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Thread: Mitsubishi Evo almost coming off track...

  1. #61
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    Quote Originally Posted by wwgkd View Post
    Dude, they do flex. Manufacturers do measure it.
    Yes; torsional rigidity.

    Measured in Nm/deg; to deflect the chassis by 1 degree would require however many Nm of torque to be applied.

    Considering that the rigidity of most modern cars is measured in thousands of Nm/deg, I doubt 300Nm from the engine is going to be doing much flexing...

    Quote Originally Posted by wwgkd View Post
    We're working on a project right now where we're analyzing how much that happens.
    Print out/ save the picture of the evo and show it to whomever is tutoring you on this project, and tell them you think it is "'chassis flex' because it is a cheap 'econo-car'".

    Tell us what the reply is, and whether they were able to keep a straight face.

    Also, as you're testing this, get an Evo, or even a Lancer, and find out how much force is required to get an equivalent deflection of 5".

    Quote Originally Posted by wwgkd View Post
    Having only 2 doors (especially with no backseat allows a much smaller and lighter car (which which both greatly help with rigidity.)
    True - a sheet of material will be stiffer with fewer holes cut into it, however, if you cut more holes out and then add reinforcement...

    BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
    BMW E46 Coupe (w/folding seats) 12,500 Nm/deg

    In instances where a car is available in 2 and 4 door versions, the 4 door is odds-on to be stiffer because;
    - Smaller doors - 2 door versions usually have larger door openings to enable better access to the rear seats.
    - B-pillars - supporting 4 doors and acting as side impact protection, they tend to be quite strong.

    I think you will find that there is probably a more "down to earth" explanation to why the Evo in question is impersonating a tripod, and it is probably due to the raised red and white lumpy things it has just driven over.

    YouTube - Gabriele Tarquini stunt

    See below - is that massive chassis flex, or cars bouncing off each other?

    Quote Originally Posted by Matra et Alpine View Post
    You missed sarcastic smiley in your comments
    I would never dream of making sarcastic comments.
    Attached Images Attached Images
    Last edited by Coventrysucks; 04-03-2008 at 01:00 PM. Reason: ETA Tarquini
    Thanks for all the fish

  2. #62
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    Nice pic demonstrating the OTHER reason .... typical barging in one-make races
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  3. #63
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    if you take an '06 long bed chevy dually
    How on earth is deliberately bending a truck comparable to the microns an Evo flexes during cornering?
    How much difference does 7 inches make compared to the peak g's that an Evo can pull in a corner?
    Just how many peak Gs do you think that Evo is pulling?
    If you'll read back, people have been arguing with me on this point, which is why I stated it again.
    But so far you seem to be the only person on the planet who thinks a roll caged Evo isn`t stiff enough. The modifeid economy shell works fine in this case, as with an Impreza STI.
    In the picture that started this whole argument, the tire of the Evo is way the hell off the ground. 5 inches may be an exaggeration, but it's not that far off.
    The car is designed with rally in mind, do you suppose that there may be a bit more travel in the suspension than say, a Corvette has?

    The car is not flexing visibly during corners and you have given us no reason to think it is.
    Horsepower wins races. Torque pulls trailers.

    http://www.nuerburgring.de/fileadmin/webcam/webcam.jpg <Live cast from the 'Ring.

  4. #64
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    Quote Originally Posted by Matra et Alpine View Post
    Well I did only ask for "some" so no need to get upset about listing 50.
    Pick a couple or proper cars and yes the Caterham - btw which version ?

    WHere do you have that citation ?
    What Colin fundamentally strove for was that to save weight and having a component do more than one task was the best way to achieve that. So he SET OUT to have flex in many of his designs. We're nto talking about a designer jsut starting otu and not sure what happens, but a leader of a major road nad race team who had access to ALl the best methodologies of the day.

    WHere did you get told this myth ?

    The real world of racing and rallying continuse to prove that 4 doors are stronger shells than 2.
    The B-pillar of a 4-door has to be stronger as it has to account for 2 sets of door iopenings and in addition the c pillar is MUCH stronger than in a 2-door.


    ah, this is where I think your confusing arises from.
    You seem to think flex is not controlled.
    EVERY component in a vehicle has flex controlled by webbing, material, thickness and layout.

