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\begin_body

\begin_layout Title
Fabrication
\end_layout

\begin_layout Abstract
The Fabrication team focused on three main goals for the Summer 2011 semester.
 Firstly, we worked on developing a system to recharge a cordless power
 drill without using an electrical wall socket.
 Our solution was to connect the battery charger directly to a car battery,
 which may be easily brought to the site.
 Secondly, we researched more effective ways to remove plugs from hole saws.
 We determined that the commercially available Lenox speed-slot hole saws
 would best resolve this problem.
 Thirdly, we developed, tested, and improved a jig to help facilitate the
 assembly of plate settler modules.
\end_layout

\begin_layout Section
Recharging Battery Powered Drill from Car Battery
\end_layout

\begin_layout Standard
Our goal was to create a system that allowed cordless drills to be used
 at the construction site for a full day of work.
 The idea was to connect a drill directly to a large portable car battery.
 
\end_layout

\begin_layout Standard
Currently, Aguaclara uses the ubiquitous DeWalt 12V 3/8
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 cordless hand drill.
 Unfortunately, the price of extra battery packs for these drills remains
 around $50 (compared to the actual drill's cost of slightly over $100).
 This drill has two settings, low (0-400 RPM) for driving large screws and
 drilling large holes, and high (0-1,450 RPM) for drilling smaller holes
 and fasteners.
 The high setting on high torque is required in order to avoid the drillbit
 getting stuck when going through multiple plastic plates.
 Assuming the typical battery in use is a DeWalt DC9071, 12V 2.4 Ah Nickel
 Cadmium Battery, the drill has a maximum power of about 200-210W.
\end_layout

\begin_layout Standard
To implement our system, we intended to find a connection through the battery
 case into the drill (See Figure 1.1 
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reference "Fig 1.1"

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), connecting the other end of a pair of jumper cables to the battery.
\end_layout

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Figure 1.1: Disassembled Dewalt 12V Battery Pack
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\begin_layout Standard
Upon further evaluation, however, we concluded that utilizing and modifying
 the DeWalt drill was not the best course of action.
 We opted to work with a Milwaukee 2411-22 instead, as this drill serves
 as both a driver and a hammer drill.
 To our knowledge, it is the only mass produced 12V cordless hammer drill.
 
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Figure 1.2: Milwaukee 2411-22
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\begin_layout Standard
We also discovered that Milwaukee manufactures a charger with a cigarette
 lighter plug for the M12 Red Lithium battery packs utilized in this drill.
 This, coupled with a simple cigarette lighter socket, could serve to charge
 the drill batteries directly from a car battery.
\end_layout

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 Figure 1.3: Milwaukee Car Charger & Adapter
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\begin_layout Standard
We found this approach preferable to others due to its versatility and reliabili
ty.
 This configuration requires no modification (and the resultant risk of
 permanent damage) to the battery or any drill components.
 Since Milwaukee manufactures the charger, we can be certain of its safety
 and performance.
 Moreover, since the adapter is removable, it allows for various charging
 methods: one could utilize the power of a car directly from the cigarette
 lighter, or connect the jumper cables to an extra car battery that has
 been brought to the site.
\end_layout

\begin_layout Subsection
Hammer Drill
\end_layout

\begin_layout Standard
Our secondary goal was to find a suitable hammer drill for drilling through
 concrete.
 The only available hammer drills from DeWalt are 18V, which would be troublesom
e to connect to a 12V car battery.
 As mentioned earlier, the only 12V cordless hammer drill currently available
 is the Milwaukee 2411-22.
\end_layout

\begin_layout Standard
Hence, we decided that it would be more economical to simply purchase the
 Milwaukee Hammer Drill.
 The Milwaukee 2411-22 M12 has multiple functions, and can serve as both
 a normal drill and as a hammer drill (which will help drill holes through
 concrete).
 It uses a 12V Milwaukee M12 Red Lithium battery pack, which is light and
 compact.
 It also has 2 speeds: 0-400rpm and 0-1500rpm.
 It takes roughly 30 minutes to charge a battery pack, which holds around
 4.5AH of charge (See Figure 1.4 
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reference "Fig 1.4"

