PatRoVa Rotary Valve engine

Discussion in 'Plans' started by manolis, Jul 18, 2016.

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  1. Jul 18, 2016 #1

    manolis

    manolis

    manolis

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    Hello all.

    At http://www.pattakon.com/pattakonPatRoVa.htm it is presented a new and different rotary valve: it comprises a pair of oppositely acting fronts / disks firmly secured to each other by a robust hub; the fronts seal a pair of oppositely arranged ports / windows (chamber ports) of the combustion chamber.

    [​IMG]

    Here is the youtube vid eo of the first PatRoVa Prototype:

    [video]https://www.youtube.com/watch?v=6Q-EGdeS0ws[/video]
    https://www.youtube.com/watch?v=6Q-EGdeS0ws

    and here is a proto of the prototype and of the cylinder head exploaded:

    [​IMG]


    [​IMG]

    This drawing:

    [​IMG]

    explains a fundamental difference of the PatRoVa rotary valve relative to all the rest rotary valves: the total force acting on the bearings of the PatRoVa rotary valve is zero, no matter what the pressure into the combustion chamber is.



    We are planning to put it on a Ducati Panigale (V-2 at 90 degrees as in the first animation of this thread) to show its advantages over one of the best poppet valve engine (like: simplicity, ability for way higher revs (actually there is no rev limit for the cylinder head), compactness, low friction, high flow capacity, smoothness etc, etc).



    On the other hand, a small RC / model engine with the PatRoVa rotary valve on the cylinder head would be an interesting start.

    Think of an RC 4-stroke engine, say 16mm bore x 15mm stroke, with ringless piston and the PatRoVa on the cylinder head, running above 40,000rpm.

    Does anybody in this thread have the tools, the will and the time to modify a high revving RC engine to PatRoVa?
    As a third party, I mean.
    Any estimation of the cost and of the time required?


    Thoughts?

    Objections?

    Questions?

    More details at
    http://www.pattakon.com/pattakonPatRoVa.htm

    Thanks
    Manolis Pattakos
     
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  2. Jul 19, 2016 #2

    lohring

    lohring

    lohring

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    Sealing has always been the problem with all rotary valves. In high pressure steam engines, only poppet valves can be made leak proof. IC engines have had the same experience over a wide range of valve types..

    By the way, I'm a fan of your variable poppet valve mechanisms.

    Lohring Miller
     
  3. Jul 19, 2016 #3

    manolis

    manolis

    manolis

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    Hello Lohring

    You write:
    “Sealing has always been the problem with all rotary valves. In high pressure steam engines, only poppet valves can be made leak proof. IC engines have had the same experience over a wide range of valve types..

    By the way, I'm a fan of your variable poppet valve mechanisms.”




    POPPET VALVES

    Thanks for being fan of pattakon’s VVA’s.
    The top is the DVVA (Desmodromic Variable Valve Actuation).
    It is presented at http://www.pattakon.com/pattakonDesmo.htm .
    It needs not valve springs.
    It is a fully variable VVA: the valve duration varies from zero to a maximum “on the fly”, the valve lift varies from zero to a maximum “on the fly”, too, and the valve duration and the valve lift vary independently from each other.
    The DVVA provides valve lift profiles like:

    [​IMG]



    ROTARY VALVES

    Quote from http://www.douglas-self.com/MUSEUM/POWER/unusualICeng/RotaryValveIC/RotaryValveIC.htm
    (Rotary Valve Internal Combustion Engines):

    “. . . many inventors have been attracted by the apparent simplicity and the uniform motion of rotary valves of one kind or another. There is also the tempting prospect of being able to run on inferior fuels because there was no hot exhaust valve always present in the cylinder to trigger pre-ignition. However, as with both steam and IC rotary engines, the simplicity was more apparent than real, and the engineering problems were daunting.

    The basic problem, is that the pressures in the cylinder of an internal combustion engine are high, due to both the compression stroke and the explosion of the fuel-air mixture. This produces large forces on the valve system, however it is contrived; the beauty of the poppet valve is that such forces simply push it harder against its seat, and have no effect at all on the valve-actuating mechanism.

    However, the geometry of rotary valve systems is inherently different; in the Aspin concept below, the vertical valve cone is pushed up axially against the cylinder head, while the horizontal Cross valve is pressed up against the top half of the bearing surfaces. In both cases this can cause excessive friction and seizure, the root of the problem being that enormous forces are acting on the valve while it is moving.”


    . . .

    ****Another contemporary concept is the PatRoVa rotary valve. Like the Cross design it balances out the forces acting on the rotating valve.****

    End of Quote

    The last paragraph in the asterisks was added recently (May 1, 2016) and is as wrong as it gets..

    I tried to explain it to the creator / owner of the above web site by emails, but it seems it is too difficult to convince somebody for the obvious.

    What is the obvious?

    When the pressure into the combustion chamber is high, say 100 bars, the Cross rotary valve is pressed “upwards” by a force equal to the pressure into the combustion chamber times the area of the “window” through which the combustion chamber communicates with the Cross Rotary valve.

    With a “window” area equal to 20cm2, the overall upwards force acting on the Cross rotary valve is (100Kp/cm2) * (20cm2) = 2tons (4,400lb).

    Such a force causes a significant distortion on the cylinder head, on the bearings of the Cross rotary valve and on the Cross rotary valve itself (the Cross rotary valve is actually a pipe having an oblique separator in the middle between its intake side and its exhaust side).

    With its two bearings away from each other, the bending of the Cross rotary valve gets significant.

    With the one side of the Cross rotary valve running cold (intake side), with the other side of the Cross rotary valve running red hot (exhaust side) and with the highly asymmetric shape of the Cross rotary valve, the thermal expansion and distortion is anything but negligible.


    Despite all these, the Cross – Bishop rotary valve:

    [​IMG]

    came so near to success (more at http://home.people.net.au/~mrbdesign/PDF/AutoTechBRV.pdf ) that FIA changed the rules in 2004 banning the rotary valves from F1.


