By on September 3, 2015


With a resume as accomplished as Dan Gurney has, he would be well within his rights to retire to a life of leisure. The man is 84 years old, after all. However, Gurney stays busy at his All American Racers shop in Santa Ana, California and he recently announced that he’s been granted a United States patent on what he calls the “moment cancelling” engine.

Gurney claims that by using two transversely oriented, counter-rotating crankshafts, the vibrations inherent in reciprocating piston engines will be reduced and reliability and efficiency will be improved, along with what he says will be turbine smoothness.

In its most basic form in a two-cylinder engine, each piston’s connecting rod spins it’s own crankshaft, with the two cranks spinning in opposite directions, cancelling out forces that would normally cause the engine to shake. Gears are used to combine and take power from the two crankshafts. Multiple cylinder engines are also possible, with the odd numbered pistons connected to one crankshaft and the even numbered pistons connected to the other.

Gurney says that the engine design has exceeded expectations when simulated in the digital domain and that he expects to have a physical prototype — an 1,800cc vertical twin — running by the end of this year. There’s a website,, describing the project, where you can peruse the simulation data and read about Gurney’s enthusiasm for the engine. The patent is #9,103,277, and you can read it here. Mr. Gurney says that the new motor would be suitable for most current motorcycle and automotive applications.

Interestingly, Gurney points out how power output was relatively low on the design brief’s priority list. The primary goal of the moment cancelling engine, according to its inventor, is smoothness, simplicity and compactness.

Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can get a parallax view at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading – RJS

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55 Comments on “Dan Gurney Patents New “Moment Cancelling” Engine...”

  • avatar

    Are current engines that rough that this patent will be a groundbreaking one? My four cylinder seems smooth enough. Seem like more complexity and moving parts to wear/break with those extra shafts in there.

    • 0 avatar

      You know where this might actually be a breakthrough? Stationary generators. That’s a market where every last fraction of a dB counts.

    • 0 avatar

      Halftruth, It may not be a groundbreaking one, but it is a different take.

      I think this design is more complex than, for instance, the BMW Twin-opposed motorcycle engine, which uses a single crankshaft and two opposed pistons to cancel out the vibrations.

      Conceivable, either of these engines, Gurney’s and BMW’s, can be assembled in multiple versions to create bigger displacement engines, similar to how the Wankel grew from a single-rotor to a twin, and later into experimental three- and four-rotor versions.

      So it remains to be seen if Gurney has entered a contender into the power-production ring, or just an also-ran.

      My dad experimented with TWO 426 cubic inch Hemis in tandem for his dragster in 1963 and the end result was shattered differentials and twisted/sheared drive shafts.

      Two cylinders and all this complexity? Not worth it IMO.

    • 0 avatar

      “Are current engines that rough that this patent will be a groundbreaking one? My four cylinder seems smooth enough. Seem like more complexity and moving parts to wear/break with those extra shafts in there.”

      You bet they are! Vibrations limit the size of a four cylinder to ~2 liters. With vibrations controlled, this engine could be scaled up.

  • avatar

    Doesnt an inline 6 essentially do the same thing?

    • 0 avatar

      The watercooled Suzuki 750cc 3-cyl two-stroke is just as smooth as the BMW in-line six.

      An early contender worthy of mention was the DKW 3=6 two stroke. Hell of a screamer, in its day.

      • 0 avatar

        What Highdesertcat said.
        I had the 750 back in the day and agree–I also had a Kawasaki KH400 3 cyl 2-stroke before that (my avatar!). Both were very smooth engines, but–

        The problem with a 3-banger is that the crankshaft ends want to harmonically vibrate in a circular path, so Suzuki used fairly squishy engine mounts to hide the vibration. Also in its favor was excellent torque at a pretty low RPM.

        The Kwacker, being a sport bike, well..they didn’t bother too much about the vibes, but it still didn’t stop me from taking it from Cali to New Mexico for a fantastic road trip.

