innovative rocking chair design with electro-magnetically induced rocking motion jorge...
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Innovative Rocking ChairDesign with Electro-
Magnetically Induced Rocking Motion
Jorge Alvarado-Colón Yocli Comas-TorresAndrés Cruz-VélezTamarys Heredia-Arroyo
Mayagüez, PR
May 14, 2005
University of Puerto Rico-Mayagüez CampusMechanical Engineering Department
• Project Description• Materials Selection• Assembly and Dynamic Analysis• Stress Analysis• Failure Analysis• Cost Analysis
Areas of Focus
Electro-Magnetic Rocking Chair
Electro-Magnetic Rocking Chair
Project Description
• The design aims for a rocking motion similar to that of a pendulum. The model that will be used for the design is that of Waltenhofen's electromagnetic pendulum.
• For the chair’s support mechanism, two bars containing pin and slot configurations at each end will be attached to each side of the rocking chair.
Electro-Magnetic Rocking Chair
Electro-Magnetic Rocking Chair
Top 3 Material Candidates
AISI 4043
Ti-6A-4V
Aluminum
Material Selection
Assembly
Electro-Magnetic Rocking Chair
Dynamic analysis
Angular velocities and accelerations were determined for the centrifugal motion of the rocking chair to estimate a rocking cycle period of 4 seconds by setting the length of the slot at the base, through which the support link bearings roll.
Electro-Magnetic Rocking Chair
Stress Analysis
The loads assumed take into account the distributed weight of the rocking chair and triangularly distributed weight of the user seating in the chair. A safety factor was empirically calculated using Collin’s method.
Electro-Magnetic Rocking Chair
Stress Analysis After calculating axial forces and bending moments, the Von
Misses stresses were calculated at the most critical point in order to calculate the cross sectional area of the support links, and a suitable inner diameter. The inner and outer diameters of the support structure were calculated.
Electro-Magnetic Rocking ChairinD
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4.0
9.0
Electro-Magnetic Rocking Chair
Static Theories of Failure
Since the material chosen is ductile, the Maximum Shear Stress Theory, which is the most conservative, was used to confirm that the structure would not fail by yielding. Using this theory, our safety factor assumption was also confirmed.
Electro-Magnetic Rocking Chair
Assuming a possible crack on the on the rod, we calculated that our chair will not fail by fracture.
Fracture
Electro-Magnetic Rocking Chair
Buckling
For a fixed free condition, the structure proved not to fail by buckling given an axial loading condition of 2500 lb (worst case scenario).
Electro-Magnetic Rocking Chair
FailureTo asses if the support structure would fail by fatigue, an S-N diagram for UHS steel was plotted, and appropriate failure theories for ductile materials were applied. For a fully reversed condition, the life cycle of the structure was 1.44 days.
N (No. cycles)
S(ksi)
100 118.3875
103 106.5488
106 18.15
108 18.15
Electro-Magnetic Rocking Chair
MaterialCost
(dollars)Solenoids (two) and base 100
UHS Steel supports 12
Massage system 50
Seat and components 100
Other electronic and miscellaneous components
20
Total cost 282
Manufacturing cost 1,000
Engineering services 6,000
Material Cost
• Massage System
• Electro-magnetic Rocking System
• Audio System
Why would anyone buy a traditional rocking chair?
PEOPLE LOOK FOR COMFORT, RELIABILITY AND
INNOVATION