Wheelbase

For the British TV series of the same name see Wheelbase (TV series). Wheelbase was a BBC television series about cars broadcast on BBC2 between 1964 and 1975

In both road and rail vehicles, the wheelbase is the distance between the centers of the front and rear wheels. Vehicles, derived from the Latin word vehiculum, are non-living Means of transport.

Wheelbase (measured between rotational centers of wheels)

1 Road
- 1.1 Bikes
2 Rail
3 See also
4 References

Road

In automobiles, the wheelbase is the horizontal distance between the center of the front wheel, and the center of the rear wheel. At equilibrium, the total torque of the forces acting on the car is zero, and thus the wheelbase is related to the weight on each tire by the following formulae:

$W_f = {d_r \over L}mg$

$W_r = {d_f \over L}mg$

where $W f$ is the weight on the front tire, $W r$ is the weight on the rear tire, $L$ is the wheelbase, $d r$ is the distance from the center of gravity (CG) to the rear wheel, $d f$ is the distance from the center of gravity to the front wheel, $m$ is the mass of the car, and $g$ is the gravity constant. A torque (τ in Physics, also called a moment (of force is a pseudo- vector that measures the tendency of a force to rotate an object about In the Physical sciences weight is a Measurement of the gravitational Force acting on an object Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object Standard gravity, usually denoted by g 0 or g n is the nominal acceleration due to gravity at the Earth's surface at sea level So, for example, when one loads the trunk with heavy goods, the center of gravity shifts rearward and the weight on the rear tire increases causing it to sink depending upon the stiffness of the suspension. Suspension is the term given to the system of springs, Shock absorbers and linkages that connects a Vehicle to its Wheels Suspension If the automobile is accelerating or decelerating, extra torque is placed on the rear or front tire respectively, and the equation relating the wheelbase, height above the ground of the CG, and the weight on each tire becomes:

$W_f = {d_r \over L}mg - {h_{cg} \over L}ma$

$W_r = {d_f \over L}mg + {h_{cg} \over L}ma$

where $W f$ is the weight on the front tire, $W r$ is the weight on the rear tire, $d r$ is the distance from the CG to the rear wheel, $d f$ is the distance from the CG to the front wheel, $L$ is the wheelbase, $m$ is the mass of the car, $g$ is the acceleration of gravity (approx. This article is about tires used on road Vehicles including pneumatic tires and solid tires. 9. 8 m/s²), $h c g$ is the height of the CG above the ground, $a$ is the acceleration (or deceleration if the value is negative). So, as is common experience, when the automobile accelerates, the rear usually sinks and the front rises depending on the suspension. Likewise, when braking the front noses down and the rear rises. :^[1]

Because of the effect the wheelbase has on the weight transfer of the vehicle, wheelbase dimensions are crucial to the balance and steering of the automobile. For example, a car with a much greater weight load on the rear tends to understeer due to the lack of weight and therefore grip from the front tires. Understeer is a term for a Car handling condition in which during cornering the circular path of the Vehicle 's motion is of a greater radius than the circle indicated This is why it is crucial, when towing a single-axle caravan, to distribute the caravan's weight so that down-thrust on the tow-hook is about 100 pounds force (400 N). Likewise, a car may oversteer or even "spin out" if there is too much weight on the front tires and not enough on the rear tires. Oversteer is a phenomenon that can occur in an Automobile which is attempting to turn Also, when turning there is lateral torque placed upon the tires which imparts a turning force that depends upon the length of the tire distances from the CG. Thus, in a car with a short wheelbase, the short lever arm from the CG to the rear wheel will result in a greater lateral force on the rear tire which means greater acceleration and less time for the driver to adjust and prevent a spin out or worse. In Physics, a force is whatever can cause an object with Mass to Accelerate.

Wheelbases provide the basis for one of the most common vehicle size class systems. Vehicle size classes are a way of classifying cars The common North American parlance is word-based while English-speaking European writers also use words to describe car sizes

Bikes

Main article: Bicycle and motorcycle geometry

The wheelbase on many commercially available bicycles and motorcycles is so short, relative to the height of their centers of mass, that they are able to perform stoppies and wheelies. Bicycle and motorcycle geometry is the collection of key measurements (lengths and angles that define a particular bike configuration Bicycle and motorcycle geometry is the collection of key measurements (lengths and angles that define a particular bike configuration The bicycle, cycle, or bike is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind MotorCycle is the title of a 1993 album by Rock band Daniel Amos, released on BAI Records. The stoppie, also incorrectly called endo, is a Motorcycle and Bicycle trick in which the back wheel is lifted and the bike is ridden on In Vehicle Acrobatics, a wheelie is a trick where the front wheel or wheels come off the ground due to an excessive amount of torque being powered to the rear wheel

Rail

In rail vehicles, the wheelbase follows a similar concept.

On vehicles where the wheelsets (axles) are mounted inside the vehicle frame (mostly in steam locomotives), the wheelbase is the distance between the front-most and rear-most wheelsets. A wheelset is the Wheel - Axle ( Wheel and axle) assembly of a Railroad car.

On vehicles where the wheelsets are mounted on bogies (amer.: trucks), three wheelbase measurements can be distinguished:

the distance between the pivot points of the front-most and rear-most bogie;
the distance between the front-most and rear-most wheelsets of the vehicle;
the distance between the front-most and rear-most wheelsets of each bogie. A bogie (ˈboʊgi (BŌ-gē is a Wheeled wagon or trolley In mechanics terms a bogie is a Chassis or framework carrying wheels attached to a vehicle

The wheelbase affects the rail vehicle's capability to negotiate curves. Short-wheelbased vehicles can negotiate sharper curves. On some larger wheelbase locomotives, inner wheels may lack flanges in order to pass curves. A flange is an external or internal Rib, or Rim (lip for strength, as the flange of an Iron beam or I-beam

The wheelbase also affects the load the vehicle poses to the track, track infrastructure and bridges. All other conditions being equal, a shorter wheelbase vehicle represents a more concentrated load to the track than a longer wheelbase vehicle. As railway lines are designed to take a pre-determined maximum load per unit of length (tonnes per meter, or pounds per foot), the rail vehicles' wheelbase is designed according to their intended gross weight. The higher the gross weight, the longer the wheelbase must be.

References

^ Ruina, Andy; Rudra Pratap (2002). Bicycle and motorcycle geometry is the collection of key measurements (lengths and angles that define a particular bike configuration In Physics, a force is whatever can cause an object with Mass to Accelerate. A torque (τ in Physics, also called a moment (of force is a pseudo- vector that measures the tendency of a force to rotate an object about In the Physical sciences weight is a Measurement of the gravitational Force acting on an object Introduction to Statics and Dynamics (PDF), Oxford University Press, 350. Retrieved on 2007-03-23. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1174 - Jocelin, Abbot of Melrose, is elected Bishop of Glasgow.

Dictionary

-noun

the horizontal distance between the front and rear axles of a road or rail vehicle

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