Introduction: The Lazarus Arm
I would like to start by saying thank you for taking an interest in my project. My name is Chase Leach and I am a senior in the WBASD S.T.E.M. Academy. This project is a submission for the Butwin Elias Science and Technology Award 2019-2020. The Lazarus Arm is a unique prosthetic design in so far as it uses only materials that could be found around the house with exclusion to the motors and Arduino Uno which were taken from previous projects that I designed. This year is that I don't have access to a 3D printer so the design of the arm was a little tricky because I was working with cardboard for a lot of the structural components of The Lazarus Arm. The goal of this project is to make a working model that can demonstrate the concept of my design. Considering the limited resources, I think the final design turned out pretty well. Thank you for the opportunity to be involved in this competition. It has allowed me to have so much fun. This competition has created cherished memories for me. Designing The Lazarus Arm and overcoming the challenges it presented has taught me a lot. Thank-you for your time and consideration and without further adieu I hope you enjoy.
All of the supplies that I used were already available to me, however I have included a list of the theoretical costs next to the materials.
Supplies & Costs
- Cardboard Box 12 x 12 x 16 ($ 0.82)
- Hot Glue Gun ($ 4.99)
- Hot Glue Gun Sticks ($ 3.97)
- Scotch Tape ($ 6.80)
- 4 x Paper Towel Rolls ($9.98)
- 2 x Toilet Paper Rolls ($6.99)
- (Amount: 8) MG90S Tower Pro Servo Motors (Total Cost: $23.99)
- 1 x Arduino MEGA 2560 R3 Board (Total Cost: $12.95)
- Wire ($8.76)
- ProtoBoard ($5.99)
- Straws ($2)
- Ribbon ($ 3.29)
Step 1: Time Required for Construction
The time that was spent on this project flew by while working on the design and construction of the arm. The portion of the project that I particularly enjoyed was the design of the elbow joint as it utilizes a method of joint construction in robotics that uses a pulley system to increase the amount of work output. The design of The Lazarus Arm took a total of 63 hours which included research to find the most effective way to make the final design as cost effective as possible. The assembly of The Lazarus Arm took a total of 15 hours and a lot of hot glue. Testing was interesting as the initial design for the prosthetic had a tendency to stall as a result of the friction created by the dental floss used in the pulley system in the elbow. All that I did was decrease the diameter of the wheels and it worked. The testing phase took a total of 12 hours. The programming phase of the project took me a total of 10 hours which is not including the time that it took me to touch up my C++ skills.
Step 2: S.T.E.M. Applications
Science- In my project, science is involved in the design of the protoboard design which allowed for power to be distributed between the servo motors in the design. It also finds a role in the physics involved with the design of the structure of the arm. More, specifically the design of the pulley system in the elbow joint which gives the arm a considerable amount of mechanical advantage allowing the arm to lift more than it could have otherwise, courtesy of Archimedes.
Technology- The technological aspect of my project came into play when I was coding the movement of the prosthetic arm using C++. It also came into play when I was installing the motors and Arduino board.
Engineering- Engineering came in to play when I was designing the the palm, the fingers, the thumb, the wrist joint, the forearm, the elbow, and the upper arm. It came into play in the redesigns, the identification of problems when they arose, and the solutions I came up with for the problems.
Mathematics- The math involved in the creation of the hand came into play when I was looking for the correct anatomical proportions of the arm segments. It also came into play when I was looking for acceptable size adjustments for the diameters of the wheels in the pulley system joint. I also used mathematics during the calculations that I made for the number of wheels that I'd use in the elbow joint to make the arm capable of moving under the weight of a coffee mug. It also came into play with the calculation made through the application of Ohm's Law for the circuit design and required voltage input.
Step 3: Engineering Design Sketches
The sketches that I have provided include my initial design for The Lazarus Arm. I believe that the design manages to remain sturdy enough for everyday use while remaining considerably cost-effective.
Step 4: Forearm Construction
I do mention the quantity and dimensions of the cardboard pieces in the video that I've attached, however I will also include a list of the pieces, dimensions, and quantities here. The list that I have included bellow was written after the construction of the forearm so if there are any discrepancies between it and the video, I would use the list.
- 2 x Paper Towel Rolls
- 4 x Pulley Arm
- 2 x Circles With Diameter Of 3 inches
- 8 x Circles With Hole And Diameter Of 2 and 3/16 inches
- 4 x Modified Paper Towels Rolls With Length Of 1 and 7/8 inches
- 12 x Circles With Hole And Diameter Of 1 and 6/8 inches
- 1 x Wooden Dowel Diameter Of 3/8 inch and Length Of 4 inches
- 2 x Rectangle Of 7 and 3/16 inches Length and 3 inches Width
- 2 x Rectangle Of 7 and 3/16 inches Length and 1 and 7/16 inches Width
- 9 x Square Of 1 and 1/2 inches in Length and Width
- 12 x Right Triangles With 1 and 1/2 inches Base and Height
Step 5: Upper Arm Construction
The upper arm construction is rather simple yet sturdy. In order to build this part of The Lazarus Arm, you're going to need some parts. I have included a video explanation of all of the pieces required, however I wanted to make sure that the explanation is comprehensive enough to be followed at home so I included a list bellow.
- 4 x Rectangle (5 inches in length and 3 inches in width)
- 4 x Rectangle (5 inches in length and 1 and 1/2 inches in width)
- 2 x Circle (3 inches in diameter)
- 2 x Modified Paper Towel Roll (1 inch in diameter and 1/2 inch in length)
- 9 x Square (1 and 1/2 inches on both sides)
- 8 x Right Triangles (1 and 1/2 inches for base and height)
- 2 x Large Arch Shape With Two Holes
- 4 x Rectangle With a Hole (3 and 1/2 inches in length and 3 inches in width)
- 4 x Circle With Hole In Center (1 and 1/2 inches in diameter)
- 6 x Circle With Hole In Center (1 inch in diameter)
- 2 x 1/2 inch Shorter Paper Towel Rolls Cut Down The Length In The Center Of One Side
- 1 x Wooden Dowel (4 inches in length and 3/8 inch diameter)
Step 6: Wrist/Palm Construction
The wrist/palm of The Lazarus Arm was actually one of the hardest parts of the design, other than the pulley system in the elbow. The part of the design that I struggled most with was how to create a design that would be capable of rotation without sacrificing any of the structural stability of the design. When I came up with the solution to my problem I initially thought that I'd be too simplistic to work, however when I put it into practice it held up to the tests that I administered. The parts for the construction of this part of The Lazarus Arm are listed bellow.
- 6 x Palm Template designs which should be sized up or down depending on The User (about 3 and 1/2 inches in length and 3 inches in width)
- 2 x Rectangle (3 inches in length and 2 and 1/2 inches in width)
- 2 x Rectangle (3 inches in length and 1 inch in width)
- 6 x Right Angle Triangles (height and base of 1 inch)
- 1 x Circle (2 and 5/16 inches in diameter)
- 2 x Circle With Small Rectangular Cutout (2 and 5/16 inches in diameter)
- 1 x Wooden Dowel (3 inches in length and 3/8 inch in diameter)
- 10 x Arch Design With Hole (about 1 and 1/2 inches in length and 1 inch in width)
- 2 x Toilet Paper Rolls With Notch Cutout For Hand Template
Step 7: Finger/Thumb Construction
The finger and thumb designs are almost exactly the same for simplicity's sake. The key differences are that the thumb has only to joints while the fingers have three and the thumb is angled similar to a human hand in anatomical position. I have attached a video explaining the construction of the fingers and thumb. The pieces that are displayed are rather simple to create, however quite a few need to be made for these parts.
- 48 x Larger Arches With A Hole (1 and 1/2 inches in length and 1 and 1/4 inches in width with hole located 1 inch from the right and 1/4 inch down)
- 13 x Smaller Arches With A Hole (1 and 1/2 inches in length and 1 and 1/2 inches in width with hole located 1/2 inch from the right and 1/4 inch down)
- 13 x Arch (3/4 inch in length and 1/2 inch in width)
- 6 x Straws (3/4 inch in length)
- 5 x Straws (1/2 inch in length)
- 4 x Straws (1/4 inch in length)
- 4 x Straws (1 and 1/2 inches in length)
- 5 x Ribbon (12 inches in length)
Step 8: Testing
The goal of the testing phase of the Lazarus Arm is to prove the concept as feasible.I have attached a video which I believe proves the concept of my design. I think The Lazarus Arm works pretty well, considering the materials used to create it.
Step 9: Possible Future Improvements
Looking at the project as a whole, I'm pretty happy with the final product. The only thing that I'd love to do is to see if I can create a 3D print of the parts that I made out of cardboard in order to see how it holds up under even greater amounts of pressure. Other than that, I'd like to take the time to improve the aesthetics of the arm. I would also like to see if I can continue to work on this prosthetic arm design to see if I can test the design in some everyday circumstances.
Step 10: Closing Remarks
I would like to express just how happy I am with the final design of The Lazarus Arm. It has proven to be viable for use in some everyday tasks and is surprising functional considering the materials that it is made from. I would like to take a moment to thank the Iseman Foundation for the opportunity to work on projects like this for the last four years. It's been incredibly educational and fun. This competition is one of the reasons why I'm pursuing a mechanical engineering major. It has been incredible to be a part of this over the years and I could never express just how grateful I am, thank you.