High feed rates and high accelerations are no longer excluded with large, heavy telescopic steel covers. Transport mechanism, for speeds between 98 ft. and 62 ft. per min (30 and 80 meters per min), eliminates high limit stop forces and corresponding noises in all operational positions, moving smoothly when covers are pulled apart as well as when they come together. Test runs at speeds exceeding 328 ft. per min (100 meters per min) and accelerations exceeding 1g were trouble-free.