The L.A.D. 4/29/2011 BME 4910 Final Report. Electric Wheelchair to Riding-Lawnmower Assist Device

Transcription

1 4/29/2011 BME 4910 Final Report The L.A.D. Electric Wheelchair to Riding-Lawnmower Assist Device TEAM # 16 Team Members: Michael Chen, Joshua Aferzon, Matthew Desch Client Information: Ronald Hiller 54 Fitts Road, Ashford CT,

2 Table of Contents Abstract 1. Introduction o Background o Purpose of the Project o Previous Work Done by Others Products Patent Search Results 2. Project Design o Alternative Designs o Optimal Design Objective Subunits o Prototype Description Operation Testing 3. Realistic Constraints o Engineering Standards o Considerations Economic Environmental Sustainability Manufacturability Ethical Health and Safety Social Political 4. Safety Issues 5. Impact of Engineering Solutions 6. Life-Long Learning 7. Budget 8. Team Members Contributions to the Project 9. Conclusion 10. References 11. Acknowledgements 12. Appendix 1

3 ABSTRACT The need for an assistive lift for easy mount and dismount of a riding lawnmower has been expressed by Mr. Ronald Hiller as his current method for mounting and dismounting his lawnmower is dangerous and ineffective. This project s task was to create a functional lift attachable lift that could safely transport Mr. Hiller from his power chair to his lawnmower chair with ease and safety. Mr. Hiller has Multiple Sclerosis, while he has full use of his upper body; he has very limited use of his legs. Mr. Hiller may stand and walk a few steps, but cannot transport himself great distances without aid. The motivation for his desire is his want to do his fair share of housework, for this he purchased a riding lawnmower that can be fully controlled by hand, but unfortunately presents difficulty in mount and dismount. The construction of the L.A.D. is based off of a barber shop or salon pumping chair. Modifications to this design included making it portable and allowing for temporary attachment to Mr. Hiller s lawnmower during use. Portability was added through the construction of a wheeled base based on those belonging to office chairs. The chair was designed to be lightweight for easy transportation either by Mrs. Hiller or Mr. Hiller himself on his power chair. In order to safely attach the L.A.D. to Mr. Hiller s lawnmower a bridge pulls out of the seat and rests on an attachment to the lawnmower seat allowing Mr. Hiller to slide himself from the L.A.D. to his lawnmower. The L.A.D. was be designed so that it is the same height as Mr. Hiller s power chair when compressed. In order to prevent the device from moving during the transfer phase to the lawnmower, a breaking system will be employed that completely locks the wheels of the L.A.D. and prevents any movement of the device. A safety railing added stability and safety for the client during the pumping phase. The design was devoid of electrical components, instead opting for a lower maintenance and a more durable design. The device was built to withstand long term storage in New England winters without failure and be able to move anywhere on the Hiller property without the hassle of a power cord. To accommodate these requirements the design is operated mechanically. 1. INTRODUCTION The Electric Wheelchair to Riding-Lawnmower Assist Device (L.A.D.) is an assistive lift for people with limited mobility to mount and dismount a riding lawnmower with ease and safety. Specifically the L.A.D. was designed for Mr. Ronald Hiller of Tolland Connecticut who has Multiple Sclerosis. Due to this Mr. Hiller has limited use of his legs and must use a power chair to get around. The client desires to do his fair share of housework and was in need to a device that would allow him to mount and dismount his riding lawnmower safely. 1.1 Background The client, Ronald Hiller, is a middle-aged man who lives with his wife in Ashford, approximately 10 minutes from the UConn campus at Storrs. Ron suffers from multiple sclerosis, an inflammatory disease which leads to the demyelination of his central nervous system. As a result of his condition, Ron has lost functionality in his legs; however, he still maintains full use of his upper body. Since he is not able to walk, he relies on an electric wheelchair to move around his house and property. To make locomotion easier, he is able to operate his wheelchair by making use of a control panel located on one of the arms of the seat. Like many others, Ron likes to stay active and as involved as he can with the upkeep of his property, mainly the exterior of his house. He is able to move from the inside of his home 2

4 to his property outside, but the limitations of his wheelchair prevent him from easily accomplishing yard work. Particularly, Ron takes great pride in the maintenance of his lawn, but was unable to do so because of his disability 1.2 Purpose Currently, the client has all the tools he needs to effectively care for his lawn, but is not able to easily and safely use them. Ron and his wife own a completely functional riding mower, which they ve had for a little over a year. A picture of this lawnmower can be viewed below. Figure 1: The client s lawnmower (front and side view). The mower is kept in a shed, and in the past, Ron has had to go to great lengths to move from his wheelchair to the mower. For example, Ron s present method for getting into his mower requires him to hold on to the pole of the basketball net in his driveway, while his wife supports him as he tries to slide from one seat to another. Here, the problem at hand becomes evident; Ron is fully capable of mowing his lawn, but has great trouble getting into his mower. The purpose of this project was to design and manufacture an assist device which will allow Ron to safely and effortlessly move from his electric wheelchair to his riding mower. The device design was essentially a mobile and stable apparatus which will act as a middle-man between his wheelchair and mower. A hydraulic mechanism was implemented to move the seat vertically (to account for the difference in seat heights) while arm supports were included so Ron can use his strong upper body to maneuver his way through the device. Additionally, Ron had also requested that his existing mower be modified to accommodate a seatbelt for increased safety during operation. 1.3 Previous Work Done by Others Products Ron s request for an easier means of transportation from his wheelchair to his mower was quite specialized. Nevertheless, there are other products which essentially accomplish the same task. One such device is the Bruno Turnout Turning Automotive Seating (model TAS-2400/2400E), which is a modified, swivel-based seat that was designed for those individuals who have trouble getting in and out of automobiles. This unit can be manually or electrically operated, and bridges the gap for a safe 3

