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Hand For Brayden


 “Helping one person might not change the whole world, but it could change the world for one person”

Brayden Benfatti is a three-year-old from Pueblo, Colorado who was born with congenital malformations on both hands. He has had several surgeries on his right hand to allow for the full use of his index finger, and better use of his right hand, but he effectively has no fingers on his left hand. He is very active and loves to be outside. Brayden and his family want more options for him to stay active and happy, and Brayden needs the opportunity to experience the same childhood activities as his peers. 

The goal of this project is to help Brayden be able to ride a bike through the assistance of a prosthetic that will allow him to grip the handlebars of a bicycle with his left hand.  Since Brayden is young, he will need to have a prosthetic that is adjustable and will grow with him. The solution the team designed is an adjustable socket that Brayden could insert his left arm into, which is attached to a magnetic passive attachment/detachment device which is clamped to the handlebar of the bike.  The socket size adjustment will utilize a BOA cable system which is a tensioning device that will route a 1mm thick plastic-coated steel cable around the circumference of the prosthetic sleeve attachment and allow the sleeve to be tightened on to Brayden’s arm to secure it in place by tightening the cable with a rotating torque dial. He will be able to turn the knob of the BOA cable himself and secure his arm into the socket. This allows him to adjust it to the correct tightness depending on his wrist and forearm’s size. The attachment portion of the prosthetic to the bike utilizes a magnet to release the prosthetic from the bike easily in the event he falls off the bike but still securely keeps Brayden attached to the bike.  

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Topic: Hand for Brayden

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Team Members

  • Ty Ridings
  • Janae Oden
  • Garett Brister
  • Elissa Himes
  • Nick Thompson
  • Chris Wilson

The Client

  • The Benfatti Family


Project Advisor(s):

Dr. Chelsea Salinas & Dr. Joel Bach

Donations Made by:


Elevator Pitch

Every kid deserves the right to be just that, a kid! One of those childhood memories that everyone has is of riding their bike with their friends. Brayden Benfatti deserves to have those same memories. Our HCDS team of 6 has worked to help enable Brayden to make these memories. We have created an adjustable bike handlebar attachment that is not only is easy to use, but it also is very safe. As Mines students this was an amazing experience to really explore and gain a deeper understanding of prosthesis.  

To use this prosthetic all the user must do is attach the base of the attachment to the handlebar of the bike and attach the adjustable socket to their arm. By utilizing the strength of magnets and geometry, the two parts connect easily. To secure the adjustable socket all the user must do is twist the BOA cable dial, located on the top of the prosthetic, until the device feels secure. The product has gone through several tests and re-designs to make sure it was suitable for our client’s needs. 


Design Approach

There were many things to consider when creating this prosthetic so it would be safe and last Brayden a long time. Since Brayden is young, he needed to have a prosthetic that would be adjustable and grow with him. The prosthetic also had to account for the length difference in his arms. The attachment portion of the design also had to have a passive detachment mechanism that would release from the bike (like a hand would) in the event of a crash to prevent any injuries related to the prosthetic. This passive detachment method should also act as a passive attachment method that would guide the prosthetic sleeve onto the bike since Brayden has poor force modulation in his left hand. Additionally, since Brayden also has limited feeling in his left hand, the team had to ensure the prosthetic would not cause any skin damage or breakdown during use.   

After meetings with the client and Brayden’s occupational therapist (separately), the client was against that idea at first (top right image). More designs were created (slideshow). After a meeting with both the client and occupational therapist again and proposing the alternate designs, it was decided that the original idea was best. From that point moderate fidelity prototypes were created in order to gauge the client reaction as well as gain feedback on the size of the prosthetic and comfort of the foam insert. Three were sent each with different inserts so that the client could decide which Braydon liked best. PETG was chosen for the 3D print material as it has good layer adhesion properties (giving it closer to isotropic performance) and ability to withstand outdoor thermal loads and UV radiation better than other typical 3D printed materials [1].

