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Past Work - Yours Truly

Another in my series of automatons focusing on the "body language" of face and eye movements.  Recent ones have been based on papier-mache masks of myself - see "On a Roll" and "Selfie".  Earlier ones include  "The Snake Pit", "Paranoid Timothy" and "Faces".

 As I had 5 "spare" masks of myself left from previous projects I decided to line them up in row with eyes and heads turning left and right to look at each other, perhaps evoking self-consciousness, nerves, guilt, scheming or some other emotion.

This is work-in-progress.  It's been through a couple of fairly major rethinks and is actually stalled at present, waiting for some materials to arrive to address the latest problem.

  mockup of automatonI started out by developing a mechanism that would translate the rotation of a vertical shaft into a cycle where the eyes turned fairly smoothly from left to right while the face paused in the ahead position before following the eyes.

I played around with possible ways of achieving this by adding fixing points to a mask so that it could swivel in a mock-up section of the future cabinet. 

The photo shows what I ended up with.

The small top wheel moves the eyes - a peg in the wheel slides between 2 parallel green rods that are hinged to the back wall.
The bigger bottom wheel turns the mask in a similar fashion but the parallel rods are further apart to achieve the pause in each cycle.  The "hinge" in this case are vertical bolts fixing the mask to the top and bottom of the cabinet.

The bottom wheel also acts as a pulley.  At that stage I was thinking of using a series of drive belts to rotate the spindles. 

  Pin wheel gears for automatonDriving this mechanism raised some other issues.

I wanted the masks to be at eye level with the winding handle at no more than chest height, and   I wanted the winding handle and the shaft to be central.  

I ended up addressing these needs by making "pin-wheel gears", shown left, so that a horizontal shaft from the handle could rotate a vertical shaft up behind the central mask. 
  Automaton - drive belt I'd never uses drive belts before and I quickly discovered that they weren't going to work on my installation.  There was too much friction and the belt kept slipping.

Back to the drawing board!
  Plastic gears and wire chainI decided to use chain and sprocket wheels to stop the slipping, and that these needed to be on a vertical rather than a horizontal plane (to stop the chain falling off).   This meant redesigning the whole mechanism.

I ended up with one big loop of chain (2-metres-long) that dropped down out of the cabinet and around the winding handle, eliminating the need for the pin-wheel gears I'd made.

As I'd already got lots of plastic gear wheels I bought some chain that was designed to work with them.  As you can see, it's made of wire - which set me up for another problem later on.
  bearings in automaton I decided to minimise friction so I ended up installing roller bearings for each of the gear wheels.

  sprockets and chain in automatonFixing the assembly that holds the winding handle and plywood reduction gears.

The wooden discs drive the mask and eye movements and are attached to plastic gears. 
  Mechanism for moving masks in automatonAssembling the mechanisms behind the masks.
  First of 5 masks in automatonFirst mask fitted.  It worked for a bit but the chain kept falling off the gear wheels.

It became obvious that the chain was stretching.  In hindsight, it's obvious that it would as it's made from wire.  Doh!!

I've now discover that proper chain and sprocket "plate-wheels", like the stuff on bikes but smaller, aren't as expensive as I expected.  I've ordered some.

A bit of a redesign will be required but nothing too major, I hope!
  automata - eye in masksAfter quite a major redesign to use chunky chains and sprockets I got the whole thing to work after a fashion.  It needs some further refinement to work smoothly and for the time being, I've got distracted by other stuff.
  Chain used for eye/mask automatonIt really is quite a chunky chain!

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