Adam Le Brese

[agony]

Originally Posted by Falc'man

And Ford Aus once made cars that looked like that... /sighs and wipes tears

: Yes it is sad to see where modern technology has taken Ford these days. :

[nugget378]

Originally Posted by EAadam

Any evidence to back your quotes ?

You asked for it...PWNED!!!!!

[Rev28K]

Originally Posted by Strucnjak

im sorry if i have bored anybody, i just feel very passionate about suspension design and dynamics. Anyone please feel free to correct any mistakes i have made.

This is going waaayyyy off topic (I like the XC by the way) but do you want to take a shot at explaining modern F1’s front control arms then?

I know that they use carbon fibre for the “wishbone” arms but they don’t seem to have visible bearings at the pivot points.

The display cars at motor shows, etc just seem to have a crease in the carbon fibre where it is meant to bend/connect with the chassis (top of the V on a wishbone)

I know that it was introduced by Ferrari a few years ago and everyone seems to be doing it but other than that….

What are the advantage/disadvantages?

[Strucnjak]

F1 wishbones typically are manufactured using a carbon flexure joint and are the most optimal with regards to weight, drag and simplicity. Typically a spherical bearing is used to provide suspension motion at the chassis, however carbon flexures are where the carbon tube tapers downs and the carbon flexes to provide the suspension movement.

Since f1 cars have alot aerodynamic download, the suspension has to be very stiff meaning little suspension travel(most of the wheel travel is through the tire). The loading that a wishbone takes is mainly in the axial direction, the vertical motion is generally reacted by the spring and damper arrangement. This means that the flexures are adequately stiff in the required direction. Manufacturing these wishbones is simple as there is only one part to make.

I think all teams run a hybrid chromo/carbon wishbone on the upper rear trailing arm, simply beacuse its the closest to the exhaust and the resins used in the carbon fibre simply degrade with the increase in such high temperatures.

I hope this helps. Below are photos of the different set ups

[Rev28K]

Bingo! “flexure joint” that’s the phrase I was after.

The idea of deliberately making something weak enough to flex, but still strong enough to last, still seems spooky to me.

I guess they are a “one race” item.

[Strucnjak]

it does seem strange, but carbon is suprisingly flexible in off plane loading (eg perpendicular to the ply angles). In plane it has a high modulus(stiffness) but out of plane it can flex quite a bit, and because your intensionally not vertically displacing the wishbones much the required stiffness can be high and carbon is very strong. I think they are throw away items, like alot of components on an F1 car however they can take a serious ammount of punishment and the fatigue properties are reasonable so they dont nessecarily need to be a throw away item. I have been investigating carbon wishbones and flexure but realistically the cost and head f*##ing involved with the manufacture are just not worth it. Plus the wheel travel on the cars i design is substantially larger and we run unspung downforce(eg downforce is tranfered straight to the wheel rather than through the chassis sprung downforce) and im able to run fairly soft wheel rates so its not really worth the effort.

[Road Games]

Originally Posted by EAadam

Any evidence to back your quotes ?

Cant wait for your next question :

[Ghiadude]

Originally Posted by Strucnjak

If you look at where the bell crank(rocker) is being reacted, it is in the middle of a member, tubes are good at resisting torsion and are reasonable in tension/comp, however bending is what kills tubes, in this instance the bell crank load is being reacted in the middle of a tube putting this member into bending, big no no. if there was some triangulation(truss structure) tying in the bell crank mount to say the node near the lower radiator mount or another major node rather then the current bent tube, then that would be ok. the push rod is taking all your vertical loads and and transferring them into the damper through the bell crank, this is a very large force. Mind you if properly sized this particular structure would be be acceptable, however looking from a race car design perspective this is really poor. Have a good look at this photo, it clearly shows what im talking about.
http://www.carpoint.com.au/carconten...mbition/04.jpg

Aero tube is good if you have your wishbone in free stream air and you are doing 200km/h plus. However here there is coachwork that is blocking the wishbones from any major air flow. Aero tube is mainly used in open wheel racing because circular tube is inherently draggy(sic), we have done wind tunnel work on circular vs aero tube on wishbones, we came to the conclusion as have many others that there is no reason to run aero tube for wishbones unless you have no other course of drag reduction, the reduction in drag is so minuscule. The other point is that aero tube is about 3 times the price of normal chromo tube and if you make the aero tube yourself from circular tubing you have effectively compromised the material by taking it past its yield. aside from looks there is no real need.

