Version: Unity 6.1 Alpha (6000.1)
Language : English
Wheel Joint 2D
Wheel Joint 2D

Wheel Joint 2D fundamentals

Use this jointA physics component allowing a dynamic connection between Rigidbody components, usually allowing some degree of movement such as a hinge. More info
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to simulate wheels and suspension. The aim of the joint is to keep the position of two points on a line that extends to infinity, whilst at the same time making them overlap. Those two points can be two Rigidbody2D components or a Rigidbody2D component and a fixed position in the world. (Connect to a fixed position in the world by setting Connected Rigidbody to None).

Wheel Joint 2D acts like a combination of a Slider Joint 2D (without its motor or limit constraints) and a Hinge Joint 2D (without its limit constraint).

The joint applies a linear force to both connected rigid body objects to keep them on the line, an angular motor to rotate the objects on the line, and a spring to simulate wheel suspension.

Set the Maximum Motor Speed and Maximum Motor Force (torque, in this joint) to control the angular motor speed, and make the two rigid body objects rotate.

You can set the wheel suspension stiffness and movement in order to simulate different degrees of suspension. For example, to simulate a stiff, barely moving suspension:

  • Set a high (1,000,000 is the highest) Frequency == stiff suspension.

  • Set a high (1 is the highest) Damping RatioA joint setting to control spring oscillation. A higher damping ratio means the spring will come to rest faster. More info
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    == barely moving suspension.

To simulate a looser and more freely moving suspension, you would use the following settings:

  • Set a low Frequency == loose suspension.

  • Set a low Damping Ratio == moving suspension.

It has two simultaneous constraints:

  • Maintain a zero relative linear distance away from a specified line between two anchor points on two rigid body objects.
  • Maintain an angular speed between two anchor points on two rigid body objects. (Set the speed via the Maximum Motor Speed option and maximum torque via Maximum Motor Force.)

You can use this joint to construct physical objects that need to react as if they are connected with a rotational pivot but cannot move away from a specified line. Such as:

  • Simulating wheels with a motor to drive the wheels and a line defining the movement allowed for the suspension.

Behavior difference to the Wheel Collider

Unlike the Wheel ColliderA special collider for grounded vehicles. It has built-in collision detection, wheel physics, and a slip-based tire friction model. It can be used for objects other than wheels, but it is specifically designed for vehicles with wheels. More info
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used with 3D physics, the Wheel Joint 2D uses a separate RigidbodyA component that allows a GameObject to be affected by simulated gravity and other forces. More info
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object for the wheel, which rotates when the force is applied. (The Wheel Collider, by contrast, simulates the suspension using a raycast and the wheel’s rotation is purely a graphical effect). The wheel object will typically be a Circle Collider 2D with a Physics Material 2DUse to adjust the friction and bounce that occurs between 2D physics objects when they collide More info
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that gives the right amount of traction for your gameplay.

Additional resources

WheelJoint2D

Wheel Joint 2D
Wheel Joint 2D