2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

Hello Pinger.

The Ducati Panigale Superleggera 1299 (cost: £72,000) has one of the most expensive, most extreme and most technologically advanced engines today.

http://www.cycleworld.com/sites/cyclewo ... 9t0702.jpg

Its crankshaft has one only crankpin (which means: the main bearings can easily be roller bearings with “singe piece” crankshaft).

For many decades in Ducati they were using roller bearings to rotatably mount the crankshaft into the crancase.

Now Ducati uses plain bearings for their top model, and they seem more than satisfied.

Thanks
Manolis Pattakos

Hi Manolis,

Ducati had, for decades built expensive motorcycles 'carefully' hand-assembled by skilled workers,
& at 1st they found it difficult to even break-even financially with their complex bevel drive OHC
designs, so 'automotive style' toothed rubber drive belt cam-drive top-ends were introduced..

The Panigale is here to extend that automated ( robot) manufacture/assembly function to the rest
of the engine, both to make production less expensive & to utilize the oil-cooling for WSBK racing..

[Tommy Cookers]

the origins and justification of the crosshead feature lie far in the past
these seem a partial reminder of how we got to where we are today
http://www.marinediesels.info/Basics/th ... nation.htm
https://en.wikipedia.org/wiki/Crosshead
the engines have a very long stroke and very low rpm because that's what the propellor wants
today they can be used down to 7 rpm
another manufacturer of this type of engine went for higher rpm, which I guess needed reduction gearing for the propellor

[J.A.W.]

...these engines have... ...very low rpm because that's what the propellor wants...

( Ok T-C, a quick off topic, but related post..
.. what can you reveal about submarine steam turbine reduction gearing.. to reduce noise via cavitation..

[Pinger]

Ta for that P & T-C, & here is an example of a 'twingle' ( 360`crank/twin-fire 2T);
http://www.motorcycleclassics.com/class ... mz16ndzhur

This was a doubled-up OSSA 250 single, & a couple of those were also doubled-up - to make a 1000/4..

Why twingle though - traction on dirt tracks? (I noticed the reference to 180 degree phasing for a race version, presumably on tarmac).

Similarly, as discussed on page circa #70, the TZ750. Why fire two cylinders simultaneously when one of the 2T's advantages is multiplicity of firing strokes thus giving the transmission an easier time (and before big bang was adopted for tarmac racing)?
Had they phased cylinders 3 and 4 90 degrees to cylinders 1 and 2 (exactly as in marine outboards) then firing would have been at (surely preferential?) 90 degree intervals. Did they not do this so as to avoid chatter on the geared coupling perhaps?

[Tommy Cookers]

my guess is that they did it as simply as possible to be very quick and so dominate by surprising the competition
using 350 crankshaft parts etc to produce the homologation quantity of 200 Formula 750 machines, called TZ750 but then actually 700 cc
presumably it was no worse for vibration than the outboards mentioned (these having 90 deg intervals for easier pull-starting ?)

Suzuki and Yamaha GP 4 cyl 2 strokes had paired firing (or very close to that) from 1964 for 40+ years
eg in all those square 4 Suzukis it gave a smaller simpler ignition system
Yamaha won WCs with the TZ500 like the TZ750

[63l8qrrfy6]

And it is anything but “rubbish at sealing”.

This is a more than 80 years old design / manufacturing.

17:1 compression ratio, compression ignition.

If it had problematic sealing, or not top fuel efficiency, it would not be used in airplanes making (for the first time; 1936) 6,000 miles without a stop.

Again, the 'it was decent 80 years ago' argument' - let's put this to rest - 80 years ago they flew sleeve valves which had an impressively high oil consumption - does that make them good too ? If you want to make a good case let me know how much oil the jumo burned and let's see how it compares to modern engines.

Your theory relating the “sealing efficiency” with the number of holes / ports on the cylinder liner needs amendments.

It's not my theory - these are published results.

The thrust of the piston skirt on specific regions at the sides of the cylinder liner spoils the shape of the cylinder liner and makes the temperature distribution around the cylinder liner uneven (this unevenness is further increased by the non uniform arrangement of the intake and exhaust valves on the cylinder head).

The FE plot shows a peak displacement of 16 micron - the radial thermal deformation of the liner will be higher than that. Secondly, depending on how it is supported you tend to see two behaviours:

1. A poorly supported liner will undergo a large 1st order deformation (almost rigid body translation) in the direction of the thrust load. 1 st order deformations have no effect on ring performance. The dominant order will still be 0 (caused by thermal deformation and to a lesser extent cylinder pressure). There will be a small 2nd order deformation but this is nothing rings can't usually handle - as I have explained before low orders do not cause issues.

2. A well supported liner will have even lower 1st and 2nd order deformation, however the contact pressure at the skirt contact patch will be higher. This however has no adverse effects on ring performance in skirt guided pistons!