    Please list the cars you think are doign it "bad", as "bouncing aroudn" you're conly going to see if a truck !! And there are reasons for that as when doing real work, flex is better than break !!
    I just spent 2 hours responding to this and coventry's post, but when I tried to post it there was some error with the site, and I lost it. I have too much work to do now to write it again, so I'll post it later. Sorry about the delay

  5. #65
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    Quote Originally Posted by wwgkd View Post
    I just spent 2 hours responding to this and coventry's post, but when I tried to post it there was some error with the site, and I lost it. I have too much work to do now to write it again, so I'll post it later. Sorry about the delay
    That always happens on the posts you spend hours doing, Murphy`s law. I developed the habit of copying my post before I hit the reply button. Used to happen to me a lot on a theology discussion board I visited.
    Horsepower wins races. Torque pulls trailers.

    http://www.nuerburgring.de/fileadmin/webcam/webcam.jpg <Live cast from the 'Ring.

  6. #66
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    Quote Originally Posted by P4g4nite View Post
    That always happens on the posts you spend hours doing, Murphy`s law. I developed the habit of copying my post before I hit the reply button. Used to happen to me a lot on a theology discussion board I visited.
    Yeah, I tried that, but there were difficulties and I got lazy. Anyways, I turned in my paper (a whole 6 minutes before the deadline) slept 32 hours straight, and here I am again, with kind of an abridged version of my original post.

  7. #67
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    Quote Originally Posted by Matra et Alpine View Post
    Well I did only ask for "some" so no need to get upset about listing 50.
    Pick a couple or proper cars and yes the Caterham - btw which version ?

    Well, I didn't know what exactly you consider "proper." It is possible to look up the numbers provided by companies and then look at the angle of deflection vs length, but that’s not exactly the same as what we’re looking at (we’re getting more complex and wanting to know what happens at likely forces at certain points in relation to other specific points); so we’re doing a lot of our own work as well as numbers provided by outside sources. Aside from the Caterham 7 (it was $36,000 all told, I could look up the specific model name if you really wanted) one of the professors mentoring us has an Evo (this was the one mentioned earlier that I had ridden in.) He bought it because he couldn't afford an M5 and the M3 sedan wasn't available at the time. He was disappointed with it, but other than that we got 3.6 inches using the forces generated in our recorded peak of 1.01g. Before you ask, no it’s not caged; but caging things is a complicated process and the overall benefits depend very much on how exactly you go about it. I’m finding that quite often the biggest benefits are in safety if you roll (because of the added strength) and they sometimes do very little to the rigidity (as opposed to strength.) This is obviously not true all of the time, but it was kind of a shock to discover that cages designed for roll safety and to stay out of the passengers’ way can be incredibly flexible up to a certain limit.
    Quote Originally Posted by Matra et Alpine View Post

    WHere do you have that citation ?
    What Colin fundamentally strove for was that to save weight and having a component do more than one task was the best way to achieve that. So he SET OUT to have flex in many of his designs. We're nto talking about a designer jsut starting otu and not sure what happens, but a leader of a major road nad race team who had access to ALl the best methodologies of the day.

    Right, well we can use road bikes (bicycles) as an impartial example for this. Road bikes strive to be light and in the pursuit of this aren't exactly the Rock of Gibraltar. Given that they will flex, they "engineer" the flex to try and control it or even take advantage of it. If they could make a 3 oz bike that would not flex under a load of 4,000lb, they'd do it in a heartbeat. This was the 50's. If it's that lightweight it will flex more. So, he decided to control it as best he could and turn it into a good thing wherever possible. "Engineering in flex" is really just trying to control existing flex more efficiently in almost all cases. I really don't want to spend hours to look it up for some argument on the internet with someone I don't know (no offense meant in the description, I was just trying to put it into perspective.) Some of the other people on the team are laughing at me enough for the time I have put into this. Once again, recall that the best available technology then is now over 50 years old. A lot has changed in that time, despite the seeming similarity of concepts such as monocoque or tubular steel frames.
    Quote Originally Posted by Matra et Alpine View Post

    WHere did you get told this myth ?

    The real world of racing and rallying continuse to prove that 4 doors are stronger shells than 2.
    The B-pillar of a 4-door has to be stronger as it has to account for 2 sets of door iopenings and in addition the c pillar is MUCH stronger than in a 2-door.
    Given two different cars, one that’s designed as a two door (meaning it’s smaller and lighter, not just a 2 door version of the same 4 door car) and one that has the size, length and weight of a four door (RX8’s and similar vehicles don’t really apply, I mean a sedan):
    1) First: 2 door cars don't have C pillars (a c pillar is the third pillar, and they only have to span 1 door, thus just ‘a’ and ‘b’ pillars.)
    2) May seem obvious, (I'm trying work up to it to be as clear as possible since there seems to be some confusion as to what I’m saying) but longer moment arms increase the force load.
    3) Longer structures have more weight and longer moment arms, and thus larger force loads.
    4) If 2) and 3), then shorter structures have smaller force loads and thus help greatly in keeping things as rigid as possible.
    5) This has been proven in racing. I can't think of an FIA GT1 or GT2 with four doors. Or any true supercars that have 4 doors. I don't consider something like a Rolls Royce Phantom 9 to be a supercar, but some people call SRT-8 Chargers super cars, making F430’s super-duper cars and Saleen S7’s ridiculously-super-duper cars.


    Quote Originally Posted by Matra et Alpine View Post
    ah, this is where I think your confusing arises from.
    You seem to think flex is not controlled.
    EVERY component in a vehicle has flex controlled by webbing, material, thickness and layout.

    Yes, as I have already said, everything flexes. Some stuff more than others. Some things flex in a much more controlled manner than others. Springs, for instance, are designed to flex in as controlled a manner is possible. That's why eliminating the less controllable forms of flex wherever possible and controlling existing flex to the greatest degree that you can is a good thing. Suspension does this well. Flexing in a controlled manner is its entire reason for existing.

    Quote Originally Posted by Matra et Alpine View Post
    Please list the cars you think are doign it "bad", as "bouncing aroudn" you're conly going to see if a truck !! And there are reasons for that as when doing real work, flex is better than break !!

    Just about everything sees separation between tire and road surface on sharp impact, but many to degrees so small that it's generally not noticeable by the driver under normal driving. Quite often it is noticeable mostly on washboard roads. It also tends to be more noticeable in stiffly sprung cars (there are more than a few sports cars intended more for the track that will skip to beat hell on rough back roads) and also on vehicles with extremely long travel.
    Yes, breaking is bad. That's why we try to reduce fatigue by having the suspension flex, instead of the other components it's attached to. If the suspension is not in optimal position it will obviously not work as well. So you see, when other components flex and move the suspension from its optimal positioning, it's a bad thing. Notice that a lot of frames have “suspension” type bits built in. They do that for better control and fatigue reduction.

    Sorry for the long delay in response time. I was on a friends computer which doesn't seem to lik eme posting on this site. I finally got mine back, so here we go.

  8. #68
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    Quote Originally Posted by Coventrysucks View Post
    Yes; torsional rigidity.

    Measured in Nm/deg; to deflect the chassis by 1 degree would require however many Nm of torque to be applied.

    Considering that the rigidity of most modern cars is measured in thousands of Nm/deg, I doubt 300Nm from the engine is going to be doing much flexing...
    I've never said anything about the engine flexing the frame. The only vehicle I've ever seen which could flex a tire off the ground purely on torque from the engine was a CJ-2a at a car show that had a 560 V8 making something over 800 HP. For that matter, I'm not even sure it's possible for an all wheel drive vehicle with a front mounted engine to flex a rear wheel off the ground no matter how much power it had.

    Quote Originally Posted by Coventrysucks View Post

    Print out/ save the picture of the evo and show it to whomever is tutoring you on this project, and tell them you think it is "'chassis flex' because it is a cheap 'econo-car'".

    Tell us what the reply is, and whether they were able to keep a straight face.
    Who do you think made the original comment? He used my account but he typed it.
    Quote Originally Posted by Coventrysucks View Post

    Also, as you're testing this, get an Evo, or even a Lancer, and find out how much force is required to get an equivalent deflection of 5".
    Ok, this is what’s frustrating me; did you not read what I said or did I not say it clearly? Because I’ve been saying that it could not be all suspension dive, that there had to be something else going on. We all looked at the picture and it didn’t seem to us at the time that it was because it had hit the bumps. That’s why one of our advising professors (incidentally, the one that first made the comment that has you all so pissed off) had us borrow his Evo to do some work on it and see how it compared to the other vehicles we had been planning on testing ourselves. It showed a lot of flex (3.6 inches,) not 5 inches, but plenty as it was.
    Quote Originally Posted by Coventrysucks View Post

    True - a sheet of material will be stiffer with fewer holes cut into it, however, if you cut more holes out and then add reinforcement...

    BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
    BMW E46 Coupe (w/folding seats) 12,500 Nm/deg

    In instances where a car is available in 2 and 4 door versions, the 4 door is odds-on to be stiffer because;
    - Smaller doors - 2 door versions usually have larger door openings to enable better access to the rear seats.
    - B-pillars - supporting 4 doors and acting as side impact protection, they tend to be quite strong.
    Right. Which is why I said in my earlier post that if the cars are the same size and weight, then the 4 door will be stiffer. Compare a sedan to a 2 door 2 seater, and the 2 seater will probably be stiffer and almost certainly be lighter. Which is why so many people on UCP and other places agree that real sports cars have 2 seats (yeah, I know 911s have a back seat, that doesn't make me like them more. Most magazines I've read agree that the Cayman handles better.)
    Quote Originally Posted by Coventrysucks View Post

    I think you will find that there is probably a more "down to earth" explanation to why the Evo in question is impersonating a tripod, and it is probably due to the raised red and white lumpy things it has just driven over.

    YouTube - Gabriele Tarquini stunt

    See below - is that massive chassis flex, or cars bouncing off each other?



    I would never dream of making sarcastic comments.
    Like I said before, it looked to me like the Evo had missed those. An Evo in another picture on the same site is also lifting the rear inside tire, and it clearly could not have been caused by hitting the bumps.

  9. #69
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    Quote Originally Posted by P4g4nite View Post
    How on earth is deliberately bending a truck comparable to the microns an Evo flexes during cornering?
    Just how many peak Gs do you think that Evo is pulling?
    But so far you seem to be the only person on the planet who thinks a roll caged Evo isn`t stiff enough. The modifeid economy shell works fine in this case, as with an Impreza STI.

    The car is designed with rally in mind, do you suppose that there may be a bit more travel in the suspension than say, a Corvette has?

    The car is not flexing visibly during corners and you have given us no reason to think it is.
    There's a difference between working well enough and being close to ideal, which is what I've been arguing. Compare an Evo to an M3, and the Evo comes out for the worse. Yes, the Evo is cheaper, but the whole argument is that it was based off a cheaper car and then modified into an expensive car, instead of starting there from the get go. Look at the comparisons that Car and Driver did with their tuner challenges, where Evos among other vehicles got turned into $100,000+ machines by respected tuners and then still got their asses kicked by a Z06 that costed half as much.

    Yes, I understand long travel suspension, but the point of it is to keep the tires on the ground, rather than allowing one to lift off. I realize that you're all going to be outraged by this comparison, but if you want to talk long travel an evo doesn't come close to my Jeep. On back roads I can slide it around corners (13.50 BFG's aren't track tires but get decent grip and as long as I stay on the gas the tail hangs out and I don't roll) without lifting a tire off the ground. Yeah, I've got a 2 inch steel tube cage (not the factory cage,) but it's a freaking Jeep with much longer travel than any car and I have no trouble with tires coming off the ground. If it's long travel suspension lifting a tire up, wouldn't I see that more so on my rig?

  10. #70
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    hmm, a question given the large deflection you say on the Evo.
    WHere are you applying the force and where are you measuring the deflection ?
    I suspect you've used the tow points or bumper mounts or body extremes.
    Body flex only matters between the suspension components and shoudl ONLY be measured between the suspension component mounting points.
    Can you confirm the procedures you're using for applying and measuring ? Cheers
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  11. #71
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    Quote Originally Posted by wwgkd View Post
    Who do you think made the original comment?
    Funnily enough, I was under the impression that it was you, as
    1 - it's your name at the top of the post
    2 - there was no indication that it was not you
    3 - you've made no mention of the fact that the comment was nothing to do with you in the 14 posts between the original comment and that above. Even though other people have questioned the validity of the statement, you haven't thought to mention that it was put forward by an "expert" until now?

    I still have no idea as Mr He is a mystery to me.

