Monday, March 7, 2016

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Thursday, May 16, 2013

Alidade in its real home

Here are some updated photos of Alidade set up in it real home in the Exploratorium Observatory between pier 15 and 17 in San Francisco.  On the left there is an accompanying book which has addition information, current and historical, on the various structures the Alidade can can sight.

 A detail with the point ring (the initials of various structures), bearing gauge,  zone diagram (showing what the zones in the map look like in section) and the map visible.

What you see through the sights, in this case when the bezel was set to Coit Tower. The angular accuracy proved to be very good with the map bearing differing from the actual bearing though the sights by less than a half degree.

Sunday, October 21, 2012


 This is final Alidade for the Exploratorium is based off of the Osborne Fire Finder and my initial cardboard model.  It is 19.5'' in diameter and composed of machined aluminum, machined phenolic as well as glass and acrylic.   It's seen sitting in the Pier 17 window (in SF) on our mock up rail, so the map in this case does not correspond to the viewable landscape as it will when placed in the Exploratorium's new Observatory Gallery at the end of the pier and one story up. Below are a few additional preliminary photos of the Alidade.

 As these were the first photos taken of the finished alidade, the map disk and point ring are made of paper and not the etched and printed aluminum that will be in the finalized exhibit. On the upper part of the map disk you can see a map of the San Francisco waterfront. On the lower part there is the color coded zone diagram which separates the view into various districts. The acrylic ruler that spans the two sights indicates the line of sight as seen in plan (normal map) and in section (zone diagram). The ruler is also graduated to indicate the approximate distance between the observer (at the center of the map) and the landmarks being viewed on the water front map. The small pocket in the lower sight indicates the initials of the landmarks being viewed so they can be looked up in an accompanying book which will provide information on the landmark's historical context and how it relates to the district in which it resides.   Currently, the design of the book is in progress, so is not pictured here.      

Heres another detail of the map and the line of sight rule.

Here is a view of the near sight and the point indicator gauge, the bearing angles are also indicated below the zone diagram.

A view of the far cross hair sight.

Rangefinder #3 model

This is a "looks like" model for the final Rangefinder, which will contain a mechanism similar to Range Rinder #2, but is asymmetrical.  It's made of hand perfected cardboard rolled around laser cut internal ribs and then affixed with gum tape.

Here are a few interface models I made to explore the positioning on the three major interactive components, the eyepiece (on the left), the range gauge (middle) and the ranging knob (to the right). The two armed model on top came from looking at British Barr and Stroud rangefinders. The final model ended up not including the right arm after the discovery of some asymmetrical Swedish rangefinders.

This is the view from behind the rangefinder. You can see the eyepiece in the center with the range gauge to right and finally the ranging knob on the far right. 

Looking form the front you can see the two prism ports where you vision would be directed out of the rangefinder.

Prayer Wheel (stroboscopic)

This was another device that came out of my experiments with Jisho Roche Adachi, a small and simple platform for short animations the Stroboscopic Prayer Wheel. 

Here is the prayer wheel in some initial drawings in Jisho's notebook, the white scrap of paper on the left of the book is the strobe trigger I planned to use.

The basic structure of the prayer wheel consists of an acrylic tube with laser cut plywood end caps.  Bearings were pocketed into the end caps allowing a threaded rod to be inserted through the wheel's body and the maple handle while still allowing the body to spin freely.

Here are the guts of the wheel, you can see the control circuit suspended above the lower plate which has a series of 8 magnets to trigger the strobe.  Three leds were mounted above the control plate and pingpong balls were stuck over them to act as diffusers, so the light would be distributed evenly.   

Finally, a weight consisting of washers and felt disks to prevent damage to the acrylic was added making it possible to spin the wheel by tipping your wrist slightly as in traditional Tibetan Prayer Wheels.

With the mechanism complete we added an eight frame velum animation sequence, to produce this very satisfying result.  

Friday, October 12, 2012

Turn table animation machine

I built this animation machine in collaboration with Jisho Roche Adachi  for  an Exploratorium event focused on time. Jisho an Illustrator / Painter and an old friend who happens to share an interest in animation machines. You can see more of Jisho's work here .  Though originally we wanted to explore using a prism shutter similar to high speed cameras, we tried using a rotating cube and later hexagonal prism which I milled out of an acrylic rod.

Shutters were supposed to spin with a wheel on the turntable (as seen in Jisho's notebook below). These prism wheels proved very hard to synch up and were abandoned after the first few days. 

 The physical design of this project ended up drawing directly from the Electrotachyscopes which I built as a student at Oberlin and the later point source projector project . The machine uses an improved electrotchyscope strobe circuit and laser etched mirror disks based off the the point source projector's slides.

The Electrotachyscopes used an optical gate trigger for the strobe which was less than reliable. For this machine I used neodymium magnets in pockets in the record platen and a reed switch in the tone arm.  This design really stays true to the record player's original form and function. The reed switch in the tone arm reads the magnets and tells the strobe to fire only when its placed over the side of the platen.  We started out with a simple ring of 12 magnets around the edge of platen. However, as this was an automatic turntable we were able to take advantage of the 7'' and 12 '' settings to play different strobe rate "tracks" in the platen. In the photo above there is an inner track of 12 flashes per rotation and an outer of 18 flashes per rotation. Due to the position of the strobe circuit, we ended up shortening the tone arm,  but if we had been able to leave it full length we may have been able to use the 10'' setting for  a third strobe track.       

Here is a detail of the strobe circuit with the adjustable Locline light arm and trigger wires running to the magnetic reed switch in the tone arm.  

Here is the machine playing a 12 frame Muybridge animation sequence as seen on the machine's movable velum screen.

Projection detail.

In another adaptation we added a spool to the top of the platen allowing it to play a loop of acetate Jisho had drawn based on video of people walking around the Exploratorium. We discover that this format could either be used to animate the film itself by shining the light through the screen behind it or as a simple shadow projector by placing the moving film between the led light arm and the screen.  

Tuesday, August 28, 2012

Cylindrical Perspective Window

The cylindrical perspective window is a drawing tool which allows a used to trace the local landscape in near perfect perspective. As another Exploratorium prototype, it based off the museum's existing perspective window. The original is a flat window to draw on with a fixed eyepiece, my version uses a curves sheet of lexan instead of flat glass which makes the entire drawing surface the same distance from the eye.  Optimally one would use a spherical window so all points were equidistant from the eye.  However, because this window is for drawing landscapes in the far field, most of the drawing happens in the middle of the window so a cylindrical window makes decent approximation of a sphere as long as you do not draw at the upper of lower edges of the window.

I decided to use a slot made of laser cut acrylic with a chin rest instead of a round hole for the view port as it avoids the need to adjust the height of the eyepiece. The rest of the perspective window is made of plywood cut on a cnc router, maple dowels and the legs are made from some cardboard tubes from butcher paper rolls. The window structure has a series of plugs that fit into the cardboard legs holding them on securely but also allowing legs a base plate to be removed for easy storage.    

 The curved window widens area you can draw on without distorting the image horizontally, making very wide angle drawings possible.

Here is an image of a drawing taken from above and to the left of the original eye position.