CEEN 311:

Kick Scooter Project

Section A Team 6

Instructor:

Dr. Lauren Cooper

Team Members:

Muhammad Akmal Mustaffa Kamal

Joseph Linden Cotchen

Nadozie Okpara

David Van Akkeren

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Project Overview:

Throughout the course of the semester, students have been learning the typical skills of a standard

Mechanics of Materials class. In addition to the concepts, this course has been centered on project-

based learning (PBL). This learning style takes the techniques learned in class and applies them to solving

real-life problems. Within PBL, it is necessary for the students to design a solution to their specified

project, analyze and solve problems as they arise, work together as a team, and make use of engineering

concepts. This PBL style of learning not only utilizes theory in real life situations but also in the process

helps the student learn and better understand the engineering material.

Objectives:

The project for this course was to design and build a foot-powered scooter out of PVC pipe and fittings.

Teams of four were selected based on self reported strengths and weaknesses. Major objectives of the

project were to develop a fully functional scooter with a break that at a minimum could support a 150 lb

rider by using only PVC structural members and have a minimum factor of safety of two while weighing

less than 14 lbs and able to fit inside a 36” x 36” x 24” envelope. The budget was limited to $40 but the

castors were standardized and provided by the professor. Additional optional objectives were to create

a collapsible scooter as well as developing and employing a real-time strain gauge circuit for the scooter.

The student-designed scooters are to be raced at the end of the semester as part of a viability test as to

whether or not the scooters will function as intended.

Requirements:

1. Safety: The scooter itself must be deemed safe and fit for riding. Scooters with excessive

deformation, the potential for buckling, poor connections, jagged edges, or protruding bolts

will not be allowed to race.

2. Weight Capacity: The scooter must be able to withstand the stress and strain of a 150 – 170

lb rider and feature a minimum factor of safety of 2 in its weakest member or connection.

3. Materials: The scooter must be made of PVC structural members however connections can

utilize metal bolts. Duct tape is not permitted.

4. Weight: The scooter must not exceed 14 lbs.

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5. Dimensions: The scooter must be able to fit into a 36” x 36” x 24” envelope.

6. Quality: The scooter as presented at the “Scoot Off” must be presentable as a finished

project. This means symmetry and aesthetics are necessary to consider.

7. Foot-powered: A major objective of this assignment was to create a foot-powered scooter.

Any other propulsion system is not allowed.

8. Ride-ability: The scooter must carry the rider in a natural position and be easily balanced.

The rider should be able to traverse varying types of terrain without excessive vibration.

Extra Credit:

1. Collapsibility: Extra points will be awarded to teams with a fully collapsible scooter that can

be easily carried and stowed.

2. Strain Measurement: Extra points will be awarded to teams that generate a strain gage

circuit that, along with LabView, will measure real-time strain of the scooter deck.

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Budget Tracking:

Cost Table

ITEM NO. Description Pipe Size Unit Cost QTY. Total Cost

1 Wheel Assembly $0.00 2 $0.00

2 Unthreaded Pipe 3/4 $1.64 1 $1.64

3 Unthreaded Tee 3/4 $0.33 19 $6.27

4 Unthreaded Tee 3/4 $0.33 4 $1.32

5 Unthreaded Pipe 1 1/2 $1.00 1 $1.00

6 Unthreaded Pipe 1 1/2 $1.00 2 $2.00

7 Unthreaded Tee 1 1/2 $1.54 1 $1.54

8 Unthreaded Cap 1 1/2 $0.78 2 $1.56

9 Unthreaded Tee 2 $2.25 2 $4.50

10 Easy-Align Socket End Class 150

Flange 1 1/2 $7.90 1 $7.90

11 Quick-Release Pin $2.13 1 $2.13

12 Unthreaded Pipe 3/4 $1.64 3 $4.92

13 Fasteners $0.54 1 $0.54

14 Spring $4.54 1 $4.54

Total $39.86

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Data obtained from Calculation:

Results

Item Value Detailed calculation

Detailed Drawings Refer to page 6-9

Free Body Diagram Refer to page 10

Shear And Bending Moment Diagram Refer to page 11 Appendix A, #1, page 14

Maximum Shear 212.1psi Appendix A, #2, page 16

Maximum Bending Stress - 267.1psi (Compressive)

- 534.2 (Tensile)

Appendix A, #2, page 15

Maximum Deflection 0.3123in Appendix A, #3, page 16

Maximum Axial Stress 18.73psi Appendix A, #4, page 17

Buckling 247.2kip Appendix A, #5, page 17

Bearing Stress 229.9psi Appendix A, #6-1, page 17

Direct Shear 339.3psi Appendix A, #6-2, page 18

Factor of Safety 5.798 Appendix A, #7, page 18

What/where was the weakest point of the scooter

The weakest point is the back section of the scooter deck (back wheel) which was subjected to shock

loading while engaging in freestyle moves

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Drawings:

A) Overall drawing:

1) Initial Idea

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2) Improvements made after the project poster activity

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B) Detailed Drawings

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10

Free Body Diagram:

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Moment and Shear Diagram

For calculation, refer to Appendix

Mmax = 392.45lb-in V = 37lb

V = Vmax = 113lb

F2 = 37lb

W = 150lb/ft Ffork = 20lb

F1 = 133lb

Mmax = 1150lb-in

9.13in 9.04in 2.96in 9.13in

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Data obtained from scoot-off, weight-in and deflection activity:

Weight 10.4lb

Deflection 0.277in

Efficiency Score 125%

Scoot-off time 1:13.00s

Scoot Off Performance Analysis:

The scooter did well in the Scoot Off performance. Despite a very competitive environment the scooter

performed better than expected under greater than anticipated forces. The scooter cornered well

around the initial roundabout obstacle and had acceptable clearance while taking turns at speed. The

scooter performed as expected over the cobblestones. Despite noticeable slowing in that section, the

vibration was within reason and likely due to wheel size and hardness. Some deflection of the scooter

deck was noticed by the rider during the competition. Deflection of the steer tube was noted as a

distraction during casual use and created instability when subjected to extreme conditions. Despite

having a functional brake, the rider opted not to use this design feature so its performance is unknown.

