Prosthetic Arm Force Reducer Team 1 – Halliday's ... - Ohio University

Once the design of the system was underway, we realized that it would be nearly impossible to
design the system to fit within Tim’s current forearm without numerous problems. Also, we
would not be able to remove his forearm due to him needing it in his everyday life. Therefore
our next step of the project was to find and order a forearm very similar to Tim’s so that we
could put our system within that forearm instead.
Our group met with Tim numerous times throughout the designing and manufacturing processes,
where we took numerous measurements of Tim’s current forearm, cable travel, wall thickness,
etc. enabling us to properly order a similar forearm from a prosthetic manufacturer. Tim pointed
us in the direction of Yankee Bionics, a prosthetic manufacturing company in Akron, Ohio that
he worked with in the manufacturing of his current prosthetic device. The company was nice
enough to donate a slightly used forearm for the use in assisting Tim. Once we received the
forearm, we finalized all of the necessary measurements and began manufacturing the
mechanical advantage system, and completed the installation. Once our system was bolted
within the forearm, the cable travel was then established. A small hole was then drilled through
the exterior wall of the forearm, allowing the cable to be attached to the hook.
Once the manufacturing was completed, the only step left in our project was to let Tim test the
overall system and see how it performed. Where, after visiting Tim and allowing him to test the
system, he was overwhelmed with how much easier our system was to open than his original
prosthetic.
7.0 Final Design
7.0.1 Introduction
A prosthetic arm force reducer was manufactured by designing a pulley mechanical advantage
system housed within the hollow forearm section of the prosthetic with a 10A60 Otto Bock
prosthetic terminal device.
This design emerged after extensive interaction with customers, primarily Tim Lang, who
precisely met the demographic we specified at the beginning of the project. Not only did this
interaction help us to identify legitimate customer needs and eliminate unnecessary design
features, but it also allowed us to take real measurements, which we used to confidently refine
the newly-emergent subsystems.
Through application of DFMA design principles, we have designed the mechanical advantage
system to meet customer expectations, be readily manufactured, easily installed, minimally
intrusive, and reasonably simple to analyze. This section concerns the implications of our design
decisions.
7.0.2 Impacts/Effects
The first major impact concerns the choice of hook that we are using. The customer’s current
hook utilizes rubber bands to supply the closing force of the hook. As a result, the customer has
resorted to attaching a large number of rubber bands in order to achieve the grip strength that can
be accomplished by using the springs available with the Otto Bock Model A60. The two-load
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