cold frame - Elephantom

COLD FRAME
ZACHARY CLEMENTE :: MICHAEL DALE :: LUKE GAY :: PETER MODEST
DONNA COHN :: IA 237 :: APPROPRIATE TECHNOLOGY
---------------------------------------------------------------------------------------------------------------COLD FRAME DESCRIPTION
---------------------------------------------------------------------------------------------------------------Our group based our project on a JUWEL cold frame, which was ordered from an Austrian company
and cost approximately $300 (including shipping). There were several aspects of the JUWEL cold
frame that we wanted to emulate, like collapsibility, and the use of a heat sensitive pneumatic piston
to regulate the temperature inside the frame. However, our group wanted to make some critical
changes to the JUWEL’s design to make the setup process highly intuitive while cutting costs. The
JUWEL frame took an hour to set it up initially, and the instructions were no help, they also were
too simple, ambiguous, and not clearly illustrated. We set out to design a cold frame for a fraction of
the cost that would functionally extend the growing season of plants, look as aesthetically cohesive as
the JUWEL frame, and auto regulate temperature inside frame using a heat sensitive piston. We also
hoped to simplify the building process, so people could easily build our low-budget cold frame, or
alter and expand the design themselves
For each cold frame we’ve used one 4’x8’ sheet of double corrugated clear plastic which costs $60 per
sheet which was special ordered from Commercial Plastics and Supply. When the order of plastic
first arrived, it was discovered that it was opaque and white- not very conducive to plant growth.
This order was sent back and a new order for clear corrugated plastic was placed. About a week after
the correct plastic was supposed to arrive, another batch of opaque plastic arrived, this was not sent
back, but used to create a mock-up. Up to this point we had been using corrugated cardboard for
our models. The idea was that the opaque plastic would be more like the medium we would
eventually work with, but it was rather more like cardboard, quite flimsy.
The rest of the materials were purchased from Home Depot;
Gorilla® Tape for sealing edges and making corner hinges
4 - 2” hinges and hardware for the lids
1 - 1” hinge for the front latch
1 - 6”x1/4” Carriage bolt for front latch
3 bolts and wing nuts to secure the one corner that separates
Rubber epoxy
Other items (found in in the shop):
2” x 2” x 17” section of fiberboard to which the latch bolts and wing-nuts are affixed,
16 small bolts and nuts for the hinges
4 1.5”x1/4” hex-head bolts for side lids
We decided to stick with the JUWEL dimensions: 40” wide, 34” deep, 11” high in the front and
17” high in the back.
We found the spring-lever contraption that held the heat sensitive piston to be rather inconvenient.
It was affixed to the lid with screws which made it time consuming to open that side and also was
complicated and costly. We needed a design that would allow the small distance that the piston
moves (approximately 1.5”) to translate into an opening in the lid that would provide adequate
ventilation to not scorch young plants. We formulated a bracket out of scraps of the sheet of plastic
that affixed to the back wall with cutout slots and bolts, making it easily removable. We did not have
a chance to test out the apparatus on the frame before our presentation, and were discouraged by it’s
failure. However, upon reviewing the calculations, it was apparent that over the course of the
semester the piston had become worn out, and could not do the same work it had originally done.
The piston suffered from constant use, people pulling the piston away from it’s casing, and
overheating. These pistons are notorious for being temperamental, so we made sure to make it easy
to replace this specific part in our design.
---------------------------------------------------------------------------------------------------------------TESTING AND EVALUATION OF PROJECT
---------------------------------------------------------------------------------------------------------------The testing for this project was a pretty simple and quick process. Unlike most of the other projects
done, we based our design off a purchased cold frame, focusing on tackling the serious design flaws of
purchased frame. With that in mind, most of our testing of the project stemmed from us berating a
flaw in the existing cold frame and asking questions such as "how is this poor design?" and "how can
we make this better?" We first recognized that we should not use detachable walls for the frame as
that was the major problem with the original frame. Attempting to figure out how to assemble the
first frame proved extensively difficult due to the “simple instructions”, which were utterly useless in
trying to figure out the overcomplicated design.
We knew that when we attached the walls, it would have to be sturdy, collapsible, and airtight. We
toyed with the idea of door hinges covered with cut up rubber from the inner-tubes from bicycle
wheels. At this point in redesigning, we didn't have any plastic yet, so we built our first model out of
cardboard, testing the duct tape hinges and locking mechanism. For the locking mechanism, we
mounted bolts into blocks of scrap wood with wingnuts that tightened connecting the walls of the
frame. Once we attached the wood blocks to the edge of one of the walls so that the bolts would be
protruding out perpendicular to the next wall, we cut notches into the joining wall so that it would
slide around the bolt and be secured by clamping the notched wall between the twisted wingnut and
the wood blocks. As the project continued, we determined that continuing to use tape for the hinges
was cost efficient and effective, so we decided to upgrade to using gorilla tape with the next mockup.