Now you show us a similar plot for your engine so we can discuss it.

Also claiming that the piston contact spoils the thermal loads on the liner is non-sense.

Another good solution is the approach of Hugo Junkers with his twin crankshaft Opposed Piston Jumo engines wherein the intake ports, at the one end of the cylinder liner, and the exhaust ports, at the other end of the cylinder, are too many and uniformly distributed. Only the thrust loads on the sides of the cylinder liner spoil the – otherwise perfect – cylindrical symmetry of load distribution, temperature distribution, etc.

No! - you get hot spots on the strips in-between the port windows - the more of them - the higher the order of distortion. Bad !

The hydrodynamic lubrication in the cross head is so superior than the lubrication between the piston skirt and the cylinder liner, that reduces several times the friction loss due to the leaning of the con-rod.

The coefficient of friction in a cross-head is comparable with the coefficient of friction in the plain bearings (around 0.001).

Completely wrong. In the crosshead the speed is not constant. Lubrication will go through dry contact at the top and bottom (when speed is 0) , transition through mixed lubrication as it starts picking up speed and go hydrodynamic around mid-section. By comparison a journal bearing operates in full hydrodynamic conditions all the time

If you compare the fitting of a piston skirt with the distorted cylinder:
then you may agree that, in comparison, the flat surfaces of the cross head fit perfectly.

Piston skirts have a carefully designed 'barrel' profile which facilitates hydrodynamic film generation.
NOT being flat is what makes them work in the first place. Your understanding of fundamental principles is flawed.

By the way, I am waiting for your “description” of what is happening with the lubricant when the piston abuts heavily on, and slides along, the port openings of a 2-stroke.

It craps itself with or without the presence of thrust loads.

[Muniix]

Here is a examinating of someone trying to invent issues about athe Bishop valve a competing technology to theirs. Requiring me to reply to all the errors, bad assuumptions, cherry picking, deception and not once does he answer an question refering to his own design, how much air does it pump or trap in the cylinder, the flow velocity any of the basic engine design paramaters.

Hello all.
...

The only independent claim of the 7,401,587:

1. A rotary valve assembly for an internal combustion engine comprising an axial flow rotary valve having a cylindrical portion, and an inlet port and an exhaust port terminating as openings in said cylindrical portion, a cylinder head having a bore in which said valve rotates about an axis with a predetermined small clearance between said cylindrical portion and said bore, a window in said bore communicating with a combustion chamber, said window being substantially rectangular in shape and said openings periodically communicating with said window as said valve rotates, bearing means journaling said valve in said bore, an array of floating seals surrounding said window, and a bias means preloading said array of floating seals against said cylindrical portion, said array of floating seals comprising at least two spaced apart elongate axial seals adjacent opposite sides of said window and at least two spaced apart arcuate circumferential seals adjacent opposite ends of said window, each said axial seal being housed in a respective axially extending axial slot formed in said bore, and each said circumferential seal being housed in a respective circumferentially extending circumferential slot formed in said bore, characterised in that said circumferential seals are axially disposed between the ends of said axial seals.

Having just one independent claim, it means that every other claim of the patent “depends” on the independent claim, i.e. every dependent claim has all the limitations introduced by the independent claim plus its own limitations.

Question:
Are the above two “still in force” patents of Bishop Innovation Limited “strong” enough?

Yes because it is the current gas sealing patent. The one you said "Rubish" when I claimed you knew the one you reered to was obsolete so you could find something to cherry pick from to support your ....'ed opinions.

Suppose you want to “bypass” the US7,584,741 patent (i.e. to make, use or sell it in the territory of the USA without paying “royalties” to “Bishop Innovation Limited”).

The simplest way to “bypass” the patent is to select a “rotary valve having an outside diameter bigger than 0.85 times a diameter of said cylinder”.

Not geometrically viable without excessive cylinder spacing.

Or, say, to use one only spark plug (or, better, a “laser spark plug” which ignites the mixture at the center of the rectangle window, wherein it is not possible to be disposed a conventional spark plug).

I would speak to an patent laywer before doing this, this patent is just the Gas and oil sealing patent, so doesn't apply to the head design.

More likely you are cherry pickin, trying to decieve the forum readers requiring me to write this post.

Suppose you want to “bypass” the other, “still in force”, US7,401,587 patent of Bishop (i.e. to make, use or sell it in the territory of the USA without paying “royalties” to “Bishop Innovation Limited”).

A simple way is to select a “slightly oblique” arrangement of the sealing means and grooves (the axial seals turn to slightly “helical” seals, which, by the way, can better fit with the oblique separator inside the Cross rotary valve).

This would add crevice volume, and no one would contemplate such stupidity.

