The goal of this team is to create a Murder Ball athletic wheelchair that can be effectively used by a quadriplegic athlete who only has mobility in one arm. The current design for a Murder Ball wheelchair requires the use of both arms and does not adequately accommodate those who do not have mobility in both arms. The team plans to address this issue by designing a new wheelchair mechanism that allows comfortable use by athletes with mobility in only one arm. The design of the mechanism will have drive rings that will be positions where the athletes able arm is located. With this design, the game will be more fairly balanced to the abilities of the athletes with one-hand mobility, and the athletes will have a better chance to be competitive in the sport they love.
Proof of Concept
The proof of concept (POC) will allow the team to test how well certain aspects of the team’s design will work. The POC primarily will be used to analyze the effects of various angular velocities on the gears as well as on the axles; specifically, to determine how well these gears operate and which thickness of the axle is to be desired to accommodate these speeds. To accomplish this, the POC will consist of a structure that will hold the axles together, while still allowing them to rotate. This structure requires three main components: the base to hold the axles in place, which can be constructed from wood, wooden axles of several thicknesses, and 3D printed gears that will connect the axles. Overall, the POC will demonstrate how well the design will function.
The POC consists of three main parts: the base, the axles, and the gears. The base’s function will be to hold the axles in place and will likely be constructed from wood; however, it may be subjected to change if it becomes too costly or a simpler way to create it exists, such as holding the axles on something. The two main axles will be used to test the effects of angular velocities on various diameters and the angle at which the axles are constrained. These axles will be wooden rods, of several different thicknesses, that will either be purchased or lathed at the machine shop. Additionally, one end of each axle must be lathed so that it has a small enough diameter to fit in to the gear. The lathed end will also need a hole drilled into the side so that a pin can connect it to the gear. Lastly, two sets of gears will connect the axles to demonstrate at which speeds the gears begin to fail, that correlate with the different shaft angles (12 degrees and 20 degrees). These gears will be designed in SolidWorks, then 3D printed. Once the parts are all put together, it will look like what is shown in Figures 1 and 2. Overall, the POC will allow the team to examine how the axles and gears will operate together under different angular velocities.
The One-Arm Athletic Wheelchair project is designed with the intentions of accommodating persons with paralysis in one arm, or disabilities alike, who want to participate in Wheelchair Rugby (Murderball). The conventional athletic wheelchair design requires mobility in both arms to properly maneuver; whereas, the One-Arm Athletic Wheelchair is concentrated on providing a chair commensurate with a quadriplegic’s finite dexterity. Such a wheelchair would be advantageous to a quadriplegic in such a way that will curtail the discrepancy in maneuverability caused by their disability; thus, improving the equity of the game as well as improving opportunities for such a person to become more engaged. The product design specification guides that the wheelchair shall effectively allow people, with mobility of a single arm, to competitively play Murderball [on approved Murderball surfaces and courts]. Furthermore, the specifications govern several requirements that the wheelchair must abide by, the wheelchair must: be able to fit through a doorway, be light enough for one person to play, strong enough to support up to 400 lbs, have wheels that are easily removable and serviceable, contain appropriate warning labels, and cost less than $1000.00 to produce. Much of these requirements are consistent with requirements of regular wheelchairs, in such that a wheelchair should be able to fit through doorways as well as support the weight of a person; however, the production cost limit is specifically suited towards the allocated project budget. Ortega Industries’ goal is to be able to reach all these requirements and create this new product within the budget given.
Team 23 started the fabrication stage on March with the ordering of the necessary materials. Among the materials ordered were: two-inch aluminum tubes with quarter inch walls and a length of 6 feet, two 4-inch aluminum cylinder with a length of 6 inches, 4.5-inch aluminum tubes with quarter inch walls, a 6-foot aluminum cylinder with a diameter of 5/8 inch and four lubricated ball bearings. Each component of the assembly was machined in the UNR machine shop. The CNC machine was used to make the bevel gears out of the 4-inch cylinders using a previously designed SolidWorks model. The CNC lathe was used to machine the axle and the outer housing, first by turning them into the appropriate lengths. For the housing, a bore was created in the 2-inch tubes for the fitting of the ball bearings. The lathed was also used to create diameter reductions through the 5/8-inch cylinder. These reductions help the wheels and the push ring stay in the correct position.