Rod ends in bending, typically wishbones should only be in tension and compression. As you can see below i have drawn two free body diagrams(please excuse the poor diagrams, im pretty poor with ms paint), as you corner you induce a lateral force and this has to be reacted into the chassis through the wishbones, since you are running a spherical bearing on the upright to allow turning, this lateral force can only be seen as a tension or compression in the wishbone as spherical bearings cannot react a torque. As with alot of cars for simplicity and cost reasons rod ends are used at the wishbone ends with a threaded lug to allow camber/caster adjustment and mounting. lets assume were only talking about a bottom wishbone on the loaded side of the car, ignore push rod/damper. In this case we are dealing with compression in the wishbone.

For the case of the rod end wishbone (which is used on this car)this compression force is being transfered from the direction of the wishbone into the direction of the rod end. This change of geometry induces a bending in the arrangement and can cause major failure at the root of the thread on the rod end, again if it is properly sized than it can be acceptable, but it is usually much heavier. you could run the rod end in plane with the wishbone as well, i run in plane rod ends on the top wishbones with concentric double adjusters for quick camber/caster adjustment.

For the case of the spherical bearing in its own housing, the compression force is reacted in plane with no changes of direction. The advantage of spherical bearings with in plane loading is that the size of the assembly can be much smaller due to the smaller loads that it sees.

In the xc's case there has been lots of time and money spent on making alot of things look good, but a little bit more effort into making the design a bit more sound and light would have been cool to see. Efficiency is what its all about in race cars.

im sorry if i have bored anybody, i just feel very passionate about suspension design and dynamics. Anyone please feel free to correct any mistakes i have made.

in hindsight a simple YES wouldve sufficed!! that has to be THE biggest ownage i have EVER read.

Thank s for the explanation i think i understand it now. I have some suspension design questions for a project that i'd like to ask if youd be so nice to answer?? ill post in the appropriate forum and let the others have a go as well. As for the XC flawed suspension it may have but dam thats hawt:evil3:

[Strucnjak]

its not flawed, i mean it still does the job, but its not as good as it could have been, its pretending to be a race car, so why not apply some race car engineering. Like i said i really like this car and the idea behind it just not the execution of the front suspension/chassis.

By all means, i know a few things not everything but ill try my hardest to answer them. Where is this appropriate forum for this sort of discussion?

[agony]

Originally Posted by Strucnjak

By all means, i know a few things not everything but ill try my hardest to answer them. Where is this appropriate forum for this sort of discussion?

I think this is where he is talking about.
http://www.fordforums.com.au/forumdisplay.php?f=20

[Nostalgia]

Originally Posted by nugget378

You asked for it...PWNED!!!!!

If that is meant to say OWNED then YES i got shut up. This guy knows his stuff. I thought the same thing myself when i saw the pics of the front suspension design. tx3dude has got a good point.

[agony]

Originally Posted by nugget378

You asked for it...PWNED!!!!!

Sure looks like a spelling mistake to me.

[Nostalgia]

Originally Posted by agony

Sure looks like a spelling mistake to me.

Possible new thread as to what PWNED means. I have a few good ones.

[Piotr]

Originally Posted by Strucnjak

Plus the wheel travel on the cars i design is substantially larger and we run unspung downforce(eg downforce is tranfered straight to the wheel rather than through the chassis sprung downforce) and im able to run fairly soft wheel rates so its not really worth the effort.

