Project Based Deep Learning Activity
Spring 2019
Student name (s): Erick Estrada
Instructor name: Jacob Swanson
ENGR 452-61 (000154) Adv Tech Elec: Manufacturing processes: parts fabrication
methods
ENGR 333-61 (000138) Mechanical Core: Manufacturing processes
Date: 10 May 2019
JUSTIFICATION:
This project-based learning activity provided a learning opportunity in the fields of both
machine shop and manufacturing processes while adding value to the project design. The
participant used machine shop and manufacturing processes that were gained from the
technical competency and applied them to the project design that enabled a required
component to be designed and manufactured.
A belt tensioner was designed, manufactured, assembled, iterated, and evaluated for
effectiveness. This activity has resulted in the depth of knowledge for the participant. New
methods of designing, manufacturing, and assembling were learned i.e designing within
Solidworks software, prototyping via 3d printing, and assembling using new techniques such
as usage of thermoset tapered threaded inserts. The Participant applied their knowledge
gained from the competency in the attempt to solve a real-world problem to make informed
design decisions while solidifying their knowledge in the subject areas described.
Implementation
Belt Tensioner
The belt tensioner below is for the transmission serpentine belt. It maintains a constant pressure on the
belt by using two springs that are compressed and decompressed via two 3/8-16” socket head cap
screws. As you torque the bolts in a clock-wise orientation, it loses contact with the belt. As you torque
the bolts in a counter clock-wise orientation, it is pushed up towards the belt and increases
tension. The assembly brackets on the left and right of the wheel are simply to prevent flexing of the
tensioner side wall during the press fitting of the dowel pin through the side wall and through the wheel,
they do not stay on during operation of the engine. This custom design was implemented over a more off
the shelf and proven solution due to design constraints that included a limited working space and the
inability to mount to the sidewalls as it could misalign the torque transducer.
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Figure 9
Key Failures and Turning Point
Another failure occurred in the design and implementation of the belt tensioner. The design constraints
were as follows: fit within 3.985” x11.5” x 4.250” (LxWxH), not mount to sidewalls to avoid
misaligning the torque transducer, low friction bearings that can reach at least 4,000 RPM’s constantly,
and a wheel with no sidewalls. An effect of the requirements was that common and proven off the shelf
components could not be installed. This led to an iteration process in search of something that worked.
In the first iteration the wheel that it was designed around had too much friction. It was visible and
obvious that the wheel would introduce significant friction into the system causing unnecessary losses.
In the second iteration excess time was spent searching for a wheel that met the following design
constraints: No sidewall, low friction, can run in excess of 3400 rpm’s, and must list the specific shaft
ID in the manufacturer spec. Due to time, this effort was abandoned and a skateboard wheel bearing in
tandem with a 3d printed wheel was used as a temporary implementation. In the third iteration feedback
was given that the design should be as close to off the shelf as possible. In this discussion the sidewall
constraint was eliminated and that made the ordering of an ideal idler pulley simpler. It was agreed that
the method of constraining the shaft be a keyway. A detail that was unknown at the time that it was
agreed to take this approach was that the wheel bearing must be keyed to hold half of the key stock
height. The other half is held by the shaft. The two together are what prevent rotation. This requires that
you broach a keyway into the bearing and although a broaching kit is available on campus, it was not the
right size and the team member working on this item had not broached before. In the third, final, and
current iteration a press-fit non keyed dowel pin will be used to hold the wheel. Based on prior
experience no known reason as to why this would fail is currently known. It is important to note that
although the failure modes and the iterative process experienced occurred, the team member who
worked on this could have been more proactive in meeting the deadlines presented.
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