Sketches and ideas

[glo...@gmail.com]

Dear friends!

I started a document (link below) which I will keep updating as we along.  Please feel free to modify it with your notes. 

In the document, there is a sketch showing one possible relationship of the installation to a person.  I am open to suggestions on the size of the structure.

Another sketch is showing two methods to achieve the same effect.  Please let me know which solution sounds/looks better to you.

There are a number of questions we need to address, some are listed in the document and some are not yet listed.

During the weekend I will try to find out what the best set up for fire is.  It would be nice to have supply lines leading to the pendulums but I am not sure how difficult that is.  I will look into a simpler approach first - having source of fire inside the pendulum spheres.  I also would like to build a model to see what issues may be encountered in making the object.

I am away this weekend without access to email.  I will respond to your messages when I return on Monday.

Warmest regards,
 - Gene

https://docs.google.com/document/d/1-jcrKw1ClFa1nWCphFwBD9nD8spk72RQ49pLGRtPusE/edit?hl=en_US&authkey=CLSAr8AK

[Jason Turgeon]

This looks great!  

I don't know if the pendulum weights need to be exactly the same.  We could try it out with two different weights suspended from something without building a whole scale model.  The method for figuring out the length is described at this page:  http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page80863&pageContentId=icb.pagecontent341734&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent341734

How it works: The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each successive shorter pendulum is carefully adjusted so that it executes one additional oscillation in this period. Thus, the 15th pendulum (shortest) undergoes 65 oscillations. When all 15 pendulums are started together, they quickly fall out of sync—their relative phases continuously change because of their different periods of oscillation. However, after 60 seconds they will all have executed an integral number of oscillations and be back in sync again at that instant, ready to repeat the dance.

I would guess that at a larger scale we might want to lengthen the period to 2 minutes or even longer.  We can have some fun figuring it out.

Other ideas:  See if we can get a bunch of used bowling balls from a local bowling alley for daytime use.  Buy 15 LED balls from Amazon (not enough mass to make them effective?)  Use clips (like a dog leash) to quickly switch between different pendula. 

Transport:  a share on the truck is about $400 and is 100 cubic feet.  If we can get this under 100 cubic feet, I will buy the remainder of the share for my own nefarious purposes.

[The Cunctator]

Pendulum weights don't have to be exactly the same.

Formula for period is basically 2*pi*Sqrt(L/g), so is proportionate to square root of length.

L = g * (T / 2 pi )^2

So for the example given, longest pendulum T = 60/51 s , shortest pendulum is 60/65 s.

If my math is right:

=> L(longest) = 34.36 cm
L(shortest) = 21.15 cm

If you quadruple the length, you get double the period. So the longest pendulum would be about 69 cm (2 1/4 feet)

[Jason Turgeon]

Haven't heard much from this group.  I'm going to assume it's been put to bed since Rob Darman decided to build his massive swinging ball project.  

Even though I didn't get to help Rob with his project, I'm still excited to see it - if you're friends with him on Facebook you can check out a picture of a largely-constructed apparatus. It looks to be about 25' high, and I know he's been casting the weights out of lead ballast salvaged from an old boat.

[peter durand]

I would say that is a safe assumption, heading over this week to do some work on it.  --- On Mon, 6/20/11, Jason Turgeon <jason....@gmail.com> wrote: