About the Frame...
Criteria
The design criteria for the frame were as follows:
- Sturdy - A lot of time was invested into planning and building this device so I wanted the finished product to be something that would last a while. Also, considering how important it is to the operation of the camera and how expensive it would likely be to replace, it stands to reason that the solar panel should be well supported to minimize its chances of becoming damaged during stormy weather or while being handled.
- Weather Resistant - Also in the interest of creating a durable finished product I set out to use materials that are weather resistant. I wanted to minimize the likelihood of rust or corrosion. And, considering that this device would likely be mounted on the roof of my house and that electronics are involved I also wanted to minimize its affinity to lightning.
- Easy to Build - I have no welding experience and only a basic collection of hand and power tools. Having to invest in specialized tools or assembly techniques just wouldn't have been practical either financially or time wise. The shape of the frame members was also a consideration. I needed flat surfaces to mount parts to.
- Inexpensive - Because this project began as a whim and I really didn't know whether or not it would actually work I couldn't justify spending large sums of money on it. Therefore, minimal expense was a recurring theme throughout the course of this project.▼
First Pass
The first pass I made at assembling a frame probably took the "low cost" criteria to too much of an extreme. The idea was to build a box that would support the solar panel on top of it while also housing the needed electronics inside. I figured plastic would be the most affordable material to use and is also easy to cut and shape. I obtained a scrap sheet of acrylic for less than $20 USD. I didn't want to compromise the weather resistance of the box by drilling a bunch of assembly holes into it so I opted to glue the box walls together instead of using mechanical fasteners (screws). The problem with this design is that I was frequently opening and closing the box to make adjustments to the wiring inside and to check on the operation of the electronics. Each time the lid was raised the weight of the solar panel would create too much stress on the hinge side of the box and the adhesive would fail. I tried several types of epoxies with no success. In my quest for a suitable adhesive I turned my attention to PVC instead of acrylic. PVC is much more readily available at local hardware stores as are a vast array of compatible adhesives. And it's also inexpensive and weather resistant. I thought if these materials are suitable for pressurized piping systems then why wouldn't they be able to withstand the stresses I was subjecting my box to? So I acquired a sheet of PVC and began cutting out the pieces I would use as walls for the next box.▼▲
Tubular
At about this same time I started to recognize that many of the problems I was wrestling with were related to my insistence on using the electronics enclosure to also support the solar panel. I finally came to realize the solar panel support had to be independent of the electronics enclosure in spite of the added expense this might create. So I started to ponder what materials I could use to build a frame with. Because of its weather resistance I preferred to continue on the path of using plastic as the primary material for this project and PVC was still very appealing to me as a suitable material for the electronics enclosure so why not also use it to make the frame? The problem I found is that PVC tubing is most commonly available in round shapes. As mentioned previously I needed flat surfaces to mount parts to. I found a web site or two that suggested it was made in square shapes but none of them offered it for sale in small quantities.▼▲
Material World
I had recently completed another project that used square aluminum tubing as a support. It was easy to work with, affordable and available in short lengths from my local hardware store. In addition to the anodized coating, aluminum is also corrosion resistant due to a layer of aluminum oxide that forms naturally on its surface. These characteristics made it an obvious second choice when I was unable to find a source for square PVC tubing. The next challenge was to find a way to connect the pieces together without having to drill a bunch of assembly holes through it that might allow storm water to seep in and become trapped inside the tubing. An internet search lead me to the website of a boltless construction system manufacturer. This system uses nylon, right angle blocks that fit snugly inside the aluminum tubing. The cost for this system is reasonable but was more than I originally wanted to spend. Its value, however, was undeniable considering I was at a loss for other options and also considering the resulting structural integrity of the frame would be greater than I imagined it could be. This system would also serve to speed up and simplify assembly, especially since the company also sells the aluminum tubing and offers to machine cut it to your specifications (for a small additional fee). After coming to terms with the higher than expected expense the decision to commit to this system was an easy one.▼▲
Dimensions
Like the local hardware store the boltless construction system manufacturer sells the aluminum tubing in 8 foot lengths. The dimensions of the frame were chosen to use as much of the purchased material as possible. The width and depth of the frame were selected to equal the width and length of the primary solar panel. The frame includes a cantilevered appendage that supports the optional secondary solar panel. The width of the appendage was sized to equal that of a piece of aluminum plate I planned to use as a reinforcing backing plate for the secondary panel plus one inch to provide a surface for mounting the lid support that provides some adjustability to the panel angle of inclination. The depth of the appendage had to equal the depth of the rest of the frame. With those lengths of aluminum tubing subtracted from the original 8 foot lengths, the height of the frame was determined by dividing the remaining length by four (four legs) and rounding to the nearest whole number to ease measurement and discussion. It should be noted that all 4 of the top frame pieces and 2 of the bottom frame pieces were ordered with a lip on them. The lips on the top pieces are to hold a remnant piece of acrylic from the first version of this project. This piece, although not water-tight, serves as a shield from storm water for the electronics enclosure that sits below. The lips on the bottom pieces are to hold the electronics enclosure. The only other pieces that needed consideration were the connecting blocks. The simplest design will require 8 of the three-way connectors, 4 for the top and 4 for the bottom. However, my design includes an optional secondary solar panel. So, in order to support the appendage for this panel two of the top connectors needed to be the 4-way type. Finally, two 2-way connectors were needed to complete the optional panel appendage.▼▲
In Summary
The resulting frame is sturdy yet lightweight and very portable. Because its components are made of only aluminum and plastic it is also very weather resistant. Adding four soft plastic pads to its bottom, one under each leg, elevates the frame slightly to keep it out of shallow puddles of storm water. further enhancing its weather resistance. The elevated frame is also easier to grab onto for moving, and is protected from scratching. Since the boltless construction system manufacturer cut the lengths of aluminum to my specifications, the only tool I needed to assemble the pieces was a wooden mallet which dramatically simplified assembly. Finally, the added expense was worth every penny considering the time saved in assembly and the durability of the finished product.▲