5 transfer in and out of the car. Prices for this device range from $ Another device, the Carony Transportation System, actually functions in correlation with the Bruno Turnout seat base. The Carony system allows the user to glide from the vehicle seat to a wheeled base, remaining seated the entire time. Although The L.A.D. (which was designed for Ron) and the two devices described above operate under the same mechanism, they are quite different in their function. The products listed above aid in transporting an individual from a van to a wheelchair, while The L.A.D. allows one to move from a wheelchair to a riding lawnmower independently Patent Search Results In the design for Ron s assist device, a hydraulic mechanism was implemented, very similar to the types of chairs that can be found in a hair salon or barber shop. This patent (US ) is comprised of a pair of sealed chambers interconnected with a hollow conduit containing hydraulic fluid. 2. PROJECT DESIGN 2.1 Alternative Designs Alternative Design One Design 1 is a wheelchair ramp constructed from raw materials. The ramp body is to be constructed from wood. The safety bars will be constructed of steel and the rotating platform will be built around a rotating wheel base. There will be no electrical systems necessary. To add weather proofing the entire base will be coated with weather proofing paint. Design 1 can be seen in Figure 1 below. Figure 2: Design 1 (front view). 4

6 Base: The base of the ramp will be made entirely of wood. This will keep costs at a minimum and avoid potential issues such as rust and manufacturing costs. The ramp angle will match that of the installed ramp in our client s home to best assure that the client s power wheelchair will be able to climb the ramp. The L-shaped design of the ramp is intended for maximum space efficiency. Because of the sheer size that this ramp will require, this was a major point of concern. The center of the platform will contain a large circular cut out to encompass the rotating platform. Free rolling ball bearings will be attached to the base of the ramp in order to allow maximum mobility. Free rolling ball bearings are the most effective method for adding mobility as it will not raise the height of the ramp too much off the ground. In addition, the ramp will be able to separate off the main platform in order for storage and convenience Rotating Platform The rotating platform will consist of a wood round top with smooth edges for maximum rotation. The top will be connected to a rotating base similar in design to office chair bases in order to allow for free rotation. The entire platform will be able to be removed from the system. The rotating platform s position can be seen in Figure 2 below. Figure 3: Design 1 (top view). 5

7 Safety bars: The safety bars will be constructed out of carbon steel in order to allow for maximum support. As the safety bars will have to span a significant distance and support a large fraction of our client s weight, the stability of the extruding safety bar will be of great concern. In order to ensure maximum stability, a support bar will be welded under the extruding safety bar for support. The support bars on the ramp platform will be constructed out of wood for economic reasons, and they will prevent the power chair from accidently falling off the ramp Alternative Design Two This design will employ the use of a large guardrail framework that will allow the displacement of a large flooring system. Ron will be able to climb from his wheelchair into the device, sit down, and place his feet in a safety rest. A large amount of force supplied by four hydraulic pistons will allow Ron to positively displace himself until he reaches the height of the lawnmower. Then, he can rotate his seat until he faces the lawnmower and climb in. He will be able to transfer himself back into the wheelchair in the same fashion once he is done using the lawnmower. 6

8 Metal Framework Wheelchair Seat Flooring Cylindrical Shell Hydraulic Pumps Figure 4: Rough Sketch of Lawnmower Assist Device Design Exterior Metal Framework A cubical metal framework will be built. This framing will serve as a support for the system as well as a guide rail for the motion of the device Shell A cylindrical shell will be constructed to provide system support. It will also allow full 360 rotation Hydraulic Pumps Four hydraulic pumps will be installed within the shell. They will serve as the main source of energy for the displacement of the apparatus. 7

9 Flooring Square flooring will be installed within the dimensions of the metal framework. Holes will be cut in intersection location of the metal framework and sealed with rubber to allow secure displacement. This also allows the metal framework to act as guiderails. In addition, a circular hole will be cut in the center to allow for the seat and two sides will be cut open to allow access from the front and back of the device Seat A circular seat will be placed in the center of the flooring and secured to the hydraulic pump shell. This will provide it a full rotational functionality. Also, the space in between the seat and the flooring will be utilized by placing a leg support for Ron to place his feet Advantages Highly secure and durable framework Safe and comfortable seating and foot rest Allows controlled displacement through hydraulic pumps Easy access to and from the device Disadvantages Bulky (will make it more difficult to move the device) Expensive Difficult attachment system between the seat and the flooring Guiderails will require maintenance to minimize friction with flooring Alternative Design Three This design is a stationary apparatus manufactured primarily out of raw metals. The main foundation of this device is found in the circular base, which is sturdy and heavy enough to support the entire structure. The lifting mechanism of this device is housed inside a metal casing, which attaches to the base. As seen in the figure below, this casing is extendable, to allow for the pump to work effectively. 8

10 Hydraulic Pump and Lift Mechanism Figure 5: Design 3 (side view). This device design incorporates vertical displacement in both the positive and negative directions by means of a hydraulic pump, much like those used in salon chairs at a barber shop. Not shown in the schematic above is a mechanical lever, which will allow the user to modify the height of the chair. The ability for this device to be adjusted to different seat levels will make it easier for the user to switch seats from one machine to the other Seat and Pull-out Bridge Located above the pump is where the user sits, allowing the chair to swivel in a range of 180 degrees, which is also surrounded by stationary arm supports. To lower material costs, the seat is constructed of wood encased in metal. A pullout bridge extends from the middle of the seat in this model, intended to attach and lock to the user s lawnmower during transportation to provide for additional safety. Once the bridge is locked in place, the user will be able to maneuver their way across it, permitting risk-free entry into the riding lawnmower. This device is intended to allow the user to both mount and dismount a riding lawnmower, with little effort and maximum support. Also, this design will be portable, so the user can store it in a shed or garage when it is not being used. 9

11 2.2 Optimal Design Objective The L.A.D. allows the user to transport himself/herself by using only their upper body from a wheelchair into the device and subsequently into the lawnmower. The apparatus, through the use of a piston, is able to positively or negatively displace the user vertically to allow access to the lawnmower and/or the wheelchair depending on their needs. The piston is similar in nature to the pressure pump used in barber chairs and employs an easily accessible mechanical system to positively displace the apparatus (negative displacement requires no energy). The entire system can rotate 360 to provide variable access to the wheelchair and lawnmower seats. In addition, the base of the system is supported on wheels to allow easier transport and/or storage of the device. Safety rails are installed to ensure the user can firmly grasp the device while in motion to prevent injury. Another safety feature is the seatbelt, which is installed on the lawnmower to prevent injury while the lawnmower is in use. In addition, a pull-out attachment board is installed in the L.A.D. This attachment board is extended from the apparatus and rests on the lawnmower attachment so that the user can slide from the device onto the lawnmower. This board may then be detached to separate the device from the lawnmower and reattached once the user wishes to re-enter the device. Finally, a novel braking system is implemented to secure the apparatus when in use. Figure 5 below shows an overview of the preliminary design. Figure 6: L.A.D. Preliminary Design (Adapted from Alt. Design 3). The L.A.D. was chosen as the best design option as it provided mobility (lacking in alternative design #1), safety (improved upon from alternative design #2) and efficiency in space and parts (improved from alternative design #3). All three alternative designs were incorporated into the design of the L.A.D. Alternative design #2 served as a base for the L.A.D., while the safety measures of alternative design #1 and the power and aesthetics of alternative design #3 were 10

12 incorporated with a smaller form factor. Safety, ease of use and ease of storage were the main goals for the current design of the L.A.D Subunits The complete lift device that is described above is comprised of a number of separate subunits that work together so that the L.A.D. can function correctly. Each of these subunits is unique in design and essential to the overall performance of the device. The following section details the design of each of these subunits, presented from the top of the system to the bottom Safety rails As illustrated in Fig. 2, the safety rails are connected to and completely surround the backside of the seat. There are two main objectives that needed to be addressed when designing the safety rails for the L.A.D. The client s condition limits usage of his lower extremities. However, he has full functionality of his upper body. Taking this into account, the first application of the safety rails is to provide the client with a sturdy structure to hold on to and grasp while positioning himself in the L.A.D. Secondly, the safety rails act as a backing for the seat. The curved design of the rails will allow the client to lean back and rest during transition from his wheelchair to lawnmower. In the actual construction of this section of the device, the safety rails will be positioned so that the user is completely secure and risk of slipping out of the chair will be negligible. Figure 7: CAD model of Safety rails. The figure shown above is a computer-generated representation of the safety rails that are to be employed in the assist device. The rails have been manufactured out of carbon steel and are hollow (not shown). For increased stability, the three metal tubes have been welded to one another, and subsequently welded to the seat as well. Also, there is a secondary attachment half way down the vertical railings for lumbar support. In an attempt to combat interior wear 11

13 and rust, the hollow ends of the rails have been covered with a wooden frame, adhered to the metal with Velcro Seat Figure 8: Safety rails. The seat design is much more complex than one would assume upon first glance, as it has several important features that are pivotal to the operational success of the overall device. Shown below is a CAD drawing of the seat and all of its components. Figure 9: CAD model of seat. 12