    In comparison to the Cross rotary valve, each disk of the PatRoVa rotary valve is pressed to the side by a force of 1,000Kp (2,200lb) (because, for the same total port area, each window (chamber port) of the PatRoVa cylinder head has an area of (20cm2) / 2=10cm2.
    Through a hub, the two disks of the PatRoVa rotary valve are connected to each other.
    The pressure force acting on the one disk through the one window counterbalances the force cting on the other disk through the other window, leaving the bearings completely unloaded.
    The high stiffness of the hub that connects the two disks minimizes the elastic distortion when the two opposite forces act, through the “windows” onto the disks.

    Quote from http://www.pattakon.com/pattakonPatRoVa.htm :

    “From a practical viewpoint:


    Leaving free (i.e. without support bearings) the PatRoVa rotary valve on the cylinder head to seat in place and seal, by its oppositely arranged fronts, the two side chamber-ports, and applying a high pressure (like 100bar) in the combustion chamber, the PatRoVa rotary valve has no tendency to move upwards, or downwards, or to the side.
    In comparison, a force of a few tons is required to keep in place a state-of-the-art rotary valve when the same 100bar pressure is in the combustion chamber; the extreme upwards force loads its bearings and causes, among others, the flexing / deformation of the spherical valve, of the shaft of the rotary valve and of the cylinder head wherein the shaft is supported.

    The cavity of the PatRoVa architecture eliminates the radial forces acting on the rotary valve and on its bearings, which is a major (if not the worst) problem of the known rotary valve designs.

    The ceiling of the PatRoVa cavity receives the heavy radial forces and releases, this way, the rotary valve from them.

    The PatRoVa cavity is a buckler that protects the rotary valve from the radial forces.”


    End of quote.



    Quote from http://www.pattakon.com/pattakonPatRoVa.htm

    Sealing

    . . .

    A more ambitious idea is to exploit the inherent characteristics of the PatRoVa rotary valve and seal the combustion chamber without using conventional sealing means.

    For the sealing between the pair of flat-fronts and their respective chamber-port-lips only the one of the three dimensions is significant: that one along the rotation axis of the rotary valve (i.e. the distance between the two disks and the width of the combustion chamber); the displacement of the rotary valve along the other two dimensions does not affect the sealing. And because the heavy forces applied on the flat fronts balance one another "internally", such a displacement is easy to be realized and to be controlled (Variable Valve Actuation).
    In comparison, the slightest displacement, at any direction, of a spherical rotary valve changes significantly the sealing quality.

    The sealing is tolerant to deformations of the cylinder head because, as before, only the one of the three dimensions really matters; significant deformations of the chamber along the other two dimensions do not affect the sealing.
    Between its chamber ports the chamber (i.e. the cavity into the cylinder head) is like an open ring (a thin open ring); if the diameter of the ring is for some reason increased (due to the high pressure into the chamber, for instance, or due to the temperature etc) it makes no harm to the sealing. The pressure in the chamber cannot essentially affect the dimension of the "ring" along the rotation axis of the rotary valve.
    Besides, the lower part of the chamber is "enclosed" and is strongly supported by the lower end of the cylinder head (which is stiff as being the roof of the cylinder).

    With the distance between the chamber-port-lips being small, proportionally small is the effect on the sealing quality of the temperature difference between the rotary valve and the chamber walls.

    The limit of the width of the combustion chamber (i.e. of the width of the cavity into the cylinder head) is set by the diameter of the spark plug (or of the injector). For instance, with a distance of 25.4mm (1 in) between the two disks, the estimated thermal (and stress) expansion/contraction is several times smaller as compared to the case wherein the two ports were arranged at the sides of the cylinder.”


    End of quote


    By the way, here is a PatRoVa rotary valve (not yet finished) on a PatRoVa cylinder head (353cc cylinder capacity: 80mm stroke, 75mm bore)).

    [​IMG]

    The manufacturing accuracy is poor.
    The surfaces are dry (not lubricated surfaces at the top).
    With manual (i.e. by the hands) cranking, the compression is 12 bars at some 300rpm.

    The leakage at 3,000rpm is ten times less than at the 300rpm of the cranking (note: the leakage in the PatRoVa is internally recycled during the next intake stroke).
    At 6,000rpm the leakage is 20 times less than at the 300rpm of the cranking.
    At 15,000rpm the leakage is 50 times less than at the 300rp of the cranking.

    It is not difficult to repeat the above “leakage” test.



    I hope they are now more clear the differences between the PatRoVa rotary valve and the conventional rotary valves.

    Are they?

    Thanks
    Manolis Pattakos
     
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  4. Jul 23, 2016 #4

    manolis

    manolis

    manolis

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    Hello all.:

    Quote from my first post:

    " On the other hand, a small RC / model engine with the PatRoVa rotary valve on the cylinder head would be an interesting start.

    Think of an RC 4-stroke engine, say 16mm bore x 15mm stroke, with ringless piston and the PatRoVa on the cylinder head, running above 40,000rpm.

    Does anybody in this thread have the tools, the will and the time to modify a high revving RC engine to PatRoVa?
    As a third party, I mean.
    Any estimation of the cost and of the time required?


    Thoughts?

    Objections?

    Questions?

    More details at
    http://www.pattakon.com/pattakonPatRoVa.htm "

    End of Quote.


    I mean a model / RC engine like:

    [​IMG]

    Here are the basic parts.
    Spot on the casing (dark green; it is a single-piece part) and think its manufacturing difficulties:

    [​IMG]

    With 20mm bore and 20mm stroke it has 6.26cc capacity.

    At 35,000rpm its mean piston speed is 23.3m/sec

    Reasonably it will make some 3hp

    Thoughts?

    Objections?

    Questions?


    Thanks
    Manolis Pattakos
     
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  5. Jul 23, 2016 #5

    Charles Lamont

    Charles Lamont

    Charles Lamont

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    It won't work. It may run, but you are never going to get it to any useful durability.

    When dozens, may be hundreds, of good engineers have spent thousands and thousands of hours and wasted millions on failing to get clever rotary valve ideas to work reliably, what makes you think you can do better?

