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17th July 2013, 21:29 | #121 | ||
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| re: Evasive manoeuvres & Rollovers? Quote:
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Regards Sutripta Last edited by Sutripta : 17th July 2013 at 21:30. | ||
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18th July 2013, 12:07 | #122 | ||||||
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| re: Evasive manoeuvres & Rollovers? Quote:
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And additionally, race car drivers would almost always want better steering response, regardless of whether it roughs their ride or makes the vehicle susceptible to toppling. They are professionals after all, and one would expect that they know well how to operate their vehicle to the best of its ability without going over the limit. Quote:
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So in this condition, what we have is: Source: Road undulations. Transfer path: Wheel -> suspension system -> Vehicle body. Now in current scenario, what we are talking about (toppling) is exactly the opposite. Large magnitude of centrifugal forces are generated by the vehicle body itself (and whatever's inside). These forces then transfer through the suspension, into the wheel and axle components. The moment which axle is subjected to causes it to lift from one side. So in the current condition we have: Source: Centrifugal force generated by vehicle body and trims. Transfer path: Vehicle body -> suspension system -> Wheel, axle components. In both conditions though, part played by the suspension is the same. Absorb forces. A rigid suspension will absorb very little portion of the forces compared to a softer one. Consider an ideal suspension. One which absorbs all forces transferring through it. What you'd have is a vehicle body getting very noticeable tilted while the wheel and axles have no unwanted forces acting on them whatsoever, and hence staying on the ground. It is simple concept really. Even in today's PC simulation games which one might play (the ones where you get to customize your cars and whatnot), they mention that stiffening the suspension will increase the tendency of your car to flip over when cornering. Apologies, I believe you were asking Guna about the tipping point. A stiffer suspension will travel much lesser compared to a softer one at the same speed is what I think he was saying. If you were asking something different then ignore my interruption. | ||||||
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18th July 2013, 12:49 | #123 | |||
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| re: Evasive manoeuvres & Rollovers? Quote:
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The discussion is about SUVs, in case you haven't noticed. Doesn't absolve us from getting data before expressing the opinion, does it? BTW, a moose cow weighs that; moose bulls can weigh upto 700+Kgs. No matter what the car size or weight is, please calculate what damage that weight can do if it enters through the windshield at 60Kmph on impact. Just the kinetic energy of 500Kgs @ 60Kmph released onto the occupants. Go ahead. I thought you earlier said "Professional driver will never tell you to swerve your car (be it SUV or otherwise) if a moose wanders in front"? That doesn't amount to driver's choice but a recommended practice, if so. It isn't, fortunately. | |||
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18th July 2013, 14:04 | #124 | |
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| re: Evasive manoeuvres & Rollovers? Quote:
Your line of argument goes that vehicle with stiffer suspension travel will reach its maximum lean (maximum suspension travel) earlier and then it will tend to lift the inside wheels whereas the softer suspension will take longer time to reach the maximum lean or max suspension travel I would like to see some back up for the data - reason being the following Let us take two cars/SUVs - one with a stiff suspension (A) and the other with softer set-up (B) Now car A travelling at 100kmph leans by around, say, 15 degree from the centre line Car B travelling at the same 100kmph being a softer suspension will lean more, (than 15 degree) Correct? Now there will be a maximum angle to which the vehicle can lean before toppling over due to the shift in CG or the mass or centrifugal force or whatever - the softly sprung car will reach this point faster compared to the stiffer one But if the maximum suspension travel is reached before reaching the above speed then the vehicle reaching this point will topple first (Assuming all other factors to be the same) Now I think only empirical evidence can prove this!! Whatever may be the result - just shows that I am sitting in office without any work whatsoever!! (FYI ramming into a large animal is never recommended - reason already explained. Just check the web for camel hits happening in middle east. Few months back there was a similar accident with an elephant where the people in the car died when the elephant fell on the car) | |
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18th July 2013, 14:27 | #125 |
BHPian | re: Evasive manoeuvres & Rollovers? Recently I happen to watch a Fifth Gear episode which demonstrated the use and need of ESC (Electronic Stability Control) in vehicles. I attribute much of the toppling sort of accidents under high speed maneuvers to lack of such safety system in majority of our cars. Europe has made it mandatory to have ESC systems in all vehicles sold from 2014. Hope our Govt. open its sleepy eyes and save some lives by making certain safety kits a must have in all cars sold here. Fifth Gear episode ( Watch from 8th min for ESC related content) : |
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18th July 2013, 16:29 | #126 | |
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| re: Evasive manoeuvres & Rollovers? Quote:
Absolutely right on this one. I used to drive a '99 Santro. It did not have a powersteering. Once while taking a 'significantly' sharp left bend at a speed of around 40, i felt the right side wheels go up in the air. Since then i resolved never to drive a 'tall boy' hatch or a UV (I have a Bolero which i dont consider to be a SUV ) at speeds above 90 in a straight line and above 30-35 while taking curves. The SUV Advertisements reminds me- does anybody remember the Safari Petrol Advertisement- the one with two guys in the parking lot of a circus/entertainment park who did not raise an eyebrow in a scary ride but completely freaked out while gunning the Safari. Thats misleading. You inveigle people to drive their SUV's at high speeds and they continue to do so without understanding the weight of the chassis, the engine and the fact that you havent equipped the 'SUV' with rear disc brakes | |
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18th July 2013, 16:53 | #127 |
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| re: Evasive manoeuvres & Rollovers? I think everyone who know how to drive a car properly should just try to feel and sense the feedback which is coming from the road to the steering and then should manouvre the car on corners. For eg: the swinging effect due to high ground clearance is clearly felt and one should just reduce the speed at the time when the car begins to loose its line on the corners. Thats why they say- be gentle on the curves. There is nothing one can do when an obstacles is seen or comes up suddenly. You can just try to steer away using the brakes and downshift as quickly as possible (engine braking) and leave the rest to car's dynamic abilities and safety features. |
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18th July 2013, 17:29 | #128 | |||
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| re: Evasive manoeuvres & Rollovers? Quote:
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Cheers. | |||
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18th July 2013, 20:21 | #129 | |
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| re: Evasive manoeuvres & Rollovers? Quote:
Understood (or think I did) what Guna was saying. Didn't agree with it, and instead of getting into long winded 'technical' discussions, gave a counterexample. Would still like to understand what you were saying. Regards Sutripta | |
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19th July 2013, 12:42 | #130 | |||||
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| re: Evasive manoeuvres & Rollovers? Quote:
And I'm not considering the delta (t) dependence because we're comparing two cars having different suspension setups with respect to each other, not with respect to time. Delta (t) in both cases will have to be same for us to compare them properly. Exactly my point! Cutting up my sentences is going to cause misunderstanding. You can be certain that I've read every post in this thread, and it was originally started for discussing standard SUVs, not the ones used in Dakar Rallies I think. As you said yourself, we would be far away from the discussion if we got into that. Quote:
Came across an interesting statistic today while reading a CCIS pdf that 8/10 frontal crashes above 90 Kmph resulted in deaths and 8/10 side impacts above 70 Kmph also resulted in the same (studies were done of seat-belted drivers). Am on work computer right now, so have access to very few websites hence can't give a link. But would be able to after I reach home if any of you wishes to take a read. My only reason for putting this up was to highlight that car-to-car impacts are not something to be taken lightly. Quote:
If we are to ignore safety signs, then we might as well conduct "Wrong-side test" which determines the maneuverability of a car in case a driver feels like ignoring the "One-way traffic" sign post. Sudden swerves/lane changing is best left for the movies methinks. Quote:
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First things first: some hard data. There is a certain component of suspension system called a sway bar or anti-roll bar which most SUVs these days incorporate. Assuming that you don't mind reading walls of theoretical texts (since we're all posting in the 'Technical Stuff' section as gthang had aptly pointed out before), I would suggest going through a usual Wikipedia page on "Sway bars", and a page titled "Anti-roll bar" on a website called www.turnfast.com for a bit of background theory. I would have tried to find some videos, but am at work as mentioned before. Net access is very much restricted. Thankfully they keep team-bhp on! Watched it too! It was a brilliant demonstration of why Europe had made ESC mandatory. One would certainly want it to be made mandatory everywhere else. The difference between a vehicle with and without it was just phenomenal. | |||||
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19th July 2013, 14:09 | #131 | ||
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| re: Evasive manoeuvres & Rollovers? Quote:
And that is ...? Quote:
What made you assume that your hypothesis of hitting an obstruction instead of swerving is correct / safer option? Your 'hope' will be tangible only if you have a rational basis. 'Hit the blessed animal and hope for the best' is not very rational - the physics is to the contrary. And 'Moose crossing' is not a speed reduction instruction, it is a warning to drivers to be cautious. But does 'being cautious' obviate the possibility of an accident? | ||
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19th July 2013, 15:23 | #132 |
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| re: Evasive manoeuvres & Rollovers? This thread has lost it's focus I feel. I personally don't understand where is the discussion heading to? Perhaps even Mr. Lotfi Zadeh would find it difficult to dish out "crisp" information from such arguments. Spike |
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19th July 2013, 15:31 | #133 | ||||
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| re: Evasive manoeuvres & Rollovers? Quote:
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Wish you had gone through the website as well. Quotes from above site: Quote:
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http://www.euroncap.com/Content-Web-...rotection.aspx Car to car, car to wall, side impact, etc., are controllable tests. You can only test the capability of the vehicle to avoid an Elk/Moose. How can you do impact tests when the outcome is random. You think the moose will fly the same way every time? Most times you will not see an Elk/Moose till it's too late because their eyes dont shine like other animals, and the natural reaction will be to swerve. Like I said before, a little background study might help before postulating. Cheers. | ||||
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19th July 2013, 17:12 | #134 | |||||
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| re: Evasive manoeuvres & Rollovers? @Spike : I'll add a little further to the obtuse angle of the thread Check this study ftp://ftp.demec.ufpr.br/disciplinas/...5_rollover.pdf Particularly the below conclusion Quote:
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Anyway, am off this thread - I feel am replying to a troll. How is anti-roll bar related to this discussion? | |||||
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19th July 2013, 20:55 | #135 | |
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| re: Evasive manoeuvres & Rollovers?
Please don't. Im relying on you, as you'll find out in a moment. @pratheesh: would you have searchable (ie not scanned) pdf's of Milliken, and Gillespie. Quote:
In the meantime, can't understand a) your original statement of 'at the same speed'. b) relevance of sudden appearance of antiroll bars in current discussion. Lets return to the original premise that harder suspension -> 'more likely' to topple. ('more likely' is unquantified as of now) Let us start with two cars, one with harder suspension than the other, but otherwise identical. (esp. identical with respect to ride height, suspension travel, suspension geometry, and weight distribution). And then apply mallumowgli's line of thought. Since his and yours conclusion are different, could you point out the fallacy in his reasoning. Regards Sutripta | |
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