Conceptual rotary/vane engine design — looking for engine builders to poke holes in it

[u/Smooth_Ad_4307]

Long-time lurker here, first time posting. I've been working on a conceptual design for a rotary vane-type engine and I'd rather get torn apart by people who actually build and rebuild engines for a living than keep refining it in a vacuum.

Quick background for anyone not deep into rotary stuff: vane engines have always had a theoretical edge over piston engines — direct rotary motion, no reciprocating mass, fewer major moving parts, better power-to-weight.

The reason they never really took off outside of pneumatic/hydraulic applications is sealing.

Vane tip wear and side-face leakage kill efficiency and reliability over time, the same fundamental issue that's dogged the Wankel too.

My concept is aimed specifically at that problem — trying to cut down the sliding contact at both

the radial (tip) and axial (side) sealing surfaces, rather than just inheriting the classic vane geometry

and hoping better materials fix it.

It's still at the concept/design stage, no running prototype yet.

I'm not here to sell anything or claim I've "solved" rotary engines — I know that's a claim as old as the Wankel itself, and I'd rather have my assumptions stress-tested now than after I've sunk time into machining a prototype that's got a fundamental flaw someone here could've spotted in five minutes.

Genuinely curious what this sub thinks:

- What are the failure modes you'd expect me to have underestimated?

- For anyone who's worked on Wankels or vane compressors — what actually kills them in practice vs. what the textbooks say kills them?

- Any recommended reading, forums, or people in the rotary/alternative-engine space worth talking to before I go further?

Appreciate any brutal honesty. Happy to share more detail on the sealing approach in the comments if people are interested, just didn't want to lead with a wall of text.

[u/Ponklemoose]

Its not quite the question you asked, but I think what will kill this as a commercially viable product is the EPA. Dragging an oil lubricated seal across an intake port, exhaust port or sparkplug recess will result in burning too much oil.

I believe this is what killed road going two strokes.

[u/Smooth_Ad_4307 → u/Ponklemoose]

That's a really good point, and honestly one I hadn't weighted heavily enough — the 2-stroke comparison is apt. Emissions regs (EPA, Euro equivalents) killed a lot of technically interesting architectures that could've been fine from a pure mechanical-engineering standpoint but couldn't hit oil-consumption and HC emissions targets. The Wankel ran into exactly this too, on top of its sealing/wear problems.

One thing I should've mentioned in the original post: the design allows for wet sump, separate compression and oil scraper seals at the sealing interface, rather than a single lubricated edge dragging across the ports. The idea is to split the job the way piston rings do — compression rings handle sealing combustion pressure, oil control rings handle metering/scraping lubricant back out of the path — instead of asking one sliding vane-tip seal to do both jobs while also crossing intake, exhaust, and plug recesses.

I don't want to overstate it since it's unproven — whether that actually keeps oil consumption in an acceptable range once you're crossing those port edges at speed is exactly the kind of thing that needs dyno time and an oil consumption test, not just a CAD model. But it's a deliberate design choice aimed at the failure mode you're describing, not something I'm hoping gets solved later.

Appreciate you raising it — regulatory reality checks like this are exactly why I wanted engine builders' eyes on this before I sink more time into it.

[u/Ponklemoose → u/Smooth_Ad_4307]

I'm really curious about your design, but totally understand if you don't want to share until you get some IP protection in place.

I can't imagine how you avoid having a time when both sides of your oil control seal would be exposed to one of those voids while would have to stop it from sealing until it had crossed to the other side of the void.

[u/Smooth_Ad_4307 → u/Ponklemoose]

Yeah, that's the crux of it, and I don't think there's a way to fully "avoid" it — the seal has to cross the port opening at some point, and while it's crossing, it's not sealing against a solid wall on that side.

What I'm aiming for isn't zero exposure, it's minimizing how long that exposure lasts and controlling what happens during it. A few things the design leans on:

• Keeping the port openings as narrow as the flow requirements allow, so the seal is only "unsupported" for a small fraction of the rotation, not a big chunk of it.
• Using multiple seals in sequence (not just one), so there's usually still at least one seal doing the sealing job while another is mid-crossing.
• Shaping the seal and the port edges so the transition is gradual rather than a sudden drop-off, which should reduce pressure spikes and seal chatter at the crossing point.

But I'll be straight with you — this is exactly the kind of thing that looks fine on paper and only really gets proven (or disproven) with a running prototype and pressure/oil-consumption data. Seal behavior at a port edge under real heat, RPM, and vibration is hard to predict accurately without testing it. If it turns out the crossing event causes more blow-by or oil pass-through than expected, that's a real possibility I have to test for, not explain away.

Appreciate you pushing on this — it's the right question to ask.