2 stroke thread (with occasional F1 relevance!)

[LucF]

Ryger Engine built by Mcd Twist Ryger Engine
125 cc, over 80% less emissions, 70 bhp, max. rpm 30.000.

Ryger Engine production running in high gear in order to meet cik regulations.

I can't find the button to attache pictures!! So .... https://www.facebook.com/mcd.twist.9?pnref=story

[jwh]

Great looking machine, even 50 years later

[manolis]

Hello LucF.

You write:
"Ryger Engine built by Mcd Twist Ryger Engine
125 cc, over 80% less emissions, 70 bhp, max. rpm 30.000."

I tried, but only very few things are available in the Internet for the Ryger engine.

Do you know the differences of the Ryger engine from a conventional 2-stroke?

Are there any patents or patent applications?

Are there any drawings?

Relative to what is the "over 80% less emissions"? (to an old 2-stroke or to a modern 4-stroke of similar power?)

From its specifications it seems the Ryger engine can run reliably at 55m/sec mean piston speed. Is it true? Can the air follow such a piston speed? Are there any piston rings? What about lubrication?



By the way, here:



is an OPRE Tilting Valve two-stroke (more at http://www.pattakon.com/pattakonTilting.htm ) with propeller speed reduction.

All the gear-wheels are supported on the two crankshafts.
The unique propeller (not shown) is secured on the red gear and rotates 3.33 times slower than the crankshafts.
2,500rpm for the propeller, 8,300rpm for the engine; with 30mm piston stroke (i.e. 60mm combined stroke) the mean piston speed at 8,300rpm is only 8.3m/sec (compare it with the 55m/sec of the Ryger engine).

Thanks
Manolis Pattakos

[J.A.W.]

Hi Manolis, of topical interest,
I note that Honda - usually such 4-stroke bent ideologues - have recently patented a couple
of new 2-stroke engine designs..

[manolis]

Hello J.A.W.

You write:
"I note that Honda - usually such 4-stroke bent ideologues - have recently patented a couple
of new 2-stroke engine designs."

I saw several articles dealing with this "comeback".

Most of the journalists do not understand what Honda proposes.

Here is the first page of the patent application of Honda in the US-PTO:



and here is the last page wherein the claims of Honda are presented:



The application is not yet examined (it is "Ready for examination").

It is "uniflow scavenged"; an exhaust poppet valve on the cylinder head is driven, through a pushrod, by a cam of the crankshaft.
While such an arrangement allows asymmetric timing (the exhaust can open first and close first) to reduce emissions, it also puts significant limitations: the exhaust poppet valve with its pushrod and rocker arms has to open and close way faster than a poppet valve of a 4-stroke revving at the same rpm.

Compare the above asymmetric timing with that of the PatATi engine at http://www.pattakon.com/pattakonPatAT.htm :







Thanks
Manolis Pattakos

[riff_raff]

The engine described in that Honda patent is obviously intended as a single cylinder engine running at low rpm. It's a long stroke, small bore configuration. And the significant mass of the crank rocker arm mechanism would not lend itself to high speed operation. If you read the text of the patent it describes the engine operating in both stoichiometric and stratified charge conditions. Honda has also taken care to provide adequate liquid cooling around the upper cylinder liner, which is a critical issue with two-cycle SI engines operating with lean fuel/air mixtures.

[manolis]

Hello Riff-Raff

You write:
“If you read the text of the patent it describes the engine operating in both stoichiometric and stratified charge conditions.”

In the claims of Honda’s patent application there is nothing about stoichiometric or stratified combustion.
The specific patent application relates only with the arrangement of the transfer ports, of the piston, of the cylinder wall, of the injector and of the kinematic mechanism.
In the prior art they are described several fuel-injected two-strokes operating in both: stoichiometric and stratified lean combustion.


