My understanding is that the cars in LFS are infinitely rigid - they don't bend at all. This is impossible in real life, even if the chassis is reinforced as is the case with racing cars. Road cars flex even more than race cars.

Yes, I know that it takes massive amounts of processing power to model the bending the way it is done in Rigs of Rods.

Anyway, my idea is to add just one pivot point to the middle of the car, so that front and back can rotate a bit in relation to eachother. Maybe another "axle" lengthwise.

I guess this would be MUCH easier on the poor processor. This does not IMO have to be represented visually in any way, saving further power in form of less polygons to deal with.

My knowledge of vehicle dynamics is very limited, so feel free to point out the flaws in my reasoning.

Discuss.

Clearly the soft body full simulation route that ROR is pursuing is not currently feasibly for LFS - hardware has yet to catch up for that.

A single pivot in the centre of the car would allow the front and rear axles to camber independtly, but wouldn't alter the camber of the left and right wheels on any axle. So you would need to allow for that as well.

One advantage though, aside from complexity, is that you wouldn't need to run at such a high time step for integration, as the combined stiffness of the chassis would be a lot less than the stiffnesses of each of the chassis components, so you more easily get away with modelling the chassis at an accurate stiffness, and not have to make it too soft for performance reasons as ROR does.

yeah i was thinking on making a topic too but, do cars on roads really flex that much?

Quote from chavm481 :

yeah i was thinking on making a topic too but, do cars on roads really flex that much?

They really do flex quite a bit. That's why there's strut tower bars.

Quote from chavm481 :

yeah i was thinking on making a topic too but, do cars on roads really flex that much?

Chassis flex is noticeable in all cars, production racing cars go to large lengths to increase stiffness as much as possible by using the rollcage to form an effective spaceframe welded directly to strut and diff mounting points, a complex rollcage comes with a large weight penalty which is still worth paying to gain stiffness.

oh i didnt know they flexed THAT much....

Enough to affect handling, and LFS is all about that

Quote from ajp71 :

Chassis flex is noticeable in all cars, production racing cars go to large lengths to increase stiffness as much as possible by using the rollcage to form an effective spaceframe welded directly to strut and diff mounting points, a complex rollcage comes with a large weight penalty which is still worth paying to gain stiffness.

Its a bit the other way around, a roll cage is mandatory in nearly any race-series. So if installed, its not more then logical to make use of it to improve the stiffness. Since cars prepped for racing are usually very stiff because of the rollcage, its makes maybe not very important to implement?

Also i doubt formula cars and gtr's have any noticable bodyflex, the monocoque chassis are incredibly strong.

Quote from chavm481 :

yeah i was thinking on making a topic too but, do cars on roads really flex that much?

well i have a car with leather interior, and when im going down a gutter on an angle, or over a speed hump with only one of the wheels, i hear the leather creak a bit. i dont notice. i jus hear it. although ive only had my license a short period.

Quote from Bluebird B B :

Its a bit the other way around, a roll cage is mandatory in nearly any race-series. So if installed, its not more then logical to make use of it to improve the stiffness. Since cars prepped for racing are usually very stiff because of the rollcage, its makes maybe not very important to implement?

A basic 6 point bolt in rollcage with single door bars, that is acceptable for just about any race series will be about a third of the weight of the rollcage in any serious GT car, even if it's built using T45 tube that is still an awful lot of weight. At work at least we do not treat the rollcage as a safety item, it's a performance item plain and simply and the single most important item on the car the vast majority of it isn't their to protect the driver. The faster a production car with a standard strutural bodyshell becomes, with higher cornering loads the more it will become hampered by its lack of structural stiffness, true competition cars need to be as stiff as possible, chassis flex is never a desirable effect in a car. I think I remember hearing a statistic that an F1 car is 6000 times stiffer than a typical road car which gives you some idea of how important it is, think of all the weight that you could save if it didn't have to be so stiff.

Quote :

Also i doubt formula cars and gtr's have any noticable bodyflex, the monocoque chassis are incredibly strong.

