In a sense yaw is the feel of oversteer being more rotation than expected and understeer being less. Drifting would be the art of creating extreme yaw while maintaining consistent trajectories.
If you are experiencing understeer or oversteer you are falling away from your cars optimal yaw. Yaw is an acceleration, what you mean is the slip or driftangle. If you want to drift you need to rip the solid tire from the tarmac. You can do this with extreme acceleration, either lateral with gaß or ritational with yaw. If you do it with yaw you need to counter steer otherwise you will spin, which would cause really high yaw rates. A good drifter remains steady and chill yaw rates all around the corner.
@@MrHaggyyPhysics was not my major but from boats and planes yaw is horizontal motion around the y axis. Nose and tail moving left and right. The other axis are pitch and roll. If the centrifugal forces are balanced by tires traction the yaw should be zero. Perhaps there's some hair splitting as drifts,bootleg turns,snap oversteer and tail wagging all seem to pivot around the engine mass and front wheels. True yaw is a sickening spin around the middle with front and back heading in opposite directions as in a full spin or beginning to slide and correcting. So you're right drift is sustained slip angle but there seems to be yaw at the moment of traction loss in oversteer and understeer also.
@@jeffarcher400 yes you have roll pitch and yaw as rotations as well as front right and up for lateral movements. Yaw is the acceleration around the "up" axis. In a stable drift you have a much higher yaw angle than you would normally. But you also corner at a constant yaw-rate or in a fixed circle around a fix point. In a normal driving situation each tire can generate a force lateral, in the direction the tire is rotating, and transversal, in a 90 degree angle to where the tire is facing. In a drift you rip the contact patch of the tarmac and generate a thin layer of liquid and gas, the nice smoke. In that state the tire can only really generate forces in the direction of rotation. So in a normal drift you have a big force in the direction your car is facing from the rear and two forces from the front. The front sums up in a force around a circle. So you are constantly rotating at a fix rotational speed - a fixed yaw rate. If you ease of the steering the circle would get bigger until the car would catch it`s grip again and you would only accelerate in a constant line. ;-) the ability of a car to translate well between rotation and acceleration is the key KPI to the question if a corner is flatout and how much speed you bleed of in a flat out corner compared to a straight line.
@@MrHaggyy That's an excellent force vector analysis. Now we can consider weight shifting dynamics from brake release,clutch engagement and throttle and it's a dance between friction plates,shocks,sway bars,brakes and the changing contours,textures and temperatures of the tiny contact patch. Love how you mentioned that floating gas interface. Even if you're not smoking it there's that hot smeary point where your tires are going away but it's loose and grippy at the same time. If I could only live at the pitch that is near madness. When everything is as it was in my childhood Violent vivid and of infinite possibility. That the sun and moon broke over my head.
Really amazed with your clean but at the same time detaiful explanation. I am ex FSAE member who worked on vehicle dynamics currently working as Systems Engineer and I will consider to join the course.
Quantifying handling metrics by yaw moment / yaw acceleration is quite common in the vehicle dynamics industry from my knowledge. Yaw acceleration is on of the most important KPI in some ISO-simulations as step-steer/sine-steer etc. Yaw gyros/accelerometers also are pretty cheap sensors so validating the simulations is not that big of a challenge.
Have you read Ross Bentley speed secrets? This is well discussed for years. Peak grip in a corner is slip angle between 6-10 degrees for modern tires/suspension packages. I’m not entirely sure what is different or new here.
ABS has the called Yaw Moment Reduction. The Yaw moment, yaw velocity is really important to calculate the lateral behavior of a car so yes manufactures take care of it
Yaw has been used in stability control systems since the late 90's. Land Rover have a Yaw Sensor in the Freelander 1 after 2002 and in the D2 if ACE is fitted, ACE needs the yaw input to correctly work. They are definitely not the first to use it as a factor in ABS and stability systems. Pllease don't fall in to the trap of "understeer and oversteeer", both are a characteristic of steering and suspension geometric design, and is measured at a set speed around a set curve. Oversteer vehicles often have the steering control mechanism in front of the axle centre, understeer vehicles usually have the steering control mecchanism behind the axle centre. ALL other phenomina of not traversing the corner as expected is skidding in one form or another, including slip angle.
for gm define transient handling(yaw) ,we would prefer to subject by the front and rear axle sideslip overshoot, yaw is quiet important for vehicle dynamic evaluation
i have azera 2009 3.3L V6 GLS & the driving experience changed years ago. it was sporty in the corners & so stable on wet street or when it rains, it's like it sticks to the ground! very amazing system!. that had me pulling my hair to figure it out. mechanically checked & fixed but nothing solved. changed angel & the 4 ABS speed sensors. plus i don't have any check lights. all i can think of is that these sensors is giving wrong feed back!
