Motorized portal illusion

Inspired by the “Portal Desk Toy” by Ada Cohen (https://www.printables.com/model/414209-botanical-portal-desk-toy) I wondered if it were possible to make a motorized version of the sculpture. 

The mechanism I ended up with is a simple pinion driving three spirals, all at different speeds and directions. The mechanism can be driven with a motor, or can be driven by hand with the knob on the front of the sculpture.

Required materials

• Filament
• 10x M3x12 socket head cap screws (DIN 912 or similar)
• Glue suitable for plastic

For the motorized part:

• N20 gearmotor (3-6V, slower is better. Something like 60rpm is already quite fast)
• Wire
• heatshrink
• DC-DC converter
• A trash USB cable
• Fuse (0.2A-1.0A) (optional)

Parts

The 3D printed parts are available in STL format, and in STEP format. There is also a STEP of the entire mechanism, the PI-A01-00. The STL files are oriented correctly, but the STEP files are not. 

The spinners are split up in separate parts. The STEP files have multiple bodies here in the same part that need to be separated in the slicer. All parts are support free. The gears (P02, P03 and P04) are best printed at a low layer height. The spinners need to be printed as clean as possible to keep the illusion working. I printed the base of each spinner black, and then changed the filament to a nicely colored one.

• 1x PI-P01-00 (the base)
• 1x PI-P02-00 (driveshaft)
• 1x PI-P03-00 (small gear)
• 1x PI-P04-00 (medium gear)
• 1x PI-P05-00 (large gear)
• 1x PI-P06-00-1 (small spinner, body)
• 1x PI-P06-00-2 (small spinner, top)
• 1x PI-P07-00-1 (medium spinner, body)
• 1x PI-P07-00-2 (medium spinner, top)
• 1x PI-P08-00-1 (large spinner, body 1)
• 1x PI-P08-00-1 (large spinner, body 2)
• 1x PI-P08-00-3 (large spinner, top)
• 1x PI-P09-00 (top)
• 3x PI-P10-00 (pillar)
• 3x PI-P11-00 (pillar cover)
• 2x PI-P12-00 (driveshaft lock)
• 1x PI-P13-00 (back leg)
• 2x PI-P14-00 (foot)
• 2x PI-P15-00 (bezel ring)

Instructions

All M3 screws tap into the plastic parts directly. Predrilling should not be needed.

The gears might have stringing after the printing. The gears can be cleaned up using small files. If the stringing is heavy, you can also use a knife, but files are safer.

The spinners are designed to prevent stringing. My earliest versions had 2 and 3 arms in a single print, but this led to massive stringing and unusable parts. The small cross section of each of the arms on the spinner meant constant starts and stops. Still, there might be some cleanup on the spinners. Be careful not to scratch the surface of the spinners. Any mark that can be seen spinning will give away the illusion.

The gear, the base of the spinner and the top of the spinner can be glued together. On the top there are alignment features to help get a good alignment. On the gear there are not. Try and get all the parts as concentric as possible.

The diameter of both the gears and the spinners need to be made to fit to the base and top. There will be a seam that needs to be filed down on all the rings, and if you are unlucky (I was unlucky) the rings will still be off slightly. For this mechanism to work properly, the parts need to run extremely smooth. The gears push the spinners up, and any friction is enough to bind the spinners. When you fit the spinners in the base and top, they need to spin freely with no noticeably binding or excessive friction. If you are impatient you can use a Dremel with a sanding disc.

On the driveshaft there will be a seam on the front and back. On my parts, these bound in the base, and needed to be filed flush with the surface.

The bezels can be glued to the base and top. The bezels are only cosmetic, they obscure the rings, preventing you from seeing them spinning. This strengthens the illusion. The exact position of the bezels is not important, but try and get them concentric to the eye.

More detailed instructions

Detailed instructions on how to assemble can be found here: https://www.instructables.com/Motorized-Portal-Illusion-Sculpture/