Week 9 Progress (Completion)

The constructions were finished this week. The hydroponic system was modified. The finalized schematic is shown in Figure 9. In stead of letting the water flow back to the reservoir from the bottom, a block is added in the middle of the left bottom pipe to block the flow of water and a tube transfers the water back to the reservoir. This modification facilitates the water flow by adding more potential difference of the water level on the two sides; however, the lowest two lettuce places are given up due to the addition of the block.

Figure 9. Finalized Schematic for the Hydroponic System

All the parts of the planter were put together, and the plants were installed into the planter. The final module is shown and annotated in Figure 10. The hydroponic system was tested and the plants were being watered. The planter is a success.

Figure 10. Final planter module

Week 8 Progress

Some modifications were made this week. Since it will be hard to cut and glue the small PVC pipe into 90-degree joints to grow lettuces, 90-degree elbow joints are used. All the materials needed for the planter were gathered this week, including the pump, tubing and tube connectors for the hydroponic system, and the 90-degree elbow joints.

The power of the pump was tested. The water in the tube can be easily lifted to 6’ high, so this pump can accomplish the expected performance for the hydroponic system. 

Some of the cuttings were done during the week with the help from Mr. Dustin Doss. Each long pipe was cut into a 2’1” piece and a 3’4” piece. Two 3” pieces were cut with the extra pieces to be used as the top end of the vertical planter. Three holes were cut on each of the two horizontal planter pipes. The holes were evenly separated along the pipe, and the distance between holes was about 11”. A 1” hole-saw was used to cut the holes, then the holes were ground to fit the small pipe. Six 1¼” long pieces were cut from the small pipe, and the pieces were installed in the holes.

The hole-cutting spots for the elbow joints were marked on the vertical pipes. The dimensions are shown in Figure 8. It will be easier to cut these holes because the elbow joints can fit in the 1” hole-saw holes without grinding. Holes are also needed on the lids of the buckets. These cuttings will be performed during lab next week. The hydroponic system will be built after the holes are cut, and the plants will be installed later during the week.

Figure 8. Surface dimensions (except for diameter) on the right vertical pipe (front view)

Week 7 Progress

Because the pump obtained from ECE department in week 5 was an air pump which does not operate for the purpose of the planter, a new pump had to be selected. The estimate water flow rate for the planter is about 2 gallons of water per minute, so the pump has to support at least 120 gallons of water per hour to the height of 6’. After comparing functioning and prices, a pump which can support a maximum of 221 gallons of water per hour at the height of 6’ was selected. This pump has a flow control, so its rate can be adjusted to about 120 gallons per hour. Tubing will be purchased after receiving the pump.

Three funnels, PVC cement, two 1” diameter PVC pipes, four plate caster wheels, and the plywood boards were brought in to the lab during the week. The funnels are in three different sizes, and the two smaller ones which can fit inside the PVC pipes will be used for guiding the water. The plywood boards will be used to build a box to put the planter in. The plywood boards were cut into three 5’ by 1’4” rectangles and two 1’4” by 1’4” squares, so these pieces can be put together to make a box as shown in Figure 7. The box will improve the stability of the planter by connecting the two water bases together as a whole. The wheels will be installed at the bottom of the box to increase the mobility of the planter.

Figure 7. Dimensions for the plywood box

PVC pipes were measured and marked so that they can be cut and put together next week. Each long pipe is slightly longer than 6’. Two cuts will be performed on each long vertical pipe. First, 8” of the pipe will be taken off, and then the approximately 5’5” remaining long pipe will be cut into a 2’1” piece and a 3’4” piece. The 8” cut shortens the height of the planter and allows the planter to fit through doors and elevators. Since each bucket is about 15” deep, the second cut divides the remaining pipe into two parts which one part is 15” longer than the other, so when connected, the pipes will appear to be evenly spread above and below the T-joint outside of the bucket. The horizontal pipes will not be cut because the maximized distance between the plants is necessary for the plants to grow well, but spots for hole cutting were marked. The pipe was measured into four even parts across its length, and the three points that separate the length are the hole spots. The 1” PVC pipes that were brought in will be cut on an angle so they can provide a lip for the plants to rest in which will allow them to get water without allowing water to get out. Finishing these cuttings and the construction of the cut parts will be the deliverables for next week.  

Week 6 Progress

Thanks to Dr. Knight and MSE department, Lebow 336 lab is used for the project. This lab will be used for supply storage and planter construction.

This week, some supplies were brought in, including two 6’ long 4” diameter PVC pipes, two 4’ long 4” diameter PVC pipes, four connectors (T-joints) and two endcaps for the pipes, and two 5-gallon buckets. The T-joints and the endcaps were tried on the PVC pipes, and they fit perfectly. It is measured that 2” of the pipe will go into the T-joints or the endcaps, so 2” at the ends should be avoided when calculating the hole-cuttings.

Since the biggest parts for the structure are accessible, an on-scale view is present when making construction plan, such as the plan for water supply in the hydroponic system. The design will be having the tubing run up one side of the planter and veer off to the middle and top rungs. The two buckets will serve as the reservoirs on each side, and the side with tubing going up has the pump. The water from that bucket will be pumped up and flow on the roots through the horizontal pipes, and then drip down in the opposite pipe to water its lettuce and will be collected in the other bucket. The water on the pump side will also go up to the top, hit the endcap, then drip down from the wall to water its lettuce. The two buckets will be connected with a tube so the water can cycle back to the pump. Funnels may be used in the pipes to guide the water to flow along the wall. A schematic of the design is shown in Figure 6. The green parts are the PVC pipes, the blue parts are the joints, the purple triangles are the funnels, the cyan lines are the tubing, and the red arrows are directions of the water flow.

