All images used in the scene must be visible when the scene is saved. Otherwise, Algodoo deletes them and images from the user's texture folder are used as default. Put at least one copy of the images somewhere off to the side of your frame of interest before saving the scene.
Nice work. Here are a few picky things:
1. Cars don't collide with each other.
2. White arrows should be below the cars.
3. Race_Track.png (3,101KB) could be Race_Track.jpg(139KB).
Scene is good regardless of picky stuff.
"Self-praise is no recommendation", but in this case I agree that this is the best tornado on Algobox. This CGI is so good it could be used in a movie (depending on the type of movie and how long the clip is shown for).