As for physically stacking tapes on a drive, I suppose you could rig up a
platform that could hold tapes up to the point where the drive was
crushed. I would weigh a reel if I was writing this at home. I will
estimate a reel weighs 4 ounces. That means the 2.9 million tapes would
weigh 725000 lbs or 362 tons.
Today while unpacking some more stuff after the move I found the pan from my
grandmother's kitchen scales (it was packed in with books and cables, go figure..)
Anyway that meant I could weigh a DECtape. The reel in the plastic case weights about
6.75 ounces, the reel on its own (with the tape on it, of course) weighs about 3.8
ounces.
So your guess was pretty good. Certainly near enough for this
Said scales are of the sliding weight type so there are no springs that could have gone
soft over the years. Yes, corrosion probably has affected the weights a bit, but not
enough
to worry about.
-tony