Figure 6. Schematics for the hydroponic system

Week 5 Progress

Revisions were made to the design. PVC would be used for the design in this term. Bamboo is very aesthetically pleasing but there are many disadvantages. One problem with bamboo is that bamboo will rot when it is exposed to water for long time. This is exceptionally inconvenient for the design since the hydroponic system design has water running through it constantly. An idea was brought up to coat the inside of the bamboo with a deck sealant to make the inside of bamboo waterproof, but this idea was not very plausible. Bamboo is also quite flexible, so when the planter is exposed to strong winds as well as intense weather, a structure made of bamboo poles will not be ideal. Also, bamboo is not grown commercially on the East Coast, so the best place to get it is from California or from overseas, but the cost for getting bamboo poles will be rather high (over $30 per pole plus extra money for removing nodes and high shipping fees). The biggest problem about using bamboo is that big hole cuts are needed on the side bamboo poles to connect the horizontal poles. The cuts need to be about the diameter of the horizontal poles, so these cuts will remove much fiber support which can increase local stress of the joint regions and cause fracture.  On the other hand, PVC pipes are much sturdier, so they can withstand the intense weather. PVC can also withstand constant exposure of water and UV. PVC pipes are much cheaper and easier to obtain. Connecting PVC tubes is much easier with the help of connectors as shown in Figure 3. After the comparison, PVC, as the material that is more available and is easier to wok with, replaces bamboo as the construction material, but constructing with bamboo or other more sustainable materials will be one of the future research focuses of this project.



Figure 3. Example T-joint connector [14]



Using T-joints instead of cutting holes on the vertical pipes not only prevent strength loss of the vertical support, but also increase the tensile strength at the connection region by increasing stress concentration factor, which is the ratio of maximum local stress to overall background stress. Based on the relationships shown in formula (1) and (2), increasing the fillet radius r or the major shaft diameter D can increase SCF. D, r, and d are labeled in Figure 4 [15]. T-joint connectors increase both the fillet radius and the major shaft diameter, so it can increase SCF. With higher SCF, the connection joint can tolerate a higher local stress σ * SCF.

SCF ∝ r/d       (1)

SCF ∝ D/d      (2)

Figure 4. Dimensions used for SCF calculation [15]

Another design revision is that the planter would lean against a wall or hook onto a wall to increase the sturdiness and allow the planter to withstand more weight.

The hydroponic design was finalized so construction of the planter can start soon. A pump was obtained from the ECE department. For pressure control, a valve can be set up to limit the pressure of the water going through the system if the pump is too strong, and the reservoir at the base of the planter needs another valve to limit the amount of water the will be circulating through the system at once to minimize the amount of water that is needed to keep the system running.

A wick system was discovered that could be incorporated into the final design for the hydroponic system and make the system simpler. Figure 5 shows an example of the wick system which at this point is in its initial phases in our design. The idea is that the water moves its way up the wick and keeps the plants watered without over watering the plants or wasting water [16]. This hydroponic wick system will be taken into consideration during construction.

Figure 5. Wick System [16]

Finally, the PVC pipes were obtained through a generous donation, so the group will begin physical construction work in Week 6.

                 

Week 4 Progress

Using bamboo as one of the construction materials was proposed. Bamboo is a sustainable nature composite material that has relatively good mechanical properties. Using bamboo also adds an aesthetic value to the product that using PVC is lack of. The final design is as follows. Two long bamboo poles with holes spaced evenly throughout the columns will be used for the vertical structure on two sides. These holes will have a semi-conical pocket that holds lettuce plants in place. These two vertical poles are connected by two more horizontal struts that will house the tomato and cucumber hydroponic systems. The entire module will be 4 feet wide and 7~8 feet tall. The bamboo poles will be approximately 6 inches in diameter and 8 feet tall.

The visit to the ACE hardware store brought some inspirations on materials selection. The main goal for the trip was to find hose that could be fed through the bamboo and connect the nutrient solution reservoir with the plants in the hydroponic system, and find a pump large enough to move the water through the system but small enough to fit well into the design and to prevent excess pressure buildup. While the trip was informative, the store did not have most of the products that were necessary for the design; however, ordering online is still an option.

Specific, concrete ideas for the hydroponic system will be brought to the following week's lab and the best design elements from each idea will be selected for the construction of the final design. Also, literature research will be continuing during the week (see [11], [12], [13] in Reference tab).

Week 3 Progress

The coarse design of the module was made, and the varieties of plants to be cultivated was discussed, as shown in Figure 1. After analyzing factors such as growth success rate, consumer demand, and ideal companion plants, The final decision is to grow tomatoes, cucumbers, and lettuce. Modifications were applied to the design of the previous week. Two vertical posts are the support of the whole planter and two parallel horizontal beams will connect the columns. These two horizontal posts will have plants growing both up as well as upside-down.The watering system for the planter is changed to a hydroponic system in the module to reduce the planter's weight and to idealize growing conditions for the plants while making the system cleaner and easier to maintain. An example of the system is shown in Figure 2.

Figure 1. Coarse Planter Design (not to scale)

Figure 2. Example of Hydroponics [10]

The material composition of the planter was discussed. The main building material or materials must be relatively inexpensive and lightweight, while being strong enough to support the weight of the plants and the running water, as well as survive outdoors conditions. Besides, the budget must be fine-tuned for consumer cost estimates. The materials selection details are to be discussed in the following weeks. 

The actual plants for the final module and presentation have been purchased as seedlings and are currently growing so that they will be of a properly impressive size by the end-of-term presentations.

The plan for the following week is to prepare for and start the mechanical design.