sjr@datacube.com (Steve J. Rapaport) (04/10/88)
A while ago in talk.bizarre (I think) there was a series of urban legends about walking disk drives. You know, the Diva-type washing-machine sized multi-platter monsters. The legend goes that there is a resonant frequency at which the drive, if periodically pushed, will rock back and forth and move around the room. Resonant frequencies being what they are, it's possible to write a program that causes the disk heads to seek at that frequency, and to start the box rocking, and eventually walking. Until it walks far enough to pull out its own plug. Operators come in in the morning and find the drive six feet from its original position, its cord forlornly dragging behind it. And the room was locked. Or imagine the horror of being the graveyard shift operator and having the disk drive suddenly move towards you, methodically and inexorably, and apparently under its own power.... Steve Rapaport
seven@nuchat (David Paulsen) (04/12/88)
While taking an introductory COBOL course about eight years ago I got to be good friends with the instructor, who had been around computers since the late 50's. He told me a story he swore to be true. Seems the hardware types had spent a number of hours installing a new 'washing-machine' 5-platter disk drive on the big Honeywell, and were just about to invoke diagnostics. Somebody hit the final key and they all sat back to wait for the machine's verdict... all of a sudden, the most GAWD AWFUL sound, kind of a ripping, screeching, freezing-bearing sound came from the new drive. Everybody turned around, in time to see the plastic-oid cover rip free from the top of the box, and the platter, spinning out of control, lift itself up out of the drive and float ABOVE the spindle before listing to port and finally diving for the floor, where it landed like a frisbee, still spinning. Stunned silence. "Well, I guess that's a 'fail'" one tech remarked. Apparently, the spindle had snapped just as the drive got up to speed. David Paulsen
mclek@dcatla.UUCP (Larry E. Kollar) (04/20/88)
I remember hearing another disk-related story in college, about 9 years ago: CDC wanted to dramatize how stable their new computer was, so they set up a complete mainframe installation, disk drives and all, in the back of an 18-wheeler. The portable power supply came up, then the mainframe was fired up. Everything worked just fine. The 18-wheeler pulled out of the parking lot, and as the driver turned, the gyroscopic effects of the rapidly spinning disk drives flipped the trailer on its side, destroying about $500,000 worth of equipment. The story was told to me as true, but it sure sounds like an urban legend. Can anyone confirm (or kill) it? Larry Kollar
vanpelt@unisv.UUCP (Mike Van Pelt) (04/22/88)
The story Larry Kollar wrote about CDC disks in a truck sounds very similar to a Univac legend, which I've been told was true. They put a Univac 1108 on a destroyer, complete with Fastrand drums. (A Fastrand drum is defined in "The Devil's DP Dictionary" as "A non-floppy rotating medium for the storage of angular momentum.") As in the CDC 18-wheeler story, everything was just fine until they tried to turn. There are two versions of the results: (1) They turned the wheel over, but the destroyer just kept going straight, and (2) the Fastrand drum cabinet ripped up out of the floor and rolled through a bulkhead. This really does have that "Urban Legend" sound to it... Mike Van Pelt
johne@astroatc.UUCP (Jonathan Eckrich) (04/22/88)
Larry Kollar wrote about a CDC disk flipping over a trailer truck...
I don't believe it. Here's why.
In order for the truck to tip over in a turn due to the spinning disks, there
is only ONE axis in which the disks could be spinning. That axis would have
to be lateral to the dimensions of the truck. I am not familiar with the
drives that CDC used but I suspect that they spun on a vertical axis? The
gyroscopic effect, refered to above, is called precesion. When a force is
applied to the side of a spinning gyro, the gyro responds as if the force
was actually applied at a position that is 90 deg. in the direction of the
spin. If the axes of the disks where lateral with respect to the truck, and
the direction of spin was counter clockwise (if viewed from standing to the
left of the truck), then maybe, just maybe, it could happen. This would
require extremely heavy platters AND very fast rotation, then the driver
would have to make a fairly fast rate of turn. I'm cross posting this to
rec.aviation, because gyros are commonly used in airplanes.
<-------.
__________ \ Rotation is counter clockwise.
/ \
/ \
| . |
|/ + |
/\ /
/ \ . /
/ ^____|_____^
/ |
Apply force here. |
Gyro responds as if force was applied here.
Jonathan