Aircraft Overhead Bin

1
Aircraft Overhead Bin

• by
• Sam Donaldson
• Gerard Mouatt
• Francis Gillis
• Rob Harmer

2
Introduction

• The mechanism chosen for this project is an
  aircraft overhead bin mechanism. Its purpose is
  to cover storage compartments on an aircraft
  where passengers store carry-on luggage so it is
  accessible during the flight. It is designed to
  take up as little space as possible while having
  enough space for small carry-on luggage. A
  simple design is required in order to limit
  weight on the aircraft.

3
Abstract

• The aircraft overhead bin mechanism is designed
  to pivot between open and closed positions.
  When broken down, or simplified for analysis, it
  is seen as a classic four bar linkage. There are
  two rockers connected to a grounded link which
  provide oscillatory motion for the door panel.
  The upper rocker is linked to the bottom corner
  of the panel and has limited motion. The lower
  rocker connected to the upper corner of the panel
  has approximately a 90 degree window of motion.
  This Grahsof mechanism has range which allows for
  small carry-on luggage to be stored in the
  compartment. The panels motion is designed so
  gravity will keep the mechanism open while a
  latch will keep the door closed. Although not
  shown, a stopper is required to halt the opening
  motion of the door which in turn provides safety
  for passengers.

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CAD Drawing
5
Brain Storming

• Need to convert the Mechanism to a classical four
  bar linkage.
• Some restraints are needed on this mechanism in
  order to slow the rotational speed down.

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Degrees of Freedom

• Grueblers Equation
• DOFs 3L-2J1-J2-3G
• L the number of links
• J1 the number of 1 DOF joints (full Joints)
• J2 the number of 2 DOF joints (half Joints)
• G the number of ground links
• Aircraft Overhead Bin
• 3(4) 2(4) (0) 3(1) 1 Degree of Freedom

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Grashof Condition

• Aircraft Bin Mechanism
• S 7.489
• L12.968
• P9.170
• Q9.434
• 7.48912.968 lt 9.1709.434
• Case I (Grashof Double Rocker)

• Grashof Equation
• S length of shortest link
• L length of longest link
• P length of one remaining link
• Q length of other remaining link
• SL PQ

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Graphical Position Crossed
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Instant Centers Crossed
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Graphical Position Open
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Instant Centers Open
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Position (Analytical)
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Velocity (Analytical)
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Acceleration (Analytical)
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Working Model
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Critical Parameters

• One way Damper
• A one way damper limits the velocity of the door
  upon opening. This is why we kept the angular
  velocity (?2.25 rad/s) and acceleration
  (a2rad/s2) small.
• Rotational Stopper
• The stopper should keep the door from opening to
  far and swinging into a passengers head. It
  must allow clearance for small luggage placement.
• Weight
• A simple design will aid in keeping the
  components weight down.

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Position Results

• The results obtained during the analysis of this
  mechanism were reasonable with respect to its
  function. The position analysis was done both
  analytically and graphically. AutoCAD was used
  for the graphical analysis. The values for all
  of the angles were very close between the two
  methods and supported the function of the
  mechanism. When the bin was in the closed
  (crossed) position, all of the values (a, b, c,
  d, ?2) needed for calculation were obtained by
  drawing the original picture from the textbook in
  AutoCAD. When the bin was in the open (open)
  position, there was no value given for ?2, so a
  value had to be assigned. The value 330? was
  chosen by drawing the four bar linkage in
  AutoCAD, estimating where the door would stop and
  then measuring ?2.

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Velocity Acceleration Results

• Values needed to be assigned to ?2 and ?2 in
  order to make calculations for velocity and
  acceleration. An educated guess had to be used
  to assign those values. The values were first
  guessed as ?2 3 rad/s and ?2 2 rad/s2. After
  using those values to make the appropriate
  calculations, the final values for ?3,?4,?3, and
  ?4 where outrageously large. We found that if ?2
  was changed to 0.25 rad/s, and ?2 was left at 2
  rad/s2, the final values were much more
  reasonable. In comparing our results from
  graphical and analytical analysis, as well as
  from the working model, we believe they support
  the real-life functionality of this mechanism.
• For a detailed look at all of the results, view
  the filename project.xls on this CD

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Results
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Conclusion

• With the completion of our analysis, we found
  that a damper was need to slow the rotation of
  the mechanism. If the bin were to open using
  gravity it would be moving at speeds to high for
  the long term reliability required. It would
  have to be a single direction damper that would
  have to be around 7 kN-m-s to achieve the
  appropriate angular velocity. There would also
  need to be a stopper installed in a position to
  keep bar a from swinging under 330 degrees.
  This would help keep the seated passengers from
  being struck by the door while also allowing as
  much possible clearance for luggage and access to
  the seats beyond the bin. While reconsidering
  the design of this mechanism, one strong
  possibility would be for the bin door to swing
  up. This would be a more practical and safer
  design.

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Sources

• AutoCAD 2006
• Norton, Robert L. Design of Machinery an
  introduction to the synthesis and analysis of
  mechanisms and machines. McGraw- Hill, 2004.
• Norton, Robert L. Working Model Software.
  McGraw-Hill, 2004.