Product Code Database
The turning radius (alternatively, turning diameter or turning circle) of a vehicle defines the minimum dimension (typically the radius or diameter) of available space required for that vehicle to make a semi-circular U-turn without skidding. The Oxford English Dictionary describes turning circle as "the smallest circle within which a ship, motor vehicle, etc., can be turned round completely"."turning, n." OED Online, Oxford University Press, December 2020, www.oed.com/view/Entry/207704. Accessed 15 February 2021. The term thus refers to a theoretical minimal circle in which for example an aeroplane, a ground vehicle or a watercraft can be turned around.
The terms ( radius, diameter, or circle) can have different meanings; refer to the section.
The curb-to-curb turning radius, which considers the chassis and wheels only without body protrusions, can be expressed as a simplified function of the wheelbase, tire width, and steering angle:
Aircraft have a similar minimum turning circle concept, generally associated with a standard rate turn, in which an aircraft enters a coordinated turn which changes its heading at a rate of 3° per second, or 180° in one minute. In this case, the turning radius depends on the true airspeed (in knots) as:
Turning diameter is sometimes used in everyday language as a generalization term rather than with number. For example, a wheeled vehicle with a very small turning circle may be described as having a "tight turning radius", meaning that it is easier to turn around very tight corners. Wheeled vehicles with four-wheel steering will have a smaller turning radius than vehicles that steer wheels on one axle.
Some wheeled vehicles are designed to Rotation around their central axis by making all wheels steerable, such as certain lawnmowers and wheelchairs as they do not follow a circular path as they turn. In this case the vehicle is referred to as a "zero turning radius" vehicle. Some camera dolly used in the film industry have a "round" mode which allows them to spin around their z axis by allowing Synchronization inverse rotation of their left and right wheel sets, effectively giving them "zero" turning radius.
Many conventionally steerable vehicles (only one axle with steerable wheels) can reverse the direction of travel in a space smaller than the stated turning radius by executing a specialized maneuver, such as a J-turn or similar skid, or in a discontinuous motion such as a three-point turn.
In practice, the values of turning diameter tend to be listed more frequently in vehicle specifications, so the term turning diameter will therefore be more correct in most cases. The turning diameter will always give a higher number for a given vehicle, and the turning diameter measurement is usually preferred by automotive manufacturers. Such mixing of terms can lead to confusion among consumers.
Turning circle is also sometimes used to refer to the path swept in the manoeuvre, i.e. the Circular arc, or the circle's circumference in the case when the manoeuvre makes a complete turn.
The wall-to-wall turning circle is the minimum distance between two walls, both of which exceed the height of the vehicle, in which the vehicle can make a U-turn. The kerb-to-kerb turning circle is the minimum distance between two raised curbs, both of which are lower than the lowest body protrusions, in which the vehicle can make a U-turn. The wall-to-wall turning circle is greater than the kerb-to-kerb measure for the same vehicle because of the front and rear body overhangs. One can find these two ways of measuring the turning circle used in auto specifications, for example, a van might be listed as having a turning circle (in meters) of 12.1 (C) / 12.4 (W).
The kerb-to-kerb turning circle can be smaller than the turning circle as it refers to only a partial circle (~180°) with the vehicle alongside one kerb to start with. To perform a U turn in a forward direction only, the centre of the turn is not coincident with the centre of the road - thus a complete circle would not be possible (without driving onto the pavement to complete the manoeuvre). It also does not take into account that part of the vehicle that overhangs the wheels where as 'turning circle' does.
Curb-to-curb
A curb or curb-to-curb turning circle will show the straight-line distance from one side of the circle to the other, through the center. The name "curb-to-curb" indicates that a street would have to be this wide before this car can make a U-turn and not hit a street curb with a wheel. If you took the street curb and built it higher, as high as the car, and tried to make a U-turn in the street, parts of the car (bumper) would hit the wall.
Wall-to-wall
The name wall or wall-to-wall turning circle denotes how far apart the two walls would have to be to allow a U-turn without scraping the walls.
Legal requirements for road vehicles
Road vehicles must be able to carry out a 360 degrees turn on an annulus with an outer radius of and an inner radius of , measured wall-to-wall. In addition, when entering this annulus, no part of the vehicle can overreach a tangent by more than ; this tangent is drawn at the outer, 12.5 m limit of the annulus.Germany: European Union: Switzerland:
New Zealand requires that road vehicles can perform a 360 degrees turn on a circle with a diameter, measured wall-to-wall. The only part of the vehicle that may reach over this limitation are collapsible mirrors.
Common uses
See also
External links
|
|
