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Post by the light works on Jan 21, 2013 17:36:34 GMT
every once in a while, the debate comes up whether it is "safer" for a car to be set up to oversteer or understeer.
(for uniformity, I am considering this to be about the manner in which the car loses control when entering a corner too fast and about the potential to recover control, and the severity of injury and damage if control is not regained. )
my personal thought is that I would much rather try to correct from oversteer than understeer, as oversteer still leaves you with some steering input; and tends to naturally direct your momentum away from something you were avoiding.
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Post by c64 on Jan 21, 2013 22:40:46 GMT
Over-steering is when the car starts to spin around. That's closely related to spinning out of control, there is a narrow border you can cross easily. When spinning out of control, you can crash to the left or right side of the road.
Under-steering is when the car follows a turn less than you command by the steering wheel but the car will remain stable all the time until it leaves the road and crashes. It's a lot easier to recover from under-steering, the advantage of over-steering is a greater speed exiting the turn but there is absolutely no safety advantage!
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Post by the light works on Jan 21, 2013 22:51:35 GMT
that is not the consequences I have found. I have found that when trying to recover from understeer, brakes are worthless, because the braked wheels are already skidding, and steering is worthless because your steering wheels are skidding.
when trying to recover from oversteer, you continue driving the front end where you want to go. if the back end passes you, you most commonly just end up facing the wrong way on the shoulder.
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Post by the light works on Jan 21, 2013 22:53:17 GMT
this was the result of an understeer situation. interestingly, we never found the driver.
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Post by the light works on Jan 21, 2013 22:55:56 GMT
more to the point, this was also the result of understeer.
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Post by c64 on Jan 23, 2013 2:22:22 GMT
If you have never found the driver, how did he tell you what had happened?
And taking two accident examples out of a gazillion doesn't proof your point. I could find a hundred examples more for oversteering is bad!
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Post by the light works on Jan 23, 2013 2:42:00 GMT
If you have never found the driver, how did he tell you what had happened? And taking two accident examples out of a gazillion doesn't proof your point. I could find a hundred examples more for oversteering is bad! that's the wonderful thing about accident investigation. she didn't need to tell us what happened, the skid marks told the story. and those are just the two examples I have photos of. wait, I think I have another. the car isn't visible. it's nose into the brush just out of the frame. |
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Post by the light works on Jan 23, 2013 2:44:58 GMT
not sure why the driver didn't correct that. he had 12 whole feet between losing his steering control and breaking off the fire hydrant, before he sailed off into the scenery.
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Post by c64 on Jan 23, 2013 14:33:19 GMT
not sure why the driver didn't correct that. he had 12 whole feet between losing his steering control and breaking off the fire hydrant, before he sailed off into the scenery. Isn't that obvious? Cruise control + water… And maybe the (heater) fan had killed her! Well, oversteering and understeeing will both make an inexpedience driver crash. The problem is that Oversteering can add acceleration while understeering always steals kinetic energy. The worst crash sites I had seen were caused by oversteering by crashing the car sidewards into obstacles or blocking the street and another vehicle crashed into it. Understeering is usually "gently" hugging the guardrail or hitting anything more or less frontal. Well, the very worst accident I have ever heard of was when I was working for a construction machine company. A big trailer full of bits of a small trailer and a heavy duty ground compaction machine snapped into 3 parts(!) and lots of tree bits mixed in came in. Someone had spotted the crash site and called the police. The police in turn looked at the crash site and called the rental company which owned the trailer and the machine from the phone number painted on the machine. The rental company asked if their customer was OK and the police asked "what customer?". "The driver who pulled the trailer with his car!" - "What car? What driver?" - Then they started to look for the car and found it, the driver was dead. I wonder what the police was thinking about the crash site. Machines on trailer don't fall out of the sky, do they? |
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Post by the light works on Jan 23, 2013 15:07:43 GMT
