Twisty Toy

I designed this simple twisty toy based on an epicyclic bar angular transmission. It's a cool little fidget toy that looks like it shouldn't turn. Works well as a stress reliever!

You can make this toy with either a wood lathe, or a 3d printer, or a laser cutter.

Supplies

Hardwood like maple and cherry

1/8" brass rod

3/8" dowel

CA glue, wood glue

Step 1: Easy Build With 3D Printer

If you have access to a 3d printer then the easy version of the Twisty Toy is 3d printed. The files are included. 3d print the two barrels and clean/drill the holes with a 9/64" bit so that the brass rods insert and turn easily. Cut seven 5 inch long 1/8" diameter brass rod pieces and bend them 90 degrees in the middle. Then insert all of them into one of the barrels first; and one by one into the second barrel. Nice little puzzle right there! To make the toy permanent and prevent the barrels from slipping off you can use CA-glue to glue a couple of short stops onto the two center brass rods. That's it. You are ready to fidget during your next Zoom meetings!

Step 2: Build With Laser Cutter

The prettier version uses wood barrels. I laser-cut a number of 3 to 5 mm thick cherry and maple disks (file attached) and then stacked and glued them into two 1-inch tall barrels. While gluing align the disks with two or three brass rods and check that the stack is straight up - not skewed. When the glue has dried, clean and redrill the 7 holes with a 9/64" drill bit so that the 1/8" brass rods turn easily. Make the brass angles as described in the previous step. Then trim, sand, and polish the outside of the barrels on a lathe (or drill press). I also made some spacers and end stops from a 3/8" maple dowel to CA-glue onto the center brass rods.

Step 3: Other Ways to Make the Twisty Toy

Without a laser cutter or 3d printer you can make the barrels on a lathe and drill the holes with your drill press. It should be obvious how to do this. The spacers and stops can be made from a 3/8" dowel.

For variety you can make bigger versions of the toy, or versions with fewer brass rods.

Cool animations of the underlying mechanical linkage are here:

Angular Transmission

Epicyclic Bar Angular Transmission

(Edit 2/21/2021) I just learned that this is also called a Hobson’s Joint, and I found this cool video of a Lego build:

Hobson’s Joint

Anyways, I'm still amazed that the toy actually turns! Enjoy!

Comments

[a41capt]

If you or your readers want to take this to the next level, this could be a consideration! I’ve seen a couple examples of it at steam engine shows and they’re always a crowd favorite.

http://www.john-tom.com/MyPlans/Steam%20Engines/ElbowEngine.pdf

[rschoenm]

Thanks for the article, very interesting. It far exceeds my capabilities and tools to build anything like that; but I sure would like to see an engine like that in action. The wooden 'Twisty Toy' version from my Instructable has also been quite popular as a little gift.

[a41capt]

Ask and you shall receive:
https://youtu.be/ApbDfmX6O10
Thanks for an excellent article on a fun toy!!!

John

[rschoenm]

Thanks! Happy New Year!

[Componenx]

The original steam engine that uses this principle is deceptively difficult to make! 6 "cylinders", but only 5 moving parts. I built one about 5 years ago as I was teaching myself machining, but never got it to turn completely (only about 77-80%). The holes just weren't precise enough. 10 cylinders might actually be easier. Glad to see a new use for this concept!

[rschoenm]

Thanks, its a fun little toy.

[fred_dot_u]

From the seventies and also a bit later, an engine appeared in the world, known as a rotary vee. Pretty revolutionary in design, the "pistons" were rods nearly identical to the rods in this gadget.
https://eatsleepride.com/c/3914/the_rotary_vee_ima...

The page above also contains links to a series of YouTube videos, six parts of ten minutes of seventies quality video tape. From what I recall of my fascination with this engine, the designer lacked computing power to optimize the design. That was decades ago, yet nothing has appeared in this century.

This gadget build makes it easy to understand the workings of the engine, as the rod ends have piston-like movement as the cylinders are rotated.

Nicely done.

[dresch]

I remember a construction article in Popular Mechanics in the late 50s or early 60s for a model steam engine with the same mechanism. And here it is, good old YouTube:
Just like I remember it... Wow.

[rschoenm]

Thanks! Very cool!

[rschoenm]

That is very interesting. We should build one of these engines. Oh well, I'm more of a woodworker🙂
Thanks for the interesting article and video links.

[dresch]

Here is an interesting video showing how these models work:
Thanks for the Instructable!

[rschoenm]

Thanks, very cool video!

[Germanprof]

Thanks, this was fun!

[rschoenm]

Wunderbar, sehr schön. Es freut mich dass Ihnen das Spass macht! Danke sehr!

[wschleter]

Nice idea! Thanks for sharing. I made one by 3D printing everything and posted it in the "I made it" section. I will also post the stl files to Thingiverse and reference this instructable.

[rschoenm]

Thanks, that looks pretty nice. Please keep us posted on your more colorful next version. I have also put the Twisty Toy on Thingiverse: https://www.thingiverse.com/thing:4758138
Thanks again!

[prhoads]

Can this be made with a 1" dowell and still use 1/8 inch brass rods

[rschoenm]

I don't see why not. Or consider making a couple of 1" square blocks or hexagonal blocks. You can make them from plain wood or layered like shown. I'm working on that right now, see pictures.

[Aarav G]

That's cool and interesting

[rschoenm]

Thanks!