In NASCAR racing the driver either say the car is running tight, or loose in the turns. The crew makes adjustments during the pit stops. These are yaw adjustments.
Yaw is one the most important factors that get measured in vehicle development. You can match it with steering torque, roll rate, pitch rate, deceleration and more to create a faux picture of what a vehicle feels like. I was a test driver for a little over a decade and I can explain what various graphs and charts mean, but I couldn't tell you if it would feel cohesive or good. You can generally tell when something is going to feel bad but good is so subjective it becomes a black hole of data collection and analysis.
Interesting video. You're right, I don't think I've ever read about this in car magazines before. In your opinion, what's the best single test to determine Yaw Acceleration? Single 90deg turn? 5 cone Slalom? I feel like a car should have ... predictable(?) yaw acceleration as well.
It would be at relatively slow speed where v^2/r is relatively low, where most of the tire's forces are used to generate yaw acceleration. The speed only needs to be high enough that yaw rate isn't limited by the steering wheel angle. So a slalom at 40~50kph would probably be a pretty good metric.
Does the yaw acceleration somehow load suspension, or are forces that act on the suspension caused only by lateral, longitudinal accelerations, downforce and normla load ?
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"the speed thru an entire corner is almost completely determined at the corner entry."
Yes yes yes. Agree 100%.
Yep, because at that point you're not loading up the tyres with lateral acceleration (and rotation saves the need for some of this g-force)
Excellent explanation sir. I finally found a channel that explains these laws/ principles in a easy to understand way with good visuals
Thanks so much!
In a sense yaw is the feel of oversteer being more rotation than expected and understeer being less.
Drifting would be the art of creating extreme yaw while maintaining consistent trajectories.
I'd agree with that.
If you are experiencing understeer or oversteer you are falling away from your cars optimal yaw.
Yaw is an acceleration, what you mean is the slip or driftangle. If you want to drift you need to rip the solid tire from the tarmac. You can do this with extreme acceleration, either lateral with gaß or ritational with yaw. If you do it with yaw you need to counter steer otherwise you will spin, which would cause really high yaw rates. A good drifter remains steady and chill yaw rates all around the corner.
@@MrHaggyyPhysics was not my major but from boats and planes yaw is horizontal motion around the y axis. Nose and tail moving left and right. The other axis are pitch and roll.
If the centrifugal forces are balanced by tires traction the yaw should be zero.
Perhaps there's some hair splitting as drifts,bootleg turns,snap oversteer and tail wagging all seem to pivot around the engine mass and front wheels.
True yaw is a sickening spin around the middle with front and back heading in opposite directions as in a full spin or beginning to slide and correcting.
So you're right drift is sustained slip angle but there seems to be yaw at the moment of traction loss in oversteer and understeer also.
@@jeffarcher400 yes you have roll pitch and yaw as rotations as well as front right and up for lateral movements. Yaw is the acceleration around the "up" axis.
In a stable drift you have a much higher yaw angle than you would normally. But you also corner at a constant yaw-rate or in a fixed circle around a fix point.
In a normal driving situation each tire can generate a force lateral, in the direction the tire is rotating, and transversal, in a 90 degree angle to where the tire is facing. In a drift you rip the contact patch of the tarmac and generate a thin layer of liquid and gas, the nice smoke. In that state the tire can only really generate forces in the direction of rotation.
So in a normal drift you have a big force in the direction your car is facing from the rear and two forces from the front. The front sums up in a force around a circle.
So you are constantly rotating at a fix rotational speed - a fixed yaw rate.
If you ease of the steering the circle would get bigger until the car would catch it`s grip again and you would only accelerate in a constant line.
;-) the ability of a car to translate well between rotation and acceleration is the key KPI to the question if a corner is flatout and how much speed you bleed of in a flat out corner compared to a straight line.
@@MrHaggyy That's an excellent force vector analysis. Now we can consider weight shifting dynamics from brake release,clutch engagement and throttle and it's a dance between friction plates,shocks,sway bars,brakes and the changing contours,textures and temperatures of the tiny contact patch.
