In (automotive)
vehicle dynamics
For motorized vehicles, such as automobiles, aircraft, and watercraft, vehicle dynamics is the study of vehicle motion, e.g., how a vehicle's forward movement changes in response to driver inputs, propulsion system outputs, ambient conditions, air ...
, slip is the relative motion between a
tire
A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...
and the
road
A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation.
There are many types of ...
surface it is moving on. This slip can be generated either by the
tire
A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...
's rotational speed being greater or less than the free-rolling speed (usually described as ''percent'' slip), or by the
tire
A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...
's
plane of rotation
In geometry, a plane of rotation is an abstract object used to describe or visualize rotations in space. In three dimensions it is an alternative to the axis of rotation, but unlike the axis of rotation it can be used in other dimensions, such as ...
being at an angle to its direction of motion (referred to as
slip angle
In vehicle dynamics, slip angle or sideslip angle is the angle between the direction in which a wheel is pointing and the direction in which it is actually traveling (i.e., the angle between the forward velocity vector v_x and the vector su ...
).
In rail vehicle dynamics, this overall slip of the wheel relative to the rail is called ''creepage''. It is distinguished from the local sliding velocity of surface particles of wheel and rail, which is called ''micro-slip''.
Longitudinal slip
The longitudinal slip is generally given as a percentage of the difference between the surface speed of the wheel compared to the speed between axle and road surface, as:
:
where
is the longitudinal component of the rotational speed of the wheel,
is wheel radius at the point of contact and
is vehicle speed in the plane of the tire. A positive slip indicates that the wheels are spinning;
negative slip indicates that they are skidding. Locked brakes,
, means that
and sliding without rotating. Rotation with no velocity,
and
, means that
.
Lateral slip
The lateral slip of a tire is the angle between the direction it is moving and the direction it is pointing. This can occur, for instance, in cornering, and is enabled by deformation in the tire carcass and tread. Despite the name, no actual sliding is necessary for small slip angles. Sliding may occur, starting at the rear of the contact patch, as slip angle increases.
The slip angle can be defined as:
[
:
]
References
See also
*Contact patch
Contact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is commonly used in the discussion of pneumatic (i.e. pressurized) tires, where the term is used strictly to describe the portion of the tire’s ...
*Frictional contact mechanics
Contact mechanics is the study of the deformation of solids that touch each other at one or more points. This can be divided into compressive and adhesive forces in the direction perpendicular to the interface, and frictional forces in the tangen ...
* Aristotle's wheel paradox
Explanation with animation of the elastic slip
website ''tec-science.com''
Tires
Motorcycle dynamics
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