As you say; back in the day, I used a few pieces of gear with those tape drives. In fact one was an HP logic analyzer. The tapes tended to come off the reels, they were not fastened to hubs. There were a couple holes near the end of tape and an optical sensor was used to stop it. Easy to take the tape cartridge apart and respool the tape. Great set of videos, I too lusted for one of these beasts.
George