Re: OT: Failure to communicate? Genesis

From: John Larkin (jjlarkin_at_highlandSNIPtechTHISnologyPLEASE.com)
Date: 10/16/04 

Date: Sat, 16 Oct 2004 08:08:51 -0700

On Sat, 16 Oct 2004 05:49:14 GMT, Fred Bloggs <nospam@nospam.com>
wrote:

>
>
>John Larkin wrote:
>> On Sat, 16 Oct 2004 05:22:25 GMT, Fred Bloggs <nospam@nospam.com>
>> wrote:
>>
>>
>>>
>>>John Larkin wrote:
>>>
>>>>On Sat, 16 Oct 2004 00:13:26 -0400, Spehro Pefhany
>>>><speffSNIP@interlogDOTyou.knowwhat> wrote:
>>>>
>>>>
>>>>
>>>>>http://www.mercurynews.com/mld/mercurynews/news/breaking_news/9932295.htm?1c
>>>>>
>>>>>I wonder if this was actually a first-angle-projection vs.
>>>>>third-angle-projection mixup..
>>>>>
>>>>>"Investigators report a likely reason Genesis' chutes did not open was
>>>>>a faulty design that had these switches improperly installed on a
>>>>>circuit board."
>>>>>
>>>>>http://www.nasa.gov/mission_pages/genesis/main/index.html
>>>>>http://www.nasa.gov/images/content/66943main_g_switch_hires.jpg
>>>>>
>>>>>
>>>>>Best regards,
>>>>>Spehro Pefhany
>>>>
>>>>
>>>>Incredible blunder!
>>>>
>>>>Which brings up the more general question: why are so many parts
>>>>symmetric?
>>>
>>>That package isn't symmetric- only one end is flanged. They don't show
>>>the circuit board- but it looks like a simple component outline in
>>>silkscreen should have minimized the chances of reverse assembly.
>>>
>>
>>
>>
>> Geez, Fred, I didn't say that package was symmetric (although it is
>> obviously easy to mount backwards.) I introduced a "general question."
>> Why do you follow me around, biting at my ankles?
>>
>> John
>>
>
>Well you launched into that symmetry thing like that was the problem- it
>seemed to me like you need glasses or something.

I do need glasses, at least to drive. Being nearsighted is a pretty
good adaptation for an engineer.

But why couldn't that part have two leads welded to the header on one
end? Then it couldn't be installed backwards, and would be more
stable, too. You'd think that a g-switch should be strapped down
better than those two dinky leads allow. And why do mechanical
engineers seem to prefer symmetric mounting hole patterns, so that
mechanical gadgets can be mounted wrong, too?

I always thought DIPs should have an asymmetric pin pattern, and be
numbered zigzag instead of around the chip.

John

Relevant Pages

  • This Weeks Finds in Mathematical Physics (Week 247)
    ... Symmetry has fascinated us throughout the ages. ... It also seems to have gotten ahold of John ... American Institute of Mathematics, Mathematicians map E8, ... In "week91" I spoke about the D4 lattice. ...
    (sci.math.research)
  • Re: John Bell: "How to Teach SR"
    ... |>>>Has anyone read John Bell's article "How to Teach Special Relativity"? ... Symmetry breaking SR symmetry is ...
    (sci.physics.relativity)