1. Group 5 Self-Assembling Picnic Table
Group Members:
Lee-Jen Chen (Andy)
Shi Li (Jeff)
Spencer Soloduka
Kwun Fong Tse (Ken)
Supervisor
Alex Kalamkarov

2. Self-assembling Picnic Table
Objective: Design self-assembling collapsible furniture
Once initiated by button, the assembly process requires no human contact
Fully functional picnic table that can be collapsed to minimized space for storage/transportation
Suitable for indoor or outdoor use
Must seat at least 4 people (100 kg each) with sufficient table space
Should be carried by one adult (< 50 lbs)
Must be safe! 1

3. Final Solution
Opened Mode
Collapsed Mode 2

4. Presentation Contents
Components: Chairs Table Central Transmission Motor and Battery Control System 3

5. The Chairs (Main Features)
Torsion Spring
Front Legs
L-Bracket
Rear Legs
Prototype (Standing)
Ropes
Chair Surface
Chair Frame
Prototype (Bottom View ) 4

6. The Chairs (Opened / Collapsed Mechanism)
Collapsing
Opening 5

7. The Chairs (Stress Analysis)
220 lb
Yield Strength of Steel ≈ 310 (MPa)
195/310 = 63% 6

8. The Table A ring is underneath the table for support and guidance.
Top View
Collapsed Mode
Opened Mode
A ring is underneath the table for support and guidance. 7

9. The Table 8

10. Table Pieces Table pieces are held together using 16 pieces of fabric.
Side View
Table Piece
Top
Bottom
Table pieces are held together using 16 pieces of fabric. 9

11. Table Piece
Each table piece is made of one piece of ABS plastic and 2 aluminum support channels.
The U bar is for connection to the central shaft. 10

12. Support Channel Stress Analysis
50lb
100lb
12’’ 6”
50lb
Under a 50lb load, the maximum stress on the aluminum channel is 210MPa (Yield strength of Aluminum alloy 6061-T6 is 270MPa).
The maximum deflection is approx. 9mm. 11

13. Central Transmission
A set of spur gears connects the motor and the lead screw.
The screw sits on a thrust bearing.
The nut does not rotate so it moves up and down. 12

14. Motor & Battery 24V DC gear motor, approx. 69W 179 RPM, 23.38 in-lbs
24V, 4200mAh NiMH rechargeable battery pack
5.0A discharge rate 13

15. Motor control circuit One-push button
Checks potentiometer connected along transmission against reference resistor (R=0 -> open, R = Rref -> closed)
4-way switch reverses polarity of motor 14

16. Safety control circuit
Purpose is to disable adjacent control circuit in the case that the table is loaded
Checks 4 strain gauges mounted on each chair against four reference resistors (uses strain gauges on unloaded material for temperature compensation)
Uses normally closed magnetic relay to control power to motor circuit 15

17. Control system – System coupling16

18. Conclusion 17

19. Conclusions – Results (Dimension)
Opened Mode
Collapsed Mode 18

20. Conclusions – Results (Total Weight)
Items
Materials
Weight (lb)
Chair (x4)
Aluminum, Steel, Plastic 24
Table
Aluminum, ABS 10
Central Structure
Aluminum, Steel
Motor & Battery
N/A 4
Control System
0.5
Total Weight:
48.5 19

21. Conclusions - Budget Components Cost Chair (x4) $360 Table $370
Central Structure
$150
Motor & Battery
$350
Control System
$175
Contingency (15%):
$210
Tax (15%):
$242
Total:
$1858
Allotted amount:
$1860 20

22. Conclusions – What’s next
Full scale prototype
Procurement of materials and custom fabrication
Consult technicians
Design build report II
Spec. components for control system
Simulation
Determine placement on system
Assembly
Testing
Modifications/optimizing
Final Design Report
Lessons learned 21

23. Thank You! Supervisors Dr. Alex Kalamkarov Shane Yates Prototype
Reg Peters
Angus MacPherson
Consultation
Dr. Robert Bauer
Dr. Lukas Swan
Funding
Shell Canada 22

24. Questions? 23