Child Passenger Safety Seat by gmx42408

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									Child Passenger
  Safety Seat
               Team Members:
Erik Bieging, Aman Ghotra & Karim Mahamud

                  Client:
        Tom Brazelton, MD, MPH
      Dept. of Pediatrics – UW Hospital & Clinics

                 Advisor:
                Mitch Tyler
         Dept. of Biomedical Engineering
                                                    1
          Recall: Background
Existing Design:
– Safest to transport
  children (<30 kg) sitting
  up in child seat
  attached to gurney in
  an ambulance [2]
– For specific medical
  conditions, EMTs must
  unstrap child out of
  seat and remove the
  seat off the gurney to
  lay the child in supine
  position on the gurney
  [3]
Limitations:
– Seat does not recline
– Seat is bulky
                               2
     Problem Statement
Develop a safe and compact child seat
for transporting children (6-30 kg) in
ambulances that allows Emergency
Medical Technicians (EMTs) to recline
the child in the seat from the sitting
position to the lying position when
strapped onto a stretcher.



                                         3
    Overview of the Prototype
Last semester we
designed a wooden
prototype that had:
–   Recline Lock (A)
–   Sliding Strap (B)
–   Back Rest (C)
–   Leg Support (D)     Overview of Design Concept




                                                     4
    Overview of the Prototype
Last semester we
designed a
wooden prototype
that had:
–   Recline Lock (A)
                        Figure A: Design Concept
–   Sliding Strap (B)
–   Back Rest (C)
–   Leg Support (D)


                        Figure B: Design Concept
                                                   5
    Overview of the Prototype
Last semester we
designed a wooden
prototype that had:
–   Recline Lock (A)
–   Sliding Strap (B)   Figure C: Design Concept

–   Back Rest (C)
–   Leg Support (D)




                        Figure D: Design Concept   6
              Accomplishments &
            Goals For The Semester
         PROBLEMS                            SOLUTIONS
      (Wooden Prototype)

1. Wooden Prototype is too        1. Build a NEW PROTOTYPE with
HEAVY and BULKY                   light yet robust materials

2. Strap mechanism difficult to   2. Replace old design with Spring-
SLIDE and LOCK                    Loaded Strap Mechanism



3. Did not Perform Prototype      3. Conduct Non-Destructive Testing
Testing last semester


                                                                       7
           Force Analysis
                             Max deceleration in a
                Fstrap
                             crash = 20g = 198 m/s2
          24”
                             Max Child Mass = 30 kg
                             Max tension in shoulder
                             straps = (30 kg)(198
Ftrack                       m/s2)/(2 straps) = 2970
    12”                      N
                             Maximum Forces:
                             –   Fstrap = 5.9 kN
                 Fpin
                             –   Fhinge = 65.2 kN
           2”
                    Fhinge
                             –   Fpin = 71.2 kN
                             –   Ftrack = 12.1 kN
                                                       8
                 Materials
Materials we intend to use for NEW
PROTOTYPE
– Safety Factor: 2
– HD Polyethylene Sheets
    Bulk Material (in place of wood)
– General Purpose Aluminum Sheets
    For Reclining Mechanism
– Estimated Mass: <3.5 kg


                                       9
             Accomplishments &
           Goals For The Semester
         PROBLEMS                            SOLUTIONS
      (Wooden Prototype)

1. Wooden Prototype is too        1. Build a NEW PROTOTYPE with
HEAVY and BULKY                   light yet robust materials

2. Strap mechanism difficult to   2. Replace old design with Spring-
SLIDE and LOCK                    Loaded Strap Mechanism



3. Did not Perform Prototype      3. Conduct Non-Destructive Testing
Testing last semester



                                                                       10
Spring-Loaded Strap Mechanism
Spring loaded T-lock
slides in slots in back
of seat
Locks into grooves
created by blocks
mounted to back of
seat
Stress on seat =
(2970N)/(.25 in2) =
2700 psi

                                11
             Accomplishments &
           Goals For The Semester
         PROBLEMS                            SOLUTIONS
      (Wooden Prototype)

1. Wooden Prototype is too        1. Build a NEW PROTOTYPE with
HEAVY and BULKY                   light yet robust materials

2. Strap mechanism difficult to   2. Replace old design with Spring-
SLIDE and LOCK                    Loaded Strap Mechanism



3. Did not Perform Prototype      3. Conduct Non-Destructive Testing
Testing last semester



                                                                       12
   Non-Destructive Testing
On Locking Mechanism
– Function: Prevents seat from collapsing
– Collar around the pin has an unknown effect
  on the mechanism
– Shear test on the pin to determine the type of
  collar




                                                   13
   Non-Destructive Testing
On Strap Mechanism:
– From our calculations a force of 2970N is
  needed to break the strap
– Conduct Tensile test
    To see the forces needed to break the strap
    Use tensile machine in the materials testing lab
On the Back Track/Grooves
– Conduct Tensile Test
     – Must withstand 2970N

                                                       14
     Non-Destructive Testing
On 5 Point Harness Buckle
– Buckle prevents the child from being ejected in
  case of an accident
– Tensile Test
      All 5 straps must withstand 2970N on each strap


On Reclining Mechanism/Supports
– Conduct Fatigue Test
      To determine the shelf life of the child safety seat
      Test by applying a static load and cyclic loading




                                                             15
               Summary
Design a NEW prototype
– Light & Robust Materials
Modify Strap Mechanism
– Spring-Loaded Strap Mechanism
Non-Destructive Testing
– Determine durability/strength of the prototype




                                                   16
                    References

[1] Safe Ride News.
http://www.saferidenews.com/html/Spec_Amb.html
[2] Detroit News.
http://www.detnews.com/2003/specialreport/0301/27/a11-
68893.htm
[3] Brazelton, T. University of Wisconsin Hospital and
Clinics. Interview.
[4] Physical Characteristics of Children.
http://www.itl.nist.gov/iaui/ovrt/projects/anthrokids/child.html



                                                              17
Questions??




              18

								
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