Alternatively, you can have the circumpherential seals extending outside the ends of the axial seals, with the axial seals disposed between the ends of the circumpherential seals.

And so on.

This would effect the clever design of how it controlls all of the gas flow issues, all carefully described.

The sealing array deals with the gas flows in and outside of the array, flowing blow-by back into intake or ported out into emissions handling for very low emissions due to its fast and complete combustion from a feature free combustion chamber bar geometry to support the dual cross tumble vortices attaching to head and piston crown and first and second squish zones to move the two offset flame kernels into the central area after to create a huge central flame kernel of nearly 30mm

Remember this is the patent you deny existed. The one that addresses all the gas sealing issues.

Bishop Innovation Limited was a multi million dollar company.
The guys worked in the Bishop rotary valve project were smart guys.

Then why they wrote such “vulnerable” patents?

A reasonable answer is that they had to present “results” and “protection” to their investors.

I bet that if they were spending their own money for the patenting, they would never file such patent application.

As usual you form opinions that are totally wrong, baseless and incorrect.
...

Here is the first claim of the PatRoVa rotary valve, for comparison (the GB2525704 patent has already be granted by the UK-IPO and is in force, the US patent is approved and is to be granted with the payment of the US480$ Issue Fee):

1. A disk rotary valve assembly for reciprocating piston positive displacement machines, the disk rotary valve assembly comprising at least: a cylinder (30); a cylinder head (5); a piston (40) reciprocally fitted in the cylinder (30); a chamber (50) defined inside the cylinder (30), the chamber (50) is sealed at one side by the piston (40), the chamber (50) is sealed at another side by the cylinder head (5); the cylinder head (5) comprising passageways (20, 17) for the introduction of gas in the chamber (50) and for the evacuation of the chamber (50) from the gas; the cylinder head (5) comprising a pair of oppositely arranged chamber ports (12), each chamber port comprising a lip (13) at its end; a disk rotary valve (1), the disk rotary valve (1) being rotatably mounted in the cylinder head (5), the disk rotary valve (1) rotating about a rotation axis (60) in synchronization to the piston reciprocation; the disk rotary valve (1) comprising a pair of oppositely arranged fronts (8), each lip (13) being in gas tight sealing cooperation with a respective front (8) of the disk rotary valve (1), the orthogonal projections of the oppositely arranged fronts (8) on the rotation axis (60) of the disk rotary valve (1) being at a substantial distance from each other; the disk rotary valve (1) comprising valve ports (10, 9), during a part of a rotation of the disk rotary valve (1) the chamber (50) communicates, through the valve port (10, 9) with passageways (20, 17), during another part of a rotation of the disk rotary valve (1) the fronts (8) seal the chamber ports (12), isolating the chamber (50) from the passageways (20, 17), the chamber ports (12) being arranged so that the total force applied on the disk rotary valve (1) due to a high pressure inside the chamber (50) to be several times smaller than the force applied separately on each front (8) due to the same high pressure inside the chamber (50).


And here is the 19th claim (which is also an independent claim) of the same patent for the PatRoVa, which may seem more simple / comprehensible to the forum member / reader:


“19. A disk rotary valve assembly for reciprocating piston positive displacement machines, comprising at least: a cylinder; a cylinder head; a piston reciprocally fitted in the cylinder; a chamber defined inside the cylinder, the chamber is sealed at one side by the piston, the chamber is sealed at another side by the cylinder head; the cylinder head comprising inlet passageways, exhaust passageways and a cavity, the cavity being a part of the chamber; the cylinder head comprising a pair of oppositely arranged chamber ports at two opposite sides of the cavity, each chamber port comprising a chamber port lip at its end; a disk rotary valve rotatably mounted in the cylinder head and rotating in synchronization with the piston reciprocation, the disk rotary valve comprising a pair of oppositely arranged fronts, the cavity being disposed between the pair of oppositely arranged fronts with each chamber port lip being in gas tight sealing cooperation with a respective front of the disk rotary valve, the disk rotary valve comprising valve ports, for a part of a rotation of the disk rotary valve the chamber communicates, through the valve ports, with some of the inlet and exhaust passageways of the cylinder head, for another part of a rotation of the disk rotary valve the chamber is sealed from the cylinder head passageways, the arrangement is such that the total force applied on the disk rotary valve due to a high pressure inside the chamber being many times smaller than the force applied separately on each front due to the same high pressure inside the chamber.”

The "pair of oppositely arranged chamber ports each chamber port compromising a chamber port lip"

and

"the cavity being disposed betwen the pair of oppositely arranged fronts with each chamber port lib being in 'gas tight' sealing cooppperation with a respective front of the disc valve."

Completely ignores thermal expansion of likely differing materials and different geometries. You have no cooling galeries anywhere, gas at pressure will escape. The exhaust port proximity will effect the lip seals effectiveness.