I was under the impression that the FIA mandated that wings must be "rigidly attached to the body work" and not to the suspension

[Strucnjak]

yes, thats true for f1 and so forth, in todays day and age i think it is a stupid rule. However the class i race doesnt mandate sprung download.

[Nostalgia]

What class do you race in ?

[Strucnjak]

formula sae...

[Rev28K]

Originally Posted by Strucnjak

it does seem strange, but carbon is surprisingly flexible in off plane loading (eg perpendicular to the ply angles). In plane it has a high modulus (stiffness) but out of plane it can flex quite a bit, and because you’re intentionally not vertically displacing the wishbones much the required stiffness can be high and carbon is very strong. I think they are throw away items, like alot of components on an F1 car however they can take a serious amount of punishment and the fatigue properties are reasonable so they don’t necessarily need to be a throw away item.

Yes, compared to a few years ago when any tangle or touch seemed to stuff up a car. Have they gone away from tethers to try and stop bouncing stray wheels bouncing away? This didn’t seem to work that well anyway.

Carbon fibre seems like a good material for blade adjustable roll bars too, if you want to lose weight at great $$$

Originally Posted by Strucnjak

Plus the wheel travel on the cars i design is substantially larger and we run unspung downforce(eg downforce is tranfered straight to the wheel rather than through the chassis sprung downforce) and im able to run fairly soft wheel rates so its not really worth the effort.

I always liked the downforce going to the wheel rather than the chassis idea.

Wasn’t it was banned from F1 in the late 60’s because they had wing (and wing bearing structure) failures leading to sudden catastrophic loss of downforce.

What class of open wheeler lets you run downforce direct to the wheels (hillclimb?)?

If it is for longer circuit races can you have moveable wings that trim the downforce for less drag on the straights?

[Strucnjak]

Carbon fibre seems like a good material for blade adjustable roll bars too, if you want to lose weight at great $$$

you wouldn't want to make them out of carbon fibre. plus the weight of an arb is all in the torsion bar so there is bugger all saving in the blades. im not convinced with blade arbs, i still like the u-bar design.

I always liked the downforce going to the wheel rather than the chassis idea.

Wasn’t it was banned from F1 in the late 60’s because they had wing (and wing bearing structure) failures leading to sudden catastrophic loss of downforce.

What class of open wheeler lets you run downforce direct to the wheels (hillclimb?)?

If it is for longer circuit races can you have moveable wings that trim the downforce for less drag on the straights?

unsprung download is good, it should be allowed back into racing. you are correct about why it was banned and thats because they didn't decouple the drag and the download from the mounts and they had a serious amount of drag and the mounts would just fail causing some serious accidents.

i believe that formula sae is the only class left that allows open wheelers to run unsprung download. The unsprung wing mounts are serious pieces of work especially the front wing mount for obvious reasons. We do race hill climbs with the fsae car but we have our own rules that allow us to run them. but most of the time they throw us in with formula libre under1300 which were not supposed to run in.

I don't believe aero elastic wings are allowed in any form of motorsport, movable and powered aerodynamics have been banned for the best part of 20 years.

[Piotr]

Yep, any moveable aerodynamic device is banned. Flexi-wings are banned for this reason as are "flip" type wings. Even the Renault mass-damper was banned because it was classified as an moving aerodynamic device.

[XAllent]

Adam's Xc Coupe to make it it's debut in complete form at this year's (2011) Motorex in Homebush!

[LethalLeigh]

Quality thread mine!, I had been wondering what happened to this car though.

[lownloud]

Strangely enough I was digging through some old magazines today and saw it..... and asked myself "I wonder what ever happened to that car?"
This is a bit spooky to find this tonight!....

[XAllent]

Ghosts of the Street Machine Dimension have informed me!

[Iggypoppin']

Got the poster of this in baremetal, looked so tough in it's nakedness! Anyone got pics?