Down Hill Ski Racer
The Human Centered Design Studio at the Colorado School of Mines is known for enabling individuals with disabilities to participate in both sports as well as other outdoor activities. Our project is focused around a 12-year-old named Audrey who is a very talented ski racer. Audrey is a right arm amputee who is missing everything on her right arm below her elbow. she has a prosthetic she uses for the rest of her arm while skiing and then attaches to a hand prosthetic in order to hold her ski pole. While skiing, even the best athletes tend to fall a good amount especially when racing at such high speeds. Her past prosthetics, which are used as a right hand to grip the ski pole, have given her trouble in the past. For example, the ski pole will not always release when she falls so she has been hurt from a fall because her ski pole won’t let go and ends up poking and scraping her during falls. Another problem is that she is getting too big and strong for her current prosthetic. The original prosthetic was made for her when she was 7 so she has grown a lot since the original design of the prosthetic. As she continues to grow and get stronger she will need a stronger and more durable prosthetic. The prosthetic also needs to be able to release the pole when she falls so it doesn’t injure her, but Audrey also has to be able to snap the pole back into place in a time efficient manner as time is very valuable while racing. With these constraints, our goal is to design her a prosthetic hand that grips the pole tightly while racing but releases when she falls and also allows Audrey to quickly remove and insert the pole in and out of the prosthetic. The grip the prosthetic has on the ski pole will also be adjustable, so as she gets stronger she can adjust the strength of the grip to her liking.
The design of the prosthetic is very similar to the cam mechanism of a ski binding. A cam mechanism uses a screw/bolt that is tightened into a spring to allow the strength of the grip to be adjustable. This way Audrey can adjust the tightness of the bolt depending on the type of skiing she is doing. The prosthetic will be machined in the shape of a right hand, with a thumb that separates and tightens around a ski pole using the cam mechanism. This makes it so it is hard for the pole to fall out unless she falls, as well as allowing her to quickly snap the pole back into place with little force needed
Live Zoom Chat
Use the link below to join us live from 8:00 – 10:30 a.m. on December 3.
Join from PC, Mac, Linux, iOS or Android: https://mines.zoom.us/j/7036830363?pwd=QVljWllYUndjV3BNS28yZytzcmxUQT09
- Tyler Blomster
- Christian Palacios
- Aaron Moore
- Erin Sweeney
- Ryan Fidel
- Lindsey Nunamaker
- Ethan Francis
- Bob Radocy
Project Advisor: Dr. Chelsea Salinas
Technical Advisor: Dr. Joel Bach
Donations Made by: TRS Prosthetics
The goal of this project is to create a functional prosthetic device for an aspiring downhill ski racer. The device must meet many constraints such as being able to withstand cold weather, quick reload after a crash, withstand a closed grip up to a desired force, release when the skier crashes, and must have an open/close design. With these design considerations in mind, our group has developed a prosthetic which functions on a CAM and follower mechanism. Additionally, a ramp shaped attachment allows for the prosthetic to be sloped at an angle, and also allows the prosthetic to be used for either the left or right hand. Further additions would include making the prosthetic machinable, and adding a grip which would allow it to be used on any sized pole. This final design came to fruition after constant iterations with past groups, and our client Bob Radocy.
The initial prosthetic(pictured to the right) used by TRS and Audrey was a basic snap in and out design that would hold the pole tightly in place. The tight grip became a problem as it wouldn’t release the ski pole if Audrey fell while skiing. This design feature also made it difficult to put the ski pole in the hand as well as take it out. Another problem would be that as she got older the prosthetic would become too small and not strong enough for her to be able to use. The advantage was that it was very simple design and fairly cheap to make. So in the spring and fall of 2020 the two design ideas below were created.
The first would be described as a ratchet system(2nd and 3rd pictures to the right). The sketch drawings for the selected design concept are shown in the second image to the right. This device is composed of three main components: the polyurethane ‘fingers’, ‘the ratcheting wheel mechanism’, and the ‘thumb’. This design was selected for its simplicity and potential for adjustability. It also has great potential in cold environments because the mechanical components can be completely enclosed within a cavity in the wrist-like portion of the device. After discussing the ratchet system design with the client and doing force tests on the prototype it was made clear that in order to make the prosthetic strong enough to work for Audrey they would need to significantly increase the size of the prosthetic and order special sized parts which wouldn’t bee cost effective. So, the group decided to move on and start brainstorming again.