These two issues ;
Sealing the chamber ports effectively, Everyone else uses gas sealing elements, and spends huge resources developing them.

A mechanism to turn the flow into the internal chamber cavity will be needed. Else fluid flow coefficient will be 0.3-0.5. You will not find a fluid flow engineer who disagrees with this statement.

Additionally Pressure inside the chamber will effect flow, a low pressure will improve the flow, the flow from the opposing port will increase pressure reducing total flow through both ports, possibly creating some strange pressure wave dynamics.

Compare the above claims with the claims of the “still in force” two US patents of Bishop.

The PatRoVa patent is a “basic patent” because it introduces a completely different kind of rotary valves not existing before.

Just like most of the rest patents of pattakon.

Granted patents to pattakon by the US Patent and Trademark Office (US-PTO):

Thoughts?

Thanks
Manolis Pattakos

With nearly as many patents as Bishop how much licensing fees do you earn, Bishop earn over $40 million a year.

So who knows how to write patents?

Bishop or Manolis?

An engine is essentially a pump, first it must pump air effectively with low losses, low energy. This requires high flow coefficients, a single large port is always best, less surface areas for friction to slow flows.

You did not answer the intake velocity or trapped air mass questions..

All you did was deflect with a bunch of incorrect opinions. You are not following the terms of this Forum, follow or stop postiiing.

[Pinger]

One more TJI/steel piston question if I may?
Does Renault (or the Renault derived unit run by Red Bull) and Honda have this?
(By performance I'd guess not, but surely if Ferrari found out about it....)

[Muniix]

I have to take Muniix's side on this.
I don't know nor care what has happened between you two, but he has a very strong point:

Engine design begins with cycle simulations which yield performance figures as well as thermal and mechanical loads.

Manolis doesn't do engine design. He is an inventor who dreams up new concepts. If a few "engine designers" bothered to look beyond the end of their nose and help him out, there are several concepts on his website that are actually superior to anything currently in production and could become viable - Pat OP for example.

that is what I initially tried to do, after he put the following at the end of his post
"I would like to know your thoughts/objections"

So I did raise a fluid flow issue and explained why their was a problem.

The response I recieved for my effort was of total denial, deflection and attack.

I have in my career starting in the early 80s had to verify vendors claims by using load testing, simulation and modelling.

The response recieved on notifing the vendors of issues, essentially decided whether we continued with them or not.

Some sent their lawers on us, they don't exist anymore.
When we used the #1 vendors equipment and it had issues, I identified a second tier vendor, Cisco Systems and working with them we built the largest Unix/Oracle system on the planet. It is still going strong today after 27 years and the cheapest most cost effective transaction system handling Licensing and Registrations in NSW Australia.

[Muniix]

You will also find that the total friction due to piston rings (worst culprit being the oil ring) is higher than the skirt friction in conventional skirt guided piston 4 strokes.

Which is a key benefit of the cross-head design.
1. Elimination of tilting of the piston improves efficiency of all the rings allowing reduced ring tension and reduced lubrication.
2. Eliminating the skirt as a cross-head bearing further reduces the quantity of oil required on the bore.

You will still have to lubricate both ring packs, but there are now twice as many (not counting the scavenging piston) I struggle to see how you can magically reduce consumption when you are effectively doubling the potential for oil loss.

I am sure this is not a deliberate attempt to mislead and you simply overlooked the fact that the extra piston contributes its own displacement, so oil consumption as a function of engine displacement remains the same were you to substitute the opposing piston with a cylinder head.

In preparing to do piston friction modelling on it initially shows a large increase in the non hydrodynamic frictional area there being three pistons with one larger one. Mudflap is likely correct.
There being an increase at least 60%+
Piston ring friction and gas blow-by modelling reveals a lot of information when your models actually replicate experimental data.

The energy required to deliver the high pressure lubrication has to be accounted for in the engine mechanical losses.

[Muniix]

...I'm not telling anyone to do anything, especially to engage with someone who has no grasp of reality.

You think it's viable to spend millions to sell a few motorcycle heads for crf 450 owners, who can't use them on the road or competition. Hmm that will be $20k+ per head, minimum and still make a loss.

Marc, the CR450F is an MX competition machine, sold in fairly large numbers worldwide..
..& AFAIR, the MX racing rules do not actually ban 4T rotary valves.. ( as for Moto 3, I dunno)..

Anyhow..
If the attributes you claim for the Bishop system do indeed give a marked performance increase..
..then there is very likely a market for them, & thus at least - also worth doing a feasibility study..
.. perhaps paid for by those prior investors - who would like to realize some return on funds spent?

When Mercedes-Ilmor dropped it after the ban by both the FIA & FIM for which there was a EU Commission investigation and before being banned Mercedes offered to cover the development costs that was the concern of Renault and the other engine suppliers. Once banned​ it couldn't be demonstrated in an arena that showed it's advantages and durability.

