jl4069
26 July 2004, 19:50
Here is an excerpt from Road and Track magazine written by Doug Milliken author of the classic, Race Car Vehicle Dynamics. Its seems rather on target:
PS- I think it would be great if some of the more knowledgable here could add to this list as I think while it is a good start its still rather general:
Handling: The Dynamicist's View (http://handling:%20The%20Dynamicist's%20View/)
Handling is really the sum of the driver and the vehicle. The driver provides the input and the vehicle responds with feedback. Without an easy way to characterize the driver, we are left to study the vehicle response, or the vehicle dynamics.
To make sense of handling, it is also necessary to define the task. For example, highway driving and racing are very different activities, with different requirements for both the driver and the car. The general question, "How do you like the handling?" can be answered in many different ways. Specific questions applicable to the road and track are needed: "How do you like the high-speed tracking?" Or, "What do you think about the balance under braking? Is it stable when you turn in?"
While all of the car's controls are important (throttle, brakes, gearbox, etc.), the steering is key to good handling. In the 1950s, aerospace-engineers-turned-weekend-sports-car-racers from Cornell Aeronautical Laboratory in Buffalo, New York, came up with a list of handling criteria originally titled "Desirable Vehicle Characteristics." The following is an annotated version of the list:
Steering response to be fast and well damped, with the car showing minimum roll angle and roll/yaw coupling. The car should follow the steering with minimum fuss. This applies to any car at any speed. But it is most important for racing — the interaction between body motions and the steering (i.e., roll steer). Some design factors to consider are low weight and rotational inertia, stiff springs, hard shock-absorber settings and wider, stiffer tires.
Steering ratio appropriate for the speed range and adequate for emergency maneuvers. Race cars require a sensitive touch on the wheel; the steering is fast for catching skids without shifting hands. For the road, the opposite extreme is the "sneeze factor" attributed to Harry Grylls of Rolls-Royce, with suitably slow steering so that the driver can sneeze and not change lanes.
Smooth steering control force with progression in normal driving, definite on-center feel and moderately fast return. Here is one area where the road car is often heavily compromised. A light car with good non-assisted steering will usually give the best road feel.
Minimum steering backlash, springiness and shake. Modern steering systems have eliminated backlash. Minimum steering-wheel vibration is desirable in street cars, leading to the use of rubber isolators, but some imprecision results.
Minimum change in car direction, pitching and control response with road roughness. Street cars deal with much rougher roads than road-racing cars.
Modest aerodynamic and tire/road steady-state stability over speed range. By definition, a stable car will return toward the original path after some disturbance, say, a bump in the road. In the equations of motion, stability has two parts: (1) Understeer and oversteer. They remain roughly constant at any speed. And to make best use of all four tires, balance is important, especially for racing. (2) Yaw damping. It decreases with speed, and is primarily a function of the tires and the wheelbase. Long-wheelbase cars with big tires have more yaw damping. Short-wheelbase cars can feel "squirrelly" at high speed.
High side forces, or ultimate cornering adhesion. One of the easiest and most common measures of "handling," yet only one part of the whole picture. This is good for lateral-g-force bragging-rights for street cars, but rarely used on the road, even in emergencies. However, it is critical for race cars because it is used on every corner.
Satisfactory skidding characteristics: adequate skid warning, gradual rear breakaway and easy natural recovery. With very few exceptions, wide tires have more abrupt breakaway characteristics and are less forgiving for use on the road. In racing, the levels of driving and of concentration are much higher, and cars with less skid warning are still acceptable.
Minimum change in behavior with braking and acceleration. Load shift to the front wheels (on lift-throttle or braking) tightens the turn, while acceleration (except rear wheelspin) straightens the turn. Many of today's street cars have had these "natural" effects tuned out completely by careful design. Steering with the throttle is fun, but too much and the car might be virtually uncontrollable.
