Furniture
Amongst other reasons I guess the 100bhp deficit may have something to do with it as well...Originally Posted by wwgkd
There's always the urban legend that in the '86 Portugal Rally in the special stage held at the Esotril race track Henri Toivonen and his Lancia Delta S4 had a time that would have placed him 6th in the grid of that year's grand prix.
Lack of charisma can be fatal.
Visca Catalunya!
Furniture
The only info I have found so far is that they may have run a shortened stage of the Estoril track.
Enjoy.
I think this warrants further investigation.
EDIT: I think I can answer this question but I am running into trouble. My solution is to send an email to the WRC and ask them - they'd surely know. However, on the website, the contact info is only for the company that owns the website.
Last edited by Kitdy; 04-02-2008 at 02:06 AM.
Super Moderator
WOw, you're loking into 5 inches of what you think is "flex" ?
Who's doing this and on what car.
THAT is about suspension compliance, clearly the car has a softer rear end with lower damping rate and the fronts having much lower rebound rate on a suspension with less travel. You'd do better measuring all the spring and damper rates under cornering conditions to find the major source. It is NOT the cahssis. A flexible chassis woudl twist to let the wheel stay on the ground. I'm afraid you're possibly going to waste time on a dead-end.
"A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'
Enthusiast
re lifting a wheel, What you're talking about there is WEIGHT, not chassis
I thought suspension tune, as in roll stiffness, was the big factor
Yeah, but why IS mass causing one to lift and not t'other?
If everything is relatively identical, as here, why isn't wheel lift down to individual suspension tuning, as in f/r balance in roll stiffness?
Enthusiast
Its all weight transfer
Yeah, but why IS mass causing one to lift and not t'other?
If everything is relatively identical, as here, why isn't wheel lift down to individual suspension tuning, as in f/r balance in roll stiffness?
If you look at both those photos you can see the lines to the corner enrty, apex and exit are completley different, in the FJ photo on the right the leading car has a wider entry(later) and nearly the same apex. The leading FJ has hit the apex and heading for the exit of the corner (weight transfer from inside wheel to outside wheel) which is why its lifting a wheel plus the fj holdens had a very high roll centre and probably a twig for a roll bar.
Here's a couple of pics of turn 1 at bathurst from the other weekend, you can see the different angles of the cars, we actually set our cars up with a fair bit of suspension droop
Photos courtesy Nathan Wong of Speedshots
Use the black tyre mark as a reference point
Both of these cars have a smoother early entry and arent on the power yet as they arent at the apex
Both these cars have a later and somewhat more violent weight transfer, no wrong or right way to take a corner but later entry more violent weight transfer looks quicker in a photo but not normally on the timesheetsboth thesre cars are on the power as they are throught the apex and heading for coner exit on the gas
SA IPRA cars 15, 25, 51 & 77
Sharperto Racing IP Corollas
http://www.sharperto.com.au/
Fanatic
It's because you aren't driving a 1960's Caddilac.If everything is relatively identical, as here, why isn't wheel lift down to individual suspension tuning, as in f/r balance in roll stiffness?
I'm dropping out to create a company that starts with motorcycles, then cars, and forty years later signs a legendary Brazilian driver who has a public and expensive feud with his French teammate.
Enthusiast
Hahahahahaa!
Enthusiast
True, an old design may be a good design, and there are some cool ones out there. Yes, I am a fan of caterhams, especially the new RS (I'd cut my own kidney out to sell on the black market for that one.) But the lower models especially, aren't really designed for the extra performance from their introduction, which is what I've been saying about $15,000 econo-car being suped up to a $40,000+ sportish car. Look at some of the higher end Caterham models that have frames with the same basic concept, but other than that aren't that closely related. The frame is a much better design than if you had just beefed them up with extra supports.
