Embedded Files
CAD- without motor/crank Rocker
CAD- without motor/crank Rocker
Physical project
Physical project
Base Structure
Base Structure
Material: Poplar
Four (2 x 4) legs
One 1.3125 diameter, oak pole with the ends tapered to a diameter of 1.25 in
42 inch long grounded planks (3" width)
rectangular support system of planks connects 2x4s
Gliding Structure
Gliding Structure
Material: Poplar
1/2 inch thick panels spanning the distance between the 2x4s
42 inch upper plank supported by two 15.25 inch planks
these vertical pieces are connected by a 35 inch plank as the bottom piece of the gliding frame
Connection of the Gliding Structure to Base Structure
Connection of the Gliding Structure to Base Structure
Four hot-rolled steel linkages (1/4 in thick, 1/4 in hole diameter)
7 inches of distance between bolts (radius of swing)
8 1/4 in diameter stainless steel bolts,
PTFE bearing sleeves, 2 per bolt
Seating Area
Seating Area
Material: Poplar
Seating portion
Five 1/2 thick slats spanning the width of the structure
Fastened to structure with 4 wood screws each
Adjustable backrest to recline at differing angles
Four slats
Fastened to structure with 4 wood screws each
Retractable foot rest
Repurposed from a chair
Fastened to the seating portion by countersunk bolts
Motor Driver
Motor Driver
Crank-Rocker
Crank-Rocker
Limits the rocking motion to an angle of 17.6 degrees in each direction (35.2 degrees total)
Motor output shaft attaches to the crank (with hubs surrounding the crank)
Crank attaches to the rocker via an L-bracket and bolt
Rocker attaches to the base structure pole via a rod clamp
This clamp holds a bolt that fits through the sleeve at the end of the coupler, allowing it to smoothly rotate as needed
Motor
Motor
110V, 90W AC Gear Motor
110V, 90W AC Gear Motor
Electric single-phase motor
0-67 rpm electric variable speed with an adjustable speed controller
Parallel shaft gear head with a 20-1 gear speed reduction ratio
The parallel shaft gear head has a helical gear and is backdrivable to help prevent damage to both the swing structure and motor
Cushion
Cushion
27.5 x 42 in customized foam to contour to Tristan's body
5 point harness attaches over the padding
Foam leg support
Project's Performance
Project's Performance
FEA Analysis
FEA of whole model with bolted joint and pin joints
When we used bolted joints area around bolt a little over constrained
with just the pin joints the stress was a lot lower
ended up going with a figure much closer to the bolted joints to be safe
Max stress in the structure approximated at 45 MPA
also modeled structure with pin joints
max stress occured in the steel Links
Fatigue analysis
Used 45 MPA as alternating stress
Sut=400 MPA for hot rolled Steel
assumed axial load, room temp, 99% reliability, hot rolled
resulting enduracnce limit Se=108 MPA
1.5*10^8 cycles (infinite life)
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