The stability of a vehicle is that occurs about the longitudinal axis. A vehicle is laterally stable in that when a slight turn takes place, the forces acting on the vehicle tend to restore it.
Vehicle Stability Control (VSC)
Helps prevent wheels from slipping sideways when cornering or sudden steering
VSC is a system that helps prevent side skids and help stabilize the vehicle while turning on a curve. According to the National Highway Traffic Safety Administration's (NHTSA) report, vehicles equipped with VSC compared to those without can effectively reduce single-vehicle accidents by 35% for automobiles and 67% for Sport Utility Vehicles (SUV).
When the vehicle senses a loss of traction or a slip, braking is automatically applied to all 4 individual wheels and engine power is reduced to help secure the safety of the vehicle. For example, if the steering wheel refuses to turn from over-speeding (under-steering), the vehicle will take control to steer toward the inner curve. Also, when the vehicle begins to spin from abrupt steering handling (over-steering), the vehicle will take control to steer toward the outer curve.
*VSC is designed to help the driver maintain vehicle control, and it is not a substitute for safe driving
Active Safety For Maneuvering
Anti-Lock Brake System (ABS)
Helps prevent brakes from locking Brake Assist
Supports unexpected braking in case of emergency Traction Control (TRC)
Helps prevent wheel slippage when the vehicle is starting or accelerating on wet or slippery roads
Vehicle Stability Control (VSC)
Helps prevent wheels from slipping sideways when cornering or sudden steering
Vehicle Dynamic Integrated Management (VDIM)
Integrated control of "Drive, Turn and Stop" and maintains driving stability
Hill-Assist Control (HAC)/Downhill-Assist Control (DAC) Supports drivers on steep hills and descending slopes Tire Pressure Monitoring System (TPMS)
Helps prevent accidents caused by decreased tire air pressure For Driving Support
Radar Cruise Control
Manages constant distance from the proceeding vehicle Lane Keeping Assist
Helps keep drivers within lanes Navigation-Brake Assist
Works with the navigation system to provide stop sign information For Visibility
Front and Side View Monitor
Helps to verify safety in hard-to-view areas
Multi-Angle Monitor
Verifies the vehicle's surroundings
Intelligent Adaptive Front-lighting System (AFS)
Changes the direction of the headlights based on the cornering angle Night View
Detects objects and pedestrians during the nighttime For Pedestrian
Approaching Vehicle Audible System Notifies pedestrians of your vehicle
Factors affecting tyre performance
The factors which influence tyre life:
Inflation Pressure
o The science and the technology that has gone into producing even the best quality of tyre will go waste if the tyres are not inflated to the recommended pressure – Pressure comensurating to the load carried. The best performance of tyres can only be achieved when the tyre is inflated to the designated pressure based on the load per tyre.
o ―Under inflation‖ or ―Over inflation‖ on the tyre tends to impact tyre life, vehicle handling and safety. There are two factors with weight distribution of the vehicle. One is contact patch and other linked to the tyre wear. This result in heat buildup/tyre temperature and thus loss of tyre life, premature tyre removals, increased rolling resistance and fuel consumption.
o ―Under Inflation‖ is more common than over inflation. Tyre users are not always conscious about maintaining or matching tyre pressure to the loads carried.
o In pneumatic tyre the ―Air carries the load‖. The best tyre performance and lower tyre CPKM are obtained by maintaining correct tyre inflation pressure.
o It is important to remember that the total weight (GVW) carried may not exceed the registered laden weight (RLW) or vehicle passing weight, but one side of the truck or one axle may be severely overloaded due to improper distribution of the load in the pay load platform or loading area.
o Improper load distribution overloads the tyre(s). This condition combines with high speed , long hauls and load transfers result in tyres wearing fast and premature removal of tyres
o Loads and Loading practices
It is important to remember that even one trip of the truck; with improper load distribution may cause irreversible damage to the tyres.
o Speed
Excessive high speeds results in increased tyre running temperature.
