Experiment 17This is a bit of a weird project isn't it?
Well Glycerine and Pyrex behave a little weirdly when combined. You might have seen the effect in a science lesson, but here it is on the left. I've filled a bowl with Glycerine, and dunked 3 glass objects in it. 2 test tubes, (which are traditionally made of Borosilicate glass) and a shot glass (made of regular glass). You can only see the bubbles of air inside the test tubes, and a very faint outline of the tube surface! This happens because Pyrex (Borosilicate glass) and Glycerine happen to share very similar refractive indexes. Light barely bends when crossing the material boundaries, and so the glass looks as though it magically disappears! Cool right!? No? What's wrong with you? |
Okay, how is this a Project though?This effect hasn't really been explored as far as I could find!
A few test tube videos on youtube, and that's it. A quick parlour trick in a classroom if you were lucky enough to stumble across it on a random-youtube-binge day? (Or had a cool science teacher) Where are the toys?! Why isn't this an amazing exhibit in a science museum? Check out this magic gif I made. Isn't there the potential to blow some minds, get people excited in science with this!? (See wonder shown in reflection of Stephen's face) |
Okay, bear with me because I'm going to interject this page with the excessive testing this took to get right..ish
What's going on here?!
So multiple experiments later, and after weeks of being stuck with the conceptual brief of "CREATE WONDER"...I think I had the idea that would work.
It had to be something that was interactive, so you could your action created the magic effect. The Glycerine couldn't be disturbed too much, otherwise slime-like trails would be left. Actually, there were many other problems to work around, enough that months later, this is the 17th idea. All the previous ideas hit problems that I couldn't overcome. (I might make a page for those failures later) |
Creating a Splash
So here's the artsy premise. What if you could replicate a splash?
Still generated by touching the centre of a surface of liquid, but with the 'splash' suddenly appearing out of nothing. Concentric rings of Borosilicate glass rippling up and disappearing....If I could create a machine capable of doing that, that would be an exhibit to create wonder.... |
Automata
Clearly automata was the answer. A machine that creates a pattern of repeating movement using cams, on interaction with the user.
Here's some of the examples I found, and low and behold, even someone who created a splash!
Here's some of the examples I found, and low and behold, even someone who created a splash!
Of course...this wouldn't be so easy. (I mean, not that those are easy to begin with but check this out)
Automata Evolved...
Look ma! No handles!
Part of the experience was replicating the movement of creating a real splash, with this. So the entire motion HAS to be created with one downwards touch in the centre of the Glycerine. I came up with a gearing system that would transfer a force downwards into rotational force to drive the cam system. The smaller the gear, the more it would turn with the same downwards distance...but the more pressure would be on that little gear. Testing was all about finding the right teeth shape, diameter of the gear, shape of each cam circle to create the right timing for the rise and fall, such that NO circle section was ever above the liquid before the button was touches. (Not sure if any of that has ever been done before actually...) |
The Bowl is bigger on the inside
Now for the real thing...
The mechanism was assembled and glued together with epoxy and did work, just in time for the design expo at NTU.
Which is the first time it would be tested with Glycerine... |
MDF is great to prototype with, making iterative changes cheaply, but it will absorb Glycerine, swell and jam over time. So, time to lasercut the final design in perspex.
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DISASTER :(
The gear system had been tested dry, as Glycerine isn't cheap and it takes a lot of glycerine to fill the bowl enough to test the mechanism.
Thus, this was the first time the mechanism was tested while submerged in glycerine and unfortunately, the extra pressure of the liquid caused the internal gear to shatter. Due to the construction, replacing the gear required ripping the whole machine apart. There would be nothing to stop the same thing happening again, so a quick redesign was made. |
We can rebuild it, better, stronger, faster, and hopefully for less than 6 million dollarsThe chamber for the gear was is 3 layers thick instead of 1, allowing for a thicker, stronger gear.
It also turned out that the laser cutter had been cutting the perspex ever so slightly differently than it had the MDF, despite appropriate settings for the materials. It was only a difference of a 1/10th of a millimetre, but it was enough to jam the gears slightly, adding to the pressure. I made sure to cut multiple variations of the new gear out of perspex, and use the one that fitted perfectly. |
It works!Well, this is it for now.
Problems still exist to overcome before I feel happy enough to submit it to science museums, such as air bubbles being created by the movement and trapped under the rings. I believe this is related to the coanda effect, and might be fixes through a curved bottom or larger gaps between each ring, I am wary to coat the rings in anything that might alter their refractive index though. The rings would also look better if they rose further with each cycle, enhancing the effect of them appearing from 'nothing'. A project to revisit at some point in the future and perfect, but I think showing the potential of the idea. |