The main challenge was balancing tolerance, durability, and smooth rotation at this scale. We went through multiple prototypes dealing with ball size, raceway depth, and surface finishing before getting consistent 20s spins.
Would love feedback from anyone who’s worked on ultra-compact mechanical systems or precision manufacturing.
If you’re curious, the project is live on Kickstarter: https://www.kickstarter.com/projects/cooloze/spinitytm-beari...
How do you handle water? Can you wash the dish it? Swimming pool? Cooking bread (flour is nasty)? Oil? Direct sunlight for 4 hours?
> We went through multiple prototypes dealing with ball size, raceway depth, and surface finishing before getting consistent 20s spins.
So you have some photos or data collected during these attempts? They may be an interesting technical post. (My lab notebook was a disaster, so I don't expect a very systematic report.)
What are the materials? For some small device we had to use bronce "nuts" over aluminum threads, because apparently aluminium over aluminium get stuck too easily.)
That said, let me try to respond to your very insightful and constructive questions.
At this scale, water tends to replace the air film and introduce surface tension and capillary forces between the ball and raceway. That adds drag rather than reducing friction, especially when combined with fine particles or residue. So your concern is absolutely valid.
Our honest answer is that we’re constantly balancing real-world usability against technical constraints. We did consider applying hydrophobic coatings to the raceway, but in practice those coatings wear off very quickly at the actual contact points inside the bearing, which makes them ineffective over time.
Instead, we focused on making the internal structural components corrosion-resistant and water-tolerant, and designed the system so that, rather than trying to completely block water from entering, it can be easily cleaned and quickly dried.
The “sticky” or sluggish feel water introduces in a micro-bearing is temporary. In practice, you can restore normal performance by blowing it dry with a hair dryer in about a minute.
The analogy we often use is washing your hair: if you’re not in a hurry, it will air-dry on its own. If you need to go to sleep right away, you use a hair dryer. In either case, the impact on the overall experience is minimal.
By the way give me a bit of time — I promise I’ll put together a more systematic report with photos and data from our testing. There’s no real secret sauce here, just a lot of trial, error, and tiny tolerances.
Usually more technical post get better traction, so if you have some interesting side quest building the device, it may be better. But it must be interesting. What is your favorite anecdote about building the device to tell to your fiends over a beer? (Bonus points if it's a technical friend.)
Some ideas from https://www.youtube.com/@Clickspring . But the guy is extremely good so it's a very high bar, it's not necessary to be as good as this guy to post here. (Anyway, I prefer a blog post with photos than a video.)
If you have two accounts, you can ask hn@ycombinator.com about how to merge them, or perhaps they will tell you to just use one of them and never use the other again.
What we’ve been more cautious about sharing at this stage are the manufacturing and process details, since the project is still in its early phase. I understand that this can sometimes come across as being less transparent, and that’s a fair concern.
One example that genuinely surprised us during testing was that laser engraving caused slight deformation, which affected how smoothly the ring could spin. Because of that, we decided to move to a different engraving method to preserve performance.
Either way, I truly appreciate the feedback and suggestions. Until I’ve properly edited my “beer story,” I’ll take a step back from posting here for now.
Thanks again for taking the time to engage and share your perspective.
It's not necessary to tell all the details, everyone has a secret sauce. Also some details are boring. Other details change too much.
> One example that genuinely surprised us during testing was that laser engraving caused slight deformation, which affected how smoothly the ring could spin. Because of that, we decided to move to a different engraving method to preserve performance.
That's very interesting! Ensure to add it. Can you rectify the ring after the laser engraving? Is the engraving customized and it is the last step?
We originally planned to use electro-etching to put the Spinity logo on every ring by default. In hindsight, that wasn’t a great idea for a brand that’s just being born.
One user even joked that when the ring spins, “spinity” sometimes reads like “stupid” — which was a very fair reminder that branding should earn its place, not demand it.
So we took the community’s advice and removed the default logo entirely. The outer surface is now intentionally left blank, which also aligns better with our minimalist design philosophy. Engraving is only done when someone explicitly requests customization.
That’s why, process-wise, engraving is always the very last step. If something goes wrong there, the part becomes scrap — which is painful, but it’s the only way we’ve found to preserve predictable spin performance in such a thin system.
In the public demo images, we also deliberately hide what we consider our main structural innovation: the internal ball-loading port on the inner ring. The opening is just slightly larger than the bearing balls (around 1.3 mm), and that detail is what allows us to compress the total ring thickness down to about 2 mm.
One of my favorite moments was a user telling us they had tried to 3D-print a bearing ring themselves and couldn’t get it to work — which makes sense. At this scale, additive manufacturing just doesn’t hit the tolerances needed for consistent motion.
Thanks for pushing me to be more open. I’m still learning how to balance protecting early-stage process details with showing genuine respect for a technically-minded community like HN.
ahazred8ta•1w ago
We don't care.
Stop spamming.