14 The first feature of the L.A.D. seat is its connection to the safety bars. In the figure above, one can observe the holes where the rails have been welded to the metal seat casing. The seat s second attribute is that it houses the pull-out bridge that will allow the user to safely transport himself from the L.A.D. to the lawnmower. The interior of the seat is specially designed to permit the user to pull the bridge in and out, until it is fully extended. To do this, two steel axels have been installed which are accompanied by two acrylic wheels on each axel. These wheels are secured in place by wooden stoppers, and correspond to the track grooves found on the underside of the bridge. Also, a swiveling mechanism has been installed to the bottom of the seat surface; this mechanism is accomplished by a custom-ordered shoulder bolt and washer. It is very important that the seat be able to rotate during use, so the client can easily transport himself in and out of the L.A.D. Figure 10: Seat mechanism Pull-out bridge Once the user displaces himself to the height of the lawnmower, he will need a safe way to transport himself out of the L.A.D. The pull-out bridge, which is stationed inside the seat while the device is idle, provides for this. The bridge has been constructed out of carbon steel like the rest of the device, and is wide enough to support the full weight of the client. In choosing the correct material for this bridge, our team was very meticulous because of the importance of this subunit to the success of the ultimate design. The pull-out bridge design can be observed in the figure below. 13

15 Figure 11: CAD model of bridge. The support bars which have been welded to the ventral side of the bridge act as tracks for the wheels to roll in, so the bridge will be able to slide in and out during use. After testing, our team realized that an intricate attachment between the bridge and the lawnmower piece would not be necessary, as it was completely stable just by resting on top of it. A figure of the actual part and how the wheels fit into the grooves can be viewed below. Figure 12: Ventral View of Bridge with Sliding Axels and Wheels. 14

16 Seat/pump connector The purpose of the seat/pump attachment is to secure the piston to the base of the seat. The connector is custom fabricated from aluminum alloy. The inferior component encapsulates the head of the piston and can be secured with a safety pin if necessary. The superior component is welded to the base of the seat and is constructed from a wider diameter material for extra support. Figure 13: CAD model of Seat/Pump Connector. Figure 14: Seat/Pump Connector. 15

17 Hydraulic pump The vertical lifting mechanism that displaces the user in the positive or negative vertical direction will be accomplished by the hydraulic pump, located in the center of the device. A schematic representation of the piston that is used in this device can be viewed below. Figure 15: CAD model of Hydraulic pump. When brainstorming the overall design of this project, realistic constraints needed to be taken into account. Pertaining specifically to this subunit, it would be quite costly and time-consuming for the team to design and construct a hydraulic pump that is unique to the L.A.D. In addition, since this pump is the source of vertical displacement for the device, it is essential that it functions correctly. With this being said, this hydraulic pump has been purchased instead of creating one from raw materials. The figure below is a picture of the NG1 hydraulic pump that is implemented in the L.A.D. Figure 16: NG1 Hydraulic Pump. 16

18 Referring to [4], the lifting mechanism of the hydraulic pump shown above is comprised of two chambers. One of the chambers can vary in volume, and includes a flexible diaphragm. The other contains hydraulic fluid and pressurized gas. To enable fluid transfer between compartments, a conduit and control valve interconnects the two compartments. To ensure a safe transition from varying heights, the control valve has a higher fluid flow rate in one direction as compared to the reverse direction. Therefore, movement of the chair in the downward direction is slower than movement in the upward direction, allowing the user to position the chair to a desired height. A schematic cross-sectional view of the hydraulic pump compartment design can be viewed in the figure below. Figure 17: Sectional View of the Hydraulic Pump Compartments. The mechanism behind the action of the hydraulic pump is quite simple. When there is no force acting downward on the variable volume chamber, the control valve is open, and the pressurized gas allows hydraulic fluid to flow from the fixed volume compartment into the variable volume compartment. As the volume of fluid in this variable compartment gradually increases, the lifting mechanism is employed. Here, the fluid occupies more space in the compartment, and it is forced to expand in the upward direction, causing vertical displacement of the support members located anteriorly (i.e. the seat). A schematic drawing of the entire hydraulic pump design and mechanism is illustrated below. 17

19 Figure 18: Sectional View of Hydraulic Pump with Stacked Compartments Pump/base connector The purpose of the pump/base connector is to attach the 5-star base to the hydraulic pump. The base attachment is custom fashioned from aluminum alloy. The inferior component is driven into the base opening and pressure locked. The superior component is mated to the bottom end of the hydraulic pump (not the rubber component) and secured with four sets of bolts. Figure 19: Pump/base connector. 18

20 Figure 20: CAD model of Pump/base connector Base From a structural standpoint, the base of the L.A.D. is the most important subunit to the design. Since the entire apparatus is designed to support a range of human weights, the base has to be secure in order to allow for this. A computer generated image of the base design can be viewed in the figure below. Figure 21: CAD model of Base. 19

