Construction of the 2-D Scale-up Cooker

Design: Cooking Bigger Pots

The 2-D Expansion

The objective for this semester was to design an oven that was capable of fitting the larger
pots that the Nicaraguan women wanted to use. The main issue with the larger pots
(below) was that they were too tall to fit in the previous design of the oven.

Therefore, we decided to increase the height of the 1-D scale up version of the oven in
order to fit the larger pots.
1_D.JPG

The dimensions of the fall 2008 1-d scale up were 42.5" x 30" x 10.75". We decided that in
order to safely fit the larger pots, that we would increase the height dimension by four
inches, resulting in the new dimensions of 42.5" x 30" x 14.75".
2_D.JPG

We hope that by constructing and testing the larger ovens we can learn more about how
sizing effects the cooking speed. While the original goal was simply to fit a larger pot inside
the oven, we hope that this oven will also allow us to learn more about the heat transfer in
the box cooker.

2-D Scale up Construction

To construct the scaled up box cooker, we followed a manual given to us by Grupo Fenix
titled "Solar Box Cooker Construction Manual". The manual includes measurements of the
individual parts of the original 30"x30" ovens currently in use in Nicaragua. It also contains
a detailed set of instructions for construction. Our team determined the dimensions for the
2-D scaled up version of the oven by first measuring the 1-D scaled up oven constructed
during the Fall 2008 semester. Our team combined the measurements from the oven, and
the dimensions given in the manual to determine the dimensions for the pieces for the 2-D
scale up.

During the construction process we tried to follow the instructions outlined by the manual
as closely as possible. We also tried to emulate the way in which the cookers were
constructed in Nicaragua by drawing on the experience of team member who went to
Nicaragua during Spring Break. There were some differences, however, in the construction
of this oven in comparison to the previous ones. The differences included using a different
wood sealant, using two pieces to form each L-shaped column, using different glass, using
different hinges and attaching them differently, and putting fiberboard on top of the
insulation in the door.

The use of a different wood sealant was the suggestion of our team's advisor Mr. Timothy
Bond. The sealant we used was "Clear Multisurface Waterproofing Sealer" by Valspar; it
claims to be for severe weather. We used two-piece L-columns because cutting L-shaped
columns is rather difficult and piecing these columns together from two separate wood
pieces makes the construction process much easier. The glass made in the United States of
America is different than obtained in Sabana Grande, Nicaragua. The hinges we used were
of a different variety; their design allowed the two different sides of the hinges to be
completely folded within one another when the door is closed. Also, we decided to follow
the directions in the manual that suggested chiseling out a recess for the hinges in the door.
This technique was not used on the previous box cookers that were constructed in the lab.
The fiberboard that was added on top of the insulation on the door was more for
convenience since the wood pieces we used for the support means were just a little under
the desired height. We decided to add another layer on top of the fiberboard to account for
this difference.

The construction process for the 2-D scale up took almost the entire semester. The main
problem in the construction process was the lack of construction meeting times. While we
had increased the number of tests for the semester, we only had one meeting time for
construction per week for most of the semester. We switched some of the testing times to
construction times later in the semester when our team realized that we needed to get the
construction done. In addition, since the entire team was taking this course for
independent study, it was difficult to maintain a constant level of commitment from every
member of the team. Fortunately, we were able to complete the new box cooker during this
semester, although we have yet to run any tests on it.