hannah mishin

Portfolio and Blog of artist and technologist Hannah Mishin.  

Arms

I laser cut the parts to the 123D cut-list and prototyped it with cardboard.

I then glued it with rubber cement. The areas I cut out with Z-Brush (edited mesh) - articulated areas- created interesting cuts in 123D make.

IMG_0076.jpg

I did not track the finger section as closely as the arm sections, and got a little lost in the puzzle mess I made.

Hence this arm will remain finger-less. I have them for sizing (dowels and joints) later in the process.

 

IMG_0075.jpg

I also began working on the specifics of the motorized joints.

I have a pan-tilt servo mount and am finding difficulty with mounting it for prototyping the movements.

I built a box.

 

IMG_0078.jpg

There were issues (apologies for the blurry photo):

IMG_00791.jpg

The movement with the flexible attachments did not allow the "arm" to articulate fully. It gave a fluidity of movement but limited the range.

So, I then moved one of the servos in a different configuration:

 

IMG_0082.jpg

The servo was mounted onto the 2nd to bottom section of wood. Attached to the servo's circular section is another bit of wood with the universal joint for the side-to-side motion and used the pan-tilt brackets to control the upward motion.

There is still a limitation.

 

IMG_0090.jpg
IMG_0094.jpg

The arm, once controlled by arduino, had not enough torque to lift the arm once it was completely down.  Therefore I decided to mount this completely differently, and use the pan and tilt directly.

Though hesitant to relinquish the naturalness of the movement allowed via the universal joint, I mounted the arm and joint onto the servo pan/tilt

 

IMG_0095.jpg

Alas- when the brackets are raised vertically, the universal joint counteracts that motion- thanks gravity.

 

IMG_0096.jpg

So I thought perhaps to use the servo gears to assist me with anti-gravity.

By adding a larger wheel on the side of the up/down servo-bracket and looping the attaching "ligament" material to the arm, through the loop and onto the side of the bracket, I could make this actionable.

 

IMG_0108.jpg

The brown wheel attached to the side should spiral around and retract the rubber -ligament sufficient enough to pull the "arm" up.

 

IMG_0109.jpg

This did not work either.

FINALLY-

I replaced the string/rubber with rigid hemp rope.  I returned to a prior set-up and based on advice, I moved the "pulling" servo farther back and extended it so that it could have sufficient torque to lift the steel rod.

Though it is difficult to manipulate a potentiometer and capture the entire action, when the dowel (driving arm) moves upward or downward in particular configurations, the steel rod has a buoyant-quality - natural mimicry.

Parallel to this development, I have begun editing the 178 files that 123D make generated for me, and have start the process of glueing the 3 thousand or so sheets of paper which will be the arms' skin.

IMG_0126.jpg
IMG_0129.jpg

I made a 3D drawing to print, a bracket to hold the arm in place against the dowel-

 

1700armbracket.jpg

My main issues have - thus far- been in mounting gears and having them align properly:

IMG_0132.jpg

I needed to make a permanent enclosure and rid myself of this shanty town;

 

IMG_0139.jpg

I inserted the brass rods- pressure fit accordingly- but alas, the bushings et. al. were not secured enough (despite rubber mallet implementation):

 

IMG_0140.jpg

I made plastic bushings and glued it all in-

IMG_0141.jpg

I also bought myself a fancy high torque servo-

 

IMG_0138.jpg

the first iteration in action-   

Was working on the code to communicate with Kinect, when ... the torque of the servo snapped the 1/2" gear shaft.

Was working on the code to communicate with Kinect, when ... the torque of the servo snapped the 1/2" gear shaft.

Was working on the code to communicate with Kinect, when ... the torque of the servo snapped the 1/2" gear shaft.

Was working on the code to communicate with Kinect, when ... the torque of the servo snapped the 1/2" gear shaft.

So to begin about re-designing the housing- I took off the small gear from the servo.  It proved to be much more easy to remove than I had imagined, despite the JB Weld. 

IMG_0213.JPG

I am printing brackets to house the exterior of the arm. 

IMG_0237.JPG