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Andy Ruina
Attends Cornell University
Lives in Ithaca, New York
36 followers|9,064 views
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Andy Ruina

commented on a video on YouTube.
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Hey man.  I've done my part.  But I am just one person.  So how am I supposed to find out how to make a balloon quiet??  -Andy Ruina (ruina@cornell.edu).
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Andy Ruina

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Andy Ruina

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Andy here, the speaker in the video above.  Responses to some relatively recent posts.

To Mortiz Saabel:  Watch Arend Schwab's video where he measures the negative trail.  If you find fault with that you should email him or me.

To DoryGuy:  Shimmy is not a problem wie have studied.  But many have.  Look for studies also on 'wobble'.  I think it is universally agreed that this has to do with deformations of some combination of  tire, frame, wheel and rider.

To JP Bevins:  You are right.  The bicycle in the parking lot has a damaged fork. This does not affect the rake (usual definition having to do with steering bearing angle), but does give the bike a large trail.  In this case that large trail probably helps make that bike more self-stable.  We do not deny the trend that often more trail gives more stability.  The point of our paper is that positive
trail is not necessary for stability.
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Andy Ruina

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reviewed:
Firma Måleri & Skylift Kim Karlsson
Granövägen 63, 22100 Maarianhamina, Finland
Now the home of Andy Ruina, Saskya van Nouhuuys, Prachi Ruina and Mieke Ruina.
Kim Karlsson doesn't live here anymore.

The address is also called Skedholmsvägen 17.
Quality Excellent
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Have him in circles
36 people
Prachi Ruina's profile photo
Kiisa Nishikawa's profile photo
Mieke Ruina's profile photo
Pranav Bhounsule's profile photo

Andy Ruina

commented on a video on YouTube.
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Watching anything move in zero-gravity is fun.  But I find this explanation of the gyro a big off.  The part where he tapes gyros together.  He seems to imply that by having three gyros pointing in three directions that he is somehow covering 3 components of some vector.  Rather, instead, he just gets a new angular momentum vector pointed along the diagonal with a magnitude  sqrt(3) larger.  

What would a viewer of this video think would happen if he taped two spinning players back to back?  I guess that most would not predict that the gyro effects would cancel and the CDs would tumble in space the same way whether they were spinning or not. I think that the explanation in the video about taping the CDs together, leads one to vague and wrong notions about the vectorial nature of angular momentum.

Reverse-engineering the astronaut's mind further, I think that he thinks that the angular momentum vector is made up of three independent positive components which have independent effects.   And he thinks he can manipulate those components separately.  So he thinks he stabilizes one axis at a time.  Rather, each time he adds a CD he is changing the magnitude and direction of the net angular momentum vector.  His final product  hasn't "covered" three dimensions. It has instead just covered a single crooked direction a bit (sqrt(3)) better. 
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Andy Ruina

commented on a video on YouTube.
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We posted a new, slightly improved version of the video.  Basically we got rid of the still photos and replaced those with videos. And we brightenned some of the darker parts. And we deleted one word of the spoken text (a redundant "also").  New version here:

Unrideable Bricycle: a cross between bicycle and tricycle - V3
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Andy Ruina

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The description of the whale hunting there is one of the saddest things I have ever heard.  I guess I will never forget it.
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People
Have him in circles
36 people
Prachi Ruina's profile photo
Kiisa Nishikawa's profile photo
Mieke Ruina's profile photo
Pranav Bhounsule's profile photo
Work
Occupation
Professor, scientist
Employment
  • Professor, scientist, present
  • USGS, Shell, Texas Instruments, Appel Farm
Places
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
Currently
Ithaca, New York
Previously
Providence, Cambridge, Boston, Washington, Arlington, Champaign Lexington, Chevy Chase - Menlo Park, Finland, Åland, Palo Alto, Israel
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Story
Introduction
Born 1953 in Providence. Moved to Champaign IL, Alexandria VA, Arlington VA, Lexington MA, Chevy Chase MD  and Cambridge, MA. Spent a year in Isael.  Went to Brown for 3 degrees. Studied, mechanics, friction and earthquakes.  Taught at Cornell in Theoretical and Applied Mechanics since Aug 25, 1980. Maried to Saskya van Nouhuys since May 15, 1993.  Two daughters: Mieke (born 1993) & Prachi (born 2001).
Education
  • Cornell University
    present
  • Cambridge School of Weston, Brown, Sidwell Friends, Taylor Elementary, George Mason Green,
Basic Information
Gender
Male
Other names
Andrew
It's good food. It's made with fresh vegetables. It's not authentic Mexican. But it doesn't claim to be. Whole meal with drinks is about 15 dollars.
Food: ExcellentDecor: Very goodService: Very good
Public - a year ago
reviewed a year ago
Now the home of Andy Ruina, Saskya van Nouhuuys, Prachi Ruina and Mieke Ruina. Kim Karlsson doesn't live here anymore. The address is also called Skedholmsvägen 17.
Public - a year ago
reviewed a year ago
2 reviews
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