Test: Bungee Cord End Condition
Part A: Slit Loop
Engineer Performing Experiment: Kristin & Dan
Start Date: 4/23/10
End Date: 4/23/10
Equipment Needed: 12” of elastic tubing
Calipers
2 Carabineers
Yard Stick
Something sturdy to attach one carabineer to
Description:
 The bungee cords are an integral part of the successful performance of the
balance bicycle.
 The chosen end conditions must be able to withstand lifecycle testing
without failure.
Test Procedure:
 Cut an approximate 1” slit in both ends of the elastic tubing approximately
2” from each end
 Measure each slit with calipers
 Create loops on each end by passing the end of the elastic tubing through
the slit
 Attach each loop to a carabineer
 Attach one carabineer to something sturdy
 Stretch elastic cord slowly to 2 feet for 10 cycles
 Remove carabineers and loops
 Measure each slit with calipers
 Repeat testing until 100 cycles have been reached
Pass/Fail Criteria:
Failure occurs if there is a change in the length of the slit
Results:
Units in inches
Cycle
Slit 1
Initial 1.21
10 1.25
20 1.22
30 1.23
40 1.24
Slit 2
1.06
1.04
1.03
1.03
1.05
50
60
70
80
90
100
1.24
1.27
1.31
1.39
1.39
1.34
1.07
1.12
1.10
1.17
1.10
1.15
Pass/Fail: Fail
Part B: Boy Scout Knot
Engineer Performing Experiment: Tim Williams
Start Date: 5/7/10
End Date: 5/7/10
Equipment Needed: 12” of elastic tubing
2 Carabineers
Yard Stick
Something sturdy to attach one carabineer to
Permanent Marker
Description:
 The bungee cords are an integral part of the successful performance of the
balance bicycle.
 The chosen end conditions must be able to withstand lifecycle testing
without failure.
Test Procedure:
 Make a bowline know in each end of the elastic tubing
QuickTime™ and a
decompressor
are needed to see this picture.
 Mark the elastic cord on either side of the knot with permanent marker
 Attach a carabineer to each loop
 Attach one carabineer to something sturdy
 Stretch elastic cord to 2 feet for 100 cycles
 Check location of marks on either side of know
Pass/Fail Criteria:
Failure occurs if either of the marks on either side of the knot are covered
by the knot
Pass/Fail:
Pass: Tubing did not creep after each 10 cycle increment of the 100 cycle test. Visual
inspection indicated that the permanent marker was still exposed on both ends of the
knot.