21 In design of the base, there are two main goals which have been met the material is able to house several wheels (so the L.A.D. can be mobile) and prevent the user from tipping over during use. In research of possible material options that would be both cost effective and able to withstand a substantial load, purchasing raw materials to construct the base would be extremely costly. The main reason for this is that the base must be relatively small (in comparison to the overall design), but dense at the same time. As one can imagine, in balancing out the additional mass that will be added to the top of the device during use, the L.A.D. must be, to an extent, bottom-heavy. To solve this problem, a pre-existing product has been purchased and modified to produce the base of this device. Our team was able to buy an office chair and extract the 5-star metal base from the bottom to implement in our design. A figure of this base, unpainted, can be viewed below (the wheels shown here are the medical grade wheels that were custom-ordered and installed after extraction). Figure 22: 5-Star Metal Chair Base Extracted from an Office Chair. The base shown in the figure above provides the support that is needed in the ultimate design of the assist device. It is made out of steel, and plated with a rough coating. At the center of the base, there is an opening for where the piston will be placed Wheels The wheels rotate within the wheel axis and have a standard rubber encasement similar to those used in shopping carts. Due to their low expense and complexity of design, the wheels have been ordered from a wheel-manufacturing facility. They are medical-grade and have a braking system to prevent movement of the device when it is in use. A computer-generated image of the entire wheel system can be seen in the figure below. 20

22 Figure 23: CAD model of wheel. Figure 24: Medical-grade Wheel Wheel assembly The wheel assembly allows the L.A.D. to be transportable. Ideally, indoor storage of the L.A.D. prevents common environmental damage. Since the L.A.D. will be used by the client outdoors, it is important that the device can be relocated. A total of five wheels are installed on the base of the L.A.D. 21

23 Wheel casing The wheel casing will be the main functional unit in a braking system that will allow the user to lock and unlock the wheels from an easily accessible position. The casings are essentially conical structures draped over each wheel with grooves cut out to accommodate the extensions of the brakes L.A.D. seatbelt A standard seatbelt was installed on the L.A.D. for extra security. Both the male and female components were bolted to the seat. This unit will allow the client to fasten himself/herself in during device use to prevent unwanted motion. Figure 25: L.A.D. seatbelt Lawnmower seatbelt This subunit is not included in the design of the assist device, but rather is implemented in the client s actual lawnmower. The lawnmower belt is a custom design, per the client s request. Since the lawnmower frequently is a bit unsecure for the client during use, the seatbelt will function as a safety precaution. Two holes were drilled in the lawnmower plastic shell, and both the male and female components of the belt were bolted down. The figure below depicts this operation. 22

24 Figure 26: Lawnmower seatbelt. The lawnmower belt was ordered from a seatbelt manufacturing facility and the custom attachment for the pull-out bridge was fashioned from aluminum and wood at the UCONN machine shop Lawnmower attachment The lawnmower attachment is completely fashioned from wood and custom-fit to the structure of the lawnmower s cup-holder. The attachment is secured with bolts and wood screws along with a thin aluminum plate to prevent deformation of the plastic framing under high stresses. The top of the component functions as a receiving terminal for the bridge, which can be withdrawn from the seat housing and rested on the lawnmower attachment. The client may then proceed to transfer himself/herself to the lawnmower seat from the L.A.D. Figure 27: Lawnmower attachment. 23

25 2.2.3 Current Design By combining all of the subunits described in the report above, one can generate an optimal design of the lawnmower assist device. This representation is an evolved form of the preliminary design shown in Fig. 6 earlier in the text, and demonstrates all properties of each subunit. Figure 28: Optimal and Final L.A.D. design. 24

26 2.3 Prototype Description The prototype deviated slightly from the optimal design. Instead of using a circular 4-wheeled base, a 5- legged base was chosen in order to improve mobility and decrease footprint. A separate breaking mechanism was not necessary as the breaking system for the medical grade wheels was sufficient in holding the device in place. In addition straight bars were chosen over curved back support bars in order to minimize operating size and provide better posture support. The bridge was changed from a solid piece into a bridged support piece to decrease weight Operation To begin operation, the user must first roll the device up to the lawnmower, making sure that the brakes on each wheel are disengaged to allow effortless mobility. At this point, it is essential that one of the legs of the 5-star base is positioned correctly behind the blades of the lawnmower. This way, the bridge can be correctly aligned with the lawnmower attachment. The figure below illustrates this positioning. Figure 29: Device wheel positioning. Once the device is correctly positioned, the brakes on each wheel should be engaged by stepping on them and locking them into place (accomplished by someone other than the user). It is suggested, but not required, that the brakes on all five wheels are locked into place before usage. Next, the user will be able to remove the metal pin that is held inside the left lawnmower arm. Removing this pin will allow the user to swing the arm down in the forward direction so that it will not be in the way during transfer. 25

