- Difficulty
- Advanced
- Build time
- 120-180 min
- Estimated cost
- $0-$25
- Age range
- 13-18
- Workspace
- A clear table about 90 cm wide
The finish line
What you will build
With a small hanging mass, the escape wheel advances one tooth per anchor half-cycle for at least ten controlled releases without running free.
Learning goals
- Identify how slow torque from a small falling mass produces tooth-by-tooth escape-wheel rotation.
- Construct and explain a stored energy-to-intermittent rotary system.
- Measure how the pallet engagement depth changes performance.
- Diagnose losses caused by pallet impact and pivot friction.
Before you build
Materials, tools, and safety
Reuse-material cost: Usually under $5 with an existing kit. Supervision: Adult help recommended for sharp or heated tools.
Tools
- Ruler
- Removable tape for motion marks
Low-cost swaps
- Use equivalent brick-compatible parts from any kit.
- Use cardboard beams and straw bearings for a larger demonstration model.
- Build a large cardboard escape wheel and anchor, driving it gently by hand instead of a falling mass.
Project-specific safety
- Keep fingers, hair, and loose sleeves clear of moving parts.
- Turn the mechanism by hand; do not attach a high-speed motor.
- Use a mass under 30 grams over a tray, and stop if the wheel runs free or the anchor misses a tooth.
Orient the build
Place the build so slow torque from a small falling mass is on your left and tooth-by-tooth escape-wheel rotation is on your right. Call the side facing you the front, the far side the back, the tabletop the bottom, and the opposite face the top.
Build it
Step-by-step instructions
Step 1
Build the tall frame
Brace escape-wheel and anchor pivots on two parallel walls.
Leave adjustment slots near the anchor pivot.
Step 2
Mount the escape wheel
Center the wheel on a low-friction axle and attach a small winding drum.
Mark one tooth brightly.
Step 3
Build the anchor
Create a rigid fork with two pallets placed to contact opposite tooth faces.
Mount its pivot above the wheel.
Builder checkpoint: After build the anchor, the first subassembly should stay aligned when handled gently.
Step 4
Set first-pallet lock
Rotate wheel gently into one pallet and adjust depth to catch securely.
Ensure the opposite pallet clears.
Watch for: If this stage binds or drifts, inspect frame flex before adding more parts.
Step 5
Set alternate release
Rock the anchor until the first tooth releases and the next meets the other pallet.
Adjust pallet angle before adding power.
Step 6
Add the regulator
Attach a light pendulum or weighted arm to the anchor axis.
Keep its swing clear of the frame.
Builder checkpoint: After add the regulator, operate the build slowly and confirm that tooth-by-tooth escape-wheel rotation begins without binding.
Step 7
Apply minimal drive
Wind string one turn and add a mass under 30 grams over a tray.
Hold the wheel before releasing.
Step 8
Tune ten releases
Start a small oscillation and count tooth advances.
Stop immediately if more than one tooth escapes per half-cycle.
Builder checkpoint: At the final checkpoint, With a small hanging mass, the escape wheel advances one tooth per anchor half-cycle for at least ten controlled releases without running free.
See the engineering
Why it works
- Input
- slow torque from a small falling mass
- Output
- tooth-by-tooth escape-wheel rotation
- Motion
- stored energy-to-intermittent rotary
- Energy losses
- pallet impact, pivot friction, air damping, frame flex
Why this works
Alternating lock and release
Two anchor pallets engage the escape wheel alternately. Each oscillation unlocks one tooth, receives a small impulse, and locks the next tooth on the opposite pallet.
Look for: Watch one marked tooth move from one locked pallet to the other during a complete tick-tock cycle.
Where the energy goes
Efficiency and losses
The ideal model leaves out pallet impact, pivot friction, air damping, frame flex. These effects turn some input energy into heat, sound, vibration, or unwanted motion, so measured performance will be lower than an ideal calculation.
Look for: Run the build slowly and locate the first place where pallet impact becomes visible or audible.
Math bite
Relate teeth to output period
Formula: wheel turns per tick = 1 / tooth count
- Escape wheel = 30 teeth
- One tooth released per tick
Substitute: turns per tick = 1/30
Result: Thirty ticks produce one wheel revolution.
A consistent regulator period makes the output rate regular.
Impact, friction, and changing drive torque alter timing.
Make it behave
Test, troubleshoot, and tune
Controlled test
Start here: Operate the anchor by hand with no hanging mass for six releases.
Success looks like: Exactly one tooth advances per half-cycle and both pallets lock reliably.
Measure: Released teeth, skipped teeth, and time for ten releases.
Change: the pallet engagement depth
Keep constant: escape wheel, anchor, regulator length, frame, and drive mass
- shallow lock
- moderate lock
- deeper lock if still free
| Symptom | Likely cause | Confirm it | Fix |
|---|---|---|---|
| The wheel runs free | Pallets are too shallow or mistimed | Test each lock by hand | Increase engagement and realign anchor |
| The anchor cannot release | Pallets engage too deeply | Rock with power removed | Reduce depth until one tooth clears |
| Oscillation stops quickly | Input impulse is low or pivot friction high | Operate anchor without the wheel | Free pivots and slightly adjust pallet face |
| Two teeth pass at once | Anchor travel or wheel spacing is excessive | Advance one half-cycle slowly | Limit swing and move anchor closer |
Choose your tradeoff
Start with reliable hand-operated locking before adding stored energy. Deeper lock improves safety but wastes impulse; too shallow a lock risks runaway motion.
Keep experimenting
Try another version
Hand escapement
Advance teeth manually without a pendulum or mass.
Regulator length
Compare timing at three pendulum lengths.
Rate graph
Record ten-release intervals as the drive mass descends.
Build together
Classroom and access options
Classroom version
Teams can compare the pallet engagement depth while keeping escape wheel, anchor, regulator length, frame, and drive mass. Assign builder, tester, recorder, and explainer roles; have each team predict the result before collecting three trials.
Access adaptations
- Use high-contrast tape to distinguish input and output parts.
- Replace a small crank with a wider handle for an easier grip.
- Add a paper sound tab and high-contrast tooth mark so releases are audible and visible.
Reflect on the design
- How did the pallet engagement depth change the measured result?
- Where did pallet impact affect the build most strongly?
- What evidence shows that alternating lock and release explains the motion?
- Which change would improve tooth-by-tooth escape-wheel rotation without creating a new problem?
Glossary
- Alternating lock and release
- Two anchor pallets engage the escape wheel alternately.
- Input
- The action or energy supplied to a system; here it is slow torque from a small falling mass.
- Output
- The useful response produced by a system; here it is tooth-by-tooth escape-wheel rotation.
- Efficiency
- The fraction of input energy that becomes useful output instead of friction, sound, heat, or unwanted motion.
Build your dreams
One build can start the next.
Share what you learned, change one variable, and help another builder understand what worked.
Explore more guidesSources and build notes
An original BrickLabClips interpretation of a standard mechanical mechanism.
- Mechanism verification: Standard kinematics were checked for motion direction, constraint, clearance, and likely friction points.
Written and edited by BrickLabClips. Published 2026-07-22; updated 2026-07-22.