You also write:
“The engine described in that Honda patent is obviously intended as a single cylinder engine running at low rpm. It's a long stroke, small bore configuration. And the significant mass of the crank rocker arm mechanism would not lend itself to high speed operation.”

The kinematic mechanism achieves the reduction of the thrust loads (friction) between the cylinder liner and the piston skirt (how? by reducing the angle the main connecting rod tilts about the cylinder axis) in expense of additional bearings, heavier parts, complication, vibrations(?), cost etc.
Can this low-revving (due to the exhaust poppet valve and to the heavy moving parts) 2-stroke engine compete a 4-stroke Honda of similar capacity (and weight, and cost) running at double revs?


In the PatTwo Harmonic engine below (more details at http://www.pattakon.com/pattakonPatTwo.htm )



the thrust loads between the piston skirt and the cylinder liner are minimized (they are several times lower than in the Honda 2stroke).



Besides being rid of reed valve(s), the PatTwo Harmonic engine is perfectly balanced (zero inertia forces, zero inertia torques, zero inertia moments).

Compare the basic kinematic mechanism of the Harmonic PatTwo:



with that of the Honda 2-stroke.

The most interesting is the load control it uses and the minimization of the pumping loss at light loads:

the engine idles (and operates at light / partial load) with the throttle valve (the dark part with the yellow lever at the middle) fully opened,
with the throttle valve progressively closing, the engine runs at higher revs and heavier loads,
with the throttle valve completely closed the engine provides at high rpm a lot of power,
and when the revs get adequately high, the wide opening of the throttle valve gives (in cooperation with a tuned exhaust, if any) full power.

It is not easy to be understood, but it is quite interesting (way more, I think, than a low-revving small 2-stroke that combines the disadvantages of the two and four stroke "schools"; let me wonder how many articles would be written about the "new" Honda 2-stroke if from the first page of the patent application the "Applicant: Honda Motor Co., LTD" and the Assignee: Honda Motor Co., LTD" were absent ).

Thanks
Manolis Pattakos

[J.A.W.]

Thanks for the excellent post ( as usual) Manolis..
I guess that its a given, - Honda will garner interest for their stuff, even if it is a smokescreen..

Here's (a historical example of) an interesting stepped piston 2-stroke inter-breathing triple by R. Olds..

( Scroll down to find diagram/drawing) .

http://blog.hemmings.com/index.php/2014 ... ds-and-the supercharged-two-stroke-diesel/

[uniflow]

You will not get much out of Luc, he is tied to an NDA, he will not spill the beans. But I'm not and I think its possible. A free piston engine will oscilate at 30,000 using air as a buffer to stop damage to the piston and in the case of the Ryger unload the rod and crank from some of its usual forces. This Ryger uses a similar system of piston cushioning with a high pressure pump below the piston. This is how it can run with poor blow down times, time / area / Pressure. This pressure side of the calculation is usually not taken into account with the usual large volume under piston pump in a stanadard twostroke. This new Ryger system has cleverly found that poor blow down can be overcome with higher transfer pressures (and I think one way reed valves in the transfer ports). This tight under piston pump also gererates a sharp inlet pulse that can be harnessed to help with transfering more incoming charge after the under piston pump has run out of puff (high pressure, low volume), but when the pipe is still pulling a vaccum. The bottom end is sealed off from the top end with a "large valve guide" . This oiled guide takes the load that the piston would normaly see on the bore. By running this guide the under piston crank pump can be very tight. Fourstroke bottom end, twostroke top end, no piston wear, no oil needed (in the twostroke section),this guide system also helps to reduce friction. Although it is said to run to 30000 rpm it's published power is 70HP @ 17500, bmep of approx 207, I should think at 30000 it's bmep would be way down ( or they would publish it). For what it's worth, this is what I think and if fact what I'm building now as a test engine.

[manolis]

Hello J.A.W. and thanks.

In your link it is mentioned as creator of the opposed piston / single crankshaft engine (TS3-like) the Sulzer brothers.
.
In this brochure:



the inventor of the kinematic mechanism of the TS3 Rootes is Bernard Forest (1887); then (1887) the inventor had to file a patent application in paper and a demonstration prototype.

Here is a GIF animation of the TS3 Rootes (based on the above kinematic mechanism):



If you compare its architecture with the PatOP engine:



you will discover many heavy parts and severe loads and friction the PatOP design avoids..

Here is a youtube video of the PatOP single cylinder, 635cc direct injection Diesel running free on a desk:



The step piston of the PatOP can be combined with a turbocharger for the twin-charge version shown at the bottom of the http://www.pattakon.com/pattakonPatOP.htm web page.

Thanks
Manolis Pattakos

[manolis]

Hello Uniflow and thanks for the explanations.

I am not sure I can follow you.
A drawing or animation would be useful.

I think that reed valves cannot operate reliably at high revs and significant pressure differences.

From what I understand, if the “dead” volume underside each piston of a PatTwo Harmonic engine like:



is substantially reduced (to provide substantial piston cushioning), some kind of “Ryger engine” results.

A significant drawback is that if you compress at, say, 20 bars the air / mixture underside the piston and then you open some transfer ports, all the energy of the compressed air / mixture is lost.

Another significant drawback is that with only 200gr reciprocating mass (piston, piston rings, piston pin, upper part of the connecting rod), at 30,000rpm the inertia force required at the BDC is 4 tons which is more than extreme (at the TDC this force is nearly 7tons). In the calculation I used 54mm bore, 54mm stroke, 108mm center to center distance for the connecting rod. If you have to take this force by compressed air acting on a, say, double than the piston surface (step piston), the required pressure is extreme.

With 20 bars pressure under the step piston acting on the, say, 50cm2 back surface of the piston (note: with 54mm bore the piston crown surface is only 23cm2), the restoring force is only 1ton (i.e. 4 times less than the required inertia force at 30,000rpm).

Worth to mention that this cushioning force gets significant only near-around the BDC. When the piston is away from the BDC (say for 1/5 of the stroke) the cushioning is insignificant while the inertia force is almost maximized.

Do I miss something?

Thanks
Manolis Pattakos

[uniflow]

At high speeds I suspect the reeds never close, but you will have to wait for Luc to tell you the full story.

[J.A.W.]

Current Moto GP riders views re: return to racing 2-strokes..

http://www.cycleworld.com/2015/08/18/wo ... e-engines/

[riff_raff]

At high speeds I suspect the reeds never close, but you will have to wait for Luc to tell you the full story.

If designed properly, reed valves are very efficient and are capable of operating at very high frequency. The main consideration with reed valves is ensuring they are designed with the proper displacement and operating stresses for the fatigue environment.

[manolis]

Hello Riff-Raff.

When the model / RC engines were using reed valves their rev limit was low.

Now the top 2-stroke model / RC engines are based on a drum / cylinder valve (a type of disk valve) made on the crankshaft, like the OS18TZ:



which makes 750bhp/lit at 30,000rpm

Here is its timing plot:



And in the following PDF

http://www.osengines.com/engines-car/os ... cnitro.pdf

is a magazine article / dyno test of it.
The engine revs reliably even above 40,000rpm.


You can’t go at 30,000rpm reliably with reed valves.
For normal size engines the limit is way lower.
And if the pressure difference at the two sides of the reed valve is substantially more than 1 bar, things get really tough (heavier reed valve pedals, extreme inertia loads, opening and closing time-lag at high revs etc).

Compare the timing and the architecture of the above OS18TZ RC engine with the PatATi model engine design:







While the crankshaft “disk-valve” of the OS18TZ enables asymmetric intake, it can do nothing for the transfer (the exhaust starts 22 crank-degrees before the transfer and continues 22 crank-degrees after the end of the transfer).
Spot on the build-in asymmetric transfer of the PatATi.

Thanks
Manolis Pattakos