Enthusiast
Yes, actually, they do. Even ignoring the sheets factory numbers we were provided (on a wide variety of vehicles, but I'm too lazy to get a hold of the person that has them right now,) if you take an '06 long bed chevy dually (rated at over 5,000lb payload) and place a 3,500lb weight (we used a basalt column, note that it's way less than the rated payload) in the back corner of the bed and put the front tire of that same side on a 7 inch block the frame will twist a hell of a lot. Not only is the line where the bed usually came up to on the cab a couple inches higher than where the top of the bed comes up to now, you can't open the tail gate because it is jammed shut. That's an extremely heavy duty vehicle designed for 5,000lb + payloads and close to 20,000lb towing flexing a huge amount. If you add more weight or mess with the positioning of the other vehicles, it gets even more extreme. When we parked a grand cherokee with one front tire on that same 7 inch block with no weight at all in it we had trouble opening the rear hatch and could not get it closed until we drove it off the block. How much difference does 7 inches make compared to the peak g's that an Evo can pull in a corner?
If you'll read back, people have been arguing with me on this point, which is why I stated it again. Yes, if you put enough development into it it can be made to work, but that doesn't mean it's as good as, especially when you're looking at the forces generated by a $40,000+ car based heavily off of something that normally costs $15,000 and gets it's ass kicked by a miata.
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.
Enthusiast
No, if it were sitting on a block it would flex towards the ground because the only force acting upon it is gravit, in cornering it flexes in other directions, such as when the weight of the car (above the wheels) rotates about it's center of gravity during hard cornering thus pulling the offside wheel into the air.
Yes, we've been finding considerable chasis flexibility. EDIT: Including some in our Caterham, that was a surprise.
UI engineering project. We're hoping to apply it to our own formula car, but we are also getting outside sponsoship.
Last edited by wwgkd; 04-02-2008 at 10:31 AM.
Super Moderator
Define "considerable" that you are finding.
BTW, the Caterham is based on Colin Chapmans basic design of the Lotus 7.
Colin was well respected as knowing how to DESIGN a chassis to PROVIDE flex to improve handling when combined with the correct suspension settings
NO chassis flex has the issue that it will create stress points where all the energy is then focussed. There is a point where you don't want to go beyond because the materials become prohibitevely expensive to provide the necessary strength. Ever wonder why c/f compnents are found in F1 suspension - where they break in the "wrong" impact - but not yet in street cars ??
Oh and you cited a TRUCK in an earlier post on twist .... you cannot use any data from a sperate chassis or twin chassis leg construction to a monocoque
FInally, your point on body roll forcing flex, then again, you're going to see that in a car with long chassis rails and limited cros-stiffening. I'd be careful, you are really taking data out of contextWHat you describe is much more the oposite corner suspension compressing under body roll forces then flex.
Do you have access to any modellling software so you can see the relative contribution from cross braces in stiffening up chassis flex.
"A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'
Enthusiast
Yes, I know I cited a truck and an SUV, which is why I made the later comment about the Caterham. I put it out there because of the comments that there is no way that any modern vehicle will flex noticeably and I'm lazy, so I used the most obvious example and shortest description. I've been addressing a lot of comments in as small a pace as I can, which is why I haven't been throwing out 5 pages of data and using overly brief sentences. I do apologize for any unnecessary confusion.Define "considerable" that you are finding.
BTW, the Caterham is based on Colin Chapmans basic design of the Lotus 7.
Colin was well respected as knowing how to DESIGN a chassis to PROVIDE flex to improve handling when combined with the correct suspension settings
NO chassis flex has the issue that it will create stress points where all the energy is then focussed. There is a point where you don't want to go beyond because the materials become prohibitevely expensive to provide the necessary strength. Ever wonder why c/f compnents are found in F1 suspension - where they break in the "wrong" impact - but not yet in street cars ??
Oh and you cited a TRUCK in an earlier post on twist .... you cannot use any data from a sperate chassis or twin chassis leg construction to a monocoque
FInally, your point on body roll forcing flex, then again, you're going to see that in a car with long chassis rails and limited cros-stiffening. I'd be careful, you are really taking data out of context
Do you have access to any modellling software so you can see the relative contribution from cross braces in stiffening up chassis flex.
Chapman made use of the flex in the same way that many road bikes do, that does not mean that abnormal flex does not inhibit suspension efficiency. Don't forget how much suspension design has changed since Colin Chapman's days. About the best route with current technology now is to reduce the uncontrolled (largely non-suspension) flex and let the actual suspension do it's work. That's why there's the constant struggle for stiffer frames (and obviously lighter weight, but it seems like less and less people are really concerned about that, and why I don't like 4 doors on a sporty car.)
