Optimal Design Report

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1 Optimal Design Report Electric Hot Tub Lift Team 1: Dylan Rinker Sebastian Pineo Ana Groff Steven Benn Brandon Calavan Faculty Advisor: John Enderle Teaching Assistant: Sarah Brittain Project for: Paige Librandi Client Contact Information: Chris and Sandy Librandi 21 Timber Trail Milford, CT (203) (home) (203) (mobile) 1

2 1.1 Introduction Our client, Paige, is a 20 year old woman who suffers from cerebral palsy that affects her vision, speech, and physical capabilities. This causes Paige to be nonverbal and have limited kinesis in her limbs, so Paige s uses an electric wheelchair for mobility and Dynavox for communication. She is highly independent and intelligent; she goes to school, work, and maneuvers in and out of her house on her own. Paige's family has asked our team to build a motorized lifting device so that Paige can be safely lifted up and over her hot tub wall and then lowered again. Our optimal design is a motorized lift that can clear walls up to 42 inches, and has a maximum capacity of 400 pounds. A cylindrical shaft is connected to the base of the lift, which will be bolted securely to the deck. The structure of the lift will be composed of stainless steel and a nylon bearing will be used to achieve the rotational motion of the lift. The lift will be installed within 2 feet of the hot tub in order to provide suitable space to maneuver. At the end of the boom there will be a customized bath chair that is attached to the stainless steel chains. This seat will be customized to keep Paige safe and also allow her to change seats in the hot tub. We are making the seat frame with PVC pipes that will allow Paige to be comfortably submerged in the hot tub. We chose this design as our optimal design because it is the most cost-efficient option and it still maintains the integrity of proposed lift. This design was chosen over our alternate design 3 because our lift meets all the requirements and will be less than 40% as expensive as the Spa Lift 40 Pro. Our design will be able to perform all necessary tasks while also reducing the total amount of money that must be spent of the project. The use of a remote and motorized winch will allow Paige more independence in using her hot tub. 1.2 Subunits Our lift design can be broken down into three separate sections; the lift structure, the lifting components, and the seat Lift Structure The lift structure consists of the base, the large stationary structure shaft, the nylon bearing, the stationary and rotatable smaller structure shafts, the boom, and the boom support. All pieces excluding the nylon bearing are made of a coated stainless steel that is corrosion resistant. The lift structure is displayed in Fig. 1. All structural components will be developed and tested in Abaqus or Solidworks to ensure the stresses and deflection are not too high and will not lead to failure of the lift. 2

Figure 1. NX drawing of lift structure. 1.2.1.1 Base The base for the lift will be modeled after the EZ pool lift base. The base will measure 16 x16 x3 and be made of stainless steel.

There is a cylinder centered in the middle of the base that measures 6.5 x5.5 x10. There are four triangular gusset welded to the base that attach to the cylinder as can be seen in figure 2.

3 Figure 1. NX drawing of lift structure Base The base for the lift will be modeled after the EZ pool lift base. The base will measure 16 x16 x3 and be made of stainless steel. There are four holes drilled in each corner that will house the four wood screws that bolt the base to the deck. The holes each measure 1 diameter and recede 2 7/8 into the base. There is a cylinder centered in the middle of the base that measures 6.5 x5.5 x10. There are four triangular gusset welded to the base that attach to the cylinder as can be seen in figure 2. These legs help add extra stability to the structure of the base. The center cylinder contains the main structural shaft of the lift. The base will weigh close to 40 lbs. Figure 2. NX drawing of the lift base. 3

1.2.1.2 Main Structural Shaft The main structural shaft will be the largest component in our lift and can be seen in figure 3.

4 Main Structural Shaft The main structural shaft will be the largest component in our lift and can be seen in figure 3. The circular shaft will measure 78 in height and have outer and inner diameters of 6.5 and 5.5. The shaft will be constructed of stainless steel and will have a total volume of in 3, and a total weight of 200 lbs. The shaft will be inserted into the base and secured by two pins that are slide through two 2 openings. The openings will be located 2 and 6 from the bottom of the shaft. The pins will be locked into place with two stainless steel clips. The pin and clip system is displayed in figure 4. The smaller stationary shaft will sit inside the main structural shaft. The nylon bearing will sit atop the shaft. Figure 3. NX drawing of the main structural shaft 4

Figure 4. Diagram of pin and clip component. 1.2.1.3 Nylon Bearing The nylon bearing is what allows for the rotation of the boom. The bearing will measure 1 in height and 6.5 and 5.

5 Figure 4. Diagram of pin and clip component Nylon Bearing The nylon bearing is what allows for the rotation of the boom. The bearing will measure 1 in height and 6.5 and 5.5 in the outer and inner diameter. The bearing will sit on top of the main structural shaft and will sit under the rotational shaft. The bearing will slide over the bearing support shaft, which will keep it fixed in the correct position. A similar bearing is displayed in figure 5. Figure 5. A metal bearing similar in size to the nylon bearing we will use Bearing Support Shaft The bearing support shaft (Fig. 6) is very important to the design of the lift multiple reasons. As mentioned above, the bearing placement shaft will keep the bearing in the correct position. The shaft also reinforces structural support in the rotational shaft. The shaft will be 28 long and will descend 13.5 into the main shaft and ascend 13.5 into the rotational shaft. The shaft will have an outer diameter of 5.5 and an inner diameter of 4.5 The shaft will have a volume of in 3 and will weigh lbs. 5

Figure 6. NX drawing of bearing support shaft. 1.

The rotation shaft (Fig. 7) will be 20 in height and 13.5 will sit over the bearing placement shaft.

6 Figure 6. NX drawing of bearing support shaft Rotation Shaft The rotation shaft is used to rotate the boom into the correct positions for entering and leaving the hot tub. The rotation shaft (Fig. 7) will be 20 in height and 13.5 will sit over the bearing placement shaft. The rotational shaft will sit atop the nylon bearing. The boom and the boom support will both be welded to the rotation shaft at the top and bottom respectively. The rotation shaft will have a volume of in 3 and will weigh 50 lbs Boom Figure 7. NX drawing of the rotation shaft. 6

The boom (Fig. 8) connects the rotational shaft to the seat of the lift and will also contain the winch. The boom will measure 44 in length to ensure easy entry into the hot tub.

NX drawing of the boom. 1.2.1.7 Boom Support The boom support (Fig. 9) is a necessary structural piece of the lift design.

7 The boom (Fig. 8) connects the rotational shaft to the seat of the lift and will also contain the winch. The boom will measure 44 in length to ensure easy entry into the hot tub. The boom face will measure 6 x6. A pulley will be welded to the end of the boom arm. The winch will be attached to the boom as close to the rotation shaft as possible. Figure 8. NX drawing of the boom Boom Support The boom support (Fig. 9) is a necessary structural piece of the lift design. The support helps distribute the forces on the boom to help lower the total deflection. The support will measure 40 in length and will be welded to the boom and the rotational shaft at 17.5 o and 72.5 o respectively. The face of the boom will measure 6 x2 and the portion that is welded to the rotation shaft will be rounded so the entire face is welded flush. Figure 9. NX drawing of the boom support Lift Components The lift components in our design include the winch, the pulley, and the connection chains. All of these items will be bought and be unmodified Winch 7

The winch we will be using is the Superwinch 12 Volt ATV Electric Winch (fig. 10). This winch has a pulling capacity of 2500-lbs and is run by a 1.3 HP motor.

The winch will be mounted on top of the boom towards the rotational shaft so as to decrease the total stress on the boom. Figure 10. The Superwinch. 1.2.

8 The winch we will be using is the Superwinch 12 Volt ATV Electric Winch (fig. 10). This winch has a pulling capacity of 2500-lbs and is run by a 1.3 HP motor. The winch comes with sealed solenoids that allow the winch to function properly outside under any weather conditions and in such close proximity to the hot tub. The winch will be mounted on top of the boom towards the rotational shaft so as to decrease the total stress on the boom. Figure 10. The Superwinch Pulley The pulley we will be using is the heavy duty winch pulley (fig. 11). This pulley has a capacity of 20,000 lbs. so it will be easily able to bear the weight of Paige and the chair. The extended length of the pulley is 12, the wheel diameter is 4, and the top opening diameter is 2. The pulley is vital to the design of our lift because it reduces the total force that will be exerted on the winch. The pulley will also ensure the cable is fed into and out of the winch in a straight and even manner Connection Chains Figure 11. Heavy Duty Winch Pulley 8

The larger set of chains will measure 50 and will connect to either side of the of the PVC structure along the horizontal seat position. The locations of the attachments can be seen in fig. 14.