There was no way to quickly get the yearly multimillion dollar returns to justify approving the next years budget. Any money available had better places that had better opportunities to return profit. The valve despite a good strategy to take it into production was blocked by a early engine rule change that came 4years early despite the agreement that the V10 would not change until 2009.

Selling heads to Crf 450 owners at some huge price like $20,000 each not a viable plan to get to a profitable business.

The manufacturers​ are not going to base Implementing it on a few apparent wins some racers had. This is commercial realty. The big engine manufacturers had to licensed it to justify continued funding.

Sneaking it into a design funded by less traditional means bypasses these issues.

When one has the data to show a power plant concept is viable and meets a growing market others are not addressing, you are going to do well especially if the competition can't match performance and efficiency, even if the do invest heavily, you are miles ahead.

[Muniix]

Hello Mudflap

You write:
“The ideal combustion chamber is whatever offers the largest flame front area, fastest burn rate and minimal flame-wall contact. Heywood specifically states that a disc shaped chamber (rectangular cross section) where the flame initiates from the side is the worst in terms of combustion speed.”


According Heywood, the Junkers JUMO 205 (first run: 1930) with the “disk shaped chamber where the flame initiates from the side”:

https://upload.wikimedia.org/wikipedia/ ... utview.JPG

should not run as it did / does:

That statement is a over simplification.

Modern diesel engines run well over 40%. What aspects should it not run as it did?

The BSFC plot (bottom middle):

http://www.pattakon.com/tempman/Junkers ... 5_BSFC.jpg

shows a 0.35lb/hp/hr (i.e. 216gr/kWh, which means a Brake Thermal Efficiency (BTE) of 37.5%).

(click http://www.pattakon.com/tempman/Junkers ... 5_BSFC.jpg if the drawing is not clear).


The peak injection pressure is only 600 bar.

Direct injection of gaseous fuels is performed at very low pressures typically between 70-200 bar. Typically 40-60 bar above peak cylinder pressure.
Additionally you can injection it to cool the charge lowering the pressure to increase filling and easier compression.

This saves evergy improving efficiency and power.

The design is old (more than 80 year old).

The 37.5% BTE is maintained in a wide range of revs (from 1,500 to 2,500).

The 37.5% is not the peak BTE of the engine.

The fuel efficient, lightweight and reliable Junkers Jumo Diesels enabled, for the first time, airplanes to travel at distances not possible before.

So,
either Heywood is not right, or the rest characteristics of the Opposed Piston Jumo 205 are by far superior than those of the state-of-the-art modern Diesels (wherein the flame initiates centrally, wherein the fuel is injected at way higher pressures (fine droplets) and with the perfect timing, wherein everything is optimized by computers, etc, etc) to justify the 37.5% “working” BTE .

Deceptive again, modern diesels are nealy 10% higher in efficiency, automotive diesels would also be at leasst 10% better at the same bore and stroke giving the same surface volume ratio where heat is lost.

Or are you letting confirmation bias effect your judgement?

Now, take the Junkers Jumo 205 and modify it to PatOP or to OPRE.

Use either the centrifugal compressor of the Junkers Jumo 205 as scavenging pump, or, preferably, a turbocharger driven by the exhaust gas.

The lube specific consumption drops a few times and the frictional losses reduce (cross-head architecture, true hydrodynamic lubrication whereon the thrust loads are taken and the torque is created.

The time provided for the combustion increases by, say, 30% due to the longer dwell of the piston at the combustion dead center (this is an advantage the pulling-rod architecture offers):

Do you actully have evidence any of these claims are true, because I can't think of any off hand, and i've read a lot, implemented lots of published models, verified them against experimental data. All with test and behaviour driven development.

Combustion is a complex process, requiring turbulence, the slower piston velocity towards and away provides next to no advantage, you are loosing turbulent kinetic energy on compression just as your are slowing your expansion, one effectively cancels out the other, net benifit is near zero.

You want an asynchronous motion fast comprression and slowed initital expansion, like what an offset crank provides, and why these are being heavily researched at the moment.

Ideally depending on fuel type you want the rod to be most inline with cylinder axis around 50-70 after TDC. This gives a more ideal motion for combustion and extraction of work.

You really need to do some combustion research, to understand all of the different combustion systems, I have studied them all, from aci, hcci, rcci, gdci, SI, PCC, Haji, TJI ... and more i can't remember atm.

Additionally all the extra mass in your cranktrain creates inertia, the crank has a large distance between main bearings, it is going to flex a lot at speed placing high loads on the main bearings, creating high friction and vibration.

The use of large big ends so you can use one piece rods add unnecessary bearing frictional area and crank mass, the crank pin is of larger diameter than it need be to support the loads, sort of inverted crankshaft optimisation, De-optimisation!

