Department of


Arch 433: Caleb Scherf’s Studio Project

Course: Arch 433
Students Involved: Caleb Scherf


This realization led  me  to  look  into  other  expandable  designs  for  precedent. In searching I  found  the  Hoberman  Ball  which  solved  almost  exactly  the  problem  I  was  investigating.    Using a  series  of  scissor  hinges  arranged  in  a  particular  way,  the  Hoberman Ball creates a sphere that can expand greatly in size.  From here I decided to create a much simpler form using a similar scissor hinge mechanism that could expand in one dimension using a single repeated hinge.

Beginning design I  first    laid   out   the   rods    to  determine exactly how    many hinges I  would  need  and  how  many  types  of  joint  would  be  necessary.    It  became  apparent  that by creating a pentagon of single crosses I would only need ten identical joints at the corners to create the desired form.  My original plan was to use ball and socket joints at these points and to allow for the rotation around multiple axis as the hinges spread out and rotated as the pentagon expanded.  Through some experimentation though I realized that this was actually not necessary, and a simple pin hinge rotating on one axis would allow for the correct rotation.

I decided to attempt to print each hinge together because the layered nature of how the 3D printer builds parts and small scale would allow the pin of the hinge to be built through a gap in the opening of the other half of the hinge with no assembly required after.  I modeled the    hinge in  Rhino and made my first print attempt where I discovered my   first    issue.  Even though the   printer is very    accurate, the   tolerances on digital were too tight and the two halves printed together as one piece.  The worst of the joining was at the pin itself because the slight sag in the plastic as it bridged the gap connected it to the bottom of the hole of the other piece.  I then adjusted the model to increase space between all moving parts as well as rounded out some edges to reduce volume and potential collision points.  This print also showed that the size of the holes for the rods would need to be increased to fit them easily.

The modified hinges printed perfectly and    I  was    able    to   assemble the   whole form.  It was at this point that I realized that without anything to hold each cross in the scissor jacks together, the   form     was    unstable and    difficult to   work with.  This    problem was solved by creating small collars that could slide onto the middle of each rod to act like  another  hinge.    These  also  required  two  prints  to  get  the  tolerances  just  right  to  allow them to   slide    into    place but    still   hold    firm    enough in  their    place when assembled and moved.  Once fully assembled I discovered that a little bit of extra space between the collars and rods allowed them to move up and down, moving the hinge point and adding another level of flexibility to the overall form.

January 31, 2018 5:48 pm

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