"Spiro" - a 5' Diameter, Wall Mounted Spirograph

Love spirograph, but want to start making wall sized poster art instead of tiny little pictures? Look no further - this is a 5' diameter version which is built to hang on a wall. In addition to the larger diameter, this spirograph is built onto a sliding track and includes a butcher paper spooling mechanism so you can readily create new writing surfaces to enjoy!

This concept of the wall mounted Spirograph was conceived by Pinterest, while the design, engineering, and installation details were left to us. The completed piece can be enjoyed at their San Francisco headquarters!

Step 1: Get a Plan, Build You Model

When projects get complex, it is really handy to build a model. Models tell you if pieces are going to fit, if parts have enough clearance to move, and give you a very good idea of weight and balance for mounting requirements. Additionally, this puts you one step closer to getting CNC paths made.

Every projects which goes through our shop has a model made of it. Our preferred modeling package is Autodesk Inventor since it has some advanced functionality like rendering, weights, automatic fastener and gear generation, and simple import of McMaster Carr catalog parts!

It was desired to keep the overall design clean - minimizing exposed fasteners. Additionally, we wanted to keep focus on the artwork, rather than the piece, so we decided to design with thick acrylic inlays where possible rather than opaque materials like metal and wood. In order to simplify installation requirements and to lower the piece weight, all other components were designed from aluminum.

Some easier components are just faster to draw by hand, so although we do love our modeling tools, don't be afraid to bust out the old pad and paper when you need it!

Step 2: Get Your CNC Parts Made

Working from our inventor model, it is a simple jump to get all of our components made by various CNC tools.

The main gear, spirograph gear, and all of our acrylic inlay work had to not only have very smooth edges to allow for tight tolerances for glue ups, but were also quite large (the main gear is 5' in diameter). Therefore, CNC milling was off the table, waterjet was not selected because it is solely a 2D process (preventing the use of grooves in the design), but also because it produces a rough, sandblasted edge. Neal's CNC has a very high torque 5' x 10' bed CNC router that was able to route a 1/2" 6061 aluminum plate for the main drive components, and could easily rip through acrylic for the inlaid components.

Many of the active drive components required precision thickness control and sizing to make sure the parts would move smoothly, thus they were sent for CNC milling at Protolabs.

The flat patterns for the side paper spools were waterjet from 1/4" 6061 aluminum plate for welding in our shop.

Step 3: Build the Wheel Carriage Arm

Of particular difficulty was building the aluminum frame of the carriage wheel arm. This needed to be made from thick enough aluminum to support the weight of the spirograph wheel, and also adopt a rather complex shape to match the circular look of the project.

Although technologies like spinning could accomodate the arch shaped wedge on the outer part of the arm, these technologies would not work for the inner conical section. Instead, this piece was made from a routed center section, and spliced together from 4 other milled sections. 4 sections had to be used in order to meet the mill bed requirements at our CNC milling contractor. The aluminum pieces were then welded and blended in house to make this part look like a single, precision cast piece of aluminum.

Step 4: Test Your Work...

For something with a bunch of moving parts, it is important to make sure the piece was going to work as expected when installed. As such, we built a test rig in our shop to assemble the piece, and try it out.

Of particular interest was testing the paper path - paper has to be kept in tension in order to prevent it from snagging behind the wheel - much like what you see with old skool news paper printing presses. To accomplish this for Spiro, we made a set of aluminum bars to hold the paper against the wall, then forced the paper up and over a piece of 3/4" melamine faced particle board. This tortuous path keeps tension on the paper over the 10' span between rollers.

Step 5: ...then Modify the Design

Unfortunately, the initial design was not as smooth as we would have hoped! One of the main difficulties in making a spriograph that mounts on a wall is that gravity is your enemy. The mass produced spirograph works because gravity holds the drive wheel against a piece of paper, and no firm mechanical linkage is required to the outside guide gear.

We tried to solve this problem by using an additional set of drive wheels between the guide gear and drawing gear. Though this was able to hold the outer wheel firmly in place, this produced quite a bit of friction and noise in the final design. Instead of this concept, we decided to build a massive 5' diameter bearing out of industrial roller wheels which encompassed the entire perimeter of the guide gear, thus eliminating the need for the smaller drive wheels in the original design.

Step 6: Install Onsite

With the new, well tested design we were ready to reinstall the piece onsite!

For safety, we also added in 3x 10 pound stainless steel counterwrights milled to match the curve of the piece. This way, when the drive wheel is released, the piece does not fall under its own weight. Using this technique, anyone can easily lift and move the 50 pound wheel with a light touch!

Step 7: ...and Write on Your Walls :)

To use the spirograph, custom made pen tubes are used with a spring firmly mounted in the back of them. This keeps the pens pressed against the paper / melamine backed writing surface even though the wheel may not ride perfectly flush against the wall!

Now its time to go play :).