User talk:Jesrad/BunkerStead

Stability of split version

With the height that you show I don't think just having heavy stuff in the bottom of the sphere will give you enough stability. I think even wind could tip it. Maybe a hanging ballast would be the way to go. Vincecate 22:48, 14 September 2008 (UTC)

I figured I'd add a ballast on the outside, but then I realized the top half was maybe 2-5% of the total mass, and the truss 10% max. The center of mass stays inside the sphere easily, just having the bank of batteries at the bottom of it, plus scrap metal, would keep it upright.

Of course that means landing aircraft there would be impractical or maybe even impossible... On the other hand, a hanging ballast could help with dynamic stability, if not static stability. I'll look into it.--Jesrad 08:47, 15 September 2008 (UTC)

On second thought, this arrangement may prove sufficient for single stead stability (when moving ?), while multiple ones are supposed to connect and form a semi-submersible platform. Another funny thought is that the top half may pivot and double up as a large sail for migration :) Procedure: move all the furniture to the basement, tilt the house and drive away. I should call that a Sunflower SailStead. At the very least side ballast tanks are needed to compensate for any quasi-static tilting load (persistent wind). --Jesrad 08:51, 15 September 2008 (UTC)

OK, I've decided on the best form of ballast: it'll be hanging from three or four cables attached to the top of the lower half, so they lie on the sides of the sphere and join below it, forming a cone. Adjusting the lengths would allow lowering or rising the ballast as well as move it off-center to adjust. The winches for the cables would be protected from the environment by short sections of concrete tunnels (trapping air when waves wash over) and easily accessible by the crew. Widening gouges along the sides of the sphere would be needed to keep the cables in place. --Jesrad 09:07, 15 September 2008 (UTC)

Follow-up calculations show that an outside ballast will be necessary for static stability, so your intuition is confirmed. Alternatives require changing completely the shape of the lower half (hemisphere ?) or doing away with a top half and stick to a BunkerStead (which would mechanically be best with a saucer shape like your own geodesic vessel). Adjustable hanging ballast as described above is probably the best option. Also, there are a number of features missing on the pictured example I'll have to add next time, too. Let's make a list:

• hanging ballast on four cables passing through four side tunnels (extending down to the "waist") and joining near the top,
• central column supported by the truss, covering the access hatch and stairs and/or elevator to the top + air vents
• docking bridge or transboarding crane, or both
• your ad here