As the rubber gets heated up its modulus (stiffness) gets reduced.
Rubber being a good non conductor of heat the residual heat is retained causing increased tyre wear and separation of components.
o Wheel Alignment
A vehicle is said to be properly align when all the steering and suspension components and set as per the vehicle manufacturer and when the tyre wheel assembly are running straight and true.
Proper alignment is necessary for perfect vehicle control, uniform and even tyre wear and safety.
Recommended to get the vehicle alignment checked and corrected as per vehicle owner‘s manual as soon as tyre are wearing unevenly or ride handling problems(vibrations, pulling to one side etc).
o Wheel Balancing
A wheel which is not properly balanced may setup vibrations which can affect steering control. Wheels, tyres and tubes are usually checked for balance before leaving factory.
This balance is achieved by positioning weights on the wheel to counterbalance heavy spots on the tyre wheel assembly.
Properly balanced tyres are important for driving comfort and long tyre life.
Tyres should be balanced when they are mounted on the wheels for the first time or when they are removed for repair or periodically as per vehicle manufacturer‘s recommendations.
o Tyre rotation
Rotation of tyre in a vehicle is recommended for a uniform tyre tread wear on all wheel position to achieve optimum tyre life.
It is preferred to rotate tyres as per vehicle manufacturer‘s recommendation or in case of any uneven tyre wear noticed.
It is suggested to check wheel alignment, wheel balance and
suspension before the tyres are rotated.
Rotation patterns /pictures to be incorporated.
o Road Conditions
Vehicle /tyre operating conditions which significantly influence tyre life both in terms of new tyre life and structural durability.
Rough/abrasive road surface
Paved road
Straight road
Broken up roads
Hilly windings roads
Unmade country roads
o Driving habits
Careful driving habits will ensure optimum tyre life, unavoidable damages besides avoiding serious road accidents. Some of the habits which cause serious damages to tyre and road accidents are:
Over speeding
Speeding over pot holes, stone etc.
Quick starts and sudden stops
Riding over road divider and other obstacles
Sharp turns at high speeds
Hitting the road, curbs, objects etc.
Running on improperly inflated tyres
o Seasonal Effects
Climatic and whether conditions in our country vary widely from region to region. Dry and extremely hot during summer, extreme cold during winter and rains during monsoon.
These variations in climatic conditions influence tyre life in terms of mileage and structural durability.
o Do's & Don’ts
Tyre Pressure checks including the spare tyre must be done regularly at least once in two weeks.
Tyre pressure should be checked using an accurate pressure gauge.
Tyre pressure should be checked when tyres are cold.
Under inflation and over inflation will cause rapid tread wear and premature tyre failures.
Tyre pressure should always be maintained as per the vehicle manufacturers recommendations, mentioned at information placard, at door, owner‘s manual.
Weight distribution
Weight distribution is very important; not only does it affect the static
weight on the different tires; it also affects how the weight shifts in dynamic conditions.
The easiest way to judge weight distribution is to determine the car's Center of Gravity (CG). This is a point in space where the mass of the entire car is accounted for. Because of its location, it can be used to simplify the effects of inertia forces. In reality, every little bit of mass is subjected to inertia, but it's much easier to make use of an equivalent condition: assume all the mass of the object is concentrated in its center point, i.e. it's CG. So instead of having to figure out how every part of a 1.5kg car reacts to a certain force, we only have to figure out how a weightless car with a 1.5kg dot in its
center(the CG) reacts to it. The latter is much easier: the force only works in the CG, and not in the rest of the car.
Of course, this only works when the CG is determined correctly. I think that's a lot of work, and it might not be accurate, so I propose a different method. It's based on the fact that when an object is statically balanced, its CG is right above the point where it's supported. By applying this in three different planes, you can determine an object's CG. Here's an example.
Here we have an object with a heavy part (dark) and a lighter part (bright) we'd like to determine the CG of. Since the right part is heavier the CG will probably be located somewhere at the right.