Additionally, we devised a ways to use strips of tape along the right angles created by the walls to
restrict the walls from opening past 90 degrees and, by affixing a washer in it, creating a way to stake
the frame securely onto the ground.
At this stage in the project we had not yet received the correct plastic, so we were improvising with
semi-transparent single-corrugated white plastic to make a proof of concept. During this process, we
moved the placement of the locking hinge that could detach to allow for collapsing should be moved
so that the bolts would be facing the back of the frame and that it should be mounted on solid piece
of wood to make the design look nicer. Additionally, we used basic metal cabinet hinges to attach
the lids to the back wall. By this point, we had gotten the correct plastic shipped to us, clear doublecorrugated sheets. When making the final design, we had very little left to do design-wise, we just
made the final frame with more care to make it look more professional. We stripped out the 90
degree tape joints except for two for staking down, outlined the sides of the walls and top panels with
tape to prevent damage to the internals of the plastic and aide in the aesthetic of the frame. For the
piston, we made a mounting bracket out of excess clear plastic that would mount on the inside of the
back wall, positioned right under the center top panel. We attached the piston's mounting bracket
by affixing four bolts onto the back wall which stuck out into the frame itself. Then we made four
circular notches that tapered downward so that one could push the bracket onto the bolts and slide it
up, locking it in place. For the two outside top panels, we attached bent threaded bolts on the top of
the front wall and the end of the top panels to allow for a swiveling lock. We were concerned with
the center top panel being pulled open by wind, as it wasn't able to be locked when fully closed. We
used an extended bolt that was bent at the tip, catching a hinged block at the top of the front wall.
We didn't end up testing anything beyond the ease of use and appeal of the design of the new cold
frame, as during the presentation, the piston failed to work. The piston that we used during the
presentation had lost it’s pushing power due to the continuous use over the semester, and the harsh
temperatures we exposed it to. However, switching the piston by unscrewing it from it’s wooden
housing will solve the problem.
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FINAL STATUS
-------------------------------------------------------------------------------------------------------------------------After much planning and designing without the materials to build with, the final cold frame came
together in a single draft. It stands with the aforementioned dimensions and all of the important
features that were planned for it.
The clear plastic is advertised to pass 92% of incident light and is very sturdy stuff considering its
weight. One 96” x 48” sheet can make the entire frame for a much-higher-than-expected cost of $60
a sheet.
The Gorilla Tape hinges dominate the design, which hold the frame steady when in its completed
form and fold very easily. The hinges on the front left and back right corners also have the 90 degree
stop worked into them, though they are on the bottom of the cold frame instead of the top. This was
decided to be the best position, as they don't get in the way of the lid. They also have O-rings
embedded in them so that stakes can be driven through to keep the cold frame from moving. The
front right corner does not have a 270 degree hold: this feature was pretty much forgotten and most
designs for it didn't do much for the structural integrity of the deployed cold frame. The black tape is
also very snappy, and gives the cold frame a nice professional look.
The locking corner works great. It was moved to the back left corner and executed with three wing
nut and bolt assemblies and a piece of scrap wood. Just a little force is required to either push the
bolts into place or remove them from the L-shaped slots. It is the most stable corner of the cold frame
and does much for the structural integrity of the frame.
The cold frame is fully collapsible, with easily removed hinges for all three lids. After completing the
design, it was noticed that the tops didn't really need to be removable, as the cold frame could easily
be stored by hanging it from a wall. The hinges are held on with nut and bolt assemblies, which
eliminate the need for backing material.
The heat sensitive piston bracket was conceived and made completely by Peter and would work quite
well if we hadn't messed with the piston quite so much. As it is, the piston we are using is not
functional, due to various tests we did on its capabilities. If the piston we have were to be replaced
with a new piston, the assembly would open the middle lid easily when the interior would get too
hot. The assembly is made out of scrap plastic taken from the sheet used to make the rest of the box.
It is mounted to the back of the frame on the inside using four bolts. It can be removed for knock
down and together with the entire rest of the frame is one of the two pieces that make up the entire
frame. The locking mechanism for it consists of four bolts and four matching holes for the frame to
be pressed up into. In the next version, the assembly will be pushed down into place, preventing the
weight of the lid from pushing it loose.
The bolt hinges all work well, though in the final version, they had to be moved after it was realized
that the tops were longer than previously thought. Though the tops move around some, after the bolt
on top is twisted into place, the lids hardly move at all. The stopping mechanism for the middle piece
works quiet well, though the hinge needed some work so it wouldn't open as easily.
The entire cold frame achieves the function we set out to do for around $120 dollars, or slightly more
than a third of the Austrian cold frame. Our group has discussed a few different ways we could cut
the costs even further.