After exploring new ideas, a cam design became a great option. The cam mechanism(4th picture to the right) used in a ski binding consists of a cam which can be in one of two positions: “open” and “closed.” This would allow for the ski pole to be released if Audrey fell as the cam would open due to the abnormal direction of force put on the pole and the prosthetic from the fall. In order to make sure the grip strength is adjustable, a bolt is used to compress the spring that controls the grip strength. So, Audrey can just loosen or tighten the bolt depending on how tight she wants her grip to be. In imitating this kind of mechanism, the device would be more dependable, easily adjustable, and more simplistic.
The final design and cam mechanism is seen here. The fingers are the bulk of the hand, and prevent the forward motion of the ski pole. The thumb acts as the physical contact point on the pole that will keep the it in place, as well as releasing the pole during a crash. Both the thumb piece and the bulk of the hand/fingers were 3D printed. The plunger acts as a contact between the spring and the thumb to allow the transition between the open and closed positions. The spring provides the force that must be overcome while going from the closed to open position. The back plate allows the follower to lock in and then screw into the hole that the spring is in, adjusting the force needed to open the thumb by creating more or less compression in the spring. Finally, the wrist block is the connection point between the user and the prosthesis. It is angled to mimic how a hand holds a ski pole.
– A silicone grip that goes around the ski pole will need to be designed in order to fit into the Prosthetic perfectly in a manner so the pole doesn’t rotate or slide up and down in the skier’s hand. This is important because ski racing poles are a specific shape and can’t be rotated like regular ski pole.
-The hand will be machined out of metal using a CNC machine. The process will be documented and iterated to make it repeatable in the future.
-The metal hand will then be used for final testing on the ski slope by our team and by Audrey to make sure it is comfortable and can handle her specific set of skills and strength.
-After this a universal handle will be created to allow the hand to be used on any ski pole
Meet the Team
My name is Tyler Blomster and I am in my 5th year of mechanical engineering at Mines. I am originally from Mckinney, TX but love living in the mountains in Colorado. I enjoy fly fishing, golfing and snowboarding in my free time and try to do it as much as possible. I love all sports and I am a pitcher on the mines varsity baseball team. I plan on pursuing a career in professional baseball after I graduate in May 2021.
Christian Palacios is a graduating Senior in Mechanical Engineering at Mines. Outside of HCDS, he has dedicated time and effort towards the Peer Mentor program as a Lead Peer Mentor, and ASME as the Treasurer. Christian is from Taft California, and enjoys watching sports, staying active, and picking up new skills.
I am a mechanical engineering student at Colorado School of Mines. I am part of the Kappa Sigma Fraternity and I am the vice president of the CSM club ski team. I enjoy working hands-on to create and design. I love the outdoors and my favorite hobbies are skiing and mountain biking.
My name is Erin Sweeney and I am going to be graduating in May 2021 from Mechanical Engineering. I am becoming an engineer to help better people’s lives. I have grown up in Colorado, learning it’s hiking trails and ski slopes. I love being outside but I also love snuggling up with a good book and my dog.
My name is Ryan Fidel. I am originally from Santa Barbara, CA and currently, I am a senior studying mechanical engineering. I will be continuing my education next year, working towards a master’s degree in mechanical engineering with a focus on biomechanics. Outside of academics, I am also on the Mines Wrestling team. I was the starting 157 pounder last year and helped mines win its first outright RMAC title in program history.
Lindsey Nunamaker is a senior majoring in Mechanical Engineering and minoring in Biomechanical Engineering. She is from Cambridge, Ohio. She wanted to be a part of the HCDS because she loves to help people and this studio aligns with the type of work she hopes to do professionally. Outside of the classroom she enjoys spending time with her dogs, skiing the Colorado mountains and traveling to see new places.
I am in my fifth and final year at Mines, born and raised in Bakersfield California, love anything that is outside in God’s creation, and after I graduate in May I will be working for Kiewit as a Field Engineer.