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I’m researching into piston engine powered, propeller driven aircraft.

However, I’m really struggling to find manufacturers that make "piston engines".

For example, I came across Rotron, but it seems like they only make Rotary engines.

Are rotary engines the same as piston engines? If not, what manufacturers build piston engines for prop planes?

Michael Hall
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Engine lover
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    Welcome to the site. Your question isn't very clear, and seems to be many questions in one. I've never heard of a rotar engine, do you mean a Wankel Rotary engine? If so, I suggest you do some research before you ask a question, and make the question applicable to aviation. You should also do research on aviation piston engines, there's a wealth of information on the web. Once you have a question which is clear and focused you can edit this question or open an new one. – GdD Mar 27 '22 at 10:41
  • @Engine lover, I believe that you ask about Rotax 503 engine on ultra lightweight aircraft design model by Quad City Challenger – George Geo Mar 27 '22 at 12:27
  • I edited your question so it at least makes sense. Please let me know if I captured your intended meaning correctly. – Michael Hall Mar 27 '22 at 23:14
  • related: https://aviation.stackexchange.com/questions/1256/what-are-the-differences-between-lycoming-and-continental-engine-designs – Michael Hall Apr 02 '22 at 01:07

4 Answers4

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You are describing a Wankel type engine, which is not a piston engine, but is a type of 4 stroke "otto cycle" engine.

They have been around since forever (the 60s), and would seem to be ideal replacement for aircraft piston engines, having the simplicity and power to weight approaching that of a turbine. You would think.

But if you read up on the Wankel's history with Mazda, and the numerous attempts to stick them in airplanes, you find they are just riddled with frustrating limitations:

  • High fuel consumption, like 2 strokes or worse (Mazda RX7s and 8s were notorious for lousy fuel economy).
  • Low torque production due to the very low "leverage" the combustion chamber is able to apply to the eccentric cam of the crankshaft. They are equivalent to an extremely short stroke piston engine.
  • Because of the low torque, they have to spin very fast to make any power, requiring very large gear reductions, although they don't suffer from the torsional resonance problems of gear reduced piston engines, because of the way the power strokes of multi-rotor Wankels overlap.
  • Apex seal wear, which Mazda finally dealt with by feeding oil directly to the Apex seals (equivalent to piston rings in a piston engine), which means they consume oil like 2 strokes.

There have been many attempts to make aircraft engines out of multi-rotor Mazdas, and they have flown, but eventually were abandoned due to technical problems (not to mention ear splitting noise levels - I saw an RX7 powered Van's RV-4 at Oshkosh in the 90s - wow what a racket it made, even with a muffler).

Roton is just another case of someone stumbling onto the configuration and making a go at getting around the engine's limitations. The configuration's simplicity and potential reliability is just so enticing.

However, there IS something new under the sun, with a new rotary design that just may be the answer.

As for propellers, oodles of propellers here.

John K
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    I love rotary engines, but sad to say, everything you wrote here is correct. They're an elegant and largely impractical power plant, with more in common with a multi-cylinder 2-stroke than with a 4-stroke piston engine. They do have two major advantages: they run well on very low octane (the 1976 Cosmo 13B I owned called for 67 octane) and they're very light for liquid cooled engines (very competitive for power-to-weight even with a 2.5:1 gear or belt reduction system). Fuel and oil consumption and emissions are what killed them, though. – Zeiss Ikon Apr 01 '22 at 15:57
  • When I was 16 an older brother's chum came to our house one day in his new '71 RX1. It was a single rotor IIRC. We were awestruck by the weird sound it made and it was reasonably quick by the standards of the day. My high school math teacher in the early-mid 70s had an RX 3. It was pretty fast. But I dimly remember the engine was toast pretty quickly and he traded it in after only a couple of years. – John K Apr 01 '22 at 18:16
  • The RX-1 was a 2-rotor 10A (1000 cc). Mazda never sold a single rotor, though NSU, Suzuki, and Sachs did (not to mention the O.S. .30 Wankel model engine). My Cosmo was scary fast -- would burn rubber in three gears, had throttle left at 110 mph in 4th (on a 5 speed), and would cruise from gas station to gas station at 90. The slightest overheat would result in end plate warpage leading to coolant leaks, and it failed emissions every yet. – Zeiss Ikon Apr 01 '22 at 18:22
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    @ZeissIkon if you haven't seen the Liquid Piston rotary, you will probably get pretty excited. I added a link to a video of it at the end of my post.. – John K Apr 03 '22 at 19:22
  • Cool video of a reconfigured rotary, but I wouldn't call it a "piston rotary". It may have definite advantages, but I think they are trying to distinguish it with a misleading name. – Michael Hall Apr 03 '22 at 21:13
  • I've heard of it, seen the animation videos. I still see quenching issues (one cause of the poor emissions of the Mazda/Wankel rotary), and the fixed seals will have the same issues the rotor mounted ones did for Mazda, IMO. There's little if any additional leverage over the Mazda/Wankel, so it'll still be a high speed, low torque engine. And they're where NSU was in 1967 (while Mazda was already making important changes to the basic Felix Wankel design) -- still trying to translate patents into something roadworthy. The only major improvements I see are compression and charge velocity. – Zeiss Ikon Apr 03 '22 at 23:11
  • I see the liquid piston's rotor has a hot end and a cold end as well -- that's going to cause problems. Maybe their internal cooling fins will solve that, maybe they won't. Mazda had fifty years trying to solve their problems. These guys haven't even sold an engine yet, AFAIK. – Zeiss Ikon Apr 03 '22 at 23:18
  • The problems with Mazda's apex seals were in part related to the dynamic forces including centrifugal forces imposed by having them on the rotor. Fixed seals are supposed to alleviate that. My main question is is there still the sensitivity to warpage of the chamber walls. – John K Apr 05 '22 at 20:36
  • @MichaelHall Liquid Piston is just the name of the company, intended to pique interest. I would call the configuration a "radial rotary", since it is effectively a 3 cylinder radial as far as the forces acting on the crankshaft are concerned. It's a radial whose single "piston" is able to visit each of the 3 "cylinders" in turn. The thing is brilliant beyond belief. Biggest problem is you are stuck with that 3 cyl radial configuration and it may not be feasible to stack them like a multi-bank radial because of where the gases have to go. – John K Apr 05 '22 at 20:41
  • Aaah, I read that as Liquid, Inc., Piston-Rotary Engine! (incorrect grouping in my head...) Thanks. – Michael Hall Apr 06 '22 at 01:01
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Although the Wankel engine is commonly called a rotary engine, in the early days of aviation, there was a rotary engine (which was a piston engine) that shared a lot of characteristics with a radial engine, with the biggest difference that the crankshaft was stationary and the crankcase turned. Here's more information:

https://en.m.wikipedia.org/wiki/Rotary_engine

RetiredATC
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enter image description herepic source

Rotary piston engines are still manufactured. Wikipedia has the following to say about them:

A rotary engine is essentially a standard Otto cycle engine, with cylinders arranged radially around a central crankshaft just like a conventional radial engine, but instead of having a fixed cylinder block with rotating crankshaft, the crankshaft remains stationary and the entire cylinder block rotates around it.

The photo is from a company that makes replica's of Gnome engines, and this article mentions Le Rhône and Oberursel replica's being produced. Rotary piston engines are easy to find!

Koyovis
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  • You win! Great answer, and beautiful photo. I had heard of these type of engines before, but it wasn't the first thing that came to mind. And given the OP's command of English in the unedited first edition, I kinda don't think this is what they meant. (if I had to guess they were visualizing an internal combustion reciprocating piston engine, with a rotating crankshaft) I could be wrong, although I bet I'll never know because Engine Lover doesn't seem interested in responding to comments. – Michael Hall Apr 05 '22 at 00:25
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See JohnK’s answer for an explanation of rotary engines.

The best-known manufacturers of piston aircraft engines today are Lycoming, Continental and Rotax.

StephenS
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