9 The connection chains attach the winch cable to the PVC structure of the seat. The chains will be made of stainless steel and can be seen in fig. 12. The connection chains will come in two different lengths. The smaller set of chains will attach to the top of the chair and will measure 20. The larger set of chains will measure 50 and will connect to either side of the of the PVC structure along the horizontal seat position. The locations of the attachments can be seen in fig. 14. The use of four chains will allow for extreme stability of the seat. The longer chains will be attached to the seat so the seat tips backwards just slightly when Paige sits in it. This will help ensure she does not fall forward out of the chair during loading both into and out of the hot tub. Figure 12. Stainless steel chains Seat The seat will, seen in Fig. 13 consists of the PVC frame, nylon mesh for the back and bottom of the seat, and three straps to help support Paige in the seat. Figure 13. NX drawing of the PVC frame of the seat and the connection chains PVC Frame 9

The seat frame will be made of 1.5 sch. 40 PVC. This is the same PVC used in pool and spa plumbing, so it will be able to withstand being submerged in the hot tub.

10 The seat frame will be made of 1.5 sch. 40 PVC. This is the same PVC used in pool and spa plumbing, so it will be able to withstand being submerged in the hot tub. The seat will measure 28 high and 20 long. There will be four 90 o elbows to make the connections that occur at the front and the top of the seat. The center of the seat will use a 3-way elbow to make the connections between the horizontal and vertical components as well as the support bar across the back. Small holes will be drilled along the base of the seat to allow for water absorption and drainage during submersion and immersion in the hot tub. This accumulation of water is necessary to ensure the seat sinks properly. The total of volume of water absorbed will be in 3 and this will add about 10 lbs. of weight to the seat during removal from the hot tub Mesh Backing Two separate pieces of nylon mesh will be used to cover the back and the bottom of the seat. Nylon is very light, but still strong enough to support Paige s weight. It will also allow water from the jets to pass through and hit Paige s back. The nylon will be wrapped around the PVC frame and sewn onto itself. The nylon will be triple stitched to ensure it will not tear while bearing Paige s weight. The pieces of nylon will measure 32 x28 for the bottom of the seat and 36x32 for the back of the seat. A similar piece of nylon mesh can be seen in fig. 14. Figure 14. Nylon mesh material that will be used for the seat Nylon Chest Strap A nylon chest strap will be sewn to the mesh backing of the seat. This strap will be used to help ensure Paige is secure in the seat and that she will not slide down while in the hot tub. The strap will measure 24 x4 which will assure enough length to adjust the strap if need be and enough width to secure Paige safely in the chair Nylon Leg Straps (2) Two nylon leg straps will be sewn on either side of the bottom mesh. These straps will be used to secure Paige s legs in place. This will assure that her legs won t float uncontrollably 10

while she is in the hot tub. The straps will measure 18 x3. Similar straps are displayed in fig. 15. Figure 15. Nylon straps that will be used for leg and chest support. 2. Realistic Constraints 2.

11 while she is in the hot tub. The straps will measure 18 x3. Similar straps are displayed in fig. 15. Figure 15. Nylon straps that will be used for leg and chest support. 2. Realistic Constraints 2.1 Engineering Standards When designing our lift, there were many engineering constraints that had to be taken into consideration. These constraints include the materials we use, the procedure for implanting the lift, the safety of our client and state regulations. The materials used for the base of the lift and the hot tub seat are vital because they support Paige and the weight of the lift. Also, the procedure used to install the foundation must be within state regulations. Our proposal and our designs are recorded to show how all engineering standards are upheld. This also includes all measurements taken, previous designs and calculations necessary implement our design. 2.2 Economic One of the toughest problems our team faced was designing a lift that meets all safety requirements while staying within our allotted budget. Since it would be too expensive to purchase a lift and then modify it, we decided to build it from scratch. This allows us to purchase all the needed subunits of the lift and still stay close to our budget. Some alterations may still be made depending on the budget of our other projects. In order to compensate for this, we would be able to replace our current surface mount anchor and build our own. These sorts of opportunities must be utilized so we can make our lift as economical as possible. 2.3 Environmental Since our lift is outdoors, the weather will be an important factor. Our lift must be durable and incorporate weather resistant properties. On the other hand, our lift should be environmentally friendly, and not affect the surrounding area. For these reasons our lift in 11

