Mechanical design of the cartridge and transport for the IBM 3480 Magnetic Tape Subsystem

The IBM 3480 Magnetic Tape Subsystem has achieved significant improvements over its predecessor, the 3420, in speed, data density, and floor-space requirements. The 3-megabyte-per-second data rate of the 3480, which is 2.4 times that of the 3420, was accomplished through the use of chromium-dioxide tape stored in a compact, single-reel cartridge threaded to a take-up reel. A sixfold increase in data density over the 3420 allowed reduction of the size of the 3480 reel, which was essential for rapid acceleration of the tape in the 3480's reel-to-reel transport. The increased data density also demanded substantial improvements in tape guiding and tape-motion control. This paper describes how mechanical analysis and design contributed to the achievement of these advances and aided in overcoming the ensuing problems.