2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

Actually Manolis,
I think Uniflow was suggesting that at very high rpm - the engine was running harmonically.. all in 'continuous flow'..

While Aprilia retained the rotary disc valve for their G.P. machines..
.. the Nippon makers were using reed valves that were good to ~13,500rpm..

& today, carbon fibre reeds are not expensive.. http://www.tyga-performance.com/site/in ... ath=71_858

They are still used in most 2T MX bikes..

See: http://www.motocrossactionmag.com/news/ ... eed-valves

[LucF]

This is a letter from the designer of the Ryger engine for you.

Dear (two-stroke) friends,

Thank