27 Figure 30: Safety pin removal and arm positioning. With the user s wheelchair positioned to the left of the device, the device seat will be allowed to be lowered to the correct height of the wheelchair by simply depressing the hydraulic pump lever (by foot) until at the desired height. Then, the user will be able to slide from wheelchair to device easily. Once transferred from the wheelchair to the L.A.D., the user should secure himself by fastening the seatbelt that has been installed in the device. With the user s back flush with the safety bars, the device can be raised. The same person who locked the wheels into place should also be in charge of pumping up the user in the L.A.D. by foot. The hydraulic pump vertically displaces the device seat best when the lever is pumped in short strokes. As the user begins to reach the desired height, he should slide the bridge out of the seat housing with his right hand, approximately a quarter of the way. The bridge should NEVER be pulled out entirely. Once the bridge appears to hover over the lawnmower attachment by approximately an inch, pumping should cease. A visual of this process can be viewed below (see Figure 32). 26

28 Figure 31: Vertical displacement of the device. Next, the device should be lowered slightly (with the user still seated) until the bridge is level and rests on the lawnmower attachment. This can be accomplished by pushing the pump lever as far as possible and holding it in position caution should be taken as to not allow the pump to decline too much. 27

29 Figure 32: Bridge placement. After both the user and whoever is assisting him have assured that the bridge is pulled out to the length of the lawnmower attachment, the seatbelt in the L.A.D. can be unfastened. At this time, the user should slide himself across the bridge using his upper body, until seated in the lawnmower chair. For increased safety, a second seatbelt has been installed in the lawnmower itself, which can be fastened here. 28

30 Figure 33: Transfer of user to lawnmower. At this time, usage of the L.A.D. is complete. Once seated in the lawnmower chair, the user can take the same pin that he removed in Figure 30 and place it back into the lawnmower arm to maintain functionality. Finally, the device can be easily rolled away from the lawnmower by following these easy steps: Depress the hydraulic pump lever 5 times to raise the bridge slightly above the attachment so the paint isn t scratched upon retracting the bridge. Push the bridge back into the seat housing until it makes contact with the back of the device. Depress the hydraulic pump lever once again to return the L.A.D. seat to the shortest height possible. Roll device to desired location. After the user has mowed his lawn, he will need to dismount the lawnmower and reenter the L.A.D. before getting into his wheelchair Testing For testing of the prototype a test subject of similar height and weight to the client was used. For the duration of the testing, the subject was instructed not to use his lower body to simulate MS conditions. The test subject was then put onto a power-chair of similar dimensions to that of the client and stepped through the process of mounting and dismounting the lawnmower using the LAD. Qualitative information was collected and the test subject was asked throughout the process to share his thoughts on the comfort, ease and feasibility of the device. In all aspects the test subjects reported positively and had no complications using this device for its intended purpose. Further testing was done by having the test subject hold up to 100 pounds during the process and recording the same information. Once again 29

31 no complications were noted and the subject was able to safely mount and dismount the lawnmower as intended. Further non-physical testing was completed in the SolidWorks CAD software suite. The final bridge design was tested for stress and strain given the client s weight, this was done to find the maximum displacement caused by the client and compare with mechanical properties of the material (see figure 26). Figure 34: Bridge CAD testing. This test verified that the bridge would be able to withstand the weight of the client. Further CAD testing verified that the device would not tilt during operation (see Figure 35, which shows Von Mises stresses and displacement at the point of weight placement). The resulting test found that the device would not tilt at an applied weight of double the client. 30

32 Figure 35: CAD tilt testing. CAD testing was also used to verify the stability of the wheeled base over time (see Figure 36). Using the cyclic testing feature of SolidWorks, it was found that the base would maintain structural integrity for more than 50 years. This timetable was the limit of the software suite; in reality the base should maintain structural stability much longer as even after 50 years of loading the software reported no areas of fracture (would be shown in red). Figure 36: CAD cyclic testing for wheeled base. 31

33 3. REALISTIC CONSTRAINTS An important aspect of project design and manufacture is the identification of potential limitations and issues, especially those concerning usability, reliability, safety and comfort for the user. Only when these potential issues are identified, can they be addressed and accounted for. 3.1 Health and Safety The main goal of this design is to provide a safer way for Mr. Hiller to mount his lawnmower without putting him at risk of falling. To address the safety of the client both safety railings and safety belts will be incorporated into the design. The most dangerous aspect of the operation of the LAD is the physical lifting of the client to the height of the lawnmower lift. The safety railings on the chair base give the client something to hold onto during lift up so in case of loss of balance or unexpected mechanical failure. In addition as per request of the client a new safety belt system will be installed on the lawnmower chair itself in order to insure continued safety when the client is operating the lawnmower. 3.2 Sustainability The sustainability of the project will be a very important aspect to take into consideration. As Mr. Hiller will be mowing his lawn often for many years to come, this project must be built to last and withstand storage. To this end this project will be made with the idea of zero maintenance required, by removing electrical parts and replacing them with an easy to use mechanical operating lever, the problems concerning recharging, winter storage and electrical failure are all eliminated. With the current design, the LAD should have no problem under sustained use with only minimal physical cleaning. 3.3 Manufacturing Manufacturing constraints will manifest mostly in the weight, mobility and footprint of the LAD. As the LAD must be stored in a small shed when not in use, minimizing footprint and size without compromising safety will be a high priority. In addition the LAD must be light weight enough so that anyone can easily move the LAD into position. However the LAD must still remain heavy enough so that a gust or slight decline does not cause it to move. To this end a braking system in the wheels will be installed. Physical constraints of each part used will also affect the project. The most important mechanism of the LAD will be the hydraulic pump that will serve to raise and lower the client to the desired height. This pump will be bought off the self from an external supplier. The properties of this purchased pump will determine the maximum weight, speed and reliability of the LAD device. Therefore choosing the right pump for the project is of the utmost importance. 3.4 Economic Economic constraints are directly related to manufacturing constraints. The materials that the LAD will be made of will depend purely on the budget allowed for this project. Ideally the LAD will be made of carbon steel in order to maximize strength while minimizing weight and size. If the budget does that allow for this then it will seriously constrain the manufacture of the LAD and alternative materials will be necessary. 32

