Ingeniously simple are the propeller machines with rubber motor: They fly up to 100 meters and the motor does not need a bit of electricity. This is because it gets its energy from a rubber band that is attached to the propeller. To ensure that nothing happens to the little powerhouses when they land, it is reinforced all around. Before take-off, you turn the propeller up by hand until the rubber band inside the plane is completely taut. And off it goes. The propeller takes off powerfully and the rubber charge is enough for a really long flight.