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Old April 29 2009, 08:23 PM   #49
Psion
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Re: Another take on the Original Enterprise...

Cary L. Brown wrote: View Post

...



Now, I plan to use something similar to that, but I'm not convinced I've got it "right" yet. Perhaps I go with three identical "box beams," or a single extrusion, or two boxes with a structural linkage between them?
Brilliant! In my ignorance, I imagined either a single super-science I-beam or a quad of box beams, but I like the look of this. The only thing I'd caution you about is the four grills visible on the inside of each original pylon. These suggest to me that there's some kind of open space beneath them.

Cary L. Brown wrote: View Post
The reason I want box-beams is that they're very effective at resisting torsion, something that more conventional open beams (like I-beams) aren't nearly so effective with. I see the nacelles as being under tremendous torsional force, so the nacelle pylon needs to be designed to resist that. Tensile force isn't nearly so much of a concern... the majority of force seen by this structure will always be torsion, around any of the three principle vectors.
Torsional? Do you imagine the engines tending to corkscrew around their axies or did I just read something into your description you didn't actually put there? I'd argue the warp engines don't add any significant force to the vessel. Rather, they "just" warp space and everything within that warp moves. The only forces I see operating on the nacelles would be inertia when the ship accelerates using impulse engines or turns/banks. And even that may be greatly diminished depending on your view of intertial dampers.

EDIT: Yeah, I definitely think I misread you ... I don't know why the image of each engine "wanting" to twist around its long axis popped into my head on the first read.

Cary L. Brown wrote: View Post
I'm actually thinking about doing a little FEA problem to determine the best practical construction for this structure. Maybe even doing it with the "strongback" and dorsal included as well?
Maybe it's best that Google failed to enlighten me on this issue, because I'd really rather not be caught faking any understanding and BS'ing my way through a reply. The depth of my exposure to engineering was writing programs for instrumentation engineers and reading P&I diagrams. So I'll ask: does "a little FEA problem" (finite element analysis?) mean you're going to calculate assumed loads and try to find an arrangement that gives you good numbers?

Cary L. Brown wrote: View Post
The one weak point in the TOS design which I can't see a practical way around is the interface between the primary hull and the dorsal. It's fine in any of the three major translational vectors (forward-aft, port-starboard, up-down) and for torsion in two of the vectors (yaw and pitch) but it's inevitably going to be fairly weak in roll. Unfortunately, there's nothing to be done about that other than adding additional structure to the dorsal (not in the way that was done for ST-09, by the way, which really doesn't help in roll, does it?). The Galaxy class "flair" (or a triangle with two dorsals at angles, perpendicular from the secondary hull axis) would be the best solution... but that's a different design, not the TOS Enterprise. Oh well...
Would it help matters if you assumed the rigid components of the dorsal went through the primary hull with the latter attached to the sides? Maybe that structure above the impulse engines is also involved.
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