34 Besides raw materials purchased materials will also depend on the budget allowed for this project. As mentioned in 2.5, the hydraulic pump will be the base of the lifting mechanism, as price of the pump increases with weight displacement capability; the price of a pump that will fit the standards of the LAD will be high. In addition the wheels and base of the LAD will most likely be purchased instead of made. The manufacturing time and waste resulting from creating these parts from scratch would be greater than the cost of buying them off the shelf. The wheels of the LAD are especially important as they provide mobility and support for the LAD. 3.5 Engineering Standards Engineering standards for people and barber chair style lifts will be maintained for this project. The maximum weight that the pump will lift is 400lbs. When welding the body and frame for the LAD welds will be done by arc welding. 3.6 Environmental The LAD will have a small environmental footprint and not require any special permits, licenses or clearance to manufacture or operate. The client has not expressed an interest in electronic components for the lift in favor of ease of maintenance. With the elimination of such components there will be no exhaust or waste produced by the LAD. 3.7 Social While there are no broad scale social ramifications of the LAD, as stated prior the goal of this project is to improve the quality of life for the client. 4. SAFETY ISSUES Safety is the central concern and objective of the LAD. The main safety issues of the device will come from the physical properties of the lift mechanism. As stated in 3.1, the lifting aspect of operation will be the most dangerous aspect of the LAD. During this time if the LAD were to lose traction, have mechanical failure or break the client would be left suspended at a dangerous position or fall. To ensure that this does not happen, safety railings are attached to the side and the back of the LAD seat so that the client can hold onto something during the lifting phase. Because electrical components were removed from the LAD design the risk of over lifting or electrical malfunction resulting in the lift becoming stuck are eliminated. The mechanical pumping level is designed for maximum ease of use as not to injure the user s arm. Another dangerous aspect to the use of the LAD is the transfer from LAD seat to lawnmower seat. The bridging apparatus will be attached completely and securely at two points to the safety belt mechanism to insure safe transfer. In addition the actual base of the LAD will be designed to move the LAD as close to lawnmower as possible in order to minimize the distance the bridging apparatus will have to span. In addition the wheels of the LAD will be able to lock into place to ensure that the LAD will not move when the client slides across the bridge. During manufacture safety must be taken into consideration with every part. Whenever possible parts will be welded together not screwed, in order to allow for maximum structural stability. The strength and stability of the LAD base will be a crucial aspect of the design. The LAD must be tested to hold at least up to 700lbs when not in operation and 400lbs when lifting. In addition the bridging apparatus must hold the same weight as the entire LAD when attached to the lawnmower without 33

35 tipping over or breaking. The wheels also must be securely attached to the base of the LAD. The choice of welds over screws is for long term usability. The LAD must not only work once, but be used repeatedly for many years. In addition the LAD must be built to be reliable after multiple winter storages. The choice of welds over screws is to prevent possible condensation and ice buildup along the threads of the screws which can cause loosening and instability. If this were to happen at a major junction of the LAD, the device may fall apart during use. Such a scenario is unacceptable. 5. IMPACT OF ENGINEERING SOLUTIONS The goal of this project is to create a lifting mechanism that will allow the client to safely mount and dismount his lawnmower and allow him to do the housework he wishes to do. Since this project is designed for only one individual, the global implant is nil. However, if this device were manufactured for mass production and consumption there would be a large market for it. There is nothing on the market that does what the LAD can do. No personal lift is designed for lawnmowers. If made to work with all commercial riding lawnmowers, this product could have great marketability not only for people with physical disabilities, but also senior citizens. In addition this product could find other uses inside and outside of the household such as use for raised pools raised hot tubs. In the market, the closest competitor to the LAD costs significantly greater and lacks the mobility and utility of the LAD [2]. Economically, the LAD would provide a low cost, easy to use alternative to more expensive and bulky personal lifts. Priced at more about one third of the cheapest personal lift on the market to manufacture, the LAD would fit a completely unoccupied price point. In addition because of the price the LAD will be covered by more healthcare plans and Medicare. Outside of manufacturing, there will be no negative environmental impact to the LAD. Because there are no electronic components, there will be no additional burning of fossil fuels or replacing dangerous acid filled batteries. Under the zero maintenance motto, the LAD will be completely selfcontained and require only minimal cleaning to maintain working order. As no special lubricants or chemicals are used, none will need to be replaced. The societal impact of the LAD will be more people who either have physical disabilities or some other type of obstacle when mounting a riding lawnmower to be able to not only mow their lawns, but at the same time get fresh air and a sense of accomplishment knowing that they are contributing the same as anyone else. Mr. Hiller s goal for the LAD is that he wishes to do his fair share of housework. All around the world this sentiment is shared by people with physical disabilities. If the LAD can help him achieve his desire, then the societal impact of this project is immeasurable. 6. LIFE-LONG LEARNING In order to design and construct the LAD, new skills were acquired that will last a lifetime. The first skill necessary was knowledge of client needs. It is important when designing something for a specific person that all the client s demands are satisfied and needs are addressed. In the case of Mr. Hiller, knowledge of multiple sclerosis and its effects on him were very important. It was necessary to understand and study the condition in order to construct a device that not only suits the needs of the client today, but also years into the future. Team working was essential to this project. Communication, work differentiation, effort, accountability and goal/deadline oriented thinking are all necessary skills that were gained and put to the test for this project. These skills will be necessary in any work environment. 34