Conventional GT cars (of the type we have in LFS) use the rollcage as the structure of the car and the standard steel body (with most panels replaced with light weight composites as an option) simply there to comply with rules virtually unstressed and completely irrelevant to the performance of the car other than adding weight, it's quite acceptable to cut and shut large parts of the standard shell when it gets bent in shunts that don't damage the rollcage, something that should never be done to a shell being used structurally. Even these cars suffer significant chassis flex and their stiffness is limited by what the rules allow and by just how much steel is worth adding before the increase in weight isn't worth it.

GT cars with monocoque tubs in the road car (not the rare cars that have no resemblence to the production car and are purpose built racing cars with a caborn fibre tub), are normally a particuarly bad choice to take racing because you're left with a tub that is never going to be stiff enough if it was designed to meet road requirements/space and cost restraints. You then have to still use the rollcage for the structure of the car but you've got the added nightmare of having to mount the thing to the tub and the tub getting in the way and not allowing you to put the cage where you want it, as well as obviously not being possible to weld gussets between the cage and shell for extra strength.

Quote from Bob Smith :

A single pivot in the centre of the car would allow the front and rear axles to camber independtly, but wouldn't alter the camber of the left and right wheels on any axle. So you would need to allow for that as well.

So adding a pivot for each axle, for a total of 3, would do?

I think the pivot solution may be appropriate to simulate the effects.
Moreover since the LFS cars (even the road cars) are 'sporty' (apart from the UF1), I wouldn't be surprised if they all of monocoque chassis instead of chassis with non-loaded skin.

They would still have different flexibility ofc, but the difference wouldn't be as big as without monocoques.

i've noticed that the cars in rfactor feel like bricks with stone wheels, their even more ridged than lfs.

Quote from ajp71 :

.....
Conventional GT cars (of the type we have in LFS) use the rollcage as the structure of the car and the standard steel body (with most panels replaced with light weight composites as an option) simply there to comply with rules virtually unstressed and completely irrelevant to the performance of the car other than adding weight, ....

.....
GT cars with monocoque tubs in the road car (not the rare cars that have no resemblence to the production car and are purpose built racing cars with a caborn fibre tub)...,

Most average GT series do have a complete steel frame or monocoque instead of the original chassis and indeed have no resemblance to the original road car. Every time i watch some gt-series of any kind i notice it is a really different car. Just the shape of the outside shell remotely resembles the road car. Take the shell away and you got basicly a formula-class car. Even engines are totally replaced and sometimes moved to an new position in "budget" class gt series.
I think the gtr-cars of lfs are in such gt/gtr-racing class, with chassis/monocoque/tubeframes several times stronger then the orginal road car they were based on.

I am not opposed to the implementation of flexing of cars since it adds realism espacially to the slower road cars, but i doubt if it should be high on the priority list.

yeah..i have seen drag cars specially the muscle ones flex their bodies....but idk what causes it to twist like that

Quote from jvcala2 :

yeah..i have seen drag cars specially the muscle ones flex their bodies....but idk what causes it to twist like that

Torque.

Quote from jvcala2 :

yeah..i have seen drag cars specially the muscle ones flex their bodies....but idk what causes it to twist like that

2000+hp and as light as possible very long tube-frame. These cars just have to be drivable in straight line...

Quote from wheel4hummer :

They really do flex quite a bit. That's why there's strut tower bars.

not in normal road driving as much as track days or something like that

Flexible chassis opens the door to kart racing

+1 for this

My most memorable experience of chassis flex was driving a Mercedes convertible around the 'Ring and not being able to open the glove box afterwards, no matter how hard I pulled on it.

In short yes chassis flex will have to be a part of the progression of lfs sooner or later, im all for it

A ROR type system might work if cut down. Make each car chassis a box. This would mean just has 16 rods. (The box edges (12) + 4 internal diagonal between box corners)

This might give enough nodes to use but still be low enough density to allow within the CPU bandwidth given the rest of the physics calcs.

Quote from Michael Denham :

My most memorable experience of chassis flex was driving a Mercedes convertible around the 'Ring and not being able to open the glove box afterwards, no matter how hard I pulled on it.

Shoulda asked to drive reverse after

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