Grade 5 · Design & Engineering · Lesson 181

Working Drawbridge

Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path.

Time2 × 45 minutesTeamsPairs; alternate builder and testerEquipmentBasic classroom design materials; no powered equipment

Your project in view

What you are making

Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path.

This generated example illustrates one possible finished design—not actual student work. Use the lesson’s sizes, connected parts and safety steps; your colors and creative details can be different.

Generated finished-project example for Working Drawbridge: Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path.
Working Drawbridge · Generated project example

Student directions · Grade 5

What will you make and do?

Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path.

Teacher overview: Students will plan the specific object described below, make and test a first version, then use their results to improve it. Read one step together, demonstrate the unfamiliar action, and let students complete that step before moving on.

  1. 1Plan your project

    Draw the bridge deck, pivot, towers, lifting strings and closed road height.

  2. 2Make the first parts

    Build two braced towers and connect the deck with an adult-prepared pivot at one end.

  3. 3Put it together

    Attach equal lifting strings and a safe hand spool. Add a stop so the bridge cannot flip backward.

  4. 4Test it fairly

    Lift, hold five seconds, lower and roll the toy vehicle across for five cycles.

  5. 5Improve one part

    Change one string point, pivot gap, deck brace or road stop and repeat.

  6. 6Show and turn in

    Submit the finished working drawbridge, two labeled ideas and before-and-after evidence. Explain which change the results support.

How will you know it works?

  • Lifts and holds open for five seconds
  • Lowers into a path the toy vehicle can cross
  • Record the stated test and explain one revision

Before you move on

Explain which measurement, input or design choice you are testing. Predict the result and record what stays the same so your comparison is fair.

Machine cutting, printer setup and electrical power-on require adult approval. A basic-materials model is a valid way to demonstrate the design when equipment is unavailable.

Keep your plan, test notes and before-and-after evidence with the printable design brief below. Use the detailed teacher plan and any coding guide for tool instructions. These steps continue across the lesson’s meetings, not all in one sitting.

For teachers

Engineering standards

This shows how the lesson connects to the national NGSS engineering standards and what student work you can collect.

Assessed

3-5-ETS1-1

Define the need in Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path. Agree on the two success checks and the listed material limits.

What students show: Two labeled ideas with the target and limits stated.
Practiced

3-5-ETS1-2

Compare the ideas using the project checks: Lifts and holds open for five seconds; Lowers into a path the toy vehicle can cross.

What students show: A selected design with a reason connected to a success check.
Assessed

3-5-ETS1-3

Test, change one feature and retest: Lift, hold five seconds, lower and roll the toy vehicle across for five cycles. Change one string point, pivot gap, deck brace or road stop and repeat.

What students show: Before-and-after results collected under the same conditions.

Materials

  • Cardboard
  • paper fasteners
  • cotton string
  • two towers
  • ruler
  • toy vehicle
  • Pencil, planning paper and the printable design brief below

Teacher preparation

  1. Gather per-pair materials: Cardboard; paper fasteners; cotton string; two towers; ruler; toy vehicle.
  2. Make one rough sample and rehearse the exact test: Lift, hold five seconds, lower and roll the toy vehicle across for five cycles.
  3. Set the size, load or distance marks mentioned in the steps before class. Demonstrate an ordinary first attempt, not a perfect model to copy.
  4. Prepare any holes, fasteners or difficult cuts for students. Check the stated safety note and clear the testing space.

Step by step

How to teach it

Meeting 1 · 0–8 min

See the job and plan

  1. Introduce the finished object: Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path.
  2. Draw the bridge deck, pivot, towers, lifting strings and closed road height.
  3. Students say what would count as a successful result.
Meeting 1 · 8–18 min

Model the unfamiliar action

  1. Demonstrate slowly: Build two braced towers and connect the deck with an adult-prepared pivot at one end.
  2. Pause so partners can repeat the action; provide prepared parts if cutting or folding blocks progress.
Meeting 1 · 18–35 min

Build the first version

  1. Attach equal lifting strings and a safe hand spool. Add a stop so the bridge cannot flip backward.
  2. Partners swap builder and checker roles halfway through. Check the working part before decorating.
Meeting 1 · 35–45 min

Try once and save

  1. Run one trial of the stated test to locate an obvious problem. Do not count a changed procedure as a fair comparison.
  2. Label and store the model; sketch its current shape and clear the work area.
Meeting 2 · 0–8 min

Predict and set up

  1. Revisit the two success checks. Agree on identical starting conditions and prepare a before/after results table.
Meeting 2 · 8–23 min

Collect evidence

  1. Lift, hold five seconds, lower and roll the toy vehicle across for five cycles.
  2. One student operates while the other records. Swap for a later trial while noting a change of operator if it affects the result.
Meeting 2 · 23–35 min

Change one thing

  1. Change one string point, pivot gap, deck brace or road stop and repeat.
  2. Keep the original results rather than replacing them with only the best attempt.
Meeting 2 · 35–45 min

Explain and clean up

  1. Submit the finished working drawbridge, two labeled ideas and before-and-after evidence. Explain which change the results support.
  2. Collect the brief and results; separate reusable materials and clean the test area.

Assessment

  • Lifts and holds open for five seconds
  • Lowers into a path the toy vehicle can cross
  • Student demonstrates the actual task: Lift, hold five seconds, lower and roll the toy vehicle across for five cycles.
  • Record includes failures as well as successes.
  • Student identifies one changed feature and uses the retest to explain the result.

Supports & extensions

  • Provide a worked first joint or sample; have students record dimensions and explain one comparison limitation.
  • Start with the smallest working version of working drawbridge before decoration.
  • Extension after success: choose one more value for the same tested feature, predict its effect and repeat lift, hold five seconds, lower and roll the toy vehicle across for five cycles.

Safety & responsible use

  • Teacher checks materials and test conditions before use. Use classroom scissors; adults prepare difficult cuts, holes and fasteners.
  • No powered tools, coding, hot glue or electrical circuits are required. Keep moving objects contained and test loads light.
  • Use only a light deck and short tabletop strings. Adults prepare holes; keep fingers clear of pivots.

No-machine alternative

Use prepared paper parts, larger pieces or an adult-assisted version of the same build. Keep the functional task: Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path. If physical testing is not possible, label sketches as predictions rather than measured results.

Printable student design brief

The challenge

Build a small cardboard drawbridge that lifts, stays open and lowers to reconnect a level path.

Success criteria

  • Lifts and holds open for five seconds
  • Lowers into a path the toy vehicle can cross
  • Record the stated test and explain one revision

Constraints

  • Use only the listed teacher-approved materials
  • Stay within the teacher-set size, load and test-space limits
  • Two 45-minute meetings; keep the first version simple

Engineer’s notes

Who uses this object, and what should it do?
Draw two possible designs. Label the working parts and circle your choice.
Which size, fold, gap or position must you measure or mark?
Before testing, predict what will happen: Lift, hold five seconds, lower and roll the toy vehicle across for five cycles.
Record each trial: condition / expected result / actual result.
Draw the ONE change you made. What stayed the same?
Record the retest. Did the change help, not help, or leave the result uncertain?
Show and explain: one result that supports your conclusion.
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