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FUTURE WORK
-------------------------------------------------------------------------------------------------------------------------While our group has not discussed continued collaboration together, the individual members of the
group have expressed interest in continuing to make better cold frames.
We have thought about
replacing the duct tape with hinges to make a possibly more permanent joint. We also discussed
altering the size of our design and potentially looking into how a cold frame could utilize vertical
farming techniques. One member of our group started experimenting cutting up plastic soda bottles
to make his own corrugated plastic. If this technology was developed further, it could provide exactly
the means to build a cold frame off of truly appropriate technology.
---------------------------------------------------------------------------------------------------------------COLD FRAME DESIGN TEAM
---------------------------------------------------------------------------------------------------------------Our design team consisted of Luke Gay, Zachary Clemente, Michael Dale, and myself (Peter
Modest).
Throughout the design and build processes we worked together to create a highly
functional and intuitive cold-frame for less than a third of the cost of purchasing one online. I will
briefly discuss what my group members did.
Luke Gay was most beneficial when he questioned our design decisions, and he sometimes
offered helpful and useful suggestions. In this sense, Luke kept our ideas practical and simple, yet I
think he needs to be more confident in his own abilities to suggest helpful design tips. Luke
definitely assisted in the building process, and always requested clear instructions before acting. Luke
showed up to all of our meetings, though could have been more punctual at times. Luke also wrote
up the description for our project.
Zach was a great member of the group. He helped through the design-process, coming up
with a simple and effective latch system to keep the cold frame together. Zach’s design was infinitely
more practical than the latching mechanism on the purchased cold frame. Zach kept the group sane,
showed up to every meeting pretty much on time, and met with me outside of meetings to work on
the project. Zach was our team’s most reliable member, and always responded to texts regarding
scheduling and design consultations.
Michael was the wild-card of the group. While he was far from reliable, he came up with
some of the best design-ideas for our group. Michael figured out how to build the cold frame’s joints
with duct tape and how to lock the cold frame’s lid using screws. He also came up with a great
method of using duct tape corners that would keep the cold frame in it’s rectangular shape, while
offering a place to stake the cold frame in the ground so it would not blow away. However, Michael
was sometimes difficult to work with because he would do a lot without consulting the group, and he
missed some critical meetings (like the day before our final was due). Michael is an interesting
character with a lot of potential- he just needs to grow up a bit.
---------------------------------------------------------------------------------------------------------------WHAT I DID
---------------------------------------------------------------------------------------------------------------I think I was the most involved and dedicated part of the cold-frame design team. I was the
one to organize meetings, and I often felt obligated to disseminate the necessary tasks among the
group.
I was also highly involved in the design process- calculating dimensions, building the
cardboard and (translucent) plastic model, building the housing for the thermal-piston, and generally
focusing on the pre-build part of the project so when we (finally) got materials we were able to build
the cold frame without hesitation or deliberation. Earlier in the semester I created a rough model of
the cold frame on Google SketchUp, followed by a highly detailed and precise final SketchUp copy
of the cold frame. The final Sketchup model is going to be available on the internet, and has all the
exact measurements and parts. From this model people will be able to easily build their own coldframes, and alter the design to fit their exact needs. I also created an additional Sketchup document
that has three different options to cut the plastic into the necessary shapes and sizes. I thought
Sketchup would be the best outlet for releasing a design because it is freeware that is supported on
Windows, Mac, and Linux. I did not want to use Adobe Illustrator, because this would make the
design more exclusive because it could only be viewed by people who have purchased the program.
While we were waiting for the correct plastic to arrive for our cold frame, I started
experimenting cutting up plastic soda bottles, and building multi-cell insulating sheets from the
plastic. I realize that this method was really inefficient because I could only get a 5 ½” x 10”
rectangle from each bottle, and I needed three layers to get the desired insulation. It took 45 minutes
to build a dual-cell insulating sheet in this fashion, but the product was both aesthetically impressive
and functionally effective. My success with the soda-bottles shows that a system could be developed
to recycle bottles (possibly melting down bottles and making larger sheets), save money, and still get
the same effects as the expensive transparent plastic sheets.
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COLD FRAME SPECIFICATIONS
-------------------------------------------------------------------------------------------------------------------------(1) Sheet Double Corrugated Plastic :: 48” x 96”
(1) Back :: 40” x 16”
(1) Front :: 40” x 11”
(2) Sides :: 34” x 11”-16”
(1) Top Center :: 20” x 35”
(2) Top Sides :: 10” x 35”
(1) Piston :: 11” (compressed) - 12.5” (expanded)
(4) Hinges :: 2”
(1) Roll Gorilla® Tape
(1) Wood :: 2” x 2” x 2”
(10) Screws
PLASTIC CUTTING TEMPLATES (CHOOSE 1)
---------------------------------------------------------------------------------------------------------------MODELS
---------------------------------------------------------------------------------------------------------------Original Concept
Soda Bottle Model (with wood)