Author Topic: How high could you make a elevator go?  (Read 12006 times)

Benjy

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Re: How high could you make a elevator go?
« Reply #20 on: January 06, 2010, 03:48:16 PM »
It wouldnt actually matter how big
the string was the height it could
go up a string is only limited to
the speed that the diabolo is going
and how long it will spin for

karatepekka

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Re: How high could you make a elevator go?
« Reply #21 on: January 07, 2010, 04:53:30 PM »
Quote
You also have to bear in mind that the increased mass would require a larger amount of work to lift it.

Yes it obviously would, but I think the point was that most of the mass should be at the rims/outer edges of the diabolo cups. Because that way it would have greater angular momentum compared to diabolo of same weight with most of the mass near the center. They are both same weight so they require equal amount of work to lift, but at the start the diabolo with mass at the edges has more energy so it would go higher...

The reason for that is that when the mass is further away from the rotation axis the object has bigger Moment of inertia which, together with angular velocity, defines objects angular momentum.

more info: http://en.wikipedia.org/wiki/Moment_of_inertia

Hope this made some sense... I really can't explain it properly in english (or even by text only...).

Arjan

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Re: How high could you make a elevator go?
« Reply #22 on: January 07, 2010, 06:19:51 PM »
Oh boy oh boy I need a 50m roll of string and find a building 25m heigh and then try how far it will come!!

Where is the logic in that? Your numbers don't match m8.

Hathaway

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Re: How high could you make a elevator go?
« Reply #23 on: January 07, 2010, 06:36:07 PM »
karatepekka he mentions putting steel bits on the rim, so they wouldn't be the same weight at all...

karatepekka

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Re: How high could you make a elevator go?
« Reply #24 on: January 07, 2010, 09:42:55 PM »
yeah, I know, but I meant that IF there were two same weighted and same shaped object with that kind of weight distributions, the one with more mass further away from center would climb higher. Now this was more of a theoretical situation I think...

...but for the actual situation discussed here: if you increase the steel bits on the rim it takes more energy to climb but it still helps, because mass increase also increases the amount of angular momentum and at the same time mass moves further away from the center, which also increases angular momentum. These two factors together make more difference than just added work on lifting the extra mass and thus the diabolo with steel bits should climb higher...

bourgeois.jason

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Re: How high could you make a elevator go?
« Reply #25 on: January 08, 2010, 01:23:12 AM »
We first have to make a few assumptions.

1) we can spin a diabolo with weighted rims at the same angular velocity as one without weighted rims
2) we don't account for energy loss due to air friction or the string rubbing itself on the backside of the wrap
3) we don't add so much weight that it becomes counterproductive (a few pounds or so)

Anyway, I actually drew up some free body diagrams to explain the situation a bit more, but I left them at work and didn't go in today.  It is true that more energy would be required to lift a diabolo of greater weight, but we can assume that we won't add so much weight that it would be counterproductive.

I'll try to scan in my diagrams and include the formulas that would be required to find the climbing height.  These are the variables that you would need.
-angular velocity
-diameter of diabolo
-diameter of axle
-static coefficient of friction between the string and the axle
-kinetic coefficient of friction between the string and the axle
-moment of inertia of the diabolo (which would require a good amount of analysis.  we could assume that the weight is distributed at the middle of the steel ring we added.  it wouldn't be accurate, but it could be good enough for our purposes)

To be honest I just thought about it and realized that it would require some Calculus to get it accurate.  You'd have to figure the change in angular velocity as the diabolo climbs.

Anyway, sorry to bore most you you.

This discussion shows that adding weight to the center of the diabolo (Finesse Evo kit, etc.) doesn't do much for the spin duration.  It just makes the diabolo feel more solid.

Peace,
Jason

NiekG

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Re: How high could you make a elevator go?
« Reply #26 on: January 09, 2010, 10:59:55 AM »
Jason, did you study physics or something? :p
Meh,

Hathaway

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Re: How high could you make a elevator go?
« Reply #27 on: January 09, 2010, 11:45:57 AM »
I seem to recall Jason saying something about working on NASA's new space suit?

bourgeois.jason

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Re: How high could you make a elevator go?
« Reply #28 on: January 11, 2010, 04:09:44 AM »
Yes, I have a degree in Mechanical Engineering and work for Oceaneering Space Systems, one of NASA's contractors.  We are designing and building the next space suit for NASA.  They contract out all of their stuff, so I'd rather work for one of their contractors, since that's where all the design happens.
http://www.nasa.gov/mission_pages/constellation/main/spacesuit.html

If you read the article and wonder why it seems as though the deal isn't final, it's because all of the paperwork wasn't signed, yet.  Don't worry though, we have the contract.

