Tuesday, October 2, 2007

Blockwatch - periscope surveillance system

This is a piece that I just finished for a show which is open again on October 13th and 14th from 2-5 pm. Location.Seven artists were invited to create site specific pieces for a suburban backyard. This particular yard had a very bunker like quality so I decided that my contribution would be a 20 foot tall wooden pan/tilt periscope. The scope works remarkably well at spying on her neighbors, who fortunately found the whole thing rather amusing. I think the warning signs that I posted around the neighborhood helped.

Here is a short video showing the scope, spying on random people walking down the lane, looking at the view, and also some detail shots showing the mechanism.

These are some further shots showing the full tower and mechanism details. The construction was pretty simple, 8 pieces of 1.5" fir dowel were used to create the upright risers. These were reinforced with cross rungs that were bolted to them. The tower is constructed in two 10' sections that are slid together over pipes in the middle, this was to make it easier to transport. The tower is stayed using 1/4" rope that is anchored to tent pegs in the ground, this arrangement reinforces the tower greatly.
As for the mechanism it can be divided into two main parts, the pan which allows the top mirror to rotate through 360 degrees, and the tilt which allows the mirror angle to be adjusted.
The pan component consists of a lower pulley with handle that is attached via an endless rope to the top, where there is a lazy susan with rope guides. Spinning the handle spins the lazy susan. The rope is kept in place with a series of eyelets.
The tilt mechanism is a little more complex, the mirror is pivoted in the center on a copper tube, at one end of the mirror are springs which keep tension on the cord, on the other is the cord itself. Pull the cord and the mirror tilts. Complicating this is the fact that mirror can spin fully round. I wanted the tilt to remain independent and unchanging from the spin so I had to run the cord through a guide that sits in the centre of rotation. This guide is relatively invisible in practice because it is located so far back from the focal plane. The tilt is controlled at the bottom with a simple wooden lever.

And these are some of the views that were discovered. The yard sits on an a fair slope, with the back alley 5 feet higher than the grade of the yard. Between this, the retaining walls, the fences and trees one doesn't normally get much of a view from this place. With a 20 foot tower thats taller than the house.. well you can see the mountains and a lot more. Oh and if you are wondering why some of the shots appear to be oriented incorrectly, it was one of the interesting optical quirks of the piece. When you have two mirrors acting as a periscope the view will appear to be right side up when the tower is viewing forward relative to the viewer, but upside down when looking backwards.


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