12 mainly comprised of stainless steel with an epoxy powder coating. The lift will have to be dissembled and taken in each winter to assure no damage occurs due to inclement weather. 2.4 Sustainability Our lift was designed with the requirements that it be long lasting with minimal maintenance. In order to achieve this we chose materials with high weather and wear resistant properties. This ensures that there are no sustainability issues derived from weather exposure or repeated use. The resilience of the seat that is lowered into the hot tub is also important. It will be repeatedly exposed to chemicals in the water such as chlorine. For this reason we are using PCV pipes to mount the seat and a mesh material for the seat fabric. This will ensure the sustainability of the seat as well as the lift. The nylon bearing must be lubricated often to ensure that it works properly 2.5 Manufacturability The manufacturability of our lift is mostly limited to money and time constraints. The materials we are using can be expensive because they provide great weather and corrosion resistance. The manufacturing of our lift will require numerous subunits that will predominantly be made of stainless steel with an epoxy coating. These various subunits will also need to be welded at any contact surfaces with other metals. This process will likely take a large amount of time due to the specificity needed to guarantee high quality work. Since we are purchasing a surface mount anchor and an electric cable hoist, we avoid a time constraint for manufacturing them ourselves. 2.6 Health and Safety It is of the utmost importance that Paige s lift does not pose any health or safety risks. The lift will constantly be exposed to wet conditions due to weather and the use of the hot tub. This makes it vital that to use a corrosive resistant coating that can withstand these conditions. The hot tub also contains chlorine which brings another variable to the materials we choose. The chlorine will be useful in the sense that it acts as a disinfecting agent for the mesh seat. This will help remove any unhealthy bacteria or microorganisms. Our lift and hoist must also be able to safely support the weight of Paige and her detachable chair. Since Paige has very limited mobility, we need the lift to be able to securely hold her in place to ensure safety. Testing of the stress and strains the lift can withstand are important to make sure the strength of the material is up to our engineering standards. The seat at the end of the boom must be capable of detaching, but it must also be completely secure when rotating to avoid any risk of injury. 3. Safety Issues There are many safety precautions that must be addressed when considering Paige s hot tub lift. Paige s physical safety while using the lift, as well as when in the hot tub, and the safety of both Paige and her operator while using the electric lift are all of utmost importance. Paige must be able to sit comfortably while in the lift seat without the worry of tipping 12

13 and falling either forward or backward. The four chain link connection must be positioned correctly along the top and sides of the seat so that Paige sits comfortably and safely. Paige will also be strapped into the seat both around her chest as well as at her legs. This will also prevent Paige from accidentally slipping down into the hot tub while in the seat. All the pieces and connections on the lift must be secure and tested beforehand to ensure no failure of the device while Paige is using it. All the PVC must be primed and glued correctly and checked for hairlines cracks to ensure no failure of the structure of the seat during use. The holes used to submerge the seat must be placed far enough apart so no stress cracks occur. The connections from the PVC to the four chains must be tested beforehand up to 300 lbs. to make sure it safely carry above the maximum weight it will be used at. The elbow connection between the boom and the stand as well as the support between them all have to be weight tested beforehand to make sure they will support the weight without deformation. The motor and winch must both be bolted properly to the base and the connection between the chain and the winch must be tested with weight as well. The base must properly secure to the decking to ensure that the base does not become loose during use. There are also electrical issues that have to be addressed involving the electric winch. The winch must be waterproof as to protect the electrical components from splash from the hot tub and rain. The motor must also be grounded properly to ensure no electrical mishaps occur. The winch will be set to only run for as long as it takes to lift and lower the seat the proper distance. The remote should ideally be waterproof but in any case it will need to be kept away from the hot tub to prevent its submersion. 4. Impact of Engineering Solutions The lift that our group designed is going to greatly impact Paige s life. Due to Paige s condition, she has very limited physical mobility. Even with this disability, Paige loves to express independence and performs many activities on her on. Our group feels that this lift will provide the perfect opportunity for Paige to gain more independence and enjoy her hot tub whenever she wants. Paige also loves to go in the hot tub with her friends and family so this lift will allow her to do this much easier and more often. Whenever Paige previously wanted to go in her hot tub, her father had to lift her and place her in the hot tub. With this lift it will eliminate all the physical strain that was required by her father to enjoy the hot tub. The modified seat will also impact Paige because it should make her feel extremely safe and secure. We want Paige to be worry free whenever she operates the lift. The lift s impact on the environment will be minimal due to the materials we chose. All the materials of our project will be able to withstand any environmental conditions that may be present in New England. Our team s lift is designed to be easy to use and very safe. Most lifts on the market are mass produced with regular dimensions that may or may not be optimal. The difference with our lift is that it is specifically designed for Paige in order to meet all her needs. We re confident this will positively impact Paige s family and hope it impacts anyone who needs a customized lift. 13

14 5. Life-Long Learning Our group has learned a lot of valuable lessons throughout the course of this project. Let alone all the field experience we ll gain, we re able to learn a lot from Paige. We have all read about cerebral palsy and various nervous disorders, but it wasn t until we met Paige that we truly understood the gravity of her condition. Paige has shown tremendous strength to be so active, outgoing and independent for someone in her situation. Witnessing the problems that Paige has to face every day also caused us to put our problems into perspective. It helped show us how we take so many things for granted and it motivated us all. Another life-long lesson we had to learn was how to manage and keep a friendly and efficient work environment. This was the first time we had to work with a team to design a project that will be used by a client. Trying to keep an organized team with a fair workload for each member is difficult. We learned how to use Microsoft Project in order to help us keep our organization and better manage our project. When we finally settled on an optimal design, the realization that we are no longer doing schoolwork, but instead we are designing a project using real-world engineering techniques was very exciting. This project is preparing us for our later engineering endeavors by creating a strong foundation for our management and manufacturing skills. This project taught us a great deal about the manufacturing process that is used by engineers. We learned the important steps required for a successful design project. It is important to document and date all of our designs and measurements so that we can justify any design choices made. When manufacturing our design, there are many important factors that must come into play. We learned how to deal with these factors and methods to help us stay close to a planned budget. We had to learn quickly what sort of equipment or resources we could afford to buy opposed to what equipment we must build ourselves. Manufacturing can also take a lot of time, so we learned how to budget our time appropriately for a design project. Our designing skills have also improved due new techniques and programs we learned to model our subunits. Using simulated designs with the CAD program proved to be much more useful than any sketches we could create. We also had to learn a program called Dreamweaver which allowed us to edit files locally and then upload them to the UConn BME website. 14

15 6. References "Aqua Creek: EZ PoolÂ Lift - #F-03EZPL." Aqua Creek: EZ PoolÂ Lift. N.p., n.d. Web. 15 Oct < "Classic Pool Lift by Hoyer (Model No. SS-HSP-1)." Hoyer Classic Pool Lift. N.p., n.d. Web. 15 Oct < Lifts/spec.cfm?productID=81698> "Heavy Duty Winch Pulley Block, 20K." Superwinch Accessories and Parts SW7750A. N.p., n.d. Web. 15 Oct < Parts/Superwinch/SW7750A.html?feed=npn>. "FlexPVC.com. Buy Flexible Pvc Pipe from the Original FlexPVC.com, Not the Imitators. PVC Pipe, Hose, Tubing, Pvc Plastic Pipe Fittings & Plastic Pvc Furniture Fittings Wholesale Discount Prices (flexable)." FlexPVC.com. N.p., n.d. Web. 15 Oct < "Metals Depot - America's Metal Superstore!" MetalsDepotÂ. N.p., n.d. Web. 15 Oct < "Superwinch 12 Volt ATV Electric Winch Â 3000-Lb. Capacity, Wire Rope." Superwinch 12 Volt ATV Electric Winch Â 3000-Lb. Capacity, Wire Rope. N.p., n.d. Web. 15 Oct < Winches-_ >. 15

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