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Radial Bi Rotary Balanced Piston Combustion Engine

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Radial bi-rotary balanced piston combustion engine mounted to demonstrate a motorcycle application
Radial bi-rotary balanced piston combustion engine mounted to demonstrate a motorcycle application

You’ve heard of radial engines and rotary engines, you probably also know a piston radial has a fixed cylinder block and a rotating crankshaft. A pistonless rotary like the Wankel has the same fixed engine block and a rotating rotor, while a piston rotary, looks like a radial, but the cylinder block rotates around a fixed crankshaft. So far, so good. So, what’s a radial bi-rotary engine? As you’ve probably guessed by now, it rotates both the crankshaft and the cylinder block, but in opposite directions, and that is what we have here, the Radial Bi Rotary Balanced Piston Combustion Engine by Devaere Engineering. After the Circle Cycle engine we wrote about a few days ago, Franky Devare thought we might like to see what he has been working on.

In this engine, the rotating cylinders are open topped and move past intake and exhaust ports, the engine works in normal four stroke fashion and modifying the position and size of the ports, can serve to create the effects of an EGR valve with a small overlap of the ports, or even make this an Atkinson cycle engine where the power stroke is longer than the compression stroke by elongating the intake port which shortens the compression stroke.

The engine is smooth and generates no rocking couple between cylinders. The counter rotating block and crankshaft decreases gyroscopic forces and the speed of the relative counter rotation, which can be changed depending on planetary gearing selected in the design gives the engine a higher effective rpm in relation to the actual rpm in either direction. The fixed ring inlet ports also eliminate the valve train, simplifying construction. The size of the ring and number of cylinders affects the number of ignitions per revolution.

Radial bi rotary balanced piston combustion engine
Radial bi rotary balanced piston combustion engine

The engine’s natural element would be in aviation, but as you can see by the concept motorcycle at the beginning of this article, it could be used in many other applications. In fact, it could even be inside the wheel instead of mounted in the frame as shown above.

The Devaere Engineering website shows the long history of the design and engine families that have led to the development of this particular engine. I would very be interested in seeing a running example.

Thanks to Franky Devaere for sending us the pointer.

Have we exhausted the possible variations of internal combustion engines yet? My guess is absolutely not. Amazing.

Link: Devaere Engineering

Video animation below:

Posted on Filed Under: Engines

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Comments

  1. I’m a fan of monkey motion (like the rocker arms in a 60’s Chrysler Hemi); and this motor has plenty of it. I like the counter-rotating aspect, which would practically eliminate vibration. However, there is a lot of rotating mass in this setup. The engine is its own flywheel, but that’s a lot of mass to overcome when accelerating.What kind of top RPM can we expect? The concept or rotating blocks and cylinders is an old one that dates to the early days of aviation and motorcycling, when spinning cylinders could receive better cooling air. Again, this looks like it would be a good diesel running at relatively low speeds. I like the concept bike here. The gear-drive rear wheel is a nice touch. Is the front wheel driven as well?

  2. Thanks to gregory.piol from France who provided me his beautiful bike-CAD-model. ( his portfolio on http://grabcad.com/library/star-cafe )

    i want to point out to mr. B50 Jim that this engine gives 12 ( or 16 ) ignition per revolution of the rotor. Regarding acceleration mass , this is not a rotary but a bi-rotary.
    A convention fourcilinder gives 2 ignitions per crankshaftrevolution , a wankel engine 3 ignitions per rotor revolution.

  3. This shares some design features with the Caminez engine from 1926. The pistons are linked in a similar manner but rather than connecting rods and crankshaft the pistons had rollers on the bottom and rode against a double lobed camshaft that drove the propeller. The engine did not rotate. Apparently it was a torque monster with serious power pulses that destroyed props. Unfortunately continued development was not pursued. This was in the days of single row radials so the idea of stacking this engines cylinder rows and offsetting them to smooth power delivery was not explored.

  4. It’s funny how any motorcycle innovation 3D rendering is automatically given all kinds of far off futuristic features like hubless wheels. Stick this thing in a frame that would otherwise house a big 4 pot and show its technical advantages – reduced weight, higher power, smaller size, etc. That should get some investment.

    Love seeing new ideas for IC’s as always.

    • Don’t worry about the specific motorcycle design shown here, it’s really only to illustrate one of the many possible applications for this engine and, as Franky notes, he used an available CAD model created for another radial engine motorcycle to make the visual a little easier to create. We’re really focusing on the engine in this article and I could have left that image out altogether, but it seemed to fit on The Kneeslider, so there it is.

      • akaaccount has a good point. Design advancements are best seen (and attract investment $) when they improve upon existing design. This is why James Parker uses the same wheelbase as a stock GSX-R for his latest GSX-RADD front-end.

        Cool design. Best wishes going forward

    • Paul C. is right, but of course it would also be nice to see it mounted in a Featherbed frame – seeing that it already is the ultimate frame for stuffing interesting engines into.

  5. I am not an engineer, but I do think that the “Curved” connecting rods would “flex” with torque and heat causing some sort of out of balance damage. Why not just ad another set of straight con rods to the “secondary” pistons?

    • The design as it stands eliminates the need for two extra crank throws for the additional two extra rods. This would cause the engine to be much wider. The extra rods cannot use the existing crank throws as it would adversely effect the natural balance created by the opposing pistons traveling in opposition to one another in a synchronized manner. As far as the arched connecting links are concerned, I don’t believe that there would be a great amount of deflection as the mass of the piston is small in comparison to the strength of the link and the crank is again relatively lightweight due to the absence of counterbalancing. The rod/link assemblies act as the counterbalance’s.

  6. Msr. Devaere —

    Thank you for explaining some of the engine’s operation. With 12 -16 power strokes per revolution, it should run very smoothly and make lots of torque. I see by your web site that the engine is intended or aircraft applications — what is its RPM range? I appreciate the elegant design that does away with valve-train components; that will decrease production costs. How close to production is the engine? I imagine a .8 liter version for motorcycle applications would make fabulous power.

    • It looks like a two stroke – kind of sleeve valve- , but works as a four stroke. Should therefore be more eco-friendly. Sealing ( as in all this kind of designs is the big issue here, but the rotor is rotating much more slower , kind of big slow rotating valve)
      0.6 to 0.8l is indeed very interesting. Not only for bikes , but i received some letters from ULM-builders who like to see their prop ( due to efficiency ) directly mounted on the 1000 rpm rotating rotor rather than on it 3000-4000 rpm rotating crankshaft.

  8. I have two comments. First, the article states that a radial bi-rotary engine’s counter rotating block (cylinders, pistons, and connecting rods) and crankshaft decreases gyroscopic forces. From the video it is apparent that the rotary inertia of the block would be much greater than that of the crankshaft and the gyroscopic forces would be substantial

    Second, since the rotating “cylinders” are open there must be some sector of the stationary portion of the engine which acts as the “head” for these cylinders. I would imagine that this cerates a sealing problem similar, but not the same, as that of the Wankel between the its rotating “piston” and stationary “head/block” which I understand was a major problem with that engine. I am wondering how Mr. Devare seals the cylinders for their compression and power strokes.

    • good remarks.
      for the first remark i have to link the best fighter aircraft at that time the bi-rotary http://en.wikipedia.org/wiki/Siemens-Halske_Sh.III ( wikipedia tomorrow closed ? ) , http://www.theaerodrome.com/forum/aircraft/19618-rotary-engine-torque-snipe-ss-d-iii-iv.html. Gyroscopic forces are related to mass and velocity. Here it is a bigger mass with low velocity counter rotating to a lower mass with bigger velocity. Therefor there is always a reduction in gyroscopic forces, that’s why these bi-rotery’s could compete with the upcoming in-line engines as explained at the end of http://en.wikipedia.org/wiki/Rotary_engine

      the second remark : as already mentioned , the rotor is spinning 4 times slower than a wankel, although having 4 time more ignitions. But it’s still a major obstacle. Ideal work-out for the Mazda engineers.

      • To be fair, the sealing problems on this design look much smaller than on a Wankel rotary or most other “alternative motion” ICE designs. In a Wankel, not only the rotor tips but also the rotor faces need sliding seals. In this bi-rotary, the seal only needs to surround the relatively small port at the top of each cylinder.

        Barring any new breakthroughs, any engine where the ports are uncovered by a sliding motion is going to exhaust a bit of lubricant, creating some challenges in keeping emissions down. That’s why poppet valves are so handy. Repeatedly smashing into the valve seat isn’t great for the metal, but it doesn’t require any lubricant in the cylinder.

  11. Looks VERY interesting.

    It doesn’t seem to benefit from one of the nice things about a wankel, though… lack of piston reciprocation. The reciprocation might be balanced, but the pistons still have a TDC and BDC, and inertia is given up each time they change direction.

    It almost looks more like a spinning double-boxer, rather than a bi-rotary. The engine does revolve, which is interesting, but it doesn’t seem to technically have rotors instead of pistons in the sense that a Wankel does..

