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Do it Labs

A package tips.
A chain sags.
A tree grows.
A rover lands.

Familiar observations become questions about mechanics. These student investigations and later computational explorations follow the questions wherever they lead.

Rendered branch junction with bark peeled back to reveal the modeled wood grain
A look inside the tree models. Explore the tree work

When does a package
slide or fall?

Everyday motion becomes a mechanics investigation. Explore how an object's geometry and the belt's acceleration affect sliding, tipping, and recovery.

Sliding and tipping
Force balance, friction, and the position of the centre of mass define the simplified motion model.
Acceleration histories
Compare motion under different acceleration profiles and examine how object geometry changes the response.

Watch the package

Will the package stay upright? A block on a conveyor with moving belt markings and rotating rollers. A stable block travels with the belt while the camera follows. The dashed load line shows initial stability. On playback, the block tips about its lower left corner or slides left relative to the accelerating belt. Belt acceleration

Where does it start?

First instability by package proportions and belt acceleration Stable at low acceleration. Short wide packages reach sliding first; tall narrow packages reach tipping first. The marker follows the controls. SlidingTippingStable 0369 123.5 Height / widthAcceleration (m/s²)
Stable · sliding first · tipping first. Static friction: 0.6.

Why do chains sag?

A hanging chain turns a small change in length into a visible change in sag. Explore its initial shape and how an assumed creep law changes it over time.

The shape of a hanging chain
Analytical catenary equations and a length constraint connect support spacing, chain length, and sag.
Length change over time
An assumed creep law adds length under sustained load. Re-solving the catenary shows how sag evolves between fixed supports.
A hanging chain between fixed supports The chain hangs symmetrically between two supports three metres apart. Increasing the chain length increases its sag. 3 m between supports Sag
Small length changes can noticeably change the sag. Creep coefficients are assumed model inputs.

How do trees carry
loads and adapt?

A branch junction, a knot, a hole: different starting points for exploring the same connection between shape, material direction, and mechanical response. The earlier student work and the ongoing models belong to one story.

Start with the shape

The earlier student investigation compared branch junctions, branch angles, and wood anisotropy in simplified finite-element models.

What changes when a sharp junction becomes a smooth curve?

Rendered branch junction showing its shape and the modeled wood grain

Same hole.
Different fiber directions.

Follow the grain around a knot. Turning the fibers changes how the load passes through the wood—and which stresses remain.

What changes when
a branch carries weight?

Compare an empty hole with a loaded branch. The unrolled trunk surface reveals the fiber paths and local failure index.

Follow the growth.
Keep the results in view.

The model adds wood around overloaded regions. Move through the model seasons to follow the front, the wood added, and the failure index together.

Touch down.
Stay down.

A lunar rover reaches the ground. The legs can store the impact energy, but where does that energy go next?

Follow the damped touchdown and its solved response, then take the challenge from energy absorption to leg strength and buckling.

Lunar touchdown

Energy-absorbing landing gear

Before touchdown

The solved response

Compression and gear force

Landing gear compression and force over time The compression rises after touchdown then settles. The force peaks at contact and then falls. Each response is normalized separately, with a cursor synchronized to the rover. 02.3 s
Compression · Gear force
Time after touchdown

Playback is slowed. The rover and plot follow the same solved vertical-motion model. Compression and force are normalized separately so the response shapes are visible without revealing the numerical design solution. The spring–dashpot model retains footpad contact and settles; irreversible crush absorption is a separate design option.

From touchdown to a design

Absorb the impact
Compare energy storage with damping or irreversible crushing. Make stopping distance part of the design.
Share the load
Consider uneven touchdown: fewer legs may have to carry the impact.
Size the structure
Check tube stress, off-axis bending, and buckling before turning the concept into CAD.