36 Drafting designs for the lift required accurate 3D models. Autodesk Inventor (a CAD program that allows for the creation and testing of 3D models) was used to create, simulate and test all components of the LAD. Proficiency in CAD software will be of great importance in future projects requiring R&D. The bulk of the skills learned for this project were machining and machine shop operation. Welding, drilling, metal working, parts manufacture and design were all utilized. Besides mechanical know how, detailing planning was also very important as each component had such detail that without a complete manufacturing plan was required. Physical experience inside a machine shop will be of use in industry whether or not direct interaction with production is required. An understanding of the physical production process will be beneficial when developing timelines and cost estimates for manufacturing. An understanding of material properties was also necessary for this project. Each material used had to fit the physical specifications required of it, in addition the interaction of different materials was taken into consideration when building each component of the LAD. 35

37 7. BUDGET 7.1 Budget The bulk of the budget was spent on raw material. In addition, fabric and decoration also took up a fair amount of budget. This project was given a $1000 budget and it was completed under budget with $167 to spare. 36

38 8. TEAM MEMBERS CONTRIBUTION TO THE PROJECT 8.1 Michael Chen The maintenance and updating of the official group website is Michael s independent responsibility. Michael was responsible for the overall design of the device. In addition Michael cut and fabricated the top and bottom seat plates as well as the insert sandwich pieces. In addition Michael cut, leveled, and drilled holes for the vertical safety rails as well as cut the horizontal safety bars. Additional fabrication included the acrylic slide wheels for the bridge, and 4 insert wheel axel holders. Michael also fabricated the pump to chair connector and the pump to base connector. The design and painting was performed by Michael. Cushioning and upholstering was performed by Michael and Matt. In addition Michael assisted Josh in the fabrication of the lawnmower attachment, specifically the fabrication of the metal support plate. Also Michael and Matt performed the physical testing for the device. 8.2 Matthew Desch Matthew served as budget director and Microsoft Project coordinator for the project. Also, Matthew was in charge ordering all materials and processing all PO s. For fabrication, Matt was the chief welder of the group and welded all components for the device. In addition he facilitated the connection of the chair to the chair and pump connector. In addition Matt also served as liaison with moving teams to transport the lawnmower on site. 8.3 Joshua Aferzon Josh was the CAD designer and tester. All CAD designs and tests, including stress/strain for all bridge designs, tilt testing and cyclic testing was performed by Josh. In addition Josh designed and fabricated the wooden lawnmower attachment. 9. CONCLUSION The L.A.D. Electric Wheelchair to Riding-Lawnmower Assist Device provides the client with a safer means to mount and dismount his riding lawnmower. Due to the client s Multiple Sclerosis, he lacks control of his legs thus climbing and dismounting a riding lawnmower is an issue. By creating a portable and sturdy lift that can attach directly to his lawnmower without hindering the function or weight distribution of the lawnmower itself we feel that we have met all the needs of the client. Stability and safety are the principle concerns of this device. As this device is mostly a labor of manufacturing, there is great necessity for careful and sound construction. The entire seat and bridge, the most important manufactured components of the device, are completely fabricated using carbon steel and welded together to ensure maximum stability and safety. The base and pump are attached together by welding and a breaking mechanism has been developed to ensure that the L.A.D. only moves when necessary. Furthermore the pump is protected from the elements via an outer casing. Sustainability is another crucial component of this project. The L.A.D. will sustain repeated use over many years as well as storage both indoors and outdoors in any weather. With this in mind, the L.A.D. was designed to require minimal maintenance, the only reason this device could fail is material breakdown due to rust and corrosion, a problem that will not occur with simple cleanings for decades. This device fulfills all the needs of the client and his family. It will provide the client with a means to operate his lawnmower safely and in an expediently. 37