Creating friction for ever on every engine produced wasting valuable fuel resources. Very irresponsible for engineers to do such things.

http://www.pattakon.com/pre/img18.gif

http://www.pattakon.com/tempman/pre_TDC.GIF


Partly QUOTE from http://www.pattakon.com/pattakonOPRE2.htm

Fuel's Viewpoint

The following animation shows the piston motion near TDC of an OPRE or PatOP engine revving at 6000 rpm versus a Conventional engine revving at 4500 rpm, for equal piston stroke and equal (1.65) con-rod to stroke ratio.

Without seeing the kinematic mechanism, how can you reply to: " WHICH is the Conventional and WHICH is the PRE ? "

-- Turbulence --

Suppose you are a fuel droplet injected either into the cylinder of the conventional or into the cylinder of the OPRE / PatOP.
What you 'see' is the 'walls' of the combustion chamber, i.e. the cylinder head (if any), the piston top and the cylinder wall.
What you 'touch' is air of some temperature, pressure, turbulence and swirl.
As you have no way to 'see' (or 'feel') the crankshaft or the kinematic mechanism, you cannot say (for sure) that you were injected and burned into the OPRE / PatOP revving at 6000 rpm or into the conventional revving at only 4,500rpm.

The fuel sees the turbulence created by the piston kinematics, mostly effected by piston velocity so again your assumptions/opinions are incorrect.

You need to update them and your design philosophy to reflect the evidence and knowledge.

Among others, this means that the rev limit of the Diesels (and their peak power) can rise by some 30%

http://www.pattakon.com/pre/droplet.gif

End of QUOTE

A pulling connecting rod is way stronger for the loads it bears (so it can substantially more lightweight) than a conventional connecting rod. The heavy loads in the OPRE / PatOP try to strengthen the connecting rods.

So why don't you optimise them, why have such large crank pins and bigend?

Compromising the design for one piece rods is not good engineering. Many issues are created, too many to list.

The engine gets shorter and more lightweight:
The PatOP prototype (64+64=128mm stroke, 79.5mm bore, 636cc capacity, 850cc built-in scavenging pump capacity, total mass (without the flywheel) 20kg, total height: 500mm)

Etc.

You also write:
“Sure, Achates have blown 100 million on testing and simulation - it only makes sense that they have managed to develop a very efficient engine. But what is to say that your engine will have similar performance - just the fact that it too uses opposed pistons ?”

In the previous (and at http://www.pattakon.com/pattakonOPRE.htm and http://www.pattakon.com/pattakonPatOP.htm ) is explained the superiority of the OPRE and PatOP designs over the conventional Junkers Jumo.

What is the current offer / product of the Achates Power?

https://www.youtube.com/watch?v=JoQkTIfAB2U

https://www.youtube.com/watch?v=JoQkTIfAB2U

What I see in the above youtube video is a redesigned Junkers Jumo 205 with reasonable / expected improvements:
better flow capacity,
optimized combustion chamber shape,
modern fuel injection,
better/modern control over the engine (electronic control versus mechanical control).

It is like giving to a good tuner an 85year old Junkers Jumo 205 and ask him to improve / modernize / redesign it from scratch (and in a “no budget” basis).

Different tuners will follow different ways / solutions.

For instance, the shape of the combustion chamber formed in/on the piston crowns of the Achates Power engines is not the only shape that improves the combustion.

For instance, the market is full of injectors / injection systems / electronic controllers that can be used in an improved Junkers Jumo 205.

The several dozens of millions of dollars invested so far to the Achates Power Opposed Piston engine projects is a good evidence that we, at pattakon, are not the only ones who think there is a promising future for the Opposed Piston engines.

So, if Achates Power really achieved the fuel efficiency they claim, this is more than good for the PatOP and OPRE engines.

It is not difficult to get why.

For instance, what if Achates Power asks to use, under the license of pattakon, the PatOP / OPRE design? With a better “basis engine” than the Junkers Jumo, their final product would be better.

Or, for instance, what Achates Power is asked to offer (under license) their technology for use in the OPRE and PatOP engines?


Thanks
Manolis Pattakos

There is so much confirmation bias in that post you wrote.

I hope you take onboard these issues I have identified, verify them, and improve your design. I've educated many people, most like learning, especially correcting false opinions. Very few get offended and keep repeating their falsehood.

Trump'ism

[Muniix]

Hello Mudflap

You write:
“Piston skirts as well as compression rings in conventional pistons also operate in a hydrodynamic regime except during reversals (but then the same happens for crossheads too). And guess what - if you have a look at a Striebek curve you'll find that the coefficient of friction is minimal during mixed lubrication and steadily increases as you go further into the hydrodynamic regime. Your argument regarding the elimination of frictional losses is invalid. You are just moving the forces from the skirt to the crosshead.”