        I still seem to gravitate toward odd cylinders–Mercedes 617 Diesel, and the newest addition to my fleet–a 1 liter Kubota diesel 3-pot. Cutest little engine you ever saw.

  • avatar
    heavy handle

    How can this get a patent when Moto GP blocks ran that way in the 80s and 90s?
    Forget the brand (I could look it up at home), but they ran a “square 4” with two counter-rotating crankshafts.

    • 0 avatar

      I looked it up for you. Here’s a link to the wikipedia article.

      Apparently the design goes all the way back to the early 1900s. I agree, I’m not sure why this would be granted a patent.

      • 0 avatar

        The patent is not for “an engine with counter-rotating crankshafts”, but the *very specific* arrangement and configuration in question.

        I don’t know if it’d stand a challenge or not, having no desire to wade into the prior art or the like, but there’s a good chance it might, if it has a meaningful mechanical difference.

    • 0 avatar

      Square four engines go back way further…Ariel introduced theirs in 1931. Tandem twins are an old idea too.

      I can’t really figure out what problem this is solving. It cancels horizontal moments, sure, but those are way smaller than the vertical moments from the pistons and small rod ends. If smoothness is the prime directive a boxer twin is far more effective at a lower parts cost (opposing cylinders even share camshaft lobes).

      • 0 avatar

        Read this patent yesterday linked from Autoextremist. It’s a mind numbingly boring treatise trying to cover off all possibilities of copying it.

        Kudos to the commenters who realized it was the U-engine, and half an Ariel Square Four. Just rearranging things without revealing fresh thought and insight is not usually patentable, because it would be obvious improvements to a person in the field.

        Just a lousy patent examiner on the one hand, and Gurney not realizing it’s all been done before on the other. Won’t get rid of all vertical shake, as also pointed out. So if anyone really saw the need for the engine and didn’t want to pay royalties, defending it would be difficult I think.

  • avatar

    Well I was going to leave a negative comment, but there are lots of uses for a compact simple engine.

    Although if that were REALLY true Mazda’s wankels would be much more prominent. Maybe they just aren’t marketing them well enough?

    • 0 avatar

      Wankels suffer from having huge swept combustion chamber area and low compression. As a result, they are very efficient at comverting the stored energy in gasoline into waste heat. In fixed applications which would benefit from co-generation, I expect that they could be made to be very efficient. However,, the well-known issues with short time between overhaul (apex-seal life) would really work against this.

      Another interesting take on the two crankshaft idea is the new Gemini two-stroke diesel aircraft engine. I saw a cutaway version at Oshkosh and it looked very interesting.

      • 0 avatar

        Mazda’s Wankels are also much better if they only have to work at a single RPM. Their design for a range extender / generator seem like a good idea, but no press release ever focuses on the downsides.

        And I would fully support replacing the coolant system in cars with a Rankine power generation cycle.

      • 0 avatar

        –and another one from Achates Power: opposed piston 2-stroke diesel based on the old Junkers Jumo 204 aircraft diesel.

      • 0 avatar

        For a range extender, a lesser service life for apex seals shouldn’t be a problem. If you’re running it enough to wear out the seals, it’s the wrong use of a range extender electric.

  • avatar

    Does it really work? It needs to actually be built, not simulated to prove it works well enough to be worth it after all the improvements made to 4 cyl. engines thru the years.

    Any new tech intrigues me.

    On a side note, nothing more has been seen by me of the eco engine of a few years ago.

    • 0 avatar

      Work? I’m sure it works; a good physics simulator should catch stuff at that level.

      Enough to be worthwhile? Yeah, that’s the tough one.

      (Re. that note, I remember that, too.

      It appears they [] notionally have a plant started in China, but production has been delayed until late 2015.

      Which means I won’t hold my breath for one actually appearing.)

    • 0 avatar

      Believe it or not a patented item does not have to work. It only has to have a unique design feature. Found this out when I was trying to get an item patented.