The band saw was used to cut the 4.5-inch tube at the appropriate angle to produce the gear housing. First, the tube was cut in half, then each half was cut at an angle. Sheet metal was cut with the band saw to create small flaps that would be used to mate both gear housing halved together during assembly. To create the two disks that would help the mating of the ring to the assembly, a saw was used to cut the 4-inch cylinder into quarter-inch disks. Then, a mill was used to make five 3/8-inch holes on the disks. A tap was used to create threading in the middle hole of the disks for the mating of the ring. In addition to the tap, a die was used to thread the axle to help fix the wheels and the ring in place.
The cones connecting the axle housing and the gear housing were sand casted along with the back-up bevel gears. The casting was performed in Fernley High School.
After buying the necessary nuts and bolts, and finding a machine shop that could weld aluminum, the team was ready to assemble the prototype. Below is a picture of all the fabricated and bought components.
The team consulted a local machine shop for the welding and the assembly of the prototype. Specific steps were taken to properly mate all components into the assembly. The picture below is the main module the team set out to create; this module does not include the wheel that are going to be used for the final prototype.
Testing and Results
To test the One-Handed Athletic Wheelchair module, the wheel and the push ring were spun separately and together to simulate going forward, backward, and pivoting in both directions. To test forward motion, both the ring and wheel were simultaneously spun forward; similarly, backwards for a reverse motion. To pivot, only either the ring or wheel was spun (depending on orientation and which desired direction). This was tested by each member of the team, who all got the same result – that the module sufficiently provided motion to the dependent wheel while allowing the independent wheel to spin freely. The results of these tests can be seen in Tab. 1. The product also had two minor issues: that the gears did not always maintain contact with each other, and that the dependent wheel became loose/unattached to the dependent axle. To address the former, spacers should be placed in the gear housing in between the gears and the cones, to make sure they are always contacting. To address the latter, two blanks could be made to attach the axle to the wheel properly (like the push ring). After these adjustments, the module should be able to perform its function properly when attached to an athletic wheelchair – providing an alternative method for one armed athletes to maneuver in wheelchairs. This method will make playing the sport easier by allowing them to control both wheels from one side in lieu of having to reach both sides with one hand. Currently, there have been no real users for the module; however, the overall consensus from innovation day was that the module achieved its goal. Additionally, Tony [the Reno High Fives coach] stated that he hopes to see the design implemented in the future and that it would allow the athletes to easier play the sport, which was the design’s intended purpose.
Table 1: The test results for the prototype.
|Issue?||None||Dep. wheel became loose||None||Gears weren’t meshing||None|
Meet the Team
Juan was born in Michoacán, Mexico and moved from Las Vegas to study at UNR. He will be graduating in the spring of 2017 with a degree in mechanical engineering and a minor in mathematics. After graduation, Juan will pursue a career and a master’s degree.
Casey is a senior Mechanical Engineering student who will be graduating in the Spring of 2017. He was born and raised in Reno, Nevada and enjoys hands-on work. After graduating, Casey plans on working and pursuing graduate school.
Robert is a senior Mechanical Engineering student who will be graduating in the Spring of 2017. He was born and raised in Sparks, Nevada. After graduating, Robert plans on pursuing graduate school.
Daniel is a senior Mechanical Engineering student graduating in the spring of 2017. He is from Lathrop, California, a small town an hour’s drive south of Sacramento. Daniel looks forward to pursuing a career in the Defense Industry after graduation, or going to graduate school.
Roberto is a Mexican-American Reno native, born and raised in the biggest little city in the world. A senior in the Mechanical Engineering program of UNR graduating in the spring of 2017. He plans to continue his education and fulfill his many aspirations. Aside from being able to invent technology that can help the world, he would like to one day be able to fly planes at top speed, test high end cars, and be a professional race car driver.