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WHEELED VEHICLES STABILITY TIPS

While the Car object is usually the easiest way to add cars to your project, experimenting with wheeled vehicles assembled by attaching wheels to a RigidBody object can be an interesting and entertaining experience.

Launch 3D Rad, press [Ctrl]+[O] and double-click the WheeledVehicle.3dr project.



This is a vehicle setup demonstrating a pretty stable front-wheel drive car, made by assembling 4 wheels and a rigid-body.

Press the [SpaceBar] to run the simulation. Try driving the car around the track. Press [Esc] to go back to the editor.

Because 'wheeled rigid body' cars don't support any built-in system to boost stability, they usually have an annoying tendency to flip over.

The best way to tackle this behavior is lowering the center of mass.

It means making the mass distribution model for the RigidBody slightly displaced downwards.



Recommended guidelines to achieve stable 'wheeled rigid body' cars are:

Make the car-body's RigidBody with a lower center of mass (see above).

Place the center of mass midway between front and rear wheels.

Try to set masses for the wheels and the car body (RigidBody) close to real world values.

Set harder, less bouncing suspensions.

Fast spinning wheels are evil! They create gyroscopic effects that are very difficult to simulate properly and can cause computation errors like wheels spinning about the 'wrong' axis, unstable simulation and even software crashes.

Top speed and wheel power factor should be raised very carefully, to avid wheels from spinning out of control

Avoid excessive lateral friction. This should always be the minimum required to achieve the desired traction effect.

Rolling friction should always be strong enough to avoid excessive sliding (but too big values may cause problems!).

WHEELED-RIGID-BODY VERSUS CAR OBJECT

The wheeled-rigid-body approach is extremely flexible, allowing for example vehicles with different sizes for front and rear wheels, tricycles etc.

On collisions, the wheeled-rigid-body tends to 'climb' the obstacle due to its lowered center of mass. In the Car object, this can be tackled by enabling collision damping.

Adjusting physics parameters for the wheeled-rigid-body requires a lot of dialog opening and closing. All settings are on one single property dialog for the Car object instead.

Achieving stable fast vehicles with the Car object is easier because you can apply banking and trajectory stabilizers that have been specifically designed for the purpose.

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