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 for disassembled battery pack).
 The complexity of the Milwaukee M12 Red Lithium battery pack was another
 reason we eventually chose not to wire the drill directly to a car battery.
 As seen in Figure 1.4 
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, the battery pack utilizes a printed circuit board, which would be hard
 to detach without damaging the connection.
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Figure 1.4: Disassembled Milwaukee 12V M12 red Lithium Battery Pack
\end_layout

\begin_layout Section
Improved Hole Saw
\end_layout

\begin_layout Standard
Numerous parts of the AguaClara plant require us to drill holes through
 plastic.
 For instance, several holes must be drilled through PVC to create the launder.
 Most notably, though, many holes must be drilled through lamella plastic
 to create the plate settler modules.
 Overall, the process can be tedious and time consuming.
 Although the existing hole saws quickly and cleanly drill holes through
 plastic, it is very difficult to remove the plug that gets stuck in the
 saw after drilling is complete (See Figure 2.1 
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reference "Fig 2.1"

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 and Figure 2.2 on 
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reference "Fig 2.2"

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).
 As it is, the plug must be pried out from an angle.
 The Spring 2011 team suggested that we try out using a self-ejecting hole
 saw arbor.
 However, such arbors can only be found for hole saws exceeding 1½ inches
 in diameter.
 Hence, we needed to find a better way to drill through PVC or a better
 way to remove the plug left over.
\end_layout

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Figure 2.1: Vertical view of plug stuck in hole saw
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Figure 2.2: Horizontal view of plug stuck in hole saw
\end_layout

\begin_layout Subsection
Self-Ejecting Arbors
\end_layout

\begin_layout Standard
There are not many self-ejecting arbors available, and it is unlikely that
 there will be any at the places where plants will be built.
 The machine shop in Hollister had some ejecting mandrils, but these did
 not really help with the removal of plugs from the hole saw since the mandril
 arms did not extend far enough.
 Hence, we decided to look for alternatives for simplifying the removal
 of plugs.
\end_layout

\begin_layout Subsection
Different Types of Drill Bits
\end_layout

\begin_layout Standard
As most holes in an Aguaclara plant are usually less that 1½ inch in diameter,
 with the ½ inch plate settler holes being by far the most common, we tried
 to find a more efficient way of drilling smaller holes.
 Numerous online forums made different recommendations.
 Ideally, a simple drill bit could be used for the large number of plate
 settler holes.
 This would avoid the need to remove a large number of plugs.
 We researched and evaluated the following types of drill bits for different
 sized holes.
\end_layout

\begin_layout Itemize
Forstner Bit: This drill bit is very effective for making perfectly shaped
 holes.
 However, it is usually used for wood, and requires the head to be perfectly
 aligned with the surface.
 In most of the examples we found, machine drills were used since it requires
 a lot of force.
\end_layout

\begin_layout Itemize
Step Bit: This drill bit was recommend for PVC tubes on several on-line
 forums.
 However, as it is more expensive, less readily available, and would probably
 require a prolonged application of perfectly vertical force, we decided
 not to pursue this option.
\end_layout

\begin_layout Itemize
Spade Bit: This bit uses a flat head to carve a hole in surfaces.
 We tried the spade bit from the machine shop on PVC pipe.
 It was extremely difficult to align the bit with the surface and the pipe
 eventually spun out of control.
\end_layout

\begin_layout Itemize
Plastic Bit: This bit can only be used for up to ¾ inch holes.
 We tried a plastic bit on the plate settlers.
 It drilled through relatively easily, but left a more jagged rough edge
 than the hole saw.
\end_layout

\begin_layout Standard
None of the drill bits we tried were able to drill through plastics as cleanly
 or as easily as a hole saw.
 While the hole saw simply cuts a hole in the material, the other drill
 bits literally shave through the entire hole.
 Hence, hole saws greatly reduce the amount of force required to drill through
 the material.
\end_layout

