21 Aug 2015

What Goes Around Comes Around - Undersea Carousel Style!

Photo: http://www.seaglasscarousel.nyc/the-seaglass-story/ 

Post by Helaine Becker

A fantastic new carousel  called Seaglass opened in New York City yesterday. According to Show Canada, the group that fabricated the structure, "visitors find themselves within a musical seashell structure of 30 illuminated fish of different changing sparkling colors and species." 

The fish are up to 4.5 m tall, made of translucent fibreglass "reminiscent of frosted colored pebbles of sea glass." They rise, fall and swirl about in invisible 'currents' much like real fish do in the ocean.  (See a video of the carousel in operation here) It looks totally spectacular, and I can't wait to get to New York so I can ride it myself!
Photo: http://www.seaglasscarousel.nyc/the-seaglass-story/ 
My friend Stephen Sywak was part of the engineering team (McLaren Engineering Group) that helped make the carousel come to life. He has very kindly answered my questions about the engineering challenges involved in making this complicated and gorgeous work of art. This is what he told me, in short:

Can you describe the carousel for me?
It's a multi-axis carousel.  There's a main turntable, but within the main turntable are three smaller turntables.  And on THOSE turntables, there are a number of "fish," like the horses on an old-timey carousel, except for a few things....

Photo: http://www.seaglasscarousel.nyc/the-seaglass-story/ 
* You ride INSIDE the fish, not on top of them
* The post that the fish move up and down on only goes BELOW the fish.  On a carousel horse, it goes THROUGH the horse, from the floor to the canopy.  Structurally, and  from a control point  of view, it's a lot harder to do it THIS way.
* The fish not only move round on the large carousel, but they swing back and forth because of the smaller carousel.  And then they swing back and forth AGAIN, on their own poles.  AND they move up and down on their own poles (There are a few fish on  the MAIN carousel that only move a little or not all; some of these are designed to accommodate wheelchairs.).

So how do you make it all go "swish?" 

The main carousel and the smaller carousels are driven by industrial motors.  The motors run gearboxes, and the gearboxes run "ring bearings" (large, geared bearings--like you would see on a tank turret).  They provide about 20-30 HP for the main carousel, and 8-10 HP each for the small ones.

The fish are mounted to custom hydraulic cylinders.  But we didn't use hydraulics to run them up and down.  The hydraulic cylinders are perfect for guiding and positioning the rods beneath the fish, and holding them stable.  They are designed to handle linear and rotary motion.  Why reinvent, when it's cheaper to buy an existing product?  (That was my idea, by the way!)  Instead, we used two standard electrical motors (and gearboxes) to do the local lifting and the local turning. 

If I recall correctly,  a giant "slip ring" at the center of the table brings in all the power and control signals.  It allows the central turntable to rotate round and round without winding up a bunch of cables.  The inner (smaller) turntables, and the fish themselves, only spin partially around.  We used "Cable Chains" to bring power and signal to them.

We used industrial control systems both for safety, and to allow us to simplify and reduce the number of signals crossing the main, central slip ring.  Basically, it's running on a network, like computers in an office, or a network you might have at home.  But it's got layers of security on it, so that it can't be "hacked."

I never ever considered the possibility that someone would hack a merry-go-round. Go figure. 


What were the key challenges in  taking this idea from the drawing board to Battery Park?

One key challenge was was that we had to work very closely with the artists to make sure that we could implement their vision.  There were a few occasions where the "artist" types even took their lead from our designers and engineers! 

On the physical side, there was the fact that the structure on which the Carousel's turntables sit is all below ground. It's about 8-10 feet "tall," but it's all under foot!   

Photo: http://www.seaglasscarousel.nyc/the-seaglass-story/ 
We also had to make sure that all the various motions of the fish (large turntable, small turntable, fish "wag" and fish "heave" up and down) didn't make the riders heave their respective breakfasts and lunches. 

Thanks for that image. What's your next coolio project?

I'm currently working on a test set-up for an actuator (motor, gears, sensors, etc.) that rotates the solar arrays  on geo-synchronous satellites. If it turns out I know what I'm doing, then I hope I get to work on some of the actuator designs for the next Curiosity mission, slated for 2020.   

WOW! From undersea to outer space! An engineer's life is full of thrills! But now the most important question of all: Do you get to ride on the Seaglass Carousel for free?

Unfortunately, no.  But it's only $5!

Ok then. I'll book my ticket to New York and get in line. 

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