    Sorry to be brutal, but I hate to see someone pouring so much effort into flogging a dead horse. My sincerest advice is to stop wasting your time. Now.
     
  6. Jul 24, 2016 #6

    canadianhorsepower

    canadianhorsepower

    canadianhorsepower

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    Not sure why you say this but
    Stihl has a four cycles engine running with ONE cam loab :fan:
     
  7. Jul 24, 2016 #7

    manolis

    manolis

    manolis

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    Hello Charles Lamont.

    You write:
    “When dozens, may be hundreds, of good engineers have spent thousands and thousands of hours and wasted millions on failing to get clever rotary valve ideas to work reliably, what makes you think you can do better?”

    Nothing more and nothing less than the architecture and the technical characteristics of the PatRoVa rotary valve.

    The PatRoVa rotary valve addresses some crucial issues / problems of the previous rotary valves, without introducing significant drawbacks.

    Think for instance: Is there another rotary valve that covers and seals big ports of the combustion chamber receiving, during the combustion, a zero total force?
    Compare the loads on the bearings of the PatRoVa rotary valve with the loads (and the resulting distortion) on the big diameter needle roller bearings required for the Bishop rotary valve.


    Or think what happens if the PatRoVa rotary valve is "lifted" by, say, 1mm (and compare it with what happens in a Cross rotary valve "lifted" by 1mm).

    Or think why leaving free (i.e. without support bearings) the PatRoVa rotary valve on the cylinder head to seat in place and seal, by its oppositely arranged fronts, the two side chamber-ports, and applying a high pressure (like 100bar) in the combustion chamber, the PatRoVa remains in place without any tendency to move upwards, or downwards, or to the side.





    You also write:
    It won't work. It may run, but you are never going to get it to any useful durability.”

    The title of this forum is “Home Model Engine Machinist”.

    Forget the unconventional rotary valve of the model engine in my last post and let me know whether, with a conventional cylinder head, the same model engine would work and would be durable.

    Then compare the ring-less piston with the PatRoVa rotary valve:

    The one part (the piston) seals the “lower” end of the combustion chamber, the other part (the PatRoVa rotary valve) seals the “top” end of the combustion chamber.

    Unless I am wrong, and despite the heavy mechanical and thermal stresses it undergoes, the ringless piston proved in practice good in both: sealing and reliability,

    Think the pressure load on the piston: with 20mm bore and, say, 50bar maximum pressure during the combustion, the downwards force on the tiny piston is some 157Kp / 350lb.

    Due to the leaning of the connecting rod, the skirt of the piston is heavily and unevenly loaded by the pressure loads and by the inertia loads; it thrusts / abuts heavily on the cylinder liner and needs good lubrication to avoid seizure.

    Think also the “thermal load” on the piston: during the combustion the piston top comprises some 40% of the total surface of the combustion chamber.

    The reciprocating piston needs to be lightweight (otherwise the inertia loads limit the red line), the same piston needs to be robust to receive the loads keeping the distortion minimum.

    In comparison to the piston of the model engine, the "life" of the PatRoVa rotary valve is by far easier and the sealing it achieves better.
    For instance, the hub between the two disks of the PatRoVa is as big in diameter and as heavy as necessary because it does not reciprocate: it rotates smoothly with half crankshaft speed.
    For instance, the clearance between the chamber windows (chamber ports) and the two disks of the PatRoVa can be substantially smaller than the clearance of the piston.



    By the way, the model engine in the last post has square design: 20mm bore x 20mm stroke.
    For a high revving 4-stroke engine a substantially over-square design is preferable.
    For instance, with 24.8mm bore and 13mm stroke the capacity remains the same (6.28cc) while the bore to stroke ratio gets equal to the bore to stroke ratio of the famous Ducati Panigale 1299 (116mm bore, 60.8mm stroke).

    [​IMG]

    With only 13mm stroke, the PatRoVa model engine has, at 50,000rpm, a mean piston speed of only 21.7m/sec, and the expected peak power becomes more some 4.5hp (3.3kW ).


    It is interesting the manufacturing simplicity.
    For instance, for the manufacturing of the casing (dark green part) all it takes is a conventional (not CNC) milling machine.




    Instead of “general purpose advises”( like: the others failed, why not you? ), please try with strictly technical arguments / objections. This is what I am asking for.

    Thanks
    Manolis Pattakos
     
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  8. Jul 25, 2016 #8

    enfieldbullet

    enfieldbullet

    enfieldbullet

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    I have a few issues with some things you said. mind that my background is in mechanical engineering and that i`m not criticizing the overall design but rather some rather flimsy conclusions you arrived at.

    first and foremost, thats a cool new rotary valve design, i`ve never seen it before and i think it could be really cool to build an engine using it. but your 40,000 rpm is just...too much. modern F1 engines arrive at 18.000 rpm. you could probably do a little faster on a reciprocating otto cycle but not much, not nearly 40.000 rpm.

    that`s because your flame front has to consume the fuel in the combustion chamber at every powerstroke and at 40.000 there isn`t enough time for that to happen. your engine would do a full turn at almost every 1 millisecond and you would have 0.5 milliseconds for combustion to occur. combustion cannot happen that fast normally, i think i remember 3 milliseconds quoted in a book in high-turbulence designs. maybe you would just have a lot of combustion happening in the exhaust pipes, and that you make a pretty inefficient engine.

    secondly, at 40.000 rpm in a reciprocating engine, the inertial forces on the piston would be a HUGE problem and you would need a super strong material or a super dimensioned part. but the more massive the part is the slower the engine`s top speed would be. which brings me to the third point

    third: it`s not just because your valves are revolving that they don`t take force to turn. they do, just like poppet valves. and by the apparent size of the drawing their moment of inertia would be pretty big. you could make their diameter smaller, but then breathing would become an issue(must reach a compromise here).

    also, a reciprocating engine with just 6cc reaching 4.5hp is just unrealistic. did you factor in the thermal problems? i mean, normally 2/3 of the power is lost as heat inside the engine and at the exhaust. and at just 6cc those small parts would have a hard time getting rid of the heat instead of melting. (also, parts weaken the hotter they are and reaching 40.000 rpm just gets more and more unrealistic)

    lastly...you drawing shows a timing belt pulley. F1 engines use gears because timing belts simply lag too much at 18.000 rpm to give accurate valve timing, you wouldn`t be able to get away with that.


