Description

In 2015, I build the first prototype of my Loxodrome Lamp, a LED shadow projection lamp inspired by Paul Nylander's "Loxodrome" wall sconce. The lamp consisted of a slender 3D printed base crowned by a Loxodrome globe. A LED inside would project shadows of the spiraling arms on the walls.

I wanted the Loxodrome to turn slowly, but accomplishing this seemingly simple feat turned out to be a far more difficult than I could have ever imagined. A functional but inadequate initial design lead me to rethink my design for the second iteration. With the aid of a new CAD tool I replaced the ineffective mechanism of the original with a compact, fully-3D printed coaxial gearbox.

Details

The Inspiration:

My project was inspired by Paul Nylander's "Loxodrome" wall sconce (http://bugman123.com/). I had recently bought my first 3D printer on Kickstarter and I knew that the Loxodrome sconce was something I wanted to tackle.

Once I became a little more experienced in 3D printing, I set out to see if I could recreate Paul's work. Having found kitwallace's OpenSCAD implementation of the Loxodrome, I printed a small version and made a comically jury rigged mockup using some plywood, a white SMD LED, a power supply and copious amounts of blue painter's tape (because I didn't want to drive nails into my wall!).

As silly as it looked, it got me thinking about how to take it to the next level.

Taking the Loxodrome for a Spin:

Not soon after I put together my mockup, I realized it would be much better if the Loxodrome could turn on its vertical axis, therefore projecting a rotating pattern of shadows on the wall.

This presented a challenge, as the Loxodrome could no longer be attached directly to the board, nor could the LED be attached to a spiral arm of the Loxodrome. For it to rotate, the Loxodrome would need to turn freely, with the LED and associated wiring suspended independently inside the rotating shell.

I modified the Loxodrome in OpenSCAD to add a 18 mm diameter opening on the bottom and a small cap at the top that would allow the Loxodrome to balance and rotate freely on the tip of a pencil.

Having found a way to make it spin, I decided to make my next prototype into a free standing table lamp.

My original lamp consisted of a tapered base with a bent piece of copper tubing on top. The copper tube would support a LED, as well as provide a tip for the Loxodrome to rest and spin around on. I replaced the dim SMD LED with a 1W white LED star for improved brightness.

Trying to Make it Turn on its Own Made my Head Spin:

I now had a freely spinning Loxodrome and a way to mount the LED inside it. However, the Achilles' heel of this design was the fact that the Loxodrome was hanging loosely on the pivot point. Making it turn on its own proved to be challenging.

At first, I mounted small ring of magnets on the bottom of the Loxodrome near the opening and tried to use a hand-wound solenoid to make the Loxodrome to turn. This merely caused it to stutter and vibrate.

Shelving that idea, I replaced the magnets and solenoid with a toothed ring (red) that would mesh with a smaller gear. The smaller gear (green) was attached to a shaft leading to a TYD-50 AC synchronous motor I hid in the base. Unfortunately, because the Loxodrome was hanging freely from the top, it could swing away from the teeth of the gear, often skipping a tooth rather than turning. Sometimes, because of roughness in the printed parts, it would freeze up momentarily, only to jerk loose, leading to a very jumpy, unsatisfying motion. Although it showed that using gears had potential, at that point it was far from an effective solution.

For a while, I put the project aside until further inspiration came to me.

Improving the Design, With Better CAD Tools:

My initial failures taught me several lessons. Hanging the Loxodrome on a pivot point from the top made...

Files

Top Assembly.stl

The outer shell of the gearbox, that slides into the top of the LampBody.

Standard Tesselated Geometry - 171.47 kB - 02/04/2019 at 03:02

Download

LoxodromeMountingAdapter.stl

The part is the top half of the GearCoreCenter and provides a snap-fit to the Loxodrome.

Standard Tesselated Geometry - 165.41 kB - 02/04/2019 at 03:02

Download

GearCoreCenter.stl

This part holds the 608 bearing and has the larger 12 toothed gear on the outside. Once the bearing is placed inside, the LoxodromeMountingAdapter is glued into place.

Standard Tesselated Geometry - 189.93 kB - 02/04/2019 at 03:02

Download

DriveGear.stl

The small six-toothed gear that rotates the GearCoreCenter.

Standard Tesselated Geometry - 45.59 kB - 02/04/2019 at 03:01

Download

Base Plate.stl

The bottom base piece that holds the motor and sits under the BasePlate.

Standard Tesselated Geometry - 132.70 kB - 02/04/2019 at 03:01

Download

Components

1 × TYD-50 Synchronous Motor Either AC or DC, at whatever RPM you desire.

1 × 608 Roller Skate Bearing

1 × DuPont 4-pin Female Connector and Pins

1 × DuPont 4-pin Male Connector and Pins

1 × 1W or 3W LED stars, mono or RGB

Discussions

Dean Segovis wrote 02/11/2019 at 02:45

Very well planned and executed. In my opinion this is a project in the running for a win.

Are you sure? yes | no

marciot wrote 02/12/2019 at 02:39

Thank you for the kind words!

Are you sure? yes | no

Dan Maloney wrote 02/04/2019 at 21:15

That's quite hypnotic. I like it!

Are you sure? yes | no

marciot wrote 02/12/2019 at 02:39

Glad you like it!

Are you sure? yes | no

Making a Coaxial Gearbox for a Rotating Lamp

Description

Details

The Inspiration:

Taking the Loxodrome for a Spin:

Trying to Make it Turn on its Own Made my Head Spin:

Improving the Design, With Better CAD Tools: