Introduction: Movable Wooden Bridge

Background Information
We are team Trinity from JI (the abbreviation of University of Michigan-Shanghai Jiao Tong University Joint Institute), which locates at 800 Dongchuan Road, Minhang District, Shanghai, China. JI cultivates future engineers by teaching students knowledge and working in a team.

The Movable Bridge is our Project 1 in the 2019 fall semester which needs us to build a bridge using balsa wood that can deploy from one side and hold as much load as possible while having a weight which is as small as possible. Below is our favorite picture of the campus and our team logo.

Project Rules
1The structure of the bridge must be made from balsa wood. Only construction electrical devices can use other materials like metal.

2. Members should be connected by using wood glue. Special connections must be permitted by TA/instructor.


3. One end of the bridge must be fixed on the bigger abutment.

4. A 90mm wide must be able to fully on anywhere on the bridge.

Step 1: The Preparation1

Here is the material list of our project

Step 2: The Preparation 2

Here is the concept diagram of our project

Step 3: Component Fabrication and Assembly

Step 1 Wood Processing
1.1 Cut out 3 pieces of wood in the length of 33cm,30cm and 18cm (Figure 1.1)

1.2 Punch holes in boards to install hinges (Figure 1.2)

1.3 Cut out 2 pieces of wood in length of 31cm(Figure 1.3)

1.4 Cut out 6 pieces of wood in three groups which length are respectively 1cm,1.4cm and 4.4cm (Figure 1.4)

Step 2 Part of Wood Assembly
2.1 Glue 1cm,1.4cm and 4.4cm groups of wood and 31cm wood (Figure 2.1)

2.2 Glue the products in 1.1 with 33cm and 30cm wood(Figure 2.2)

Step 3 Assemble woods and hinges
3.1 Dig away unnecessary wood(Figure 3.1)

3.2 Assemble hinges and woods(Figure 3.2)

Step 4 Connect Circuit Devices
4.1 Design Circuit and Write code(Figure 4.1)

4.2 Test the Circuit

Step 4: Final System View

Step 5: Rethink and Lesson

1. Always do, not just say. Making a bridge like this may be not so difficult, but design can take up much of time. A lot of assumption will not help too much. When we truly make our own bridge, we know the advantages and disadvantages and make progress.

2. Make full preparations. Design requires us to have abundant knowledge and be familiar with the process. They are what we can do before.

3. Start early and plan clearly. As the process is difficult,much time should be spent.Starting early is necessary when doing projects.Thus, when we find something wrong, we can have more time to fix and improve.A clear plan can make a big difference in teamwork.It can save all members’ time and lead to a better result.

4. Divide the work properly. When we were making the bridge, we did not divide the wor k properly. We let our leader did too much work, and left some of us just a few. This made us can’t maximize everyone’ ability and value to finish the project.

Step 6: ​ Experience and Notice

Accidents happening to us

On the Gameday,when we apply the retraction part,at first the motor turns as planned,but Suddenly the motor stops.At the very moment,we can just check the circuit and even try to reconnect all parts.But they don’t work.We can do nothing but give up the retraction and deployment parts.

Our Finding Reasons Process

After Gameday,we rethink the reason.First,we simply connect the motor with two 7V batteries and it runs.Then,we change the Arduino board and all the DuPunt lines,but it doesn’t work.Finally,we know the question lies in the driving board,which is impossible for us to substitute in Gameday.

What we learn and want to share

When we make the bridge, we put too much attention to project rules rather than functions of bridge itself. Our excessive care for results lets us redesign structures once and once again.So we have no time to recheck circuit.Although we final result is not so good,we enjoy the process we learn and make the bridge together.We hope others find happiness from it.Only caring about scores may cause bigger problem like us.

Step 7: Troubleshooting


Find information and learn more about bridge structures and functions.After having first design,work together to do a model.


When using wood glue,it is necessary to be careful.After gluing,a heavy thing should be on the adhesion.


Step by step,be careful to have everything connected.


Design and check the circuit carefully.Make sure that all electrical components work normally.


After having models,rechecking their functions is necessary.Test and improve the structures.

Having Trouble:

When the bridge doesn’t work as wished,keep calm and follow steps which showed before to find problems.Solve them.

Step 8: Appendix


[1],[2] S. Johnson and I. Wei, “Manual Guideline,” VG100 canvas, Sep 24,2019.

[3] Qiu Tianyu, “Lab 2,” VG100 canvas, Sep 30,2019