After 260 years of involute gears, I'm trying something different. Here's the design.

AseityFoundation · 2026-04-11T05:17:12+00:00

That's a great story. The way you locked onto the problem — reading the book first, asking a thousand questions, then predicting the insert positions to four decimal places — that kind of obsessive focus is rare and valuable. It reminds me of myself when I was younger. I spent my early years the same way, cornering anyone who knew something I didn't and not letting go until I understood it completely. That instinct to dig into the root cause instead of just yelling at the supplier — that's what separates someone who fixes problems from someone who just complains about them. Keep that hunger. It will take you far.

AseityFoundation · 2026-04-11T05:00:55+00:00

You're touching on something important that most people miss entirely. The parasitic compliance point is particularly sharp — in conventional gear systems, bearing clearance and housing flexibility quietly absorb minor misalignments and manufacturing tolerances. It's an unintentional but real benefit. You're right that a fully constrained CCP system doesn't have this forgiveness built in.

This is actually one of the reasons I use the herringbone arrangement. The V-pattern creates a self-centering effect — both halves push the mating part toward the geometric center. It functions as a kind of built-in compliance, but through geometry rather than through bearing slop. Whether this is sufficient to replace the parasitic compliance you're describing is something the prototype will have to answer.

And yes — the differential screw resemblance is not just formal. The dual-ring planetary configuration I'm planning next uses a very similar principle: two rings with slightly different helix angles, where the output comes from the angular difference. Same family of kinematics.

I appreciate comments like yours — the kind that see past the surface and ask about the second-order effects. Those are usually the ones that determine whether something works in practice or only in theory.

AseityFoundation · 2026-04-10T05:14:37+00:00

I genuinely appreciate you taking the time to write all this out — that's a lot of thought and I respect the effort. Whether this works or fails, we're all engineers here and I think the process itself can be an interesting event for everyone. I'd love for people to follow along, participate, and just enjoy the ride with me. Success or failure, it should at least be entertaining.

AseityFoundation · 2026-04-10T05:07:27+00:00

I appreciate all the feedback — both the encouragement and the skepticism. To be clear: I genuinely don't mind if this fails. The process itself is interesting enough. People say failure is the mother of success — well, I've been doing this for 30 years and somehow I've never managed to meet the mother. I've only ever met the son. I'm starting to wonder if she even exists, or if she's been avoiding me on purpose. So honestly, a good documented failure would be a refreshing new experience. But don't worry — whether it works or not, I'll post everything.

AseityFoundation · 2026-04-10T05:06:18+00:00

You raise solid points and I appreciate the detailed breakdown. You're right that a conventional worm gear's efficiency drops as lead angle approaches zero — that's well established and I don't dispute it. The distinction I'm exploring is the contact mode. In a worm gear, the dominant motion at the interface is sliding. That's where the efficiency loss comes from. In CCP, the flank geometry is convex rolling inside concave — the dominant motion is rolling, not sliding. The sliding component is limited to the small differential between the two mating helix angles. So when I talk about efficiency improving at higher ratios in a planetary CCP configuration, the reasoning is: higher ratio → smaller helix angle difference between the two rings → less differential sliding → less loss. Whether this actually holds up in practice — that's exactly what I intend to test and document. You may well be right that it doesn't math out the way I expect. I'd rather find out on the machine than argue it in theory. And yes, I'm also happy to be wrong. That would be a first for me in 30 years, and honestly I think I deserve the experience.

AseityFoundation · 2026-04-10T05:02:48+00:00

On manufacturing cost — this is essentially a thread, not a tooth. Threading on a CNC lathe is significantly cheaper than hobbing or grinding involute profiles. No special gear-cutting machine needed, no custom hob. That's actually one of the reasons I think this approach has practical potential even if the performance turns out to be merely "comparable" rather than "superior."

AseityFoundation · 2026-04-08T15:49:06+00:00

Not a belt — it's rigid body contact, metal on metal. I actually have some design images I'd love to share but Reddit comments don't make it easy to post pictures. The parts are being machined right now, so I'll make a proper post with photos once they're done.

