Instability of long cylinders

--- In spacesettlers@yahoogroups.com, "Xenophile"
>
> --- In spacesettlers, "Bill" wrote:
>
> > If I remember my physics correctly a cyclindrical gyroscope has a
> > magic length (I believe its 4.5 diameters but its been fifteen years
>
> For the traditional Gerard K. O'Neill Island Three, the cylinder
> diameter is given as four miles, and the length as twenty miles. This
> make the length five or even six times the diameter, depending on
> whether you think "twenty miles" means the length of windows and
> valley floors (the part between endcaps), or the overall length,
> endcaps and all. So we can't get out of it by claiming that the
> cylinder is too short for such a thing to happen (we could get out of
> it by making shorter cylinders).
>

The traditional one may still be a valid length. In my problem set we
were discussing a solid cylinder not a cylindrical shell.

More importantly the design that ONeill came up with was part of a
after class physics seminar for his first year students. I can make
myself believe that part of designing this, ONeill, or at least one of
the physics students, solved the same problem I did for a shell
instead of a solid cylinder.

Short answer since there is a minimum length a cylinder must be before
it destabilzes, anyone building such a habitat would be wise to stay
underneath it as well as putting active dampeners, and a few other
fail safe mechanisms.

Bill