To sum up, handling has many dimensions. It's really too simplistic to talk about "good handling" in an overall sense. It's all about compromises and a good balance of handling design factors for the intended purpose of the car. — Doug Milliken
PS- I think it would be great if some of the more knowledgable here could add to this list as I think while it is a good start its still rather general:
Handling: The Dynamicist's View (http://handling:%20The%20Dynamicist's%20View/)
Handling is really the sum of the driver and the vehicle. The driver provides the input and the vehicle responds with feedback. Without an easy way to characterize the driver, we are left to study the vehicle response, or the vehicle dynamics.
To make sense of handling, it is also necessary to define the task. For example, highway driving and racing are very different activities, with different requirements for both the driver and the car. The general question, "How do you like the handling?" can be answered in many different ways. Specific questions applicable to the road and track are needed: "How do you like the high-speed tracking?" Or, "What do you think about the balance under braking? Is it stable when you turn in?"
While all of the car's controls are important (throttle, brakes, gearbox, etc.), the steering is key to good handling. In the 1950s, aerospace-engineers-turned-weekend-sports-car-racers from Cornell Aeronautical Laboratory in Buffalo, New York, came up with a list of handling criteria originally titled "Desirable Vehicle Characteristics." The following is an annotated version of the list:
Steering response to be fast and well damped, with the car showing minimum roll angle and roll/yaw coupling. The car should follow the steering with minimum fuss. This applies to any car at any speed. But it is most important for racing — the interaction between body motions and the steering (i.e., roll steer). Some design factors to consider are low weight and rotational inertia, stiff springs, hard shock-absorber settings and wider, stiffer tires.
Steering ratio appropriate for the speed range and adequate for emergency maneuvers. Race cars require a sensitive touch on the wheel; the steering is fast for catching skids without shifting hands. For the road, the opposite extreme is the "sneeze factor" attributed to Harry Grylls of Rolls-Royce, with suitably slow steering so that the driver can sneeze and not change lanes.
Smooth steering control force with progression in normal driving, definite on-center feel and moderately fast return. Here is one area where the road car is often heavily compromised. A light car with good non-assisted steering will usually give the best road feel.
Minimum steering backlash, springiness and shake. Modern steering systems have eliminated backlash. Minimum steering-wheel vibration is desirable in street cars, leading to the use of rubber isolators, but some imprecision results.
Minimum change in car direction, pitching and control response with road roughness. Street cars deal with much rougher roads than road-racing cars.
Modest aerodynamic and tire/road steady-state stability over speed range. By definition, a stable car will return toward the original path after some disturbance, say, a bump in the road. In the equations of motion, stability has two parts: (1) Understeer and oversteer. They remain roughly constant at any speed. And to make best use of all four tires, balance is important, especially for racing. (2) Yaw damping. It decreases with speed, and is primarily a function of the tires and the wheelbase. Long-wheelbase cars with big tires have more yaw damping. Short-wheelbase cars can feel "squirrelly" at high speed.
High side forces, or ultimate cornering adhesion. One of the easiest and most common measures of "handling," yet only one part of the whole picture. This is good for lateral-g-force bragging-rights for street cars, but rarely used on the road, even in emergencies. However, it is critical for race cars because it is used on every corner.
Satisfactory skidding characteristics: adequate skid warning, gradual rear breakaway and easy natural recovery. With very few exceptions, wide tires have more abrupt breakaway characteristics and are less forgiving for use on the road. In racing, the levels of driving and of concentration are much higher, and cars with less skid warning are still acceptable.
Minimum change in behavior with braking and acceleration. Load shift to the front wheels (on lift-throttle or braking) tightens the turn, while acceleration (except rear wheelspin) straightens the turn. Many of today's street cars have had these "natural" effects tuned out completely by careful design. Steering with the throttle is fun, but too much and the car might be virtually uncontrollable.
To sum up, handling has many dimensions. It's really too simplistic to talk about "good handling" in an overall sense. It's all about compromises and a good balance of handling design factors for the intended purpose of the car. — Doug Milliken