How to Build a Moveable Bridge

Hello, we are team TOF. We are here to share our project, Movable Bridge,for our Vg100 course at the UM-SJTU Joint Institute(JI for short).

JI is an international engineering institute founded by University of Michigan (UM) and Shanghai Jiao Tong University (SJTU). It is located on the campus of SJTU, in Minhang district of Shanghai. It is devoted to cultivating creative, competent, and leading engineers for the world.

VG100 is a course set up as an introduction to engineering for all the freshmen at JI. The instructors are Dr. Shane Johnson and Dr. Irene Wei. During the course, students are divided into groups of four or five to work on engineering-based projects. The Movable Bridge is our first project.

The logo of our team, a photo of our team members, the logo of JI, and a photo of JI building are shown above.

Connotation of Our Team Name, TOF:

• Treasure Our Friendship
• TO Fly
• Trust Our Force
• Never give up (as it has the same pronunciation as “tough”)

Team Members:

Cao Hangrui, Chen Xi, Zhang Chenyan, Yao Jiaji, Guo Yuanqi

Competition:

Each group builds a bridge model with balsa wood and tests it on GAME DAY, Oct.17th. The bridge should complete a function test, a weight test, load test and an optional assembly test.

Competition Regulations:

• The bridge should be made only of balsa wood, wax paper and cotton strings. Special materials can only be used for connection. The glue must be ELMER wood glue.
• The size of the bridge should be no less than 700 mm in length, no less than 200 mm in inner width and no more than 250 mm in outer width.
• The bridge should be able to be fixed on two abutments (250*200*200 mm).

Rules:

• The function should meet the following requirements:

a. let a small car A pass on it

b. detect a big car C under the bridge

c. stop another small car B from the other direction

d. be lifted up to let car C pass beneath it

e. be laid down to let car B pass on it.

• The load is tested by putting weights on vertical axis. The vertical load increases to 1 kg if the deflection is under 4 mm. If the deflection reaches 4mm before 1kg is put on the bridge, the maximum weight before this point will be recorded to calculate the score.
• The lightest bridge will gain 40 points and other bridges lose 2 points successively.
• A group can gain bonuses if their bridge can be put in a box with 200 mm * 250 mm * 300 mm can be rebuilt within 5 mins.
• Each group has 4*30 s to fix their bridges during the test.

Our Scores and Place:

Our team gained 80.73 points and ranked 3rd among all 19 groups. Our bridge came first in the weight test, with a weight of about 240 grams.

Video:

http://v.youku.com/v_show/id_XMzg4NDA3NTY0NA==.html?spm=a2h3j.8428770.3416059.1

Step 1: Concept Diagram

Shown above is the concept diagram for our movable bridge. The bridge is a one-side open bridge, with one tower, several components and two abutments.

Construction parts:

1) Bridge deck: Three main girders compose of the main structure, with other cross girders connected to them. The cross section of main girders are hollow, with a square hole in every one of them.

2) Bridge tower: The right triangle structure is designed to stabilize it, and a plastic pulley is put on the top.

3) Piers: four piers are used to reduce the horizontal deflection.

Function parts:

1) Motor: the motor is used to provide torque for the bridge to lift up. Cable will be intertwined with it and the middle of the bridge.

2) Servomotor: To let the blocking lever down to stop car.

3)LED: To warn the car when the bridge is lifted.

4)Sensors: To detect the position of the car and ship.

Step 2: Material & Tool List

Most of the materials above are bought through online services. Only wood glue is permitted when connecting wooden parts.

Step 3: Circuit Diagram

1.Shown above is the circuit diagram. All red wires means 5V power supply, and all black wires are connected to the GND. All blue wires are data lines.

2.The core part of it is the Arduino Nano board. By uploading the code into the Arduino Nano board, it sends signals to different components to meet function requirement.

3.The motor is driven by L298N motor driver. Change the speed by PWM signal.

4.Connect the two servos, three different infrared sensors to different data interfaces. Connect the two green LEDs and two red LEDs seperately to different data interfaces.

5.Pay attention that the Arduino Nano board cannot bear extreme voltage, and make sure there is no short circuit.

Step 4: 1.construct the Bridge Structure

Read 1.1~1.4 to learn how to build the structure of the bridge floor.

Our advice:

• When gluing, hold the structures together for enough time.
• When cutting, be careful and don't hurt yourself or others.

Step 5: 1.1.Construct Box Girder Framework

i)Cut off wood pieces:12*740mm*10mm*3mm, 24*90mm*10mm*3mm.

ii)Stick together every 4 pieces of the same size to make box.

iii)Take one of the longer girders, stick 6 shorter ones on its four equal points symmetrically.

iv)Stick other two box girders on parallelly.

Step 6: 1.2. Complete the Framework

i)Cut off wood pieces:8*110mm*16mm*3mm

ii)Add them among box girders to strengthen the structure.

iii)Add tiny wood pieces to strengthen the connections.

Step 7: 1.3. Construct the Bridge Floor

i)Cut off wood pieces:8*110mm*10mm*3mm
ii)Add them on box girders to form a better plane. (You can reorganize these pieces as long as a plane is formed since these components have nothing to do with load-bearing.)

iii)Stick a piece of paper on the bridge.

Step 8: 1.4. Construct Bridge Approach

i)Cut off wood pieces:8*90mm*10mm*3mm, (right triangle)3*13mm*50mm*3mm, 2*52mm*210mm*2mm

ii)Construct 4 T beams and stick them between the end of long box girders.

iii)Stick triangle pieces on poles of long box girders.

iv)Stick the board on triangle pieces to make a slope.

v)Stick a piece of paper on the whole structure.

Step 9: 2.construct the Structure on the Shore

Read 2.1~2.2 to learn how to build the structure on the shore ( the tower and the ramp that allows cars go onto the bridge).

Step 10: 2.1. Construct the Tower

i) Cut off wood pieces:8*300mm*2mm, 2*60mm*100mm*2mm, 2*10mm*60mm*3mm

ii) Make 2 box girders as described above.

iii) Stick them together to form an angle of 15°.

iv) Trim the tower and stick it on one of the boards.

v) Stick 2 battens on the bottom of the tower.

vi) Stick a pulley on the top of the tower.

Step 11: 2.2. Make Paper Hinge

i) Cut off paper pieces:5*40mm*80mm Cut off wood pieces:1*210mm*50mm*3mm

ii) Stick the board on the 2 boards in 2.1.

iii) Stick every paper piece on the inverse sides of the board and bridge approach to make hinges.

Step 12: 3.Assemble the Bridge

1.Stick LEDs on steering engines.

2.Fix one servo on the board, and fix another one on the other side of the bridge.

3.Stick a tiny pole on each of the steering engines. (80mm approximately)

4.Fix an infrared sensor on the bottom of tower.

5. Fix one infrared sensor in front of the tower, and fix another one on the middle of the bridge on the other side.

6. Fix a motor behind the tower with a plastic axis on it.

7. Link the middle of the bridge and the axis with a cotton cable.

Step 13: Final System View

Make some subtle adjustments and our bridge is done!

Step 14: Appendix for Potential Problems：

1. You can also use some brushes to dip the glue, for it is easier to control the use level.

2. When connecting wires, use the corresponding color to different wires or it will be difficult to distinguish later.

3. When some components cannot function well, use some test programs to figure out which one is wrong. Also check the contact points of the wires.

4. Before function, make sure the string is tighten or the bridge might not be raised to its ideal height.

Thank you for watching this document. Hope you enjoy it! For more information, you can contact us at email [e-mail]