Of course we have the software, and it is funner than hell to use since we get to try out all of our ideas and see how well they work, as well as comparing existing ideas. What we're finding out is that there is a lot more flex in existing frames than we would have thought, as well as more undesirable/uncontrolled flex on other components between the tires and the center of gravity. Yes, I do know that a lot of this can be partially controlled by such things as adjustable roll bars, and that there are other issues than just traction, such as smoothness and compliance. Still, flex should be limited to controlled environments, not showing up in flexing body panels (it's kind of like watching an arrow in flight in slow motion, there was a lot more movement than we expected, maybe partially due to the fact that like the arrow, it's normally hard to see a the car goes flying by.)
Super Moderator
Give us some real examples of this measured flex you've encountered.
The truck was a VERY poor example as they are not constructed the same. It's like saying an F-18 would corner better because it's stiffer chassis
You confuse "uncotrolled flex" and designed flex. Colin used designed in flex. The perfect example were the first replacement chassis from Spyder for the original Elan. It was so stiff that the handling was made worse. Needing a complete re-design of the dampers and springs to get it back. It's like tyre wall compliance. Top cars are designed using the flex as part of the suspension confirguration.
Also, 4 door cars have been proven to be stronger and stiffer than two doors because of the additional components of the passenger safety cell.
So again, I would suggest you are careful not to use myths to determien your plans
Also, in the "Other components", remember that in real world you HAVE to have some high frequency short duration movements. Something that can't be built into current spring/damper units. Competigion cars have the mainly rubber bushes replaced with polyurethane ones of varying compliance. The final being replacement with rose joints and ZERO movement, but somehting impossible to survive on anything other than a super smooth race track
"A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'
Enthusiast
I did give you an example, as well as pointing out why I don't want to list 50 different cars, and also pointed out why I used the truck. Do you have a specific request that I could look up, or will the Caterham work?Give us some real examples of this measured flex you've encountered.
The truck was a VERY poor example as they are not constructed the same. It's like saying an F-18 would corner better because it's stiffer chassis
You confuse "uncotrolled flex" and designed flex. Colin used designed in flex. The perfect example were the first replacement chassis from Spyder for the original Elan. It was so stiff that the handling was made worse. Needing a complete re-design of the dampers and springs to get it back. It's like tyre wall compliance. Top cars are designed using the flex as part of the suspension confirguration.
Also, 4 door cars have been proven to be stronger and stiffer than two doors because of the additional components of the passenger safety cell.
So again, I would suggest you are careful not to use myths to determien your plans
Also, in the "Other components", remember that in real world you HAVE to have some high frequency short duration movements. Something that can't be built into current spring/damper units. Competigion cars have the mainly rubber bushes replaced with polyurethane ones of varying compliance. The final being replacement with rose joints and ZERO movement, but somehting impossible to survive on anything other than a super smooth race track
Colin Chapman did what he could with what he had and was continually trying to improve upon what he had. He figured if there was going to be flex then he was going to make the best of it (this design philosophy is where most of the mystique of "engineered in flex" comes from) This is actually a common phenomenon, especially where weight is a top priority such as the example I used of road bikes (bicycles for any real bikers out there.) Once again, suspension technology has changed a lot since then, along with chassis technology.
Four door cars of the same size and weight as a 2 door have been proven to be stiffer, largely due to the B pillar and smaller door openings. Having only 2 doors (especially with no backseat allows a much smaller and lighter car (which which both greatly help with rigidity.)
Yes, some parts have to give, but any large movements should ideally be confined to suspension. Bushings that have several inches of give are a bad thing. Suspension that keeps the body level and the tires on the road at all times is a good thing, so obviously you need movement, but you want it to be as controlled as possible instead of flexing (which then unflexes in an erratic manner, usually) or bouncing around.
Super Moderator
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 ?Colin Chapman did what he could with what he had and was continually trying to improve upon what he had. He figured if there was going to be flex then he was going to make the best of it
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 ?Four door cars of the same size and weight as a 2 door have been proven to be stiffer, largely due to the B pillar and smaller door openings. Having only 2 doors (especially with no backseat allows a much smaller and lighter car (which which both greatly help with rigidity.)
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.controlled as possible instead of flexing (which then unflexes in an erratic manner, usually) or bouncing around.
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 !!
"A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote
