Physics The Physics discussion thread

[Giorgos Kostis]

Click unwatch thread on top of this page. To the right from the pagenumbers row.

Thanks

 

[RC45]

If anything, we've tried to help you, and it's something everybody has seen. The only one trying to undermine in this case the game it's you, spreading all this nonsense, clearly showing three things; one, that you never read (or rather, you don't pay attention while reading), second, that your knowledge is clearly inferior than what you think, and third, that your only intention was, and is, to attack the game and grab some attention.

I am making a mod that will allow me and others to experience the C5 in its many flavours, from stock to ridiculous. I know what these flavours are. I know what this car feels like at all levels of development and I know I can do it more justice than someone who does not have the very broad base of experience I have with this chassis in real life. I would like to use this game to deliver the experience, simply because it is one of the better looking game engines that permits modding.

If I have direct questions I ask them - otherwise I am making factual statements and presentations where I have found what I believe are deficiencies - for e.g. when I adjust the Kunos C7 to have dimensionally correct steering tie rod location the handling and chassis model goes completely wrong - which suggests either the game engine has some deficiency Kunos are compensating for by using the incorrect tie rod/steering location or the model data is sorta fudged to deliver the C7 in game the way it is, which feels very good even with the mis-configured steering tie rod data - and when I post this type of thing I am anticipating the audience to offer a realistic suggestion or confirm that these areas are the compromises we have to make.

Either way I will accept the response - just keep the personal knocks out of the responses.

And as for folks wishing to poke fun at me and my foibles - have at it, I am very comfortable in my skin - and even more so in my ability to deliver the right feeeeeeeeeeeeeeel as this is my toy car after 15 years of development. I kinda do know what these cars should feel and behave like.

A big question is whether the physics engine will behave correctly if I use the accurate suspension setup used on the car here - super sticky 315 width fronts, 345 rears running a wider track and aggressive aero that begins working as slow as 30mph - or would it just be easier to fudge the numbers by using cheater tyres and or exaggerated down force LUTs for the cone chasing version of the car?

Folks,
your discussion is getting to kindergarten levels of conversation. Final warning. Move on or I'll have the thread closed (personal note: I REALLY BELIEVE this thread should've been closed btw)

The last 20 (the last thing decent I saw is in page 11) posts I see nothing but blah blah blah blah blah blah blah blah dog food meat blah blah blah gin and juice is good blah blah blah...

I really believe this thread had potential but all gone down the drain, but I truly believe in redemption and that you can discuss AC physics of your ongoing projects or in general in an adult, polite, educated fashion.

Three strike mode engaged.

Makes sense and note taken.

So, are we getting that fudged C5 at any point ?

Only as part of a 30 car mod pack. 1999 FRC, 2001 - 2004 Z06, modded FRCs, Z06s based on popular community real life cars, and a few of the memorable Speedvision GT C5 Z06 race cars (all built from the C5 Z06 race kit GM sold in up through 2002.)

Coupes and Verts may follow at some point in the future.

And the level of fudging is going to be no more than the Kunos C7 needed

 

[mclarenf1papa]

aggressive aero that begins working as slow as 30mph

What do you mean by "begins working"?

 

[RC45]

What do you mean by "begins working"?

Begins working; as in, you can feel the effect of,.is noticeable, contributes positively to handling at low speeds vs aero that comes into play under heavy braking from high speed or lends overall stability in high speed bends etc.

With the C5 its tricky to use aero to address lift and stability without impacting cooling - so many folks don't bother outside of competition cars because few of the mods needed are easily reversed. You can't just slap on a wing and call it quits. I guess I am a sucker for punishment - our street car runs pretty aggressive aero.

In stock form the car is a bottom feeder that scoops air up into the front of the engine compartment to feed the radiator and a/c. This air piles up in the engine bay. The air also enters the front wheel wells from the brake cooling ducts and hangs around without vacating in a timely manner. The Z06 also has stylish looking mesh vents in the front where the other models had fog lights - air rushes in here and fills the front bumper cavity and again just piles up.

None of these are really major issues at low speeds, but contribute to front end lift at higher speeds. The coupe suffers less from this than the Z06 but not by much.

On a stock body C5 Z in autocross situations you might use tyres, ride height, camber, toe and spring, anti-roll bar, bushing and shock upgrades to deliver the best mechanical grip possible without worrying about the front end lift.

But with body modded cars you can be very creative with splitter and rear wing setups to develop down-force at low speeds that when combined with good tyres and alignment can make for a great auto crosser that carries its 3000lb weight very well.

I would hope that if the game engine follows orders as provided by the LUTs, then it should just apply the appropriate down-force at the appropriate speed.

As for the actual aero changes that are used to generate the down-force we end up with, out back they are a 68" to 70" wide adjustable rear wing, rear deck gurney flap/ducktail spoiler. Up front they are vented hood to help evacuate the engine bay air; vented fenders to help evacuate the front wheel wells, front wheel well gurney flaps to reduce turbulence into the front wheel wells and direct air around the tyres, Front splitter with under tray all the way back the behind the front axle, front radiator intake with closed ducting to route air flow up into engine bay and out the hood vents. Body side skirts and rear wheel gurney flaps/fairings help keep the air from rolling under the car - but to be effective they are often too low to survive much street driving.

There are other specifics appropriate to more race dedicated cars and cars that run in series that do not allow side windows or do permit rear diffusers but none of them are easy to live with on a car that sees street duty.

And that is the goal of the mod, to open all these known quantities up to be enjoyed in period correctly configured form.

An example, for the longest time the wheel/tyre setup of choice was to run C4 ZR1 rear wheels on all 4 corners in a square 17x11 315 setup. Another was CCW classics in 17x11 315 and 18x13 345.

These will all be pre-configured setup choices with decent default setups and appropriate setup envelopes to allow for track specific changes needed.

 

[mclarenf1papa]

Begins working; as in, you can feel the effect of,.is noticeable, contributes positively to handling at low speeds vs aero that comes into play under heavy braking from high speed or lends overall stability in high speed bends etc.

With the C5 its tricky to use aero to address lift and stability without impacting cooling - so many folks don't bother outside of competition cars because few of the mods needed are easily reversed. You can't just slap on a wing and call it quits. I guess I am a sucker for punishment - our street car runs pretty aggressive aero.

In stock form the car is a bottom feeder that scoops air up into the front of the engine compartment to feed the radiator and a/c. This air piles up in the engine bay. The air also enters the front wheel wells from the brake cooling ducts and hangs around without vacating in a timely manner. The Z06 also has stylish looking mesh vents in the front where the other models had fog lights - air rushes in here and fills the front bumper cavity and again just piles up.

None of these are really major issues at low speeds, but contribute to front end lift at higher speeds. The coupe suffers less from this than the Z06 but not by much.

On a stock body C5 Z in autocross situations you might use tyres, ride height, camber, toe and spring, anti-roll bar, bushing and shock upgrades to deliver the best mechanical grip possible without worrying about the front end lift.

But with body modded cars you can be very creative with splitter and rear wing setups to develop down-force at low speeds that when combined with good tyres and alignment can make for a great auto crosser that carries its 3000lb weight very well.

I would hope that if the game engine follows orders as provided by the LUTs, then it should just apply the appropriate down-force at the appropriate speed.

As for the actual aero changes that are used to generate the down-force we end up with, out back they are a 68" to 70" wide adjustable rear wing, rear deck gurney flap/ducktail spoiler. Up front they are vented hood to help evacuate the engine bay air; vented fenders to help evacuate the front wheel wells, front wheel well gurney flaps to reduce turbulence into the front wheel wells and direct air around the tyres, Front splitter with under tray all the way back the behind the front axle, front radiator intake with closed ducting to route air flow up into engine bay and out the hood vents. Body side skirts and rear wheel gurney flaps/fairings help keep the air from rolling under the car - but to be effective they are often too low to survive much street driving.

There are other specifics appropriate to more race dedicated cars and cars that run in series that do not allow side windows or do permit rear diffusers but none of them are easy to live with on a car that sees street duty.

And that is the goal of the mod, to open all these known quantities up to be enjoyed in period correctly configured form.

An example, for the longest time the wheel/tyre setup of choice was to run C4 ZR1 rear wheels on all 4 corners in a square 17x11 315 setup. Another was CCW classics in 17x11 315 and 18x13 345.

