Lifts

Just like with Drivetrains, there are many types of lifts — each with its own strengths and weaknesses. Choosing the right lift depends on how high you need to reach, how much weight you need to carry, and how complex you want to build.

Why does this matter?

Many VEX games require placing or stacking objects at elevated goals. The right lift lets your robot reach those heights quickly, reliably, and without tipping over.

Four Bar Lift

A Four Bar Lift is the most popular lift in VEX robotics. It is stable, easy to build, and has one very special feature: whatever you attach to it stays at the exact same angle no matter how high or low the lift goes.

Unlike a simple single arm (which tilts backward as it rises), a four bar lift keeps a claw or intake perfectly level throughout its entire range of motion. This is incredibly useful for interacting with goals!

How it Works

The lift is named for its four rigid segments (bars), connected at four pivot points:

• The Tower (Ground Link): The fixed, vertical frame attached to your robot’s chassis. It does not move.
• The Top Arm: A long beam that pivots on the tower and connects to the top of the claw assembly.
• The Bottom Arm: A second beam equal in length to the top arm, mounted underneath it.
• The Output Link (Coupler): The moving plate where your claw or intake is attached.

Because both arms are the same length and the spacing matches on both ends, the system forms a parallelogram. This forces the output to always stay parallel to the tower — regardless of the arm angle.

Power

Only one motor is needed to power the entire four bar lift, since all bars are mechanically linked.

• Correct way: Mount the motor’s gear at the base of the tower where the arm pivots. This keeps the heavy motor low on the robot, which is better for balance.
• Wrong way: Mounting the motor on the moving claw plate means the lift has to carry the motor’s weight up with it, reducing lifting power and making the robot top-heavy.

Pros

• Simple to understand and build.
• The attachment angle stays constant the whole time — great for scoring!
• Only 4 pivot points, so there is very little wobble.
• Moves in a predictable arc that is easy to control.

Cons

• Maximum height is limited by the length of the arms. Very long arms might violate robot size rules.
• Because it swings in an arc, the robot’s front-to-back length changes as the lift moves. This can cause problems when driving right up to a wall.

Double Reverse Four Bar (DR4B)

The Double Reverse Four Bar (also called DR4B or RD4B) is like two four bar lifts stacked on top of each other — but facing opposite directions. This allows it to reach much greater heights while still keeping the output angle perfectly level.

How it Works

Imagine the bottom four bar pointing forward as it rises, and the top four bar pointing backward. They are joined in the middle by a moving center plate.

• The lower four bar rises from the robot chassis.
• The upper four bar is attached to the lower lift’s top and rises in the opposite direction.
• Because both halves are geared together and move in opposite directions, their arcs cancel each other out — the net result is perfectly vertical travel!

Pros

• Can reach roughly double the height of a standard four bar using the same footprint.
• Travels straight up and down — the robot can park against a wall and the lift still has room to move.
• Maintains consistent angle just like a standard four bar.

Cons

• Much more complex to build — requires precise alignment to work properly.
• Heavier than a simple four bar, which can affect balance.

Scissor Lift

A Scissor Lift is one of the most recognizable lift types. It uses folding, crisscrossed beams (which look like scissors opening and closing) to travel perfectly straight up and down.

How it Works

A scissor lift converts horizontal (sideways) pushing force into vertical (upward) movement:

• The X Frames: Pairs of equal-length beams pinned together in the middle to form an “X” shape. Multiple stages are stacked on top of each other.
• The Slider: One bottom corner of the lowest X is fixed in place. The other bottom corner is mounted on a sliding track. When the slider moves inward, the X expands upward.
• The Drive: A motor or pneumatic cylinder pushes the sliding corner. As the corners are pushed together, the whole structure rises.

Important: Starting from Flat is Hard!

When the scissor lift is fully collapsed (flat), the pushing force is almost parallel to the beams. This gives the motor very little leverage — it is like trying to push open a folded map from the side. The formula for required lifting force is:

When the lift is flat, the angle θ is close to 0, making sin(θ) very small, which means the required force becomes very large. Motors often stall trying to start from a fully flat position.

Fix: Add rubber bands or helper springs that assist the lift only at the very bottom. This gives the motor the extra help it needs to get started.

Pros

• Travels perfectly straight up and down — great for driving against walls or goals.
• Collapses very flat but can expand to a great height.
• Adding more stages increases height without changing the base footprint.

Cons

• Many pivot points mean more potential wobble and slop.
• Very difficult to start from a fully flat position (see above).
• Heavier and more complex than arm-based lifts.

Six Bar Lift

A Six Bar Lift is an improved version of the four bar lift. It uses the same parallelogram principle but adds an extra pair of linkages. This gives it greater maximum height and more outward reach without making the robot’s base any bigger.

It works on the same angle-retention principle as the four bar — the output attachment always stays level.

Best Practices: Bracing

No matter which lift you build, bracing is essential. Bracing means adding extra structural support to prevent the lift from wobbling or twisting under load.

Common bracing strategies:

• X-Bracing: Cross two beams diagonally between two vertical uprights. This prevents the uprights from leaning toward or away from each other.
• 5-by Bracing: A horizontal beam connecting both sides of the lift every few holes, keeping everything aligned and square.

Always brace your lift before testing under load. A lift that wobbles will throw off your autonomous code and can damage parts over time.