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Project 3b: Prosthetics for Percussion (ETSU)


This endeavor was crafted to cater to the unique needs of a middle school student navigating life with bilateral amputation. Our foremost aim was to craft a specialized prosthetic arm, intricately engineered to facilitate her engagement in percussion activities with a perfect fusion of finesse and skill. With exacting attention to detail, we were required to harmoniously integrate drumsticks into the design, enabling her to pursue her musical passion with confidence. Yet, our aspiration transcends mere functionality; we sought to give her a profound sense of empowerment, nurturing the confidence and elegance required to wholeheartedly embrace her love for percussion. 

Team Members: Micah Wilson – Austin Elliott – Landon Deaton

Problem Statement

Our client, a middle school girl with bilateral amputation, desires to actively participate in percussion within her band class. Our challenge was to develop a prosthetic arm solution that allows her full engagement while addressing the need for ease of use and long-lasting performance. Our goal was to design a prosthetic arm equipped with a drumstick attachment that seamlessly integrates into her activities, providing convenience and robustness without sacrificing usability. 

Design Specifications

The design specifications entail creating a prosthetic arm solution that addresses the user’s needs effectively. This involves implementing a secure and adjustable drumstick holder mechanism to ensure a stable grip during percussion activities. Additionally, customization of the prosthetic arms’ dimensions is crucial to provide a snug yet comfortable fit tailored to the user’s arms. Lightweight materials and ergonomic contours are essential for promoting ease of wear and natural movement, facilitating intuitive use. Moreover, durability is paramount, necessitating the selection of robust materials and construction methods to withstand daily use and repetitive motions associated with percussion activities, ensuring long-lasting performance. 

Background Research

After discussing with one of our ETSU professors, we found that TPU would be the material of choice for this project. This is because it is safe for human contact while also being very durable and flexible. During prototyping we can use regular PLA for testing. This is because PLA is our cheapest option when it comes to prototyping. There is not a lot of prosthetic arm designs when it comes for attaching drum sticks. Although, we were able to find some similar ideas to help us navigate through this task. We have attached three similar but different designs below.

Concept Design 1

For our initial design concept, we drew inspiration from latching strap systems to secure the prosthetic to the arm. Functioning similar to ratchet straps, pulling the lever tightens the strap incrementally. Such mechanisms are prevalent in equipment like wakeboarding, snowboarding, and motocross boots.

Concept Design 2

Our next innovation adopts the BOA system, renowned for its multiple attachment points interconnected by a cable. Through a simple dial rotation, the cable is tightened, facilitating a secure clamping of the prosthetic. Widely embraced within the field of prosthetics, this system offers both reliability and adaptability.

Concept Design 3

This concept is similar to Concept Design 1 in the manner which it straps to the arm. However, the buckle strap is replaced with a velcro strap and latch. Using velcro straps provides an easier process for tightening and securing the arm, but can be a less durable alternative over time.

Selected Concept Design

We feel as if best final concept design system is to utilize the BOA “CLICK” design system. This is because it would fasten the prosthetic arm most securely while also distributing the compression around the patients arm evenly. We also believe the RAM mounting system is the best option for mounting the drum stick. This is because it gives the user the most adjustability for the angle at which the drum stick is fastened.

Decision Matrix

Overview of Selected Design

The chosen design utilizes TPU material, offering both durability and flexibility for the prosthetic. Additionally, it incorporates a versatile ram mount system, providing nearly 360-degree mounting possibilities for the drumstick. This design also adapts an athletic sleeve on the inside of it to fit to the users arm better while also providing comfort.

Describe Design Details

Our design utilizes ESUN 95A TPU material, ensuring both durability and flexibility for the prosthetic. This specific TPU, known for its reliability, enhances the prosthetic’s performance. Additionally, it incorporates a versatile RAM mount system, offering an array of attachment options and nearly 360-degree mounting possibilities for the drumstick, ensuring optimal customization and convenience.

To further enhance user experience, the design incorporates a Uline cooling arm sleeve on the interior, optimizing fit and comfort. Crafted with the user’s preferences in mind, both the TPU material and sleeve are elegantly black, meeting the user’s aesthetic desires. The integration of the athletic sleeve not only improves the fit but also enhances comfort during extended use.

Engineering Analysis 1

When searching for the right material to print for the arm we had ideas of 3 different materials, PETG, PLA, and TPU. After looking into how we wanted to design the arm we found that the TPU material we have would be the best material for this application. TPU-95A is an exceptional choice for crafting prosthetic arms due to its versatile properties tailored for functionality, comfort, and longevity. The material, eTPU-95A, has great elasticity properties that are not easy to deform and allow for comfortability and confidence for the user in daily activities. This material also has a high tear resistance and wear resistance which allows for use of its application without hurting its performance. Giving the user a functional and comfortable piece of equipment that will have properties of high durability is why eTPU-95A makes a great option for a prosthetic arm. 

Engineering Analysis 2

Using the technical data sheet for the material we chose allowed us to obtain a sense of how durable and applicable our material was. With the mechanical properties of the tensile strength and elongation at break. We can infer some information such as the material’s strength, ductility, and brittleness vs ductility. From the given information of our material, we can infer that our material is highly ductile. With the tensile strength and a high elongation at break of 800% of our material, we can see that our material would be able to stretch extensively without fracturing. This makes our material durable enough for the daily use of the arm  

Engineering Analysis 3

When looking at the thermal properties of eTPU-95A, we can see that they are not given in the technical data sheet for our brand, but we can use the general values found by looking into the thermal properties of TPU-95A. These values range from a minimum value of40 to –4 degrees Fahrenheit which could cause the material to be brittle. The maximum temperature values of 248 to 302 degrees Fahrenheit. Experiencing these temperatures could cause the material to soften or deform, affecting the structural integrity and performance of our part. Knowing that the user will not be using the arm in these environments, it’s safe to say that the selected material will not have any problems caused by the thermal properties. 

CAD Drawings

Bill of Materials

Instructions for Safe Use

For safe use of the prosthetic arm attached to a drumstick for playing percussion instruments, it’s essential to ensure a proper fit and secure attachment of the drumstick to the designated mounting point on the arm. The user should maintain balance and stability while practicing controlled movements to prevent strain or injury. Prior to extended use, warm-up exercises and stretches can help prepare the muscles and joints, reducing the risk of fatigue or discomfort. Regular monitoring of comfort and environmental conditions is advised, with attention to maintenance and cleaning after each use. Additionally, it’s crucial to watch for signs of skin irritation and ensure that the prosthetic arm is not too tight, as this could restrict blood flow and cause discomfort. Consulting with healthcare professionals or prosthetists for guidance and assistance in case of any issues is recommended.

Project Summary/Reflection

There are multiple design ideas with the arm that we printed. However, the design matrix we made aided in our decision. Therefore, the design we chose was proven to be the safest and most practical and useful. Due to our remote position on this project, we utilized the measurements provided by the TTU team assigned this project and were able to formulate our own design. With the help of peer advice and own own research conducted at ETSU, the proper material was chosen for the arm in terms of thermal, mechanical, and material properties. We would like to thank everyone that helped with our project in any way and hope that what we achieved with this project provides our client with more than adequate help in their request given our remote position.


2024 Spring