\begin_layout Subsection
New Hole Saw Kit
\end_layout

\begin_layout Standard
There are some hole saws available with slanted slits and grooves at the
 side that make it easier to pry out plugs.
 However, these may not be available everywhere.
 If at all possible, we strongly encourage the purchase of Lenox speed-slot
 hole saws in the future.
 We purchased a 7/8 inch Lenox speed-slot hole saw (See Figure 2.3 
\begin_inset CommandInset ref
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reference "Fig 2.3"

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).
 It was very effective in cutting through the lamella plate modules, and
 removal of the plug was made easier by the groove.
\end_layout

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Figure 2.3: Lenox 7/8 inch Speed-slot Hole Saw
\end_layout

\begin_layout Subsection
Specialized Tool
\end_layout

\begin_layout Standard
We worked on developing a specialized tool to help us remove the plugs from
 the hole saws.
 One idea was to use a bent metal rod to pry the plug out (See Figure 2.4
 
\begin_inset CommandInset ref
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reference "Fig 2.4"

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).
 Another idea was to somehow elevate the pivot in order to use a regular
 screwdriver to pry the plug out (See Figure 2.5 
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reference "Fig 2.5"

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).
\end_layout

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Figure 2.4: Bent prying end of tool
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Figure 2.5: Lever end of tool
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\begin_layout Standard
Initially, both of these tools worked effectively.
 However, with the introduction of Lenox Speed-Slot holesaw, the lever tool
 has become less relevant.
 The bent prying end of the tool also proved to be inadequate as the flimsy
 metal bent in the opposite direction when we tried to pry plugs out.
 This problem may be solved by creating a tool from a less malleable metal.
\end_layout

\begin_layout Section
Plate Settler Modules
\end_layout

\begin_layout Subsection
Aligning the Sheets with a Jig
\end_layout

\begin_layout Standard
We liked the Spring 2011 team's idea of using a jig to align the plates
 before drilling.
 Assuming a plate seperation of 1 cm and an angle of 60 degrees with respect
 to ground, we found the desired gap between jig plates.
\end_layout

\begin_layout Standard
\begin_inset Formula 
\[
gap=\frac{1cm}{\tan60}=0.57735cm
\]

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\end_layout

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name "Fig 3.1"

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Figure 3.1: Sample Stacked Plate Settlers
\end_layout

\begin_layout Standard
We decided that a 1 cm spacing between plates, which would require a 0.577
 cm gap between the top of each plate, would require an impractical level
 of precision.
 Given that we had to use scissors to make the jig, and that further alignment
 has to be done as the module is constructed, such precision was unrealistic.
 Instead, we chose to model a 2 cm seperation, which requires a 1.15 cm height
 difference.
 We constructed a new jig in accordance with these specifications (See Figure
 3.2 
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reference "Fig 3.2"

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).
\end_layout

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\end_layout

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name "Fig 3.2"

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Figure 3.2: New Plate Settler Jig
\end_layout

\begin_layout Subsection
Cutting through Plastic
\end_layout

\begin_layout Standard
Cutting the plate settler material is a fairly difficult task as there isn't
 a specialized tool to cut through it.
 We attempted to use the machine saw in the machine shop to slice it into
 pieces.
 However, this shredded up, instead of snipped, the material.
 One sixteenth of the material was lost, leaving a jagged edge.
 A strong pair of scissors proved the most effective at slicing through
 the pastic sheets (See Figure 3.3 
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reference "Fig 3.3"

\end_inset

).
\end_layout

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Figure 3.3: Comparison between scissors (left) and saw (right)
\end_layout

\begin_layout Subsection
Constructing a Mock Plate Settler Module
\end_layout

\begin_layout Standard
We constructed an entire plate settler module using the jig we created (See
 Figure 3.4 
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reference "Fig 3.4"

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 for schematic).
 Although this does not adhere strictly to the specifications of current
 AguaClara plants, we feel that the process has demonstrated the efficacy
 of the jig.
 It increased our efficiency and accuracy greatly, eliminating the need
 to repetitively align each of the plates.
\end_layout

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Figure 3.4: Schematic for plate settler module
\end_layout