We try to balance it on a sharp edge, and this is the position in which the object stays put. So we know the CG is somewhere right above the point where the object is supported.
The red line contains all the points above the point where the object was being supported, so the CG has to be located somewhere on the red line.
We can follow the same procedure, but in a different dimension. Again, we can draw a red line on which the CG is located.
Because this is a 2D example, trying to balance the object 2 times is sufficient to determine it‘s CG (circled in purple). For a car, which has 3 dimensions, you'll need to do it 3 times. It might impose some practical problems, but this is where you'll have to use your imagination.
Now that we know where the car's CG is located, we can easily calculate the amount of weight on the tires, and the weight distribution.
First, let's have a look at the front-to-rear weight distribution:
The wheelbase is the distance between the front and rear axle, F is the distance between the CG (green) and the front axle, R is the distance between the CG and the rear axle.
Weight on the front axle = weight of the car*(R/WB) Weight on the rear axle = weight of the car*(F/WB) or, in percentages:
Front weight percentage = (R/WB)*100%
Rear weight percentage = (F/WB)*100%
obviously, this will have its effects on handling: more weight on a tire means more grip. So if the CG is located further towards the rear, the car will have a lot of rear traction, which is nice to have if acceleration is important. If the CG is located further towards the front, the car will have a lot of steering, but it might lack rear traction, which increases the risk of spinning out.
In some cases, lateral weight distribution is a major concern, especially in so-called LTO (left turn only) cars, which race on oval tracks. It's basically the same deal:
TW is the tread with, the distance between the centers of the tires at the axle, E is the distance between the CG(green) and the centerline of the left side tires, I us the distance between the CG and the centerline of the right side tires. If the front and rear axles aren't equally wide, E and I have to be measured at the CG.
Weight on left side = (I/TW)*weight of the car
Weight on right side = (E/TW)*weight of the car
Or, in percentages: left side weight percentage = (I/TW)*100%
Right side weight percentage = (E/TW)*100%
Note that if you need to know the amount of weight on one tire, you need to multiply the weight of the car by 2 factors, one of the lateral balance, and one of the longitudinal balance, for example:
Weight on left front tire = Weight of the car*(I/TW)*(R/WB) Weight on right front tire = Weight of the car*(E/TW)*(R/WB) Weight on left rear tire = Weight of the car*(I/TW)*(F/WB) Weight on right rear tire = Weight of the car*(E/TW)*(F/WB)
Note that this is only true when the car isn't tweaked; spring preload should be the same on the left and right hand side.
Again, having the CG away from the center of the car has consequences for the car's handling: having it toward the left improves the car's ability to turn left, but it might make it very difficult to drive the car in a straight line, especially under acceleration.
The height of the CG is also very important: it determines the car's roll characteristics and weight transfer.
Sadly enough, that isn't all there is to it; inertia has been left out, rotational inertia to be more precise. Here's an example:
These drawings represent two cars, the first one on the left has all the heavy stuff (blue) located at its ends, far removed from the CG (purple). The
second one on the right has all the heavy stuff lined up right in the middle, very close to the CG. Both cars weigh just as heavy, and their CGs are in exactly the same place.
So both cars will transfer the same amount of weight while braking or cornering, and their roll angles will also be identical. Yet they won't handle the same, because their rotational moment of inertia is different. The first car will react slowly, turn in a little sluggishly and it will generally be more reluctant to change direction. Some might say it is slow, others might find it very stable, and it‘s the same thing. The second car will feel like the
opposite: it will change direction very quickly, and it will feel very nimble, and thus also unstable.
So, rotational moment of inertia doesn't change how far the car's chassis moves, it changes how fast it does so. It's kind of like swinging a baseball bat with a big, heavy tip: you'll need a lot of effort to get it going, and once you get it going, there's not much you can do to alter its course.
