Maximum yaw rate

[murpia]

What's the maximum yaw rate a vehicle is likely to see during an extreme situation such as a spin or J-turn? (Something that a vehicle can recover from undamaged, not during a collision situation).

I know that the Bosch ESP yaw rate sensor (for example) tops out at 100deg/s, but is that just the upper bound for an 'elk' test or slalom situation, not the vehicle maximum?

Thanks, Ian

 

[evelrod]

I have nothing but anecdotal evidence...I have a video, "in car" of my race car doing "360's" at a rate of ~360deg/sec !!!

Rod

 

[GregLocock]

Wow, that is scary.

In a maneuver my rule of thumb is that the driver of a production car is unlikely to recover by steering from a yaw rate in excess of 40 deg/s, and even 20 deg/s is pretty aggressive at typical speeds (70-110 kph).

But that is a rule of thumb only. Might be easier to think in terms of latacc (m/s/s)=v(m/s).omega(rad/s)

Whoever calibrated the ESC on my car (Fiesta) seems to think less than 20 deg/s at 100 kph, working back from the steering wheel angle velocity. That means I have to drive very very smoothly on gravel roads if I don't want its 'help' (no Scandinavian flicks for you). I don't think it is calibrated for gravel roads, in a straight line at 100 kph cruise it goes off on some patches!

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GregLocock]

Moose test, that is 4m lane offset at 70 kph with 13.5m to do the lane change has a max yaw rate of 25 deg/s, 0.8 g.

At 80 kph that is 27 deg/s and 0.9 g.

That's modelled, using one of the canned models, obviously not correlated. I'm a bit surprised it hit 0.9g.




Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[murpia]

Thanks for the info guys.

Would a high yaw rate 'incident' such as a handbrake turn, spin or J-turn form any part of a normal road vehicle test profile? I.e. is a maximum yaw rate likely to be specified for on-board equipment durability in the same way that vibration and acceleration tolerance is?

Thanks, Ian

 

[GregLocock]

We have a whole sequence of tests for limit handling including J turns (not that they are much help), but we don't deliberately spin the car out - although of course throttle on in turn and brake in turn often do cause spin outs if you are trying really hard in a non electronic car. J turns in a truck will give you maybe 70 deg/sec just as the thing stops.

Anyway I guess I'm saying that 100 deg/sec seems a reasonable limit for the instrumentation, unless you are playing dodgems with Rod.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.