Make Architecture



6 – 3D Printing a crank, ratchet and pawl

My initial goal was to produce a ratcheting freewheel using the 3D printer…  something that could be used like a miniature, self enclosed slot machine mechanism or coaster bike. I imagined this could then be combined with some of the other gear explorations I’ve done to create a more complicated machine.  As it turns out, this alone is a very (overly) complicated thing to produce.

Precedents from bikes:

So, I looked at creating a simple ratchet and pawl system on its own. basically this:

which could turn into something more interesting like this weight movement machine or combined with a crank arm:

Finally, I designed a very simple crank wheel meeting a ratchet/pawl wheel to test the mechanism.


  • Rhino 3D digital model
  • 3D printing machine that uses plastic


  • design the gears, post, cranks, and ratchet system in rhino
  • send the file to the lab for printing
  • bake the printed piece to remove the wax scaffolding that holds it together in printing


In the design process, it was key to consider exactly how the wax scaffold would be able to exit the mechanism (aka drainage) and also how the different parts would register/fit with each other since they would not be dissemble-able.  I made the pins that hold the gears fit permanently into the gears with a flange at the top.  I wanted to make something that could ONLY be printed and not assembled from off-the-shelf hardware.

This is the simple gearing system I designed:

to explain the construction of this, i separated it into individual parts below.

first, the base with fixed pivots.

then the 2 gears that are not connected to the base so they can turn freely

then the crank handle which is connected to the left gear and fits over the top of the pivot head on the left.

then the ratchet and pawl that work on the right gear.  these parts all all connected by free turning pivot posts.

here’s a closeup on how the pivots work so that they are not connected to the pawl and ratchet arms but will not slip out due to flanges on the bottom/top sides.

and the much anticipated 3D print of this file from the Invision…..

here it is with the wax scaffolding- looking promising.

then i put it in the toaster oven to bake the wax off of the plastic.  set at 150degrees.

it came out of the oven in great shape!  As you can see, it printed at about 3.5″ x 2″ total.  all the parts were moving as expected, even the ratchet and pawl were working… !!!!

unfortunately, the residual wax coating started to re-solidify as i was testing all the parts.  also, the amature parts were about 1/32″ thick (extremely thin!) and with the resistance of the wax i snapped the ratchet part on its pivot…

This project could have been more successful with a couple of changes:

– thicker components (minimum 1/16″)

– an oil bath to remove any wax residue before forcing the parts to function….


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Instructor: Nick Gelpi TA: Skylar Tibbits TA: Varvara Toulkeridou
Class Times, Monday, 1-4pm - room 5-216
4.184 is an intensive introduction to methods of making explored through a wide range of brief but focused 1-week exercises. We'll engage the real and leave behind representation in the focused context of this class gaining skills for utilizing a range of fabrication machines and technologies from lasercutting, waterjet, 3D printing, welding, formworking-molding, casting, gears, joints and composites.
In this workshop we'll constrain ourselves to the territory of the 1:1. Students will represent architectural constructions at full scale and develop a more intimate relationship with technology by engaging the tools and techniques that empower us. We will gain access to the most cutting edge machines and technologies in the MARS lab at the Center for Bits and Atoms.
The second layer of information for this course will be to look at a series of case studies in which construction methods and technologies have played a dominant role in the design process .
Over the past 20 years, architects have focused on the technology of representation to create new ideas of what architecture could be. Looking back today, much of that research failed to substantially change the way we design buildings by focusing on apriori formal configurations. This class makes the contention that this failure comes from a lack of considerations of the potentials within fabrication knowledge. We look to the future of what building might become, given the expanded palette of personalize-able technologies available to us as architects. Students will participate in curious technological and material investigations, to discover the potentials, known and unknown, for these various technologies.
The sub-disciplines of what's drawn and what's built have been compartmentalized and disassociated as the representational tools of architecture have distanced themselves from the techniques of making. At the same time the technologies for “making” in architecture have provided us with new possibilities for reinventing how we translate into reality, the immaterial representations of architecture.


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