LEGO pistons operate using compressed air to create linear motion within a cylinder.
The Core Mechanism
At its heart, a LEGO piston works by leveraging the power of air pressure. The piston is a movable part housed inside a cylinder. When compressed air is introduced into the cylinder, the force exerted by the air pushes against the piston, causing it to move.
According to the reference provided: "When air enters the cylinder, the force of the expanding air will either force the piston up or down, depending on which air port the air has entered from."
Think of it like blowing into a balloon – the air pressure inside expands and pushes the balloon's surface outwards. In a LEGO cylinder, this pressure is contained and directed to push the piston instead.
Double-Acting Design
A key feature of LEGO cylinders is their "double-acting" nature. Unlike single-acting cylinders that only use pressure for motion in one direction (returning via a spring or gravity), double-acting cylinders use compressed air for movement in both directions.
As stated in the reference: "All LEGO® cylinders are double-acting cylinders, meaning compressed air can enter the cylinder through two air ports."
This design provides greater control over the piston's movement, allowing it to be extended or retracted using air pressure.
How Ports Control Direction
LEGO cylinders have two distinct air ports. The direction the piston moves is determined by which port the compressed air enters and exits.
| Air Entry Port | Air Exit Port | Piston Movement Direction |
|---|---|---|
| Port 1 (e.g., Bottom) | Port 2 (e.g., Top) | Moves Up (Extends) |
| Port 2 (e.g., Top) | Port 1 (e.g., Bottom) | Moves Down (Retracts) |
To make the piston move, compressed air is supplied to one port, while the other port is typically vented to allow the air already inside that section of the cylinder to escape.
Key Components
- Cylinder: The housing containing the piston.
- Piston: The movable disc or rod inside the cylinder.
- Ports: Two connection points for air hoses.
- Seals: Internal components that prevent air leakage past the piston and out of the cylinder ports.
By connecting LEGO pneumatic hoses to these ports and supplying compressed air (usually from a hand pump, air tank, or electric compressor), builders can create mechanisms that lift, push, pull, or clamp objects in their LEGO models.
