Heaviest Data Tape Reel

The heaviest data tape reels ever used were the 400-lb (181 kg) paper tape reels fitted to the IBM Selective Sequence Electronic Calculator (SSEC), an electromechanical computer that was operational from January 1948 to August 1952. Only one was ever built, occupying a large room at IBM's headquarters in New York City, USA.

Most early computers used punched cards, magnetic tape, or paper tape (as used on telex machines) for data input and storage. IBM’s SSEC was a huge and quirky machine, built just before general acceptance of John von Neumann’s EDVAC approach as the basis of computer architecture. According to computer pioneer Herb Grosch, who worked with the machine,

"About those tapes: the card plant in Endicott got enormous rolls of card stock from the paper mills. For regular card manufacturing they slit the rolls to three-inch width (card height). For the SSEC they furnished rolls eight inches wide (card length). The resulting rolls weighed 400 pounds, and had to be hoisted onto the SSEC with a thoughtfully-provided chain fall!”

Making punched card was a significant, and highly profitable, part of IBM’s business which meant it operated its own plants to create the cards. This involved taking industrial-size rolls of card stock, 3 or 4 feet in diameter, and slicing them into 8-inch wide rolls. 7.75 inches was the standard width of an 80 column punched card. Then IBM chopped the roll into individual cards 7.75 inch by 3.25 inch.

For SSEC they used the entire roll as a paper tape 7.75 inches wide. Unlike standard paper tape, which was flimsy and had only 6 tracks for holes, this was very rugged and had 80 holes across. So it had higher speed and higher capacity.

SSEC had 3 tape drives, each loaded with a 400lb roll of paper tape. Each tape could be used for temporary storage during the calculation. As the machine worked a punch entered data onto the tape. It was fed directly through 10 tape readers in sequence, giving up to 10 opportunities to read that data back as the tape passed through them. (Being paper tape, there was no way to erase it). The readers could also be configured with loops of pre-punched tape.