Comprising a strong U-shaped magnet and a pair of brass rails with 4mm socket terminals. A brass axle with plastic discs is free to roll along the rails and completes the electrical contact between them. When the axle is placed on the rails between the poles of the magnet and a power supply unit is connected, the axle is repelled and rolls along the rails away from the center of magnetic field. Dimensions 175x60x58mm high.