    but,

    let me also say this:

    i disagree with `many other tried and they failed, why would you suceed?`. failure is very subjective in engineering, because we live mainly in trade-offs .

    did the rotary engine fail? not really...it works...just has bad emissions and etc. but it does work and in SOME application it must be a good choice.

    and most of all, i think experimentation is always valid. i say go for it, build it, measure it, improve it. just don`t expect to suddenly have the greatest engine of all time. all things in engineering start rough and then get refined. the 4 cycle reciprocating engine is SO GOOD because people invested a LOT of time in making it better.(it started out VERY bad).

    and even though ultimately there`s a limit in how good you can make something, that does not mean you are wasting time testing new things out.
     
  9. Jul 25, 2016 #9

    manolis

    manolis

    manolis

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    Hello Enfieldbullet.

    Thanks for your technical arguments and the opportunity to explain a few things.


    You write:
    “first and foremost, thats a cool new rotary valve design, i`ve never seen it before and i think it could be really cool to build an engine using it. but your 40,000 rpm is just...too much. modern F1 engines arrive at 18.000 rpm. you could probably do a little faster on a reciprocating otto cycle but not much, not nearly 40.000 rpm.
    that`s because your flame front has to consume the fuel in the combustion chamber at every powerstroke and at 40.000 there isn`t enough time for that to happen. your engine would do a full turn at almost every 1 millisecond and you would have 0.5 milliseconds for combustion to occur. combustion cannot happen that fast normally, i think i remember 3 milliseconds quoted in a book in high-turbulence designs. maybe you would just have a lot of combustion happening in the exhaust pipes, and that you make a pretty inefficient engine”



    50,000rpm sounds as too much, but it is not too much.

    Let me explain it.

    The Ducati Panigale 1299 has 116mm bore, 60.8mm stroke and runs reliably till 11,500rpm of the rev limiter.

    In the 24.8mm bore x 13mm stroke PatRoVa model engine (same bore to stroke ratio with the Ducati), the flame has to travel a 116/24.8=4.7 times smaller distance.

    Provided the flame front propagates at the same rate (speed) in the Panigale 1299 and in the PatRoVa model engine, the second burns the mixture until at least 11,500*4.7=53,800rpm

    Actually, the flame in the Ducati Panigale extends slower than the flame in the PatRoVa model engine because the shape of the combustion chamber of the first is not good: it is a thin disk (116mm diameter, 5.24 mm average height for 12.6:1 compression ratio), with deep valve pockets on the piston crown and necessarily abnormal shape of combustion chamber walls.
    In the one case the flame extends at the two only dimensions (thin disk), while in the second case, wherein almost all the mixture is concentrated into the chamber formed between the two disks of the rotary valve (the clearance between the flat piston crown and the cylinder head is quite small: the limitation is to avoid the piston-cylinder head collision at high revs), the flame extends in three dimensions and proceeds faster with lower thermal loss.

    So, as regards the combustion, 50,000rpm is OK for the oversquare PatRoVa model engine.


    From the practical viewpoint, take the OS.18TZ model engine ( http://www.pattakon.com/tempman/osmz2110-dynotest-rcnitro.pdf ).
    2-stroke with 16mm bore and 15mm stroke.

    The dyno test in the above PDF shows the peak power at 30,500rpm and the maximum rpm at 42,500.

    Here is the port timing (quote from http://www.pattakon.com/pattakonPatAT.htm ) :

    [​IMG]

    Its is a tiny engine that provides 750bhp/lit. To achieve such high specific power it is required the efficient burning of a good quantity of fuel inside the cylinder.



    You also write:
    “secondly, at 40.000 rpm in a reciprocating engine, the inertial forces on the piston would be a HUGE problem and you would need a super strong material or a super dimensioned part. but the more massive the part is the slower the engine`s top speed would be. which brings me to the third point”


    The abovementioned OS.18TZ model engine revs reliably at 42.500 rpm wherein the mean piston speed is 21m/sec and the maximum acceleration of the piston (with, say, connecting rod to stroke ratio 2.0) is 19,000g (g=9.81m/sec^2).

    With 13mm stroke versus the 15mm stroke of OS.18TZ, the PatRoVa model engine has a mean piston speed of 21.7m.sec at 50,000rpm and a peak inertia acceleration of 23,000g. With longer connecting rod (say, 3*stroke=39mm from center to center) the maximum acceleration of the piston falls at 21,000g (only 10% higher than in the OS.18TZ).

    An advantage of the 4-stroke is that its piston is shorter than of a 2-stroke because it needs not to cover and uncover ports on the cylinder liner. It also runs colder (it burns every other reciprocation; and there is no side of its piston skirt thrusting over hot exhaust port).

    According the previous, when a 4-stroke model engine with 13mm piston stroke is operating at 50,000rpm, the inertia forces on the piston is not a problem (at least not a huge problem) and the existing materials used already in the model engines are OK.



    You also write:
    “third: it`s not just because your valves are revolving that they don`t take force to turn. they do, just like poppet valves. and by the apparent size of the drawing their moment of inertia would be pretty big. you could make their diameter smaller, but then breathing would become an issue(must reach a compromise here).”


    No. There is no comparison of the loads.

    With a rotary valve rotating at constant angular speed, the only resistance is the friction between the valve and the cylinder head. But there is no force pushing the PatRoVa rotary valve onto the cylinder head. So the friction is quite small. The sprocket has to provide this small torque to the rotary valve, and this is all.

    Note: the rotary valve does not accelerate / decelerate during each crank rotation; it just rotates with half crankshaft speed.
    If necessary, the upper sprocket can be elastically connected to the rotary valve shaft (to allow the rotary valve to rotate at more-or-less constant angular velocity despite the slightly variable angular velocity of the crankshaft (think how the clutch disk is connected to the clutch hub))


    Parenthesis.