The rotational moment of inertia can be calculated too: the rotational
moment of inertia of a body around an axis is the sum of all the elementary masses of the body multiplied by their distance to that axis squared. For simple-looking bodies like cylinders, cubes and cones and such, you can do this by hand, but for real-life applications you'll need a sophisticated CAD program.
Note that it's also important around which axis you're calculating the rotational moment of inertia. Consider the following example:
These drawings represent identical cars, except for the fact that they have their weight distributed differently: the first one has its heavy components (blue) lined up along its lateral axis (purple) and the second one has its heavy stuff lined up along its longitudinal axis.
Consider the first car. If we calculate the rotational moment of inertia around its lateral axis, we have to multiply all of the masses with their distance to the axis squared. In this case, we have to multiply most of the mass with a very small distance squared, resulting in a very small value. On the other hand, if we calculate its rotational moment of inertia around its longitudinal axis (not drawn), we have to multiply most of the mass with a very large distance squared, resulting in a large value. So, the first car has a very large moment of inertia around its longitudinal axis, and a very small one around its lateral axis. In other words, this car will react very slowly while cornering;
it will move from side to side (roll) very slowly. But, it will move from front to rear (pitch) very easily, this might be beneficial for quick braking, but it will make the car bounce back and forth in bumps, making it very unstable.
For the second car, the opposite is true: it has a large value for its rotational moment of inertia around its lateral axis (not drawn) and a very small one around the longitudinal axis. This means that the car will roll quickly, and be very responsive in turns, but it will be very stable front to rear. This helps stabilize the car in bumps while maintaining good cornering abilities.
Maybe now you can understand the hype about mid-mounted motors in full-scale cars: the motor is by far the heaviest item, so by positioning it
centrally, the car's rotational moment of inertia is reduced, making for a more nimble handling car.
Most modern vehicles‘ engines are located to the front of the driver.
However, some manufacturers place locate the engine at some location point behind the driver. Due to the weight of the engine, its location can
substantially impact a vehicle‘s handling, behavior, and response
characteristics. The goal of this article is to discuss the dynamic differences among front-, mid-, and rear-engine configurations.
Have you ever lifted the hood of a modern passenger car, only to find no motor? For most drivers, this has not occurred, as most vehicles‘ engines are located up front. But if you drive a mid- or rear-engine vehicle, you would be accustomed to having only storage space up front under the hood.
The goal of this article is to discuss the different engine locations and their impact on vehicle dynamics.
Front-Engine Vehicles
By far the most common engine location is at the front of the vehicle, ahead of the driver and the front axle line. While the earliest automobiles used a variety of engine locations, front-engine vehicles quickly became the norm for financial and engineering reasons. For example, most front-engine vehicles feature relatively easy access to the motor for maintenance and repair.
Positioning the engine ahead of the driver also impacts space considerations such as permitting permits a full-size interior. In addition, most front-engine vehicles feature large cabins, usually with seating for four or more
occupants, including relatively spacious rear seating areas. Interior sound levels are also reduced because the engine is not directly adjacent to the cabin. The static weight distribution of front-engine vehicles (the weight of the front and rear of the automobile expressed in percentages) is generally favorable with between 50-66% of the vehicle‘s weight over the front wheels (Bondurant ‗ Blakemore, 1998). Most front-engine vehicles feature relatively easy access to the motor for maintenance and repair.
Placing the engine up front also has some disadvantages. First, braking ability is somewhat diminished. Diminished braking occurs because weight transfers forward under braking (Karasa, 2001), leaving relatively little weight remaining over the rear wheels during braking and thus, limiting the ability of the rear tires to contribute the braking task. Second, accelerative ability is limited somewhat by the relative lack of static weight over the rear tires when, the weight of the vehicle shifts rearward upon acceleration
(Scotti, 1995). Despite its relative drawbacks, the front-engine layout remains the most popular.
Mid-Engine Vehicles
In a mid-engine configuration the engine is located directly behind the cabin
In a mid-engine configuration the engine is located directly behind the cabin