    Don’t get me wrong… it looks VERY cool, and technically quite interesting. I am just talking semantics.

    I also wonder about cooling airflow from a fan that remains stationary relative to the cylinder sleeves. I suppose that still having air-screw properties compared to incoming air, that it does channel air… but why not have radial curved veins in the stationary part of the engine housing, or gear the fan to spin faster than the housing RPM, like the crankshaft RPM to draw more airflow?

  12. Sometimes you just have to build something to see if it works or it doesn’t. This looks like it will work and all the talk in the world won’t prove how well. Build it and see.

  13. Franky,
    Looks really good!!! It looks to me like this design has many merits – especially for swinging a prop. (as mentioned).

    What is the perimeter speed at the port seals versus piston speed at the rings/skirt? Would there be any benefit in adding a second port to each cylinder to 1. increase volumetric efficiency with loop-scavenging? 2. reduce the chance of contaminating the fresh charge with exhaust? The intake and exhaust ports would be offset to run different paths, so I guess that would increase friction, too.

    I’ve got to build my new two-stroke concept…

  14. OK. So how is fuel supplied? How is the fuel metered to control engine speed? How would an exhaust system be fitted to properly attenuate exhaust noise? Something has to be fixed to the frame to allow for the relative motion between the… rotating output (shaft or crankcase) of the engine and the vehicle frame in order to transfer the rotary motion to the driven element (wheel). Cool idea, way too complex to be practical.

    • The outer casing is stationary, and holds the intake filters, and the exhaust pipes, and would presumably integrate the motor mounts.

      The cylinder block inside spins within the housing at 1000RPMs.

      The piston assembly and crank-shaft counter-rotate inside the cylinder block at 3-4000rpms.

      The valve action occurs as the rotating cylinders pass by the intake port during the intake stroke, then seals against the inside of the stationary outer ring during the compression and power strokes, and passes by the exhaust port during the exhaust stroke.

      Sealing the cylinder tops against the inside of the stationary housing ring would be the issue, with thermal cycling, and compression force trying to push the cylinder and piston away from the ring, or deforming the ring outward.

      Liquid cooling would be a significant challenge, and air cooling would produce potentially un-even or significantly changing thermal effects, which could throw dimensional tolerance variables into the issue of keeping the engine sealed efficiently.

      The theory is interesting… as it compounds boxer-style piston counterbalancing on two axes, and compounds two counter-rotating actions to increase effective RPMs.

      The practical challenges of keeping things closely interacting effectively and on-time, seem significant.

      • Maybe the seal at the top of the cylinder could be pressed against the outer casing with a spring, as with the rotor apex seals in a Wankel. That would allow for thermal / wear variations.

    • And I would imagine fuel would either be delivered by an injector in the intake tract, or a direct fuel injector mounted directly through the outer ring, followed by the spark-plug.

      Fuel and spark are left off the digital mock-ups.

  15. Yes, there it is.
    For myself, and I suspect others, the entree to technology is the motorcycle. Interesting mechanical design becomes compelling when interjected with the simplicity and relative affordability of motorcycling.
    Thank you Franky for a beautiful and elegant design and for putting it into an image that I can easily see myself using.
    In my time as a cyclist the leap from dreaming of a machine and riding that dream has been startlingly swift. I look forward to seeing and hearing this motor run.

  16. 12-16 ignition cycles per revolution with limited external surface area would make a lot of heat. I wonder if this would be a good application for a type of water or methanol injection.

  18. Very nteresting…
    Just a doubt, wouldn’t such a rotating mass make a bike very stable on straight but hard to go into corners?

  19. Interesting, but how many problems does it create to try and solve a couple?

    The main problem I see is the engine rotates the opposite of the crank. So half the power the engine creates goes directly into spinning the engine and not the wheel. Then combine that with extra weight from all the moving parts and the engine doesn’t sound so great. Interesting design, but unless I am missing something, it is not going to work well.

    Another bad thing about it, that is a lot of rotating mass, put it in a bike and it won’t want to steer.

  20. Rotor Root Engine2 – two combustion chamber RRE2
    Power per 1 kg weight of the engine ” power density” – 110 kwt/kg.
    None of the crankshaft, pistons, valves, camshaft.
    Absence of friction only rolling friction
    No lubrication system, clutch, gearbox.
    Uses compressed air, gasoline, diesel fuel, bio-fuel and gas.
    Working in water and underwater conditions with no atmosphere.
    I have developed a design of RRE2, and centrifugal compressor for air and gases. a complete set of drawings.
    I am looking for partners for prototyping, testing and implementation.