    The requirements seem initially “opposite” / “incompatible”:

    On one hand the PatRoVa rotary valve needs a stiff structure (which means heavy weight) wherein the high pressure acting on the two disks through the windows of the combustion chamber will cause only a tiny change in the clearance between the disks and the respective window lips:

    [​IMG]


    [​IMG]


    On the other hand, the rotary valve should be capable for extreme revs without significant friction.

    The above rotary valve (88mm diameter) has been tested alone (i.e. without a piston in the cylinder) at 11,000 rpm (i.e. 22,000rpm of the crankshaft) for several minutes without significant temperature increase of the cylinder head.
    Are there any normal size reciprocating piston engines running at 22,000rpm?

    End of parenthesis.


    As regards the inertia loads, comparing the PatRoVa rotary valve with the poppet valve is like comparing the day with the night.

    As a piston, the poppet valve accelerates and decelerates in synchronization with the crankshaft.

    During, say, 240 crank degrees the poppet valve opens and closes (frequency: 1.5 of the crankshaft frequency).
    Its restoring spring has to be strong enough to accelerate the poppet valve to close following the ramp of the camshaft.

    In the Ducati Panigale 1299, the intake valve lift is 16mm for a piston stroke of 60.8mm. This means that the acceleration of the valve is (1.5^2)*(16/60.8 ) =0.59 or 59% of the acceleration of thepiston.

    Note: the opening and the closing of the valve is far from being pure sinusoidal;
    the acceleration of the piston, due to the limited length of the connecting rod, is not sinusoidal , too.

    But in the lump sum the acceleration of the valve is more than half of the acceleration of the piston.

    With the intake valve weighing 46.8gr, the overall reciprocating “valve mass” is about 100gr (it is the valve mass plus half of the spring mass, plus a part of the mass of any linkage like, say, the cam follower).

    At 11,500rpm the acceleration of the piston of the Panigale is about 5,600g; according the previous, the acceleration of the inlet poppet valve of the Panigale is more than 2,800g.

    This means that the spring has to be capable to apply a restoring force of at least 280Kp (about 600lb) to the valve (actually more, for safety), otherwise the valve cannot follow the cam lobe. This means that the camlobe has to apply to the valve / valve spring an even stronger force (necessary for the acceleration of the valve / valve spring and for the compression of the valve spring) in order the valve to move as it moves.

    For the motion of the conventional poppet valves they are required extreme forces (which means stress on the parts involves (including the timing chain or belt), friction, wear, cost etc.)
    Ducati solved partially the problem by eliminating the restoring valve springs (Desmodromic cylinder heads: the valves not only open positively – as in the conventional valve trains – by they also close positively, without the need of restoring springs).
    The Panigale seems ideal for the application of the PatRoVa rotary valve in full size.
    But Ducati refuses to sell a Panigale without its expensive cylinder heads (they reasonably cost a dozen of times more than the PatRoVa cylinder heads), so we are looking for a Ducati Panigale with destroyed cylinder heads to modify it to PatRoVa.


    I hope it is now clear:

    There is no comparison. The load on the timing chain or belt of a conventional engine (say a sport single cylinder or a V-2) is dozens of times more than in the PatRoVa rotary valve.

    By the way, a broken timing chain or belt is – typically - a catastrophe in the case of poppet valve engines (valves / piston collision, destroyed pistons and cylinders and casing). In comparison, all it requires a broken belt or chain in a PatRoVa engine is the replacement of the broken belt or chain.



    You also write:
    “also, a reciprocating engine with just 6cc reaching 4.5hp is just unrealistic. did you factor in the thermal problems? i mean, normally 2/3 of the power is lost as heat inside the engine and at the exhaust. and at just 6cc those small parts would have a hard time getting rid of the heat instead of melting. (also, parts weaken the hotter they are and reaching 40.000 rpm just gets more and more unrealistic)”


    The OS.18TZ 2-stroke model engine with only 3cc capacity provides 2.28bhp at 30,500rpm (750bhp/lit).
    With 6.28cc capacity the 4-stroke oversquare PatRoVa model engine has an easier task: only 4.5bhp.
    As for the cooling of the parts, a 4-stroke is better / easier in this area than a 2-stroke.



    You also write:
    “lastly...you drawing shows a timing belt pulley. F1 engines use gears because timing belts simply lag too much at 18.000 rpm to give accurate valve timing, you wouldn`t be able to get away with that.”

    If necessary, gear wheels can replace the timing belt and the sprockets.
    On the other hand, as explained in the previous, the timing belt of the PatRoVa engine has a far easier job than the timing belts in the poppet valve engines.

    Thanks
    Manolis Pattakos
     
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  10. Jul 25, 2016 #10

    enfieldbullet

    enfieldbullet

    enfieldbullet

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    Mr. Pattakos,

    thank you, that was a great response. you seem to have a pretty solid plan.

    with that in mind, if you ran all of the calculations, i think its time to build a prototype to test it out as you pointed out. there certainly are some people on this forum which could help you with construction.

    I`ll certainly take a closer look at your design once i get home today.

    Best Regards,
    Rodrigo.
     
  11. Jul 26, 2016 #11

    manolis

    manolis

    manolis

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    Hello Rodrigo.

    You write:
    “Mr. Pattakos”

    Just Manolis, please.


    You also write:
    ”there certainly are some people on this forum which could help you with construction.”

    For the case these people need some more details for the casing / cylinder head, these animations may help:

    [​IMG]

    [​IMG]

    (the cooling fins and the rotary valve became bigger).

    Thanks
    Manolis Pattakos
     
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  12. Jul 26, 2016 #12

    blighty

    blighty

    blighty

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    i have model helicopter standing by for the prototype. :cool:
     
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  13. Jul 27, 2016 #13

    manolis

    manolis

    manolis

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    Hello.

    Here is one more animation showing the rotary valve and the cylinder-head-cover from various viewpoints:

    [​IMG]

    The design is quite simple.
    However, if anybody needs the CAD drawing, here is an email for communication: man@pattakon.com

    Thanks
    Manolis Pattakos
     
  14. Jul 29, 2016 #14

    manolis

    manolis

    manolis

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    Hello again.