So, the cross-head design and the hydrodynamic lubrication increase the frictional loss!


Write to Wartsila and MAN (the two makers of giant marine two-stroke engines) to explain the annual saving in case they will eliminate the cross-head and ask a percentage of this saving.

I am joking.

Typical response of an opinionated person who doesn't actually understand all the issues involved in sufficient detail. These are slow speed engines with very low bore to stroke ratio so a valid compromise even if they had a choice.

The cost of developing an alternative with durability, optimised and setup for production, convincing the market including training and support would be huge.

On the other hand, did you see the leaning angle of the connecting rod of the Wartsila X92?

It is from -30 to +30 degrees about the cylinder axis.

A conventional engine having the double connecting rod to stroke ratio (2:1 instead of 1:1 of the Wartsila X92) halves the thrust load between the piston skirt and the cylinder liner.

According what you write, the Wartsila X92 with double thrust force and higher coefficient of friction (it utilises the “inefficient” hydrodynamic lubrication instead of the “efficient” mixed lubrication) should have more than double frictional losses due to the leaning of the connecting rod.
We talk for the most efficient engines in the world (the giant marine 2-strokes).

Again you need to study friction models. What contributes to friction, the big offenders and small ones. Then you can accurately assess a design and make valid statements.

For decades in Ducati they were using expensive angular contact roller bearings to rotatably mount their crankshafts in their crankcases for the sake of, supposedly, lower friction and higher revving (the roller bearing makers give these roller bearings as heaving 0.002 coefficient of friction).

Then they replaced the angular contact roller bearings with conventional plain bearings:

Quote from CycleWorld:

http://www.cycleworld.com/sites/cyclewo ... 90x207.jpg

The new plain bearings versus the old 35/80/21 angular contact ball bearings. The plain bearings bring significant advantages in load capacity, mechanical quietness and additional crankshaft rigidity. They also save money in production. The main-end plain bearings do not feature the usual groove and admission hole because Taglioni has always favored axial admission lubrication circuits, which require less pressure. With axial admission, the oil flow does not need to overcome the centrifugal force found in a radial admission layout.

End of QUOTE


The hydrodynamically lubricated plain bearings have a coefficient of friction similar to the coefficient of friction of the cylindrical roller bearings (in the range of 0.001).

With hydrodynamic lubrication the coefficient of friction of the cross-head is similar.
The lubricant is provided under pressure between the flat slides (or slippers) and the flat slideways of the cross head.
It is a forced lubrication (not the “splash” lubrication of the conventional “trunk piston” engines wherein, among others, the cylinder liner undergoes significant deformation).
And it has to do with flat surfaces that perfectly fit with each other.


This allows the makers of the top fuel efficient internal combustion engines of the world (which, by the way, are burning cheap “heavy fuel oil”) to play with very short connecting rods, not possible in conventional “trunk piston” engines.


I would really appreciate if you could describe the situation met in the conventional 2-strokes (like, say, in the Junkers Jumo of Achates Power, or in the Junkers Doxford (or OPOC) of EcoMotors ) wherein the piston skirts abuts heavily on the ported cylinder liner.
Things are even worse at the exhaust side.
What happens there with the lubricant?
Shortage of lubricant means scuffing.
Plenty of lubricant means emissions, worse combustion and lubricant consumption.

With the cross head architecture of the OPRE and PatOP engines, only a thin film of lubricant is required to prevent the contact of the piston rings with the cylinder liner.


Thanks
Manolis Pattakos

What happens in your engine at 6,000 rpm a completely different operating environment than the slow speed engines typically of your design?
Inertial forces, crank flexing, bearing friction and loads due to crank flexing.

Manolis I gave you what is considered the best reference on cranktrain friction and vibration. It actually calculates a real apparent inertia function. This is referenced by everybody doing research in this field.

You discounted it with some put down of the authors. I can show the email if needbe.

Btw, revealing other's emails is generally a federal offence. Especially when it contains information on third parties and their confidential activities.

You should study friction models then you will have a better understanding.

Maybe then your posts would not be full of erroneous claims, repeated again and again.

Cross heads are used partly for compactness and to support the low bore to stroke ratio, it's a required compromise and fine for low engine speeds. High speed not so much, there are better ways of achieving the reduction in piston side loads.

Marc
I really wanted to discuss flame kernel optimisation 2T and 4T agnostic. Techniques to improve combustion with SI engines. That was hours ago, too tired now.

[Muniix]

And it is anything but “rubbish at sealing”.

This is a more than 80 years old design / manufacturing.

17:1 compression ratio, compression ignition.

If it had problematic sealing, or not top fuel efficiency, it would not be used in airplanes making (for the first time; 1936) 6,000 miles without a stop.

