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Gravity Harps for Bjork

The Gravity Harps are the final version of the pendulum instrument and are featured in Bjork’s current Biophilia show in Manchester UK.

The idea was born during a slightly tense meeting after the Manchester parameters had changed. The Pendulum Ring was out for now. We needed a new idea. We had about 4 weeks and the clock was ticking. I drew this idea on a scrap of paper:

How this plays a complex song took a lot of explaining, and still does.

Prototype 0:
I went back to the workshop with Marina and we built an ugly mock-up with PVC pipe and cardboard to check if the size and proportions made any aesthetic sense. They didn’t. But we banged away at it until we felt better about it.

Prototype 1:
The next prototype was used to test whether the combination of swinging and rotation worked at all, mechanically and aesthetically. And James Patten needed to start testing a control system that was smart about the physics of pendulums. Here’s some of the slow video we shot of the tests:

Prototype 2:
The next version needed to make some music. That meant Marina and I needed to finish prototyping the harps. Our 2nd prototype harp was made of fiberglass, walnut, spruce and all the epoxy we could find. This is the harp Bjork used on the new album. Here is Marina putting the strings on for the first time.

And here is it under computer control:

I think this still tells the story pretty well:

It was finally starting to look like a win. So we pressed onward through weeks of 18-hour days.

Prototype 2:
There were so many parts to figure out. And Karl Biewald And Doug Ruuska machined some great mechanical solutions.

Our new harps would have larger shells of a home-made walnut veneer composite:

And the new stands would be cantilevers, hanging from the building’s columns:

James and I finished troubleshooting at 5AM on the day of a 9AM demo for Bjork.

The demo went really well! Our final prototype setup looked much like this nice photo by James Patten:

I needed a robo-sitter in Manchester. Ryan Wistort was by far the best choice. I’m not sure how much I should be saying yet about the installation in Manchester. But these random bootleg videos are already out in the wild. It’s not good documentation, but it does feature Bjork!

Special thanks to (chronologically):
Marina Porter
Karl Biewald
Doug Ruuska
James Patten
Ryan Wistort


13 replies »

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  1. Thank you so much for this detailed post about a great and interisting project. It sounds like a good idea to make a model por my physycs class, anyways, I hope to hear more about you and new things like this in the future. Thank you in advance.

  2. [...] Andy Cavatorta’s version of the story can be found in his WordPress blog entry. It all started from scratching in a piece of paper. “The Pendulum Ring was out for now. We needed a new idea. We had about 4 weeks and the clock was ticking. I drew this idea on a scrap of paper. How this plays a complex song took a lot of explaining, and still does.” The most admirable part is the originality of the project. “This is the prototype,” Cavatorta said to The New Yorker reporter who asked him how long the design process had taken him,  from prototype to finished product, which means only one gravity harp exists. [...]

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