\begin_layout Standard
The first step was to measure out the exact length of one plate (See Figure
 3.5 
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), and subsequently cut a piece of that length.
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Figure 3.5: Measuring and marking the length of a plate
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\begin_layout Standard
Using this first piece as a template, we then drew a line to mark each subsequen
t plate (See Figure 3.6 
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reference "Fig 3.6"

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) and proceeded to cut the initial sheet into multiple plates.
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Figure 3.6: Using the first plate as a template
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\begin_layout Standard
After cutting the desired number of sheets, we aligned them on the jig (See
 Figure 3.7 
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reference "Fig 3.7"

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 and Figure 3.8 
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).
\end_layout

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\end_layout

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Figure 3.7: Aligning the plates on a jig
\end_layout

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\end_layout

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Figure 3.8: Cross-section view of aligning plates on jig
\end_layout

\begin_layout Standard
After marking out where each hole should go on the top plate, we proceeded
 to drill through the whole stack (See Figure 3.9 
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reference "Fig 3.9"

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).
\end_layout

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\end_layout

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Figure 3.9: Stack of plates with holes drilled through
\end_layout

\begin_layout Standard
Finally, we slotted the pipes, spacers, and caps in to create the full module
 (See Figure 3.10 
\begin_inset CommandInset ref
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reference "Fig 3.10"

\end_inset

).
 Note that, as the spacers were of larger diameter than the structural pipe,
 they pushed the plates further apart than would be expected.
 To compensate, we used spacers that were not 2 cm in length, but 1.5 cm
 in length.
\end_layout

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Figure 3.10: Cross-section view of complete plate settler module
\end_layout

\begin_layout Standard
Overall, we were satisfied with the jig.
 One reservation, however, is that, given the imperfections in the construction
 process, it would be hard to ensure precision while using the jig.
 As the jig levels are of exactly the same thickness as the plates, it would
 be easy for the plates to slide between different levels of the jig.
 In essence, although the jig did make the process of aligning the plates
 more efficient, it did not increase accuracy.
\end_layout

\begin_layout Subsection
Alternative Jig
\end_layout

\begin_layout Standard
We decided that creating a jig with levels of a slightly greater thickness
 may be preferable.
 However, as it would be difficult to obtain materials of exactly the same
 curvature as the actual plates, we decided to implement this idea using
 flat material.
 This new jig was constructed using a transparent acrylic sheet roughly
 1.5 times the thickness of the plates (See Figure 3.11 
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reference "Fig 3.11"

\end_inset

for how we cut through the new material and Figure 3.12 
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reference "Fig 3.12"

\end_inset

 for new Jig).
 
\end_layout

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\end_layout

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Figure 3.11: Cutting through new material
\end_layout

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\end_layout

\begin_layout Standard
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name "Fig 3.12"

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Figure 3.12: Re-engineered jig
\end_layout

\begin_layout Standard
This new jig proved to be extremely effective.
 There were no longer incidences of plates sliding between levels.
 Further, the flatness of the surface proved to be more of an advantage
 than a disadvantage, as it allowed us to better observe how the plate were
 lining up (See Figure 3.13 
\begin_inset CommandInset ref
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reference "Fig 3.13"

\end_inset

).
 Overall, this new implementation increased both accuracy and efficiency.
 The only shortcoming of this new jig is that it is both larger and heavier
 than the previous jig.
 However, given the jig's relatively small size compared to other tools
 and components, this should not be a significant issue on the site.
\end_layout

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name "Fig 3.13"

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Figure 3.13: Alignment of plates with new jig
\end_layout

\begin_layout Standard
We then took the process a step further, using the same acrylic material
 to construct a longer jig, in line with the current specifications used
 in most AguaClara plants.
 This new jig is capable of accomodating 10 lamella sheets with an expected
 gap of 2.5 cm between them.
 In addition, the new jig has two vertical plates on its left and top edge.
 These will allow the user to simply shove the sheets into a corner, rather
 than aligning them by hand (See Figure 3.14 
\begin_inset CommandInset ref
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reference "Fig 3.14"

\end_inset

for image on new jig).
\end_layout

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\end_layout

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Figure 3.14: New Jig with alignment plates
\end_layout

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