    Quote Originally Posted by wwgkd View Post
    did you not read what I said or did I not say it clearly?
    I don't know; who said it or not is becoming increasingly unclear.

    Quote Originally Posted by wwgkd View Post
    That’s why one of our advising professors had us borrow his Evo to do some work on it and see how it compared to the other vehicles we had been planning on testing ourselves. It showed a lot of flex (3.6 inches,) not 5 inches, but plenty as it was.
    Ok, this is what’s frustrating me; did you not read what I said or did I not say it clearly?

    I asked you to "find out how much force is required to get an equivalent deflection of 5"."

    According to the info you have already given, c. 33,000Nm
    Last edited by Coventrysucks; 04-13-2008 at 03:43 PM. Reason: m
    Thanks for all the fish

  12. #72
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    Quote Originally Posted by Matra et Alpine View Post
    hmm, a question given the large deflection you say on the Evo.
    WHere are you applying the force and where are you measuring the deflection ?
    I suspect you've used the tow points or bumper mounts or body extremes.
    Body flex only matters between the suspension components and shoudl ONLY be measured between the suspension component mounting points.
    Can you confirm the procedures you're using for applying and measuring ? Cheers
    No, we're measuring from suspension mount points, which is how we're applying the force. We take off the suspension, bolt it in to our test frame and apply the forces we calculated (using 3D modeling) from the dimensions and peak recorded g force from driving it. But that's only on the ones we measured. The numbers we were provided (we can't test a huge number ourselves for time and money reasons) were done in a similar manner, but details may vary slightly.

  13. #73
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    Quote Originally Posted by Coventrysucks View Post
    Funnily enough, I was under the impression that it was you, as
    1 - it's your name at the top of the post
    2 - there was no indication that it was not you
    3 - you've made no mention of the fact that the comment was nothing to do with you in the 14 posts between the original comment and that above. Even though other people have questioned the validity of the statement, you haven't thought to mention that it was put forward by an "expert" until now?
    Ok, I was a little ticked that everyone was telling me to go talk to someone who knew what they were talking about instead of at least asking me where I got the info first, so I was a little rude and I appologize. Since the topic was so close to what we were doing I showed the picture to the people I'm working with (for future reference, grad students and our professor "mentors") and that first comment was made by one of the professors, Bob Stephens. Still, it's been all of us contributing but mostly me typing and I didn't think it mattered that much. I have been getting a lot of comments from people who did not read what I was saying at all, since there comments were answered before they even posted. I've also getting comments like "thank you captain obvious" when it was a response to something someone actually said. I would have thought it was obvious, too, but people were arguing that point.
    Quote Originally Posted by Coventrysucks View Post

    I still have no idea as Mr He is a mystery to me.



    I don't know; who said it or not is becoming increasingly unclear.



    Ok, this is what’s frustrating me; did you not read what I said or did I not say it clearly?

    I asked you to "find out how much force is required to get an equivalent deflection of 5"."

    According to the info you have already given, c. 33,000N
    We didn't try to find an equivalent deflection of 5 inches, we only found what happened under real life force loads, so I don't know how much it would take. Looking at the location and amount of mass distributed around the vehicle and looking at stress loads on individual members is a lot of work and not something we'd normally do if there wasn't a reason to, so I don't think we will be looking at what it takes to get 5 inches. The reason I asked if I hadn't been saying things clearly is that I never said that the frame alone accounted for the 5 inches, but that there is no way that suspension dive could account for 5 inches. There are, of course multiple cause for pretty much any mechanical phenomenon in anything as complex as a vehicle, so it is not all chassis flex, but there is a lot more flex in the frame and subframes in a family hauler (not a minivan, certainly, but still a lancer has 4 doors and is low in the price range) than a lot of people are giving it credit for. Thus this argument.

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    good pict of evo !!! those clio cups definately run stiff as they are always bouncing around and trying to drift each corner. makes for good racing

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    Quote Originally Posted by wwgkd View Post
    I didn't think it mattered that much
    Context will have an influence on how people respond to you. Especially considering the high quality of your initial contribution to the thread, it is not surprising that people may not guess that your later posts are backed up by professional opinions, and therefore are less likely to respond in the same way.

    Quote Originally Posted by wwgkd View Post
    I don't know how much it would take.
    Can you not extrapolate the answer from the data you already have?
    Thanks for all the fish

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