I was trying to figure out a way to get a video of me diaboloing while in the suit, but I think I'd get fired for that stunt.

-Jason

Hathaway

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Re: How high could you make a elevator go?
« Reply #29 on: January 11, 2010, 09:58:06 AM »
While slightly off topic, thats pretty cool.

NiekG

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Re: How high could you make a elevator go?
« Reply #30 on: January 11, 2010, 01:18:31 PM »
While slightly off topic, thats pretty cool.
I second that, and I'd like to add: awesome!
Meh,

Benjy

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Re: How high could you make a elevator go?
« Reply #31 on: January 11, 2010, 07:29:47 PM »
Diabloing in an anti-grav chamber (3d would be easy)

kurrygrodan

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Re: How high could you make a elevator go?
« Reply #32 on: March 14, 2010, 05:11:05 PM »
Ummm... I just got to ask this.
If you diabolo in space and then throw it up, would it then spin forever since there's no resistance? :-|
-Fredrik, Kurrygrodan
http://www.youtube.com/user/kurrygrodan - Show dat channel some love!

Not Skilled Yet

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Re: How high could you make a elevator go?
« Reply #33 on: March 15, 2010, 02:25:09 AM »
Yeah,because there's no friction with the air, because it's a vacuum, and no friction from the string.
fluffy kitty

kurrygrodan

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Re: How high could you make a elevator go?
« Reply #34 on: March 15, 2010, 10:16:56 AM »
oh, nice! I better become an astronaut then... :-|
-Fredrik, Kurrygrodan
http://www.youtube.com/user/kurrygrodan - Show dat channel some love!

bourgeois.jason

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Re: How high could you make a elevator go?
« Reply #35 on: March 16, 2010, 12:57:42 AM »
Quote
If you diabolo in space and then throw it up, would it then spin forever since there's no resistance?

Not quite.  You would first have to place it in some kind of orbit to ensure that it doesn't get pulled by gravity into some large mass, like a moon or planet or star.  Even if you did place it in orbit around the earth, it would be hit by something called Micro Meteor Flux, which is small dust-like particles that float around in space.  If it is hit by enough, it would eventually slow down.

Of course, I'm being way too literal here.  Of course, for the purposes of our discussion, you could spin a diabolo forever in space.  :P

-Jason

Richard

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Re: How high could you make a elevator go?
« Reply #36 on: March 16, 2010, 11:18:12 AM »
Yeah,because there's no friction with the air, because it's a vacuum, and no friction from the string.

There's still friction with the string so it wouldn't last forever

hellebaard

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Re: How high could you make a elevator go?
« Reply #37 on: March 16, 2010, 03:25:10 PM »
that's only if you let the diab be on the string. there's now gravity in space, so the diab can't fall, you know ;)

Hathaway

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Re: How high could you make a elevator go?
« Reply #38 on: March 17, 2010, 02:36:54 PM »
There is gravity in space... In fact everything in space is always falling towards the planet but just at the same speed, hence the feeling of weightlesness.

Of course I'm now expecting Jason to post something making me look stupid... However very interesting to read (please do!)

bourgeois.jason

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Re: How high could you make a elevator go?
« Reply #39 on: March 17, 2010, 03:39:53 PM »
Hathaway,

You are correct about gravity in space.  There is no spot in the universe where gravity doesn't exist.  Actually, the International Space Station experiences almost the same gravitational acceleration pulling it towards the earth as we do.  The difference is that the ISS is moving REALLY fast.  This makes it all of the forces balance out to keep it in orbit.  Imagine the ISS as a diabolo doing suns around your sticks and the string as the "force of gravity" holding the diabolo from flying off into space.  Of course, it isn't the exact same, but you can visualize it.

The feeling of weightlessness is just the point where the sum of all forces gets really close to zero.

For the purpose of this very pointless ( :P) discussion, though, we could say that a diabolo put in orbit around the earth would spin "forever" if it was not contacting any other object.

-Jason
 

 

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