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

[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.

[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.

[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.

[Aarav G]

That's cool and interesting

[rschoenm]

Thanks!

[we4sel]

That's awesome. I remember seeing a small steam/air engine built on this principle.

[rschoenm]

Thanks!

[MarkH342]

Nice presentation. Thanks. I'm wondering if one could be made with 3 hubs and the rods bent into a Z. Would be challenging to bend the rods with the middle hub in place. Will I attempt it? ?

[rschoenm]

I think that could work. You could build a bending jig from a board and nails. Or you could skip the middle barrel.

[Makerneer]

Cool! That gif image was a great addition and really helped show how it worked, nice instructable!

[rschoenm]

Thanks! It is a neat little toy, easy to make. I was hoping the animated gif would actually show as an animated title image.