9 |
64.6 |
75.4 |
86.2 |
97.0 |
|
|
Inside Radius |
(inch) |
12.11 |
15.14 |
18.17 |
21.20 |
24.23 |
27.26 |
|
|
|
(cm) |
30.8 |
38.5 |
46.2 |
53.8 |
61.5 |
69.2 |
|
|
|
|
|
|
|
|
|
|
|
| Middle Cone Sect |
Outside Radius |
(inch) |
10.29 |
12.86 |
15.43 |
18.00 |
20.57 |
23.14 |
60.4 |
|
|
(cm) |
26.1 |
32.7 |
39.2 |
45.7 |
52.3 |
58.8 |
|
|
Inside Radius |
(inch) |
6.17 |
7.71 |
9.26 |
10.80 |
12.34 |
13.89 |
|
|
|
(cm) |
15.7 |
19.6 |
23.5 |
27.4 |
31.4 |
35.3 |
|
|
|
|
|
|
|
|
|
|
|
| Inner Cone Sect |
Outside Radius |
(inch) |
5.42 |
6.78 |
8.13 |
9.49 |
10.85 |
12.20 |
18.4 |
|
|
(cm) |
13.8 |
17.2 |
20.7 |
24.1 |
27.5 |
31.0 |
|
|
Inside Radius |
(inch) |
1.82 |
2.27 |
2.73 |
3.18 |
3.63 |
4.09 |
|
|
|
(cm) |
4.6 |
5.8 |
6.9 |
8.1 |
9.2 |
10.4 |
|
|
|
|
|
|
|
|
|
|
|
| Center Disk |
Radius |
(inch) |
1.71 |
2.14 |
2.57 |
3.00 |
3.43 |
3.86 |
|
| (Target Radius) |
|
(cm) |
4.4 |
5.4 |
6.5 |
7.6 |
8.7 |
9.8 |
|
|
|
|
|
|
|
|
|
|
|
| Minimum Length |
of Material* |
(inch) |
33.93 |
42.41 |
50.90 |
59.38 |
67.86 |
76.35 |
|
|
|
(cm) |
86.2 |
107.7 |
129.3 |
150.8 |
172.4 |
193.9 |
|
|
|
|
|
|
|
|
|
|
|
| Minimum Width |
of Material* |
(inch) |
27.25 |
34.06 |
40.87 |
47.68 |
54.49 |
61.30 |
|
|
|
(cm) |
69.2 |
86.5 |
103.8 |
121.1 |
138.4 |
155.7 |
|
|
|
|
|
|
|
|
|
|
|
| Target Sphere |
Diameter |
(inch) |
3.43 |
4.29 |
5.14 |
6.00 |
6.86 |
7.71 |
|
|
|
(cm) |
8.7 |
10.9 |
13.1 |
15.2 |
17.4 |
19.6 |
|
|
|
|
|
|
|
|
|
|
|
| * If cooker cone is
cut from a single sheet of material with no splices. |
|
|
|
 Figure 7 Bill and Alan with Completed Cooker |