Again, the 'it was decent 80 years ago' argument' - let's put this to rest - 80 years ago they flew sleeve valves which had an impressively high oil consumption - does that make them good too ? If you want to make a good case let me know how much oil the jumo burned and let's see how it compares to modern engines.

Your theory relating the “sealing efficiency” with the number of holes / ports on the cylinder liner needs amendments.

It's not my theory - these are published results.

The thrust of the piston skirt on specific regions at the sides of the cylinder liner spoils the shape of the cylinder liner and makes the temperature distribution around the cylinder liner uneven (this unevenness is further increased by the non uniform arrangement of the intake and exhaust valves on the cylinder head).

The FE plot shows a peak displacement of 16 micron - the radial thermal deformation of the liner will be higher than that. Secondly, depending on how it is supported you tend to see two behaviours:

1. A poorly supported liner will undergo a large 1st order deformation (almost rigid body translation) in the direction of the thrust load. 1 st order deformations have no effect on ring performance. The dominant order will still be 0 (caused by thermal deformation and to a lesser extent cylinder pressure). There will be a small 2nd order deformation but this is nothing rings can't usually handle - as I have explained before low orders do not cause issues.

2. A well supported liner will have even lower 1st and 2nd order deformation, however the contact pressure at the skirt contact patch will be higher. This however has no adverse effects on ring performance in skirt guided pistons!

Now you show us a similar plot for your engine so we can discuss it.

Also claiming that the piston contact spoils the thermal loads on the liner is non-sense.

There's a good paper published on cylinder liner wear comparison between conventional, offset and twin crankshaft arrangements. They measured wear at many points down and at 0,90,180,270 the liner using a motored engine, using a straight aluminium liner. The results were interesting. The cancelling of side thrust from the twin crankshaft, the offset crank showing​ slightly reduced wear. They performed a SI combustion pressure simulation showing the twin crankshaft arrangement provided 4.8% more rotational torque, with ultra lean you can target superior crank rod angle, reducing TDC pressure, friction and vibration.

Another good solution is the approach of Hugo Junkers with his twin crankshaft Opposed Piston Jumo engines wherein the intake ports, at the one end of the cylinder liner, and the exhaust ports, at the other end of the cylinder, are too many and uniformly distributed. Only the thrust loads on the sides of the cylinder liner spoil the – otherwise perfect – cylindrical symmetry of load distribution, temperature distribution, etc.

No! - you get hot spots on the strips in-between the port windows - the more of them - the higher the order of distortion. Bad !

The hydrodynamic lubrication in the cross head is so superior than the lubrication between the piston skirt and the cylinder liner, that reduces several times the friction loss due to the leaning of the con-rod.

The coefficient of friction in a cross-head is comparable with the coefficient of friction in the plain bearings (around 0.001).

Completely wrong. In the crosshead the speed is not constant. Lubrication will go through dry contact at the top and bottom (when speed is 0) , transition through mixed lubrication as it starts picking up speed and go hydrodynamic around mid-section. By comparison a journal bearing operates in full hydrodynamic conditions all the time

If you compare the fitting of a piston skirt with the distorted cylinder:
then you may agree that, in comparison, the flat surfaces of the cross head fit perfectly.

Piston skirts have a carefully designed 'barrel' profile which facilitates hydrodynamic film generation.
NOT being flat is what makes them work in the first place. Your understanding of fundamental principles is flawed.

By the way, I am waiting for your “description” of what is happening with the lubricant when the piston abuts heavily on, and slides along, the port openings of a 2-stroke.

It craps itself with or without the presence of thrust loads.

He definitely needs to read up on many things, I don't know where he gets his opinions from, wishful thinking, more likely he is just making known false claims hoping gullible people believe him seems to be his MO. Given after you raise an issue he goes off onto 4 other forums repeating the same falsehood.

Makes one wonder how someone learns this behaviour, then again he has the same surname as the fascist military dictator that took over Greece in a Koo.

I believe Hybrid Power Plant are the future using a hybrid energy storage combining Graphene ultra capacitors and chemical energy storage/batteries. There's opportunity to gain TE via increased load from harvesting power into storage so you get additional energy from same fuel consumption. Traction control needn't retard timing reducing TE and harvest excess torque into energy storage and on changing up a gear the harvesting load improves synchronisation for faster, smother changes especially when timed to optimal crank angle. Similarly for downshifting. Lots of clever strategies can be implemented and you only need a mild or micro hybrid system.

[J.A.W.]

Marc, I 'd suggest you go back & give your posts a though edit..
..again including the deletion of needlessly unpleasant emotive stuff aimed at a member here..

& FYI, those sleeve valve aero-engines of 70-80 years ago..
..actually demonstrated oil consumption figures no worse, & often better than rival poppet valve aero-mills..