Because you're already using a Rigidbody, you could use collision.rigidbody.AddForce(...) instead of collision.rigidbody.MovePosition(...), and then let the physics engine take care of it.

Alternatively, the conveyer belt could make itself the parent of the rigidbodies that hit it, so that they would then use its transform coordinates. That would force the children objects to align with whatever conveyer they hit last.

collision.transform.parent = transform;

I made up a little example project.

I use a low friction physics material (low friction only in one direction like ski's) It adds forces to the touching objects in the direction of the conveyor.

Fiddle with the conveyor 'physic material' dynamic frictions and the Conveyor components speed variables. The visual scrolling is UV scrolling, this is seperate from the forces applied to the other objects

Get it here http://users.on.net/~edan/cam/visible/Conveyor.zip

Here's the conveyor belt force operator that worked for me: //Push on things which collide with this floor var speed:int = 100; function OnCollisionStay(collision : Collision) { //An object is on the conveyor if (collision.rigidbody) {

    var tilt : Vector3 = Vector3.right;
    var roty = transform.parent.transform.rotation.y;

    //Fudged this to get conveyors to push in the right direction
    if(roty==0.7071068){
        tilt = Vector3.back;
    }else if(roty==-0.7071068){
        tilt = Vector3.forward;
    }else if(roty==0){
        tilt = Vector3.right;
    }else {
        tilt = Vector3.left;
    }
    //Try other Forcemodes
    collision.rigidbody.AddForce(tilt * speed * Time.deltaTime,  ForceMode.VelocityChange);
}

}