  • avatar

    You have to give the legend credit for bringing an ICE in a time that electric propulsion dominates the news, and without even claiming better fuel efficiency. Btw, most 80 year olds will need an hearing aid to be able to appreciate an engine’s smoothness.

    • 0 avatar

      It may be appropriate because of a trend toward range-extending power generation aboard electric propulsion vehicles, like the Volt.

      A Volt going up a winding mountain road with its gasoline engine running sounds like a screaming banshee and is neither quiet nor vibration-free on the INSIDE of the vehicle.

      This type of engine may provide a compact, vibration-free alternative to power the on-board generator on future PEVs.

      • 0 avatar

        This is a very good point. Range-extended EVs are disadvantaged because they have to carry the weight of both batteries *and* an ICE, but the weight penalty may be worth it for buyers who regularly (but not every day) go farther than electric range permits. This engine, if it works as expected, will be very good for that application.

        I think in the future most people will drive battery EVs most of the time, but there will be plenty of market space for range-extended EVs, hybrids, and even some straight ICE vehicles.

        • 0 avatar

          Why not use a small inline-6 and be done with it?

        • 0 avatar

          If you’re substituting a range extender for additional battery capacity, it’s pretty much a wash on weight.

        • 0 avatar

          dal20402 – – –

          I gave you a suggestion for choosing a pickup truck that would fit comfortably in your garage, but did not get a response. Did you get that suggestion?

          I am re-quoting that item here:

          “Thank you for giving some garage dimensions. I certainly agree that a garage is a useful building for MANY other functions and assets, other than vehicles.

          In fact, there was a time (1970’s) when I told my wife, “Honey, I know it’s snowing, but why would you waste a perfectly good garage by putting a car in it?” (I think she filed for divorce a short time later….(^_^).)

          Anyway, back to a pickup that can fit and perhaps meet some of you other needs. If I calculate properly, 240 inches is 20 feet of depth, and the width of the garage-door opening is 7.5 feet.

          Although full size pickups may be a bit of a squeeze, a larger-than-ordinary midsize might be a good compromise. I faced much of the same issue, when I chose my 2010 Nissan Frontier. Here are some of its dimensions, using the 2015 model as an example:
          1) Width = 73 inches = ~ 6.1 feet;
          2) Length (Crew Cab; short bed) = 206 inches = 17.2 feet*;
          3) Fuel consumption = 19/23 MPG (Manual)
          4) VQ4 V-6 engine, with 260 HP and 280 lbs-ft torque.

          * If you were to choose a King Cab with short bed, it would be about 16 feet in length, and still seat 5 people.


      • 0 avatar

        The present Volt has an engine selected for availability and cost. If it’s also unpleasant in use, that’s no surprise. I’d think they could do better without going to something exotic.

      • 0 avatar

        That’s probably because said engine is driving the wheels. The Volt is not a pure range extender like the i3.

  • avatar

    If the design is as promising as the computer simulations indicate, this could be the perfect side-by-side 2 cylinder motorcycle engine. I like smaller off road/enduro bikes but after riding them for hours the vibration really starts to annoy.

  • avatar

    This could be good for 2 and 3 cylinder engines. But i dont see it being useful for 4 or more. Cross plane cranks are good enough and simpler at that point. The rotational inertia of car engines isnt something thats a big deal like it would be in a helocopter or large slow speed engine.

  • avatar

    Good for Dan Gurney, still sharp at 84.
    Lets see what happens when his shop builds it. Probably cheaper and faster than going further with digital simulation.
    As the owner of a residential 7.5kva generator (B&S V twin) I think if they can get only 3dB reduction, that would be significant – half the SPL and a 1/5 perceived noise reduction while 10dB would make it sound half as loud. But I wonder if a better muffler than the little fart cans they use on small generators would be more economical.

  • avatar

    Taylor’s massive two volume text, “The Internal Combustion Engine in Theory and Practice” reveals primary, secondary, and tertiary vibrations in ICE’s. The “Shaking” phenomenon Gurney describes is usually related to primary vibrations. What about the other two?
    How does this compare to the turbine like smoothness of the 120-degree crank, BMW in-line 6-ciylinder engine, which solved the vibration problem decades ago?

    This Gurney thing looks like a mechanical Rube-Goldberg devices that will simple add mass and complexity.


  • avatar

    Dan built – and won a F1 race with – his own design of both a 12 cylinder engine and car. He has been a winner in every endeavor of racing he has entered. I would never bet against his abilities.

    • 0 avatar

      The Eagle engine was designed by Aubrey Woods and manufactured by Weslake Engineering.

      Sadly, Dan’s last 10+ years of indycar racing were a bust. He went about seven years without a win in the 80s, then came back in the 90s and went winless again. Once the 1972 Eagle was obsolete, he didn’t do much more.

      • 0 avatar

        The 1991 Eagle MKIII Toyota GTP car was something of an achievement, winning 21 of the 27 races it competed in over three seasons and being credited by many with killing the class it dominated.

  • avatar

    Without knocking (see what I did?) Mr. Gurney’s engine design, his patent claims are exceedingly narrow (each independent claim is around one column long), reciting specific dimensions and values (e.g., “the second inside radius being greater than 0.13 inches and less than 0.7 inches” and “said intake valve undercut angle being between about 30-42 degrees”). The inclusion of such values makes it easier for one to design around the patent by providing an engine with measurements outside of the recited values. In the patent world, the less you claim, the broader the patent. That said, given what they had to work with, it looks like his patent attorneys did a pretty good job.

    -ChiefPontiaxe, registered patent attorney

    • 0 avatar

      I noticed that too. Most of the claims seem to be based on the valve and port geometry and there doesn’t seem to be much there about the counter-rotating twin cranks. Maybe that’s an old idea.

      I suppose part of the art in your job as a patent attorney is taking a concept that might be hard to protect in an of itself, either prior art or non-patentable, and then making claims that protect the only practicable way to effect the concept.

    • 0 avatar

      As you found out, the patent is less about the counter rotating cranks and more about the VERY specific intake dimensions to get the engine to breathe unbelievably efficiently at very moderate rpms. The piston speeds, intake and exhaust velocities, coupled with no vibration, allow for the engine to produce buckets of hp while maintaining all of the mechanical aspects of the engine to stay within the “easy to live a long time” realm.

      You could make a counter rotating engine with different port geometry, but then it wouldn’t have big HP and wouldn’t be efficient. Efficiency is claimed…

      280hp from a 1.8l ultra compact twin is impressive. The engine is intended to last forever…

  • avatar

    seems like it would be easy to design a version that *truly* shuts down cylinders for economy or if one is damaged since they arent all dependant on the same crankshaft

  • avatar

    Harley Davidson should sign up for this motor today.

  • avatar

    Looks like a way to have a transverse engine and a longitudinal gearbox with rear wheel drive.

  • avatar

    Harley doesn’t want a smoother engine. With their demographic, if it ain’t shakin’ it ain’t a Harley.

    • 0 avatar

      The quieter smoother, more powerful V-Rod was once described to me (by a Harley dealer) as “Sounding like the Jetson’s flying car”.

      It’s *not* their biggest seller…

  • avatar

    Interesting concept. I could see how it would be smoother, especially for a twin where both pistons rise and fall together. I’m not sure however how quiet it will be with that long straight-cut gear train.

    Listen to a modern Triumph triple idle. All the gear-driven engine accessories ain’t quiet.

  • avatar

    Companies like Capstone Turbine are better positioned to capture the generator market. Very smooth, very efficient in their sweet spot, and reasonably accommodating towards different fuel types

    • 0 avatar

      When I worked in a steel mill back in the 70’s, I used to have to start a natural-gas fed International Harvester stationary turbine generator once a month for testing – even with the exhaust pipe exiting the building, the noise was ear-splitting once it spun up.

  • avatar
    daniel g.

    The kawasaki kr 250 use a similar concept?

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