I guess the conversion into German changes the definition of some of those words. in english the way the guy hugged the fire hydrant was anything but gentle. now in comparison, when I spun my parents' car out coming into a corner too fast certainly did not add kinetic energy. I barely bent over the reflector I hit on the inside of the corner. the worst crash sites I have seen involved people leaving their lane of travel and hitting something head-on. the very worst was a guy who took a corner wide - not through understeer, but through drunk driving - hit a pickup head-on, and quite literally tore his car apart through the passenger compartment. the front end was in one ditch, the rear end was in the other ditch, the roof was in the middle of his lane, and the driver was lying on the center line of the road. the only way oversteering adds acceleration is if the driver has his foot hard on the throttle, and even then, because the vector of travel is changing, the kinetic energy is also changing vectors; which means unless it is a deliberate action, like drifting a corner, there is a net loss of kinetic energy. meanwhile the only way understeering reduces kinetic energy is if you are braking - which since your front wheels; which do most of the braking, are already skidding, you have a lot less braking available; which means it is stealing a lot less kinetic energy. but why take it from me. I have here the words of someone whose opinion I would imagine you respect. "I've raced AWD. Here, you can have both effects depending on what you do but in general you are fastest when the car is "pushing" over all wheels, over- and under-steering at the same time you could say. The problem is that there is a clear limit. If you come close, you feel the wheels grinding and hear the tear and wear but it doesn't take much to cross the limit and then the car just "slingshots" out of the corner and there is no way to recover until you are far out off the track. Read more: citadelofmyths.freeforums.net/index.cgi?action=display&board=transport&thread=373&page=2#10841#ixzz2IoNP46AR" |
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Post by c64 on Jan 23, 2013 15:52:13 GMT
I guess the conversion into German changes the definition of some of those words. in english the way the guy hugged the fire hydrant was anything but gentle. now in comparison, when I spun my parents' car out coming into a corner too fast certainly did not add kinetic energy. I barely bent over the reflector I hit on the inside of the corner. the worst crash sites I have seen involved people leaving their lane of travel and hitting something head-on. the very worst was a guy who took a corner wide - not through understeer, but through drunk driving - hit a pickup head-on, and quite literally tore his car apart through the passenger compartment. the front end was in one ditch, the rear end was in the other ditch, the roof was in the middle of his lane, and the driver was lying on the center line of the road. the only way oversteering adds acceleration is if the driver has his foot hard on the throttle, and even then, because the vector of travel is changing, the kinetic energy is also changing vectors; which means unless it is a deliberate action, like drifting a corner, there is a net loss of kinetic energy. meanwhile the only way understeering reduces kinetic energy is if you are braking - which since your front wheels; which do most of the braking, are already skidding, you have a lot less braking available; which means it is stealing a lot less kinetic energy. but why take it from me. I have here the words of someone whose opinion I would imagine you respect. "I've raced AWD. Here, you can have both effects depending on what you do but in general you are fastest when the car is "pushing" over all wheels, over- and under-steering at the same time you could say. The problem is that there is a clear limit. If you come close, you feel the wheels grinding and hear the tear and wear but it doesn't take much to cross the limit and then the car just "slingshots" out of the corner and there is no way to recover until you are far out off the track. Read more: citadelofmyths.freeforums.net/index.cgi?action=display&board=transport&thread=373&page=2#10841#ixzz2IoNP46AR" If you don't brake, the act of under-steering eats up kinetic energy automatically. Of course you have less braking forces available than just going straight. I really hate it when people in front of me brake in the middle of a corner just BECAUSE the road is slippery! What was real sad but funny to watch was when I still had my racing car. It was meant to hug tight corners unlike ordinary cars which are more rigged for comfort but a lot of people tried to keep up and followed closely, especially the owners of cars with ugly extras which shouldn't be installed on any vehicle meant to actually move faster than 6kph! It looks really cool when bushes seen in your rear mirror swallow an entire car! Just like a Rabbit™ vanishing into its den. > in english the way the guy hugged the fire hydrant was anything but gentle. Our guardrails are designed to deform but not break. So a car is guided gently to stay on the road and braked by friction and deformation. |
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Post by the light works on Jan 23, 2013 16:32:22 GMT
it eats up about as much kinetic energy as depressing your clutch and steering straight ahead. unless you are driving a rear drive car and step off the throttle. then it eats about as much kinetic energy as stepping off the throttle and steering straight ahead.