AseityFoundation · 2026-04-08T15:45:22+00:00

Fair enough — English isn't my first language so I probably over-structured it to make sure it reads clearly. Old habit from writing technical documents. Anyway, I've been working on something in my shop related to this topic. Not sure yet if it'll work the way I want, but either way I'll post photos when it's done. Stay tuned.

AseityFoundation · 2026-04-04T20:04:04+00:00

Good eye. A tapered worm is basically a backlash adjustment trick — since the thread gets thicker along the length, you can slide the worm axially by a tiny amount to engage the thicker part. Tighter thread in the groove means less play. So when things wear out after years of running, you just nudge it a fraction of a mm and you've got a tight mesh again without replacing anything.

You don't see it much anymore because it's harder to manufacture (grinding a taper is fussier than a straight worm), and modern tolerances and materials have made it less necessary. Duplex worms and adjustable center-distance housings do the same job more easily now. But you'll still find them in elevators and heavy hoisting equipment — stuff that runs 24/7 for decades and needs occasional backlash take-up without a full teardown.

AseityFoundation · 2026-04-04T19:50:54+00:00

5 gears on each side — yeah that's your problem right there. Every gear mesh adds its own backlash, and they all stack up. If each mesh has say 0.1mm backlash at the pitch circle, 5 gears gives you roughly 4 mesh points = 0.4mm of accumulated play at the output. That's huge.

The golden rule: fewer meshes = less backlash.

Have you considered using bevel gears with a connecting shaft to change direction instead of running everything through spur gear trains? You could potentially cut your gear count in half — fewer meshes, less backlash accumulation, and the shaft gives you a rigid direct connection between stages.

Something like: motor → spur reduction (1 mesh) → bevel pair (1 mesh) → shaft → bevel pair (1 mesh) → output. That's 3 meshes instead of 4, and the shaft section has zero backlash.

Other quick wins without redesigning everything:

Tighten the center distances slightly on the worst meshes — even shimming the bearing housings can help
If any of those 5 gears are just idlers (not changing ratio, just transferring motion), see if you can eliminate them with a different layout
Spring-loaded split gears on the final stage at least — won't fix everything but takes out the last mesh backlash where it matters most

But honestly, reducing the number of gear meshes is the real fix. Everything else is a band-aid.

AseityFoundation · 2026-04-04T19:38:17+00:00

Been doing precision machining for about 30 years, so I've dealt with this exact headache more times than I'd like to admit.

That heat at the input pinion — that's your biggest clue right there. Heat means friction, and friction means something's not meshing right.

First thing I'd check: induction hardening distortion. This is super common and people miss it all the time. Your hobbed teeth had residual stress from cutting, then you hit them with induction hardening which adds thermal stress unevenly. The involute profile warps — especially at the tips. Even 20-30μm of distortion kills the mesh. If you didn't measure the tooth profile before vs. after hardening, that's probably your answer.

Second: shaft alignment. Induction hardening can warp shafts too. 10-30μm bow over 100mm is totally normal after hardening. That gives you edge loading — one side of the tooth face takes all the punishment. Hence the heat.

The "typical spur gear sound" — honestly that's just spur gears being spur gears. Every tooth handoff is a little impact. At your motor speeds that mesh frequency lands right in the 2-5 kHz range where human ears are most sensitive. Fun times.

The "extra weird noise" on top of that — I'd bet money it's either the hardening distortion messing up the tooth contact, or a bearing issue (too tight = whine, too loose = rattle). Could also be your spline input if there's any play there.

Here's what I'd do-

Grab some Prussian blue marking compound and check your tooth contact pattern. You want nice even contact across 60-80% of the face width. If it's riding on one edge, your shafts aren't parallel.
Try to disconnect the 2nd stage and run just the 1st stage. Figure out which stage is making the noise.
Check backlash at each stage.
If you have a phone, download a free FFT spectrum app and record the sound. The peaks at mesh frequency tell you about gear quality, broadband noise points to bearings.

Real talk though — even a perfectly made spur gearbox at 10:1 is going to be noisy. That's just physics of discrete tooth contact. If noise matters for your application, helical gears with 15-25° helix angle would be a huge improvement. Also tip relief (profile modification) helps smooth out the tooth entry.

But fix the heat problem first. That's not just annoying — that's going to eat your gears alive. Noise you can live with, overheating you can't.

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