An example vehicle frame disclosed herein includes a convex surface to face the ground when the vehicle frame is in a first operating position and face away from the ground when the vehicle frame is in a second operating position, the vehicle frame rotatable about a longitudinal axis of the vehicle frame between the first and second operating positions, and a concave surface opposite the convex surface, the concave surface to face away from the ground when the vehicle frame is in the first operating position and face the ground when the vehicle frame is in the second operating position.