These will all be pre-configured setup choices with decent default setups and appropriate setup envelopes to allow for track specific changes needed.

I think 30 is a bit of an exaggeration, and if not, it's shows the entire problem with the concept of feel. Aerodynamics work on the square of speed formula, that is, at lower speeds they will always have much less downforce than at high speeds. There's no exception to this - besides massive aero stalling/separation, but parts are specifically designed not to do that. So even if that autox car has a huge ScZ, adding 10 liters of fuel or getting the tires a little hotter is going to have a more noticeable effect (at 30 you're only going to have *maybe* 20 lbs of downforce from that wing - assuming a 0.8 ish ScZ, which is typical for a big rear wing, and I'm sure a decent portion of that is just counteracting the car's inherent lift).

Besides that, the mod is definitely an interesting concept and I'm sure it would be well received.

 

[RC45]

I think 30 is a bit of an exaggeration,

Says you because its the opposite of what I said. It is almost as if your counter points are obtuse just to argue.

and if not, it's shows the entire problem with the concept of feel.

But you include this 'out'. I am telling you the speed yet you insist on arguing.

and There's no exception to this -

Who suggested there was an exception?

besides massive aero stalling/separation, but parts are specifically designed not to do that.

And again your point? For goodness sake please stop assuming that you are the only person that understands the topic at hand.

I am telling you I have hands on experience - I not only know, I have done! I am not theorizing here or playing pretend cars - I am telling you from practical example of running low speed high drag high down-force setup vs high speed lower drag setups.

I have an actual real life car that has served as an actual real life test bed that has been used to practically demonstrate and experience these different setups and results.

As an example with full down-force (extended undertray/splitter and full wing & 3/4" gurney flap) the car loses about 30mph top end (neutral wing and high speed splitter already limits top end to 175mph) and It is slower through 120mph.

Clearly demonstrating that there are wing and splitter setups that are effective at low speed and that these obviously are not suitable for higher speeds.

TLDR; My real life car has fully adjustable aero for testing purposes.

So even if that autox car has a huge ScZ, adding 10 liters of fuel or getting the tires a little hotter is going to have a more noticeable effect (at 30 you're only going to have *maybe* 20 lbs of downforce from that wing - assuming a 0.8 ish ScZ, which is typical for a big rear wing, and I'm sure a decent portion of that is just counteracting the car's inherent lift).

'That autocross car' is my car. As in I have practically tried various setups on that car.

And you have again made my point. At 30mph the net down-force of 5* wing and extended splitter is more like 60lbs+. The inherent lift is already negated by the previously detailed front body mods that eliminate the lift issues of the stock body that really only come into play at higher speed. Hood and fenders counter the lift on their own. This has been tested for and demonstrated.

The splitter extension and high AOA wing with gurney flap do work. But again you seem to assume this to not be the case and go off with the "scientific Pro-Tips©"

And I would rather remove 10 liters of fuel than add 10 liters, which is why the car already has carbon fiber body panels, light weight seats and 2 piece rotors. The low hanging lightening fruit has already been picked.

Besides that, the mod is definitely an interesting concept and I'm sure it would be well received.

Yeah, this passive aggressive approach is not working - you can't just go on the attack and then wash those previous attacks with a little sugar coating at the end.

BTW, having to defend every post as if it was a Congressional hearing is pretty irritating - I thought you might like to know this specifically as you seem to be missing the social queues that its a counter product discussion style.

And honestly, it is a waste of time. You have clearly chosen to counter and disagree with everything I post - so be it.

I really don't feel like sharing my 15 years of C5 experience with you or anyone else any more.

It is more hassle than it is worth.

You win.

According to you everything I say is rubbish, I have no understanding, no real world or practical hands experience at all and as such everything I produce would be junk.

The AC community obviously has no need for a nice in depth C5 Corvette mod, especially one that didn't involve you and the rest of the resident AC so-called physics gurus.

Don't worry, I won't be muscling in to you exclusive territory - it is obvious and evident that only YOU and few other elites have the knowledge, understanding, practical real life experience to call upon to make any mod ever. Anyone else that even thinks of it is not just wasting the communities time but is also directly insulting you for even daring to think they might be able to do it.

Your exclusive domain and territory is secure.

Good day.

 

[mclarenf1papa]

? That wasn't passive aggressive nor was it and argument nor was it an attack...My point was that the difference of 20 lbs on an axle isn't going to be very noticeable (or distinguishable from other factors - e.g. a little more or a little less fuel - it doesn't matter which), and either way AC should handle it correctly.

And you have again made my point. At 30mph the net down-force of 5* wing and extended splitter is more like 60lbs+

Genuinely I'm trying to help here. Are you sure it's 60? That's a 2.6 ScZ, which is as high as this (20* 63" double element rear wing for reference + front and rear diffuser):

I'm not arguing, the number just seems improbable.

 

[garyjpaterson]

Can anyone help with this?

Is it possible to work out spring rates (not wheel rates, I know) of a spring based on a springs free length, its length under load and the load?

For example a front spring (there only is one, its a single leaf spring) has a static height of 0.173m, a loaded height of 0.084m, and the load is 345kg, is it possible to work out the force in N that spring exerts, and therefore the spring rate?

I've tried, but really I have no idea if I am doing it correctly.

I got 3381N for the front, and 6223N for the rear. From that (using the height difference) I worked out that the front stiffness is 37989N/M, and the rear is 51430N/M.


Also I have damping stiffness values, but they are in INCH LBS! I've tried converting them but the values I got seemed very very low (relative to the spring rate values I calculated...)
They are as follows:

Front Bump: 400 in.lbs
Front Rebound:1100 in.lbs

Rear Bump: 400 in.lbs
Rear Rebound: 1200 in.lbs

If anyone can shed some light that would be marvellous!

 

[Stereo]

Dampers should have units force/speed so for example 400 s.lbf/in which would be 70000 s.N/m (the unit AC uses)

 

[mclarenf1papa]

For example a front spring (there only is one, its a single leaf spring) has a static height of 0.173m, a loaded height of 0.084m, and the load is 345kg, is it possible to work out the force in N that spring exerts, and therefore the spring rate?

345 kg *9.806(gravity) = 3383N
3383N/(0.173-0.084)m = 38,011 N/m
So yes you're doing it correctly.

Also I have damping stiffness values, but they are in INCH LBS! I've tried converting them but the values I got seemed very very low (relative to the spring rate values I calculated...)
They are as follows:

Front Bump: 400 in.lbs
Front Rebound:1100 in.lbs

Rear Bump: 400 in.lbs
Rear Rebound: 1200 in.lbs

If anyone can shed some light that would be marvellous!

http://www.convertunits.com/from/lbs/in/to/N/m

 

[garyjpaterson]

Righto, thanks for that. Bit puzzled now, my damper rates seem really high - front Bump at 70000 N/M are over 1200% damped, rebound over 3000% damped!

I'm guessing the values I have for the dampers must be off in some manner.

 

[Stereo]

The other option I can think of is it could be measuring a torque around some lever arm, at a speed of 1 in/sec. Which would make it ballpark 10,000 sN/m depending on the length of the lever. I don't know what the dampers are physically like, I just remember some older cars using torsional dampers instead of the currently common linear ones.

 

[William Levesque]

@Avo77 @PhilS13

Since the other thread got shut down I guess you can share what you find here.

 

[PhilS13]

@Avo77 @PhilS13

Since the other thread got shut down I guess you can share what you find here.

Still a work in progress for now

 

[Avo77]

Why the thread has been DELETED?!?
I hate this kind of things...

 

[burrito]

From the title of the thread

Does anyone know of a way to visualise the physics collider in-game?

 

[mclarenf1papa]

From the title of the thread

Does anyone know of a way to visualise the physics collider in-game?

"set editBoxes 1" in the console ingame if I remember correctly.

 

[burrito]

How do you activate the console? (I've never needed to before )

NVM: found it

 

[Deleted member 130869]

Righto, thanks for that. Bit puzzled now, my damper rates seem really high - front Bump at 70000 N/M are over 1200% damped, rebound over 3000% damped!

I'm guessing the values I have for the dampers must be off in some manner.

The Group C Porsches have very high values too so you should be ok.

 

[Joseph Maxx]

Why the thread has been DELETED?!?
I hate this kind of things...

Because it had devolved into a never ending bash fest by a bunch of bickering children and there was absolutely nothing being shared that would be of value to the community