    In the previous animations no attention has been paid to the lower end of the engine (crankshaft support, easy manufacturing).

    Here:

    [​IMG]

    things get substantially better and simpler.

    The replacement of the timing belt gets quite simple, too.

    The relative dxf file has been upgraded.

    Thanks
    Manolis Pattakos
     
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  15. Jul 30, 2016 #15

    Mechanicboy

    Mechanicboy

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    The big question: Will the engine be repairable if the leak is coming from the rotary valve? Probably not! That means it costs a lot to replace a complete cylinder head + rotary valve.
    Who would have interest to have such a motor that can not be overhauled by the owner when the engine lost compression caused by leaky rotary valve.

    I have a Webra T4 with Aspin rotary valve, not problem getting sealed rotating Aspin valve in cylinder head after the rotary Aspin valve was lapped together with very fine lapping paste on the cylinder head.

    Comparing between the engine with traditional valve system and rotary valve in power / weight ratio: The engine with rotary valve is much heavier due to the bigger cylinder head which means extra weight + rotary valve weighing more than valves in the cylinder head. I has SC 91 four stroke and Webra T4 to compare: The SC 91 four stroke engine is much lighter and powerful than Webra T4.

    Why invent a new engine that weighs so much and can not fix later again when there are already effective and repairable 4 stroke engine on the market? :rolleyes:
     
  16. Jul 30, 2016 #16

    manolis

    manolis

    manolis

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    Hello Mechanicboy.

    You write:
    The big question: Will the engine be repairable if the leak is coming from the rotary valve? Probably not! That means it costs a lot to replace a complete cylinder head + rotary valve.
    I have a Webra T4 with Aspin rotary valve, not problem getting sealed rotating Aspin valve in cylinder head after the rotary Aspin valve was lapped together with very fine lapping paste on the cylinder head.”


    Quote from http://ralphwatson.scienceontheweb.net/rotary.html (for all: do read it; you will like it).

    “I first became interested in the rotary valve as applied to internal combustion engines around about 1939, after reading an article in a motor cycle magazine describing an Aspin rotary valve four stroke engine. This engine had a capacity of 250 c.c. and it was claimed to produce 29 h.p. at 14,000 r.p.m., using low octane petrol.
    At the time, I was living in Nelson and serving an engineering apprenticeship. On occasion I watched a group of engineers, led by the well-known aviator George Bolt, race one metre hydroplanes on the local model boat pond.
    These model boats were powered by 30 c.c. engines and ran tethered to a central pole in the pond to provide quite exciting action. Being an enthusiastic experimenter, the Aspin engine came to my mind and I decided that I should give them some competition.
    With great, but what turned out to be misguided enthusiasm, I built a model engine based on the Aspin design, which incorporated a cone type valve the same diameter as the cylinder bore, rotating in the cylinder head. The combustion chamber was contained within the rotary valve, which rotated to line up in turn with the spark plug, exhaust port and inlet port.
    Full combustion pressure was applied to the valve, forcing it into the taper of its conical seat with the object of ensuring a good seal, but this arrangement could result in the valve seizing in the head due to lack of clearance and lubrication. In order to counter this, the Aspin design incorporated a roller thrust bearing on the valve stem.
    I used the same arrangement but could not attain an adjustment whereby the bearing took the load and a satisfactory seal was achieved. When adjusted so that load was on the bearing, the seal leaked and the engine had poor compression and would not run. With load on the cone the valve would seize. After suffering much frustration with broken drive shafts and stripped gears, the engine was eventually run for short periods with load on the cone, thanks to a copious supply of castor oil. This was supplied under pressure to the valve face, by means of a hand pump. My goal of fitting the engine into a model hydroplane came to naught and George Bolt and company remained unopposed at the model pond.
    However I was able to test the engine running against a brake and it recorded 1/8 h.p. at 8,000 r.p.m., which was a disappointment when related to the figures quoted in the article which had inspired my efforts.
    Many years later the story came out that the Aspin engine was tested by the motorcycle manufacturers Velocette, who found that it produced only half the horsepower claimed, the suggestion being that the original testing had been carried out with a wrongly calibrated tachometer.”
    Here are the drawing and some photos of the “Cross – Ralph Watson” Rotary Valve engine:

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    End of Quote.



    According your experience with your Aspin rotary valve engine (Webra T4), the first question coming in your mind is “Will the engine be repairable if the leak is coming from the rotary valve?”

    Let me ask:
    what is the relation between the TBO (time between overhauls) for the lower end (including the piston and the cylinder liner) of your rotary Aspin Webra T4 or of your conventional poppet valve SC91 (I suppose they are more or less the same) and the TBO of your Aspin Webra T4 cylinder head ?

    I.e. how many times you make the regrinding of the Aspin rotary valve before you need to repair something in the area below the cylinder head.


    Quote from a previous post:

    “Forget the unconventional rotary valve of the model engine in my last post and let me know whether, with a conventional cylinder head, the same model engine would work and would be durable.

    Then compare the ring-less piston with the PatRoVa rotary valve:

    The one part (the piston) seals the “lower” end of the combustion chamber, the other part (the PatRoVa rotary valve) seals the “top” end of the combustion chamber.

    Unless I am wrong, and despite the heavy mechanical and thermal stresses it undergoes, the ringless piston proved in practice good in both: sealing and reliability,

    Think the pressure load on the piston: with 20mm bore and, say, 50bar maximum pressure during the combustion, the downwards force on the tiny piston is some 157Kp / 350lb.

    Due to the leaning of the connecting rod, the skirt of the piston is heavily and unevenly loaded by the pressure loads and by the inertia loads; it thrusts / abuts heavily on the cylinder liner and needs good lubrication to avoid seizure.

    Think also the “thermal load” on the piston: during the combustion the piston top comprises some 40% of the total surface of the combustion chamber.

    The reciprocating piston needs to be lightweight (otherwise the inertia loads limit the red line), the same piston needs to be robust to receive the loads keeping the distortion minimum.