The final prototype is composed of two main subsystems: the socket for Brayden’s arm and the clamp to the bike’s handlebars. These two parts are connected by a magnetic attachment point. The magnetic attachment point detaches readily in the event of a crash but stays attached to the bicycle during normal use. It consists of one 10-lb disk and one 15-lb disk magnet, each epoxied into a 3D printed PETG casing with conical walls. The magnets are very hard to pull apart when force is applied to them perpendicular to the magnetic connection, but when pulled apart at an angle (with the help of the conical walls) the magnet easily detaches. 

The sleeve is based on a previous HCDS project, the adjustable Boa sleeve, and consists of a 3D printed PETG conical socket with a Boa cable as a means of adjusting the circumference of the prosthetic sleeve to fit Brayden’s arm. The insert covered in a soft moleskin (to prevent any chafing or skin breakdown on Brayden’s hand.

Bicep Design

Shallow Socket & mAGNETIC SOCK

Wrist Support

Various Mounts

Design Solution

Model simulation was conducted using the SOLIDWORKS (SW) Finite Element Analysis (FEA) package for static studies. The team approximated Brayden’s weight at 37 lbs.  based on his current weight provided by his mother.  For the FEA, the team assumed Brayden will apply at maximum 25% of his full body weight to the prosthetic. The reason for using 25% of the client’s body weight as an approximated load was due to previous discussion with project advisors and research done by the team [2]. The team found that biomechanics studies have shown typical handlebar loads to be 15-20 pounds for a full-grown rider under normal riding conditions [3]. This means that the typical handlebar load is about 5-10% of the average, adult rider weight [3]. Based on discussions with Brayden’s occupational therapist [4], it is evident that he may modulate his left arm with excessive force due to the lack of sensory feeling in his left arm, and in order to add in additional factor of safety, the team chose to approximate the load on the prosthetic as 25% of Brayden’s body weight. 

In the table below, all FEA results can be found showing minimum Tresca factor of safety (FOS) with respect to yield (using yield strength of 7250 psi for PETG). All parts were printed following best practices – meaning that the layers were printed in an orientation parallel to the direction of anticipated tensile loads and perpendicular to the direction of anticipated bending loads [5]. For all loading conditions and socket types, the FOS is well above 1 (where failure would occur) when compared to the isotropic yield strength. Since Fused Deposition Modeling 3D printed parts are typically weakest when the adhesion between different layers is stressed, it is safe to assume that a better estimate of part safety is given by analysis of the typical layer adhesion strength rather than the strength of the isotropic plastic. Typically, the strength of layer adhesion in FDM 3D printing is roughly 50% the strength of the isotropic plastic (or plastic in the direction perpendicular to the layers) [6].  Therefore, we must further reduce the FOS by using the 50% strength rule for layer adhesion when compared to typical isotropic material strength. This means that if the part were to fail due to poor layer adhesion, it would still have a minimum FOS of 4 for the worst case seen below in the table (vertical load on the socket). This FOS is acceptable to the team as research shows an FOS of 3-4 would be required “for use with materials where properties are not reliable” such as with FDM 3D printed materials [7].  

Load Configuration Handle Bar Attachment Min. Tresca FOS   Socket Min. Tresca FOS  
Vertical Load 170 8.2
Compressive Load 110 80
Horizontal Load 74 12

Along with the SOLIDWORKS verification, tests were performed to validate these claims. The final prototype was tested by Ty Riding’s son. This was due to the inaccessibility to Brayden (pandemic). As seen in the video above Ty’s son is show riding, crashing, and fit testing the prototype. In the left video below, you can also see Ty’s son testing the range of motion of his arm in the socket by measuring the angle he can turn the front wheel without the socket binding on his arm. In the right video below, you can see how the magnets work as a passive attachment mechanism and guides the socket onto the correct placement on the bike. These tests validate that the teams design works, is safe, and is easy to use.  