The final time for group 6 was 1:13.00. Following the race, the scooter was subjected to shock loading

while participating in freestyle moves as well as to assess failure strength. The scooter deck eventually

failed in the back section of the deck just prior to the rear wheel. The breakage occurred at the junction

of two of the tee sections in non-linear fractures.

The completed scooter weighted 10.4 lbs and had a deflection of 0.277 inches. The weight was 112% of

the class average and 111.6% of the class' average deflection. The scooter had a structural efficiency

score of 125%. The lower than average scores were due to several factors. When loaded, a moderate

amount of deflection occurred due to the connection of the steer tube to the deck. A higher schedule

PVC or two concentric tubes glued together could have reduced this. Additionally, the length of the deck

was considerably longer than others in the class. The scooter was designed to comfortably carry a 6 ft.

rider while satisfying all technical requirements. If the deck length was reduced to a normalized length the

deflection would have been significantly reduced.

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Overall Summary:

The process of integrating PBL with Mechanics of Materials concepts by designing a PVC scooter was a

great experience overall. The project encouraged in-depth thinking and helped make the learning

process of the math more meaningful and will help make the overall concepts stay longer in memory.

One of the major issues faced was budgetary constraints. The original design presented during the

prototype presentation was well over the $40 limit. Once the original design’s budget was itemized,

several of the parts were cost prohibitive and that led to scrapping the entire first design. The second

design was drafted with part costs heavily in mind while maintaining the prescribed scooter

requirements.

This project was definitely worth the effort. When groups elect to give ample time for the construction

process, the students use more of the concepts learned in the class than in a standard mid-term testing

structure. By including at least one written problem pairing the scooter project to the material learned

during that week’s class, students could practice and apply their understanding of concepts to real-

world problems just as they will following graduation. This project was a great way to combine all the

topics of Mechanics of Materials into a single project especially in a condensed summer semester.

During a standard length semester, either more requirements should be added to the scooter design or

lighter than average testing should be used in addition to the scooter project.

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Appendix A:

Item Calculation

1) Moment and Shear

Diagram:

Assumption:

- Scooter fork is 90˚ to the scooter deck

- Scooter deck is parallel to the ground

Calculation:

1) Moment from fork

- To find the internal bending moment at A, use the FBD of

the scooter fork with the cut at point A and find the sum of

the moment at the point of cut.

∑ ( ) ( )

( )

2) Support reactions

- To find By , use the FBD of the scooter deck and find the

sum of moment at point A

∑

( )

( )

- To find Ay , use the FBD of the scooter deck and find the

sum of forces on y-axis

∑

3) Shear diagram

- V=0 when

( )

4) Moment diagram

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Diagram:

- Diagram can be seen on the next page.

2) Maximum Shear and

Bending Stress:

Assumption:

- Scooter fork is 90˚ to the scooter deck

- Scooter deck is parallel to the ground

1) Maximum bending Stress at 18.17in from point A

( )

( ) (

( ))

( )

( ) (

( ))

( )

( )

( )

( )

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2) Maximum Shear located at 0in to 9.13in from point A

(

)

(( ) ( ) )

( ) ( )

3) Maximum Deflection:

Assumption:

- Scooter fork is 90˚ to the scooter deck

- Scooter deck is parallel to the ground

By using case #2 in the table attached in references section,

( )

(( )

( ) ( ) )

√

( )

√

Maximum total deflection from calculation is a hint more than the

actual deflection which was measured at 0.277in because of a few

reasons:

1) The load (weight of the person) during the activity was slightly

less than the assumption used in the calculation

2) The calculation did not take into account of the PVC couplings,

tees and connectors.

3) The pipes were consisting of a bunch of short length pipes

instead of three long PVCs.

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4) The measurement taken during the deflection activity was not

so accurate judging from the difficulty to align the caliper due

to the triangular shape of the deck

5) The scooter was slightly angled instead of parallel to the

ground hence affecting the measurement

4) Maximum Axial Stress in

Scooter Steering Fork

1) Section Properties

Outer diameter = 1.9in

Inner diameter = 1.5in

A =

= 1.068

2) Calculation

From FBD, member AB

=> P=> 40lb sin (30) = 20lb

=

= 18.73psi

5) Bucking Analysis of Scooter

Fork

By using,

I= ( )

, where do and di is the outside diameter and inner

diameter

Outside diameter = 1.9in

Inner diameter = 1.5in

E = 420,000psi (obtained from www.professionalplastics.com)

I = 0.3912

Therefore, Critical load is

( )

( )( )( )

( )( )

6) Analysis of Relevant

Stresses

1) Bearing Stress

From drawings, the bearing area was 0.087

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2) Direct Shear

Using,

(

)

( )

7) Overall Factor of Safety Using, (gotten from www.plasticintl.com)

, where

M=102.49lb/in,

y= 0.525, and

I=2[

(

)]

By using the same diameters as above,

Therefore,

F.S =

=

=5.798

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Appendix B:

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