    In comparison to the piston of the model engine, the "life" of the PatRoVa rotary valve is by far easier and the sealing it achieves better.
    For instance, the hub between the two disks of the PatRoVa is as big in diameter and as heavy as necessary because it does not reciprocate: it rotates smoothly with half crankshaft speed.
    For instance, the clearance between the chamber windows (chamber ports) and the two disks of the PatRoVa can be substantially smaller than the clearance of the piston.”

    End of Quote.


    According the previous, the PatRoVa Rotary Valve model engine will need service in its cylinder head every, say, 5 repairs of the bottom mechanism.

    Even then, you can polish (in a milling machine) the working flat surfaces in the cylinder head / cylinder cover, and replace the PatRoVa rotary valve by an oversized one (as happens in the normal engines wherein after the re-grinding of the cylinder liners, the piston rings are replaced by the next size piston rings).



    You also write:
    “Comparing between the engine with traditional valve system and rotary valve in power / weight ratio: The engine with rotary valve is much heavier due to the bigger cylinder head which means extra weight + rotary valve weighing more than valves in the cylinder head. I has SC 91 four stroke and Webra T4 to compare: The SC 91 four stroke engine is much lighter and powerful than Webra T4.”


    Here is a photo of the Webra T4 cylinder head / rotary valve (from the AVION MAGAZINE ) :

    [​IMG]

    Look at the intake and exhaust ports on the cylinder head.
    Due to the Aspin architecture (wherein the size of the ports is limited by the necessarily big hole (in the center) though which the shaft of the Aspin Rotary Valve passes through to find, at the other end, the bevel gear) the intake port area is small.

    The diameter of the cylinder seems some 3.5 times bigger than the diameter of the intake port.

    The intake valve port area in the SC91 (27.7mm bore, 11.5mm intake valve diameter) seems about 50% bigger than the intake port area in the Webra T4.

    This agrees with the only 1.1bhp at 11,200rpm of the Webra and the 1.5bhp of the SC91 at some 10,000rpm.


    Please do a calculation about the force onto the bearing of the Aspin rotary valve of your Webra T4 during combustion (suppose 50bar maximum pressure).
    A rough estimation says some 150Kp.
    The worst is the affect of the above load and bearing on the clearance between the Aspin rotary valve and the cylinder head.
    As the revs increase, things get tough for the bearing.

    Do the same calculation for the PatRoVa rotary valve. If you calculate anything else than zero, do the calculations again.



    You also write:
    “Why invent a new engine that weighs so much and can not fix later again when there are already effective and repairable 4 stroke engine on the market?”

    As compared to the Webra T4 Aspin rotary valve engine, your conventional 4-stroke engine (SC91) is lightweight and strong.

    But is it? In absolute numbers, I mean.

    For instance, the Honda VTEC B16A2 1600cc 4-cylinder 16-valve engine used as the basis for the VVA-roller prototype at http://www.pattakon.com/pattakonRoller.htm has from the factory (and it is a normal size engine, not a tiny one) the same specific power withe the SC91.

    With only 2 valves per cylinder and “push rods” for their actuation, its rev limit is very low (at 10,000rpm of its peak power, 24.8mm piston stroke means only 8.3m/sec).

    It is too risky to increase the revs (and you gain nothing in power because of the limited valve area): the valves will hit the piston crown (as in the normal size poppet valve engines).

    The intake valve area is too small.
    With 15cc cylinder capacity, your single intake valve port area is less than half than the total intake port area of the PatRoVa model presented in this forum (worse even for the exhaust).
    Besides, the capacity of your SC91 is 2.4 times bigger than the capacity of the PatRoVa model engine.
    2*2.4=4.8, and 4.8*10,000rpm=48,000rpm
    This is why I estimate 50,000rpm for the peak power of the PatRoVa 6.28cc (24.8mm bore, 13mm stroke) model engine.
    With same specific torque (mN per liter) with the SC91, the PatRoVa rotary valve (which is 2.4 times smaller in capacity) will make two times the power of the SC91.

    As for the weight, I don’t think all these parts (covers, camshaft, pushrods, rocker arms, valves, valve springs) in the SC91 valve train weigh less than the PatRoVa rotary valve.

    And don’t forget the almost half piston stroke of the PatRoVa (think what this means for the weight of the crankshaft and of the con-rod, for the vibrations etc).

    In total, the expected specific power (bhp per liter of capacity) of the PatRoVa seems some five times higher than the SC91.


    Do I miss something?


    If anything is confusing, please let me know to further explain.

    Thanks
    Manolis Pattakos
     
    larry1 likes this.
  17. Jul 30, 2016 #17

    Mechanicboy

    Mechanicboy

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    Seeing that you downloaded my photo of Webra T4 who is located in RC Universe where my nickname is Motorboy in RC Universe.. :)

    SC 91 FS weight 0,64 kg, approximately 1,4-1,5 hp versus Webra T4 weight 1 kg, 1 hp. Also i will select low weight and high power to use in the model aircraft.
     
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  18. Jul 30, 2016 #18

    manolis

    manolis

    manolis

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    Hello mechanicboy.

    You write:
    “Seeing that you downloaded my photo of Webra T4 who is located in RC Universe where my nickname is Motorboy in RC Universe..”

    The photo has been replaced.


    For the rest, is it now clear the limitations the Aspin architecture introduces?

    For instance, think what happens if you lift for 0.5mm the Aspin rotary valve of your Webra T4: no compression at all.

    Then think what happens if you lift for the same 0.5mm the PatRoVa Rotary Valve. Nothing.
    The PatRoVa Rotary Valve is so insensitive in this kind of displacement that this characteristic can be used to control the timing and overlap:

    [​IMG]

    For more: http://www.pattakon.com/pattakonPatRoVa.htm

    Thanks
    Manolis Pattakos
     
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  19. Jul 31, 2016 #19

    Hopper

    Hopper

    Hopper

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    As someone who has spent some time trying to get conventionally valved engines to flow more intake charge into the cylinder and get the exhaust gasses out as quickly as possible, when I look at this rotary valve, the first thing I see is a very tortuous path for the gasses to flow through. Basically in the intake charge enters the combustion chamber sideways and then hits a brick wall and then has to turn 90 degrees to go down into the cylinder. Allthis immediately after the intake charge has already made one rightangle turn to get through the disc valve.
    It is comparable with the intake path of an old sidevalve engine, (but inverted) which is very inefficient compared to today's overhead cam engines where the intake port is an almost straight, vertical shot from intake down to the bottom of the cylinder.
    I have difficulty seeing how this cylinder head will flow at anything other than lowish rpm.