Love how you mentioned that floating gas interface. Even if you're not smoking it there's that hot smeary point where your tires are going away but it's loose and grippy at the same time.
If I could only live at the pitch that is near madness.
When everything is as it was in my childhood
Violent vivid and of infinite possibility.
That the sun and moon broke over my head.
Very calming explanation.😊
Really amazed with your clean but at the same time detaiful explanation. I am ex FSAE member who worked on vehicle dynamics currently working as Systems Engineer and I will consider to join the course.
Thanks for the kind words!
Quantifying handling metrics by yaw moment / yaw acceleration is quite common in the vehicle dynamics industry from my knowledge. Yaw acceleration is on of the most important KPI in some ISO-simulations as step-steer/sine-steer etc. Yaw gyros/accelerometers also are pretty cheap sensors so validating the simulations is not that big of a challenge.
That's true. More that it's less talked about in mainstream automotive media.
😂 nice to see a FS car on You Tube. Yes yaw us used and discussed a lot in vehicle dynamics and functional safety.
Have you read Ross Bentley speed secrets? This is well discussed for years. Peak grip in a corner is slip angle between 6-10 degrees for modern tires/suspension packages. I’m not entirely sure what is different or new here.
Excellent video. Well explained
Great content, keep it coming :)
Thanks, will do!
ABS has the called Yaw Moment Reduction. The Yaw moment, yaw velocity is really important to calculate the lateral behavior of a car so yes manufactures take care of it
Thanks i2, yaw velocity is indeed used for ESP intervention, it's what I tried to explain at 2:10
Great video! Wasn't aware of this metric before coming across this video
Glad to hear :D
Yaw has been used in stability control systems since the late 90's. Land Rover have a Yaw Sensor in the Freelander 1 after 2002 and in the D2 if ACE is fitted, ACE needs the yaw input to correctly work. They are definitely not the first to use it as a factor in ABS and stability systems.
Pllease don't fall in to the trap of "understeer and oversteeer", both are a characteristic of steering and suspension geometric design, and is measured at a set speed around a set curve. Oversteer vehicles often have the steering control mechanism in front of the axle centre, understeer vehicles usually have the steering control mecchanism behind the axle centre. ALL other phenomina of not traversing the corner as expected is skidding in one form or another, including slip angle.
for gm define transient handling(yaw) ,we would prefer to subject by the front and rear axle sideslip overshoot, yaw is quiet important for vehicle dynamic evaluation
i have azera 2009 3.3L V6 GLS & the driving experience changed years ago. it was sporty in the corners & so stable on wet street or when it rains, it's like it sticks to the ground! very amazing system!. that had me pulling my hair to figure it out. mechanically checked & fixed but nothing solved. changed angel & the 4 ABS speed sensors. plus i don't have any check lights. all i can think of is that these sensors is giving wrong feed back!
In NASCAR racing the driver either say the car is running tight, or loose in the turns. The crew makes adjustments during the pit stops. These are yaw adjustments.
Yaw is one the most important factors that get measured in vehicle development. You can match it with steering torque, roll rate, pitch rate, deceleration and more to create a faux picture of what a vehicle feels like. I was a test driver for a little over a decade and I can explain what various graphs and charts mean, but I couldn't tell you if it would feel cohesive or good. You can generally tell when something is going to feel bad but good is so subjective it becomes a black hole of data collection and analysis.
Thanks for the great feedback! ❤
Interesting video. You're right, I don't think I've ever read about this in car magazines before. In your opinion, what's the best single test to determine Yaw Acceleration? Single 90deg turn? 5 cone Slalom? I feel like a car should have ... predictable(?) yaw acceleration as well.
It would be at relatively slow speed where v^2/r is relatively low, where most of the tire's forces are used to generate yaw acceleration. The speed only needs to be high enough that yaw rate isn't limited by the steering wheel angle. So a slalom at 40~50kph would probably be a pretty good metric.
Anything to do with autocross is great for yaw.
Usually you drive two right hand and two left hand circles with an inner diameter of 4 to 6 meters.
Does the yaw acceleration somehow load suspension, or are forces that act on the suspension caused only by lateral, longitudinal accelerations, downforce and normla load ?
Yaw acceleration results in yaw rate. Yaw rate results in lateral acceleration. Lateral acceleration loads the suspension through roll.
@@racetracksetup *as long as you have traction