Golf Prosthesis Final Design Report (P11)

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Specification Verification

 Jim Taylor trying on our “golf cuff” prototype design for the first time
Figure 31. Jim Taylor trying on our “golf cuff” prototype design for the first time.

Our final two designs met each of our desired specifications such as weight, cost, ease of use, and functioned to allow the user to play golf independently. After discussions with Jim, we discovered that both devices accomplished many of our desired functions. Although Jim was uncomfortable actually hitting a golf ball with our devices he did mentioned that they were both simple and easy to understand. In addition, Jim was easily able to put on and take off both devices. In regards to weight, neither device exceeded 1 pound, which met our initial design requirement of 2 pounds or less. Finally, both devices were easily manufactured using the rapid prototyping machines in the ME lab were under our initial requirement of $200.

Conclusion

What we learned

The golf swing is a very complex movement, especially for an upper extremity bilateral amputee. Because most upper extremity bilateral amputees use body powered prosthetic devices flexing the shoulders during the golf swing becomes a big concern. Flexing the shoulder blades puts tension of the cables that connect to the prosthetic hooks to the body of the user, causing the hooks to open. This same movement is created during the golf swing. In addition, through personal testing we realized that the forces generated at impact can also cause the hooks of the users prosthetic to open (i.e. the normal force of the ground against the club generated at impact creates a resultant downward force on the hooks causing the hooks to stretch open).

Everyday prosthetic arms have three key limitations that need to be addressed in future iterations of these golf prosthetic designs:

  1. Grip pressure. Everyday use prosthetic arms have significantly lower grip strength (1-2lbs) compared to Jim Taylor’s golf arms (5-6lbs of grip force). We’ve found that by adding sheep castration bands to the hooks, however, that the grip pressure can easily be increased to 5lbs.
  2. Durability. Jim’s hooks are made to be very durable. Instead of your standard aluminum hooks, Jim has stainless steel hooks. In addition, Jim uses high strength cables, as opposed to the standard strength cables, which allow him to open and close his hooks when his grip pressure is further increased.
  3. Flexing elbow joint for above the elbow amputations. Jim’s right prosthetic functions very much like a ratchet, which can be unlocked to maneuver the elbow into position and then locks into place when tension is relieved from the cable. This function allows the user to hinge their artificial elbow at will, however, during a golf swing this function can be inadvertently triggered and can cause the user to lose control of the club and potential injure themselves.

Successes

Through this project we created a golf adaptation form bilateral upper extremity amputee users that met many of our key design requirements. Our design is simple and easy to understand, it is easy to use and to take on and off of the club, and most importantly helps the user play golf independently, without the assistance of others. In addition, our designs are durable, function well by means of securing the club in place prior to and during impact with the golf ball, they are adjustable, and are also drastically cheaper to manufacture than any other product currently available on the market. According to Jim Taylor after his visit, “This is the best attempt I’ve seen at creating at creating an adaptive device for a bilateral amputee. . . You guys have almost done in a matter of months what took me 10 years to do.”

Comparison between Jim Taylor’s prosthetic golf
Table 5: Comparison between Jim Taylor’s prosthetic golf arms and our two final designs based on critical criteria such as cost, weight, and time required to put on and take off the device.
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