    Also, the exhaust gas heating the one-piece combined rotary valve, which then heats the incoming intake charge seems less than ideal.

    Looks like an interesting machining project for someone though, to make your prototype. Good luck with the project!
     
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  20. Aug 1, 2016 #20

    manolis

    manolis

    manolis

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    Hello Hopper.

    You write:
    “As someone who has spent some time trying to get conventionally valved engines to flow more intake charge into the cylinder and get the exhaust gasses out as quickly as possible, when I look at this rotary valve, the first thing I see is a very tortuous path for the gasses to flow through. Basically in the intake charge enters the combustion chamber sideways and then hits a brick wall and then has to turn 90 degrees to go down into the cylinder. Allthis immediately after the intake charge has already made one rightangle turn to get through the disc valve.”

    I think you mean like this:

    [​IMG]

    The two symmetrical incoming gas streams find each other and proceed downwards to the cylinder.
    The one gas stream constitutes what you call “brick wall” for the other gas stream, and vice versa.
    On the symmetry plane (it is parallel to the rotary valve disks, it also “bisects” the combustion chamber) the speeds of the two gas streams are identical / compatible; this “imaginary brick wall” (i.e. the above symmetry plane) is quite different than a true “brick wall” on the surface of which the speed of the gas stream is necessarily zero spoiling the gas flow.


    If something fits with the term “brick wall”, this is the head of the conventional poppet valve:

    [​IMG]

    wherein the incoming gas stream finds a real “brick wall” (the poppet valve head) and changes direction, with the average turn angle being some 90 degrees. Then the incoming gas stream changes direction again “downwards” along the cylinder axis.


    Talking for “brick walls” and flow restrictions, in a photo from the CycleWorld magazine they have been marked by circles / ellipses some restriction of the flow in the Desmodromic Ducati Panigale 1299 (one of the most technologically advanced engines today):

    [​IMG]

    The intake valves at a part of their periphery (green circles) are so close to the cylinder liner that the flow is substantially restricted.

    At their neighboring area (cyan ellipse), the one intake valve becomes an obstacle (a “brick wall”;) for the gas entering through the other intake valve, and vice versa.

    The exhaust valves at a part of their periphery (red circles) are so close to the cylinder liner that the flow is substantially restricted.

    During overlap, the close neighboring of intake and exhaust valves (yellow ellipses) causes the short-circuiting of intake and exhaust spoiling the scavenge of the combustion chamber and allowing in a part of the incoming through the intake valves charge to escape to the exhaust.

    See how the cooling liquid holes are arranged on the Panigale cylinder head bottom: all but one are at the exhaust valve side.


    Think why the Ducati Panigalle 1299 has such extreme-over-square design (116mm bore for 60.8mm stroke for 643cc cylinder capacity):

    More specific power (PS/cc) requires higher revs.
    Higher revs require shorter stroke and larger bore.
    Larger bore allows bigger poppet valve which go together with higher valve lift.

    As the revs increase the piston acceleration increases proportionally with the revs square and decreases proportionally with the stroke. The reduced stroke limits the acceleration of the piston.

    As the revs increase the acceleration of the poppet valves increases with the revs square, it also increases with the valve lift.

    At the end, the ratio of the increase of the valve acceleration relative to the increase of the piston acceleration is about 3 (for an 20% increase of the piston acceleration, the increase of the valve acceleration is 60%).

    At extreme revs the required forces in the valve train get so strong that a good part of the power provided by the piston on the crankshaft is consumed into the valve train.

    You can find a more detailed analysis for the previous at http://www.f1technical.net/forum/viewtopic.php?f=4&t=10966&start=975



    You also write:
    “Also, the exhaust gas heating the one-piece combined rotary valve, which then heats the incoming intake charge seems less than ideal.”

    Follow the exhaust gas and see how quickly and directly it passes through the exhaust ports of the rotary valve. This fast pass cannot heat substantially the rotary valve.

    In comparison, the head of the exhaust poppet valve and the lower half of its stem are into the “hell”. If you wanted to heat the exhaust poppet valve by a hot gas stream, this is the most efficient way. In order to protect the exhaust valves from overheating, you need a lot of cooling around their valve seats. A good part of the incoming fresh charge falls onto the hot exhaust valves and is heated reducing the volumetric efficiency of the engine. And later, during combustion, the compressed hot charge is in touch with the red-hot exhaust valve, reducing the compression ratio and the thermal efficiency of the engine.

    If I was asked to point at the worst thing in a conventional reciprocating piston engine, I would point at the exhaust poppet valves. And if I was asked for the second worst thing, I would point at the intake poppet valves.



    You also write:
    “I have difficulty seeing how this cylinder head will flow at anything other than lowish rpm.”

    In previous post I was explaining to Mechanicboy that the specific intake port area (cm2 / cc) of his SC91 4-stroke model engine is five times less than the specific port area of the short-stroke PatRoVa (6.28cc) model engine (double port area for 2.5 times lower capacity).

    Things get even worse for the exhaust port area of the SC91(which is some 6 times smaller than in the PatRoVa model engine).

    Do I need to say more? Five times higher specific port area, and you talk for lowish rpm!



    You also write:
    “Looks like an interesting machining project for someone though, to make your prototype. Good luck with the project!”

    It is also an easy machining.
    Some simple (but precise) milling and lath work and the PatRoVa model engine is ready to run.
    In comparison, the manufacturing of the cylinder head / valve train of the ringless OS 4-troke FL70 :

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    seems as a nightmare.

    Thanks
    Manolis Pattakos
     
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