The Bathysphere Yoyo Design

The Bathysphere was released a bit ago now, but I wanted to share some of the work that went into its design and development. Being a collaboration design, between myself and TRT, the process gets drawn out a bit, and this project actually started in 2022. Let’s look back!

I’ve known Bruce & Jess of Turner Return Tops for quite a little while now, at least as far as my yoyo work is concerned. They were a great help with the Mk1 Contact 2nd run, and they had since started their own little yoyo company. It made sense to collaborate on something. One day, an idea popped into my head.

2:28 PM Mark: here's an idea for our 2025 collab:
double rim
Yoyo design: Sometimes it’s easy!

It turned out that most of the time we spent working on this yoyo was to refine the small details. These matter a lot, of course – but our job was made easier by having a straightforward goal to reach.

The play and feel of a round yoyo like this depend a lot on the specifics of weight, size, and rim – there are a lot of models to compare against, so it’s important to have something distinct, either via reducing the yoyo to its bare essentials, or by embellishing rare features to make them stick out. The Bathysphere already had some constraints on the design based on the core idea, and much of the work was spent refining the amount of mass and spin power.

After a week of back-and-forth CAD files, we had this:

Early draft with a straight section near the bearing

The initial draft lacked some of the classic shape of the production Bathysphere, starting out with more of an open, straight to round configuration, though this was compressed and shmooved into its current shape. The weight was gradually reduced, settling on a target weight of just under 64g with One Drop’s flat cap side effects installed.


Prototype draft with a rounder shape and a shmoove groove

Naming this yoyo was a bit of a struggle, but here’s some free ideas that we discarded. Perhaps you could recycle them. Please, name your yoyo the Dust Buster. We need that in this community.

  • The Tectonic Collision
  • Flotsam & Jetsam
  • Dust Buster

Bathysphere came up and it seemed appropriate since they are round. It matched TRT’s watery theme

This isn’t a yoyo, but it does go up and down
Source: Wildlife Conservation Society Archives

From here we mocked out some color ideas, then ordered prototypes. Bruce mailed some Side Effects to the machine shop, and they got to work!


It turned out great, but needed some small tweaks for production. It ended up getting a little bit more rim weight (prototypes felt light!) but not much else changed.


How do you package a submersible? Clearly a nautical theme was the way to go. I was happy with the recent Mk1 Unicorn packaging, so I sketched up a tube in FreeCAD:

At Jess’s suggestion, I added a window on top so we could see the colorway without opening the package.

I brought the files into blender so I could texture map it and imagine how the final yoyo would look.

Many, many revisions later we had something more colorful, then scrapped it, then started again with what ended up being the final design. We grabbed bits and pieces of nautical lore (hull markings, rivets, an octopus) and stuck it together into the fantabulous tube print.

Pretty close to final! Note the side effect engraving, a separate mini-project that’s part of the whole

Meanwhile, the side effects arrived!

Very good work by One Drop

The side effects were needed by the machine shop to assemble the Bathysphere, so these were mailed along.

To recap, making the Bathysphere required a lot of separate little projects that all come together in the end. Not all of these are documented here, of course:

  • Concept
  • Technical drawing
  • Naming things (very difficult)
  • Ordering and forwarding parts
  • Getting quotes from suppliers
  • Package design
  • Sticker design
  • POG design
  • Engraving design
  • Paying invoices
  • Testing / Packaging
  • Contacting Retailers

Wait, POGs?

The art features Bruce and Mark, inside of the famous round deep-sea diving vessel.

Don’t forget to keep yours so you can battle your POG opponents at your next yoyo meetup!

Bathysphere – Blue Ringed Octopus

A lovely project! Thank you TRT!

Release and Reception

Tsukasa Takatsu posted a very nice review of the Bathysphere.

The Mk1 x TRT Bathysphere sold out in about a day. How about that? We’re working on a 2nd run, with more fun colors to enjoy. Thank you all for the support! See you soon!