I hardly believe in guy having on the table Milliken's "Race Car Vehicle Dynamics" and praising GT5P physics.
If that's aimed at me I would prefer it if you addressed it directly to me and would also point out that I use a range of sources.
In addition, yes I have praised parts of GT5P's physics, but I've also been very critical of a lot of it as well.
I'm not sure how to interpret this remark. If you are implying that I intentionally tried to mislead people into adopting a particular interpretation of that source, then you are mistaken. The reason I provided a link to the article is so people could check it out for themselves and draw their own conclusions.
If I had in any way though that you had set out to intenionally mislead people I would not have typed a lengthy reply, I would have deleted the post and issued you with a 10 point infraction. The AUP clearly states misleading intentionally is not permited.
You seem to have got rather defensive over the simple act of me not agreeing with the conclusions you have raised and explaining why.
No, it wasn't cornering forces alone, it was
the sudden loss of traction that occured when the Evo ran off the tarmac and onto the grass as I surmised in my post. In fact, to back up this assertion, here is a link to a research article conducted by the UK’s Cooperative Crash Injury Study (CCIS) "...one of Europe’s largest car occupant injury causation studies."
http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0481.pdf
Which is a quite interesting study on the type of accidents suffered in various roll-overs, it does not however explain the exact causes of the roll-overs, the type of vehicles involved (but its does discuss the most common vehicles to roll - see later) or the exact conditions involved.
Its also (from a vehicle dynamics point of view) rather vauge in the terms used, and in a couple of cases potentialy misleading.
Among the findings in this study is the fact that "off-road soft surfaces such as grass or earth were the most frequent roll initiators." Even more frequent than loss of traction due to excessive speed while cornering, which I must admit suprised me a bit.
Does the study state that all of these off-road soft surfaces are smooth dry grass?
No, it actually fails to catagorise them in am way at all, they could (and most likley are) a wide mixture, including embankments, ditches, soft earth.
As such its imposiable to conclude anything about the causes of roll over from a sentance as loose as "off-road soft surfaces such as grass or earth".
"off-road soft surfaces such as grass or earth
Apparently not, according to the government study I linked above.
In fact "The most common roll initiation influence was offroad
soft ground (grass or earth) applying force to both wheels (right or left)."
If anything, transitioning from pavement to grass increases the chance of a rollover.
Once again the phrase.........
"The most common roll initiation influence was offroad soft ground (grass or earth) applying force to both wheels (right or left)."
.....is far to vague to drag any real conclusions from. What is the force involved mentioned here? What was the car? What were the speeds? Was the 'off-road' surface flat? Was the 'off-road' surface soft enough for something to dig it? Was a curb or other pivot point present at the road edge?
As none of these are even discussed its impossiable to say, and that is not a dig at the document in question. Its not a study of the causes of roll-overs, its a study of the type of injury suffered in roll-overs.
No, apparently it's more likely that going off-road onto grass will cause rollovers according to the data in the study listed above.
I disagree. That document shows that going off-road is the most common type of roll-over, it doesn't actual discuss (in dynamic terms) what the cause of the roll over is at all.
Evidently, wheel-slip and roll over aren't mutually exclusive events:
"A significant proportion of the cars were identified as
‘sliding’ laterally to some degree prior to the roll and
off-road soft surfaces such as grass or earth were the
most frequent roll initiators."
I don't believe I said they were 'mutually exclusive' and the key part of your quote is 'to some degree'.
Its also worth noting that the document seems to use the term sliding in a non-dynamic manner, describing it at least once as 'a loss of control' Its certainly not described as 'slip' from all four wheels. Its perfectly possiable (and I can describe this in full technical detail if you like) for a car to be under or oversteering (and as such a driver could have lost control) before the grip limit has actually been reached on any of the tyres.
One thing you have also missed from that document is the roll-over frequency by vehicle type. The most likely (outside of commercial vehicles) is off-road vehicles with 30%, and by quite a long way from the second place type (which is a loose description of sports) at 18%.
Well, if you liked the previous link, I hope you like this one as well.
I think it makes a compelling argument that a roll over like the one we saw in the now-infamous YouTube video is quite possible.
My main points:
1) The transition from tarmac to grass can cause rollovers like the one in the Evo clip. In fact grass/earth are the most frequent causes of roll over incidents in the study above. And that study has a pretty large sample size--1,341 incidents of rollovers.
2) Just because it is more likely that a high COG SUV will rollover, that doesn't necessarily mean that a car such as the Lancer
couldn't plausibly roll over as it does in the video. It was travelling at a what appears to be reasonably high speeds (although admittedly unknown), and it did what one should apparently do if they
want to roll a vehicle over:
make a sudden steering input onto grass or an earthy surface at high speeds...while cornering.
I hope I don't come across as argumentative, but I felt as though I should respond. When I saw the video, I thought it looked really innovative and realistic. I guess I'm just trying to defend that initial impression. I greatly respect your opinion on this matter, and I just happen to disagree. Your expertise in this field is unquestioned in my view. I'm just trying to argue for my position as well as I possibly can
(Trust me, I don't want to make a habit of getting into confrontations with Moderators)
It is an interesting document (so thanks once again) but it actually does nothing at all to add to the perception that the Evo roll-over is realistic.
Yes a large number of factors are at play in the video that are unknown (such as speed, exact nature of the grassy surface, etc), however from my knowledge of the dynamics involved and having experienced (both first and second hand) roll-overs in a number of circumstances, it does not look 'right'.
The car rolls to easily and with little to no precurser, its the same with the Audi roll-over that was seen in an earlier demo of FM3, the cars a bit to eager to roll-over.
Keep in mind what I said earlier, the second document does not show the real causes of roll-over, rather the most common types of roll-over (two very different things). It does not provide anywere near enough data to determine the actual cause of a roll-over when a car leaves the road.
Lets be honest a car leaving the road and going down a 20degree earth embankment would meet the reports criteria, but its the angle of the bank that would cause a potential roll-over in that case, not the surface. I'm sorry to say but its far to vague to be of use in this discussion in either direction.
Regards
Scaff
cant wait
I knew there was something about Forza 2 I hated and it was that grass was like hot tar, I swear if you weren't wearing a seatbelt in the Forza world you'd go straight through the windscreen because that grass slows you down by a ridiculous amount. 
