deh0654@sjfc.UUCP (Dennis Hamilton) (04/27/88)
Jonathan Eckrich wrote: > 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. Prior to the development of compact removable disk packs (with the introduction of the IBM System/360, essentially), disk stacks were large *and* non-removable. Although the first one was vertical (the IBM RAMAC unit), there were also some large units designed with horizontal axis of rotation. However, the story about disk stacks doesn't sound too credible: the moment of inertia of a disk stack is not nearly so impressive as that of a horizontally-axised *drum* with its large outer surface. The Fastrand I and II drum units were much more imposing in this regard, and the problem of shipboard use not something to be taken lightly. Concerning the story about shipboard 1108's, that is a mix of the wrong technology. Fastrand may have been considered for use aboard ship, though I can't imagine their placement on anything smaller than a cruiser or aircraft carrier. The computer technology would have been defense equipment out of Univac St. Paul, probably something between the CDC 1604 and Univac 49x in architecture. Although there is certainly a high degree of "urban legend" to these stories, the shipboard case is actually quite plausible. Whether the problem of gyroscopic effect was very difficult to remedy or not is a different matter. Someone who knows the masses involved in gyrostabilizers might want to indicate how hard or easy it is to interfere with the steering of a vessel. It would certainly be the case that motion of the ship would be a problem for the drive unit, and some sort of steps would have to be taken to minimize the resulting stresses. Fortunately, disk technology was revolutionized before there would have been much need to solve such problems on a regular basis. The current vertical-axis units must still present problems with respect to roll of the ship. I wonder what kind of special measures are taken, especially to prevent head crashes as the result of such forces interacting with the drive unit. Dennis E. Hamilton