Next Steps

A client’s needs table that was created at the beginning of this project had three Demand/Wishes: A passive attachment method for prosthetic to handlebar, an adjustable socket, and some way to account for differing lengths between Brayden’s right and left arms. The device that the team has come up with meets each of these client needs/expectations.  Next steps with this project would be more testing with Brayden. Since Brayden is young and has experienced several surgeries, the team has encountered several setbacks with testing. These setbacks include the fact that Brayden recently had a surgery that he was recovering from most of the semester which prevented any testing, and the fact that experiences of these surgeries has led to Brayden being hesitant to having anything tightened around his arm.  Going forward with this project, a re-design option using different colors and kid-friendly visual modifications could be used to make the attachment more appealing and less daunting. 


[1] 3DPROS, “Optimizing Strength of 3D Printed Parts,” 3DPros, 2019. [Online]. Available: printed-parts. [Accessed: 02-Mar-2021]. 

[2] M. D. Claudia Boyd-Barrett|Medically reviewed byPaul Young, “Average weight and growth chart for babies, toddlers, and beyond,” BabyCenter, 2020. [Online]. Available: [Accessed: 02-Mar-2021].  

[3] Turpin, Nicolas & Watier, Bruno. (2020). Cycling Biomechanics and Its Relationship to Performance. Applied Sciences. 10. 4112. 10.3390/app10124112. 

[4] Jen Pascoe,  private communication November 2020.  

[5] B. Hudson, “How to design parts for FDM 3D printing,” 3D Hubs, 2020. [Online]. Available: [Accessed: 02-Mar-2021].  

[6] Y. Zhao, Y. Chen, and Y. Zhou, “Novel mechanical models of tensile strength and elastic property of FDM AM PLA materials: Experimental and theoretical analyses,” Materials & Design, 02-Aug-2019. [Online]. Available: [Accessed: 02-Mar-2021]. 

[7] Engineering ToolBox, “Factors of Safety,” Engineering ToolBox, 2010. [Online]. Available: [Accessed: 02-Mar-2021].  


Meet the Team

Ty Ridings

Ty Ridings is a senior in the Mechanical Engineering department at Mines with plans to finish his undergraduate degree in December 2021. Ty intends to intern for a second term with an aerospace company this summer and plans to hire on fulltime with their mechanical engineering department upon graduating. Ty enjoys spending time with his wife and 4-year-old son, snowboarding, mountain biking, backpacking, and working on his parents ranch back home in southern Colorado.  

Janae Oden

I live by the motto “Ready Fire Aim”. If you spend to much time trying to get things right you’ll never get it done. Fail and recalculate. I am senior graduating in May 2021 with a BS in Mechanical Engineering and minor in Computer Science: Robotics and Intelligent Systems. I am an overall weirdo with a Nightmare Before Christmas obsession. I enjoy baking and doing crafts in my spare time.

Garett Brister

Garett is a graduating senior in Mechanical Engineering. He is an avid mountain biker and has enjoyed racing for the Mines club cycling team. His primary career interest lies in the aerospace industry, and after graduation he plans to continue his internship in the space industry before continuing to graduate school at CSM. 

Elissa Himes

Elissa is a graduating senior in Mechanical Engineering with a minor in Robotics. After graduating, she plans to complete an internship in the aerospace industry before continuing her education at Mines with a master’s degree in Robotics. Elissa enjoys mountain biking and hiking in her free time.  

Nick Thompson

Nick is a senior in mechanical engineering with a minor in electrical engineering. He plans on returning to Mines in the Fall to complete a master’s degree in mechanical engineering, with an emphasis on solid mechanics and manufacturing. He enjoys skiing, hiking, and camping, among many other activities. 

Chris Wilson

Chris is a senior Mechanical Engineering student graduating in December 2021. His post-graduation goals include continuing to work at a local 4×4 van conversion shop, and eventually starting his own company doing the same thing. When not in class, Chris can be found climbing outside or skiing anywhere with good snow.