we use the same basic guardrail design here.
oversteer skid:
understeer skid:
oversteer:
understeer:
oversteer:
understeer:
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Post by c64 on Jan 23, 2013 18:27:42 GMT
we use the same basic guardrail design here. oversteer skid: they look similar but after a collision, they remain OK as seen in the video. Ours bend and stretch at the slightest impact to eat up as much kinetic energy as possible. Of course they are not magic |
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Post by the light works on Jan 24, 2013 2:10:28 GMT
we use the same basic guardrail design here. oversteer skid: they look similar but after a collision, they remain OK as seen in the video. Ours bend and stretch at the slightest impact to eat up as much kinetic energy as possible. Of course they are not magic that didn't look very OK to me. it was sticking out into a lane of traffic. here's how our look after a truck hits them. this was not an oversteer accident. this was trying to balance a truck on a retaining wall and somehow still being right side up when it fell off. woops, the bent spot is behind the firefighters. |
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Post by silverdragon on Jan 26, 2013 10:19:02 GMT
Under steer or Over steer... if you can set a car either way, why not set it as neither?... Otherwise, know which its going to do and drive accordingly.... Mine will under-steer at speed, so I slow for corners........  ....... Or am I over simplifying this too much?.... |
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Post by c64 on Jan 26, 2013 16:10:52 GMT
that didn't look very OK to me. it was sticking out into a lane of traffic. here's how our look after a truck hits them. That doesn't matter, accident sites become cleared. Do you think its better for the guard rail to remain mostly intact or is it better to trash a couple of grands in guard rail sections and have less dead bodies to scratch from the road? |
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Post by the light works on Jan 26, 2013 16:22:20 GMT
Under steer or Over steer... if you can set a car either way, why not set it as neither?... Otherwise, know which its going to do and drive accordingly.... Mine will under-steer at speed, so I slow for corners........ ....... Or am I over simplifying this too much?.... well, obviously, balanced slip is best. but that is more work than many carmakers want to be bothered with. |
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Post by the light works on Jan 26, 2013 16:24:53 GMT
that didn't look very OK to me. it was sticking out into a lane of traffic. here's how our look after a truck hits them. That doesn't matter, accident sites become cleared. Do you think its better for the guard rail to remain mostly intact or is it better to trash a couple of grands in guard rail sections and have less dead bodies to scratch from the road? here we have fittings they stick on the end of the guardrail so if a car hits the end, it crushes the guardrail rather than punching into the car. it will save the lives of some drivers, but it bends the guardrail 90 degrees to the dise - and half the time, they are installed so it pushes the guardrail into the traffic lane. so it not only wrecks the guy who didn't stay on the road (which can't be avoided) but the guardrail also has the potential to wreck the innocent guy behind him. |
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Post by c64 on Jan 26, 2013 18:24:47 GMT
Under steer or Over steer... if you can set a car either way, why not set it as neither?... Otherwise, know which its going to do and drive accordingly.... Mine will under-steer at speed, so I slow for corners........ ....... Or am I over simplifying this too much?.... well, obviously, balanced slip is best. but that is more work than many carmakers want to be bothered with. And those who do either put the engine into the middle of the car or put an engine which is as light as possible into the front and a heavy gearbox into the rear. But don't worry, you can DIY! |
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Post by silverdragon on Jan 27, 2013 7:18:43 GMT
Guard rails in the uk, the end section is sent downwards and buried in the sand....
Guard rails are also easy-fix, its been looked at, and having the rail ripped off is MUCH better than the vehicle leaving the carriageway, and replacing rails should be easy ....
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