zero suspension vehicle

[gjaegy]

Hi,

I am trying to model the tug push/tow operation, where a tug vehicle, linked to an aircraft through a tow bar, is pushing or towing an aircraft on an taxi way.

The tug vehicle is modeled using a standard ray cast vehicle, which is controlled by the user. The user drives the tug in order to push/tow the aircraft at the right location.

I have tried to model this situation by modeling the tow bar using a cylinder shape, linked to the tug and to the aircraft using two universal constraint. This part seems to work.

I have then tried to model the aircraft physic using another raycast vehicle, but this leads to some issues: I have many different potential aircraft types that might be attached, and I can't afford to configure each of them for physics.

I haven't found any way to have a generic controller for all of them, without having the gears crossing the ground, or staying in the air, etc... So it actually appears to me that suspensions would have to be set up for each type individually.

I would like to solve this issue by having a vehicle with no suspension at all (so no compression, no relaxation). This will allow me to use this physic objects chain for all aircraft types without having to configure them independently. Unfortunately I didn't manage to have 0 suspension, whatever setting I use...

Is there a way to achieve this ? Is there a better option for my problem, maybe shouldn't I be using the raycast vehicle for the aircraft ?

Thanks a lot,
Greg

[sparkprime]

You should just calculate the suspension info from the plane data, i.e. mass, size, etc.

[gjaegy]

thanks sparkprime... I am unsure how to achieve that

I have now decided I will create a generic shape for all aircraft type, a box shape, 3 gears, and I will scale the box according to the front gear position. So I can maintain a constant behaviour by having a constant shape, the box having a constant W/L/H ratio and the gears being at the same relative location.

Now, first I am unsure wether I need to scale the mass or not.

Also, even if I have read all the documentation concerning the raycast vehicles, including the notes made by Kester (http://docs.google.com/Doc?docid=0AXVUZ ... 4Zmo&hl=en), I am still struggling with some properties (m_suspensionRestLength1 and m_maxSuspensionTravelCm - BTW why is the second parameter using centimeters ??!).

What I want to achieve is to make sure the wheels center altitude is the same as the body box shape min altitude (like on picture). I also want all the body pitch (rotation along x) is 0, in other words, that the chassis is parallel to the ground. I know I can change the gravity center for that.

but really, I have some difficulties to find the math that would let me do that ! any help would be really really welcome

Thanks
Greg

car.png

[razerstam1]

I would like to solve this issue by having a vehicle with no suspension at all (so no compression, no relaxation). This will allow me to use this physic objects chain for all aircraft types without having to configure them independently. Unfortunately I didn't manage to have 0 suspension, whatever setting I use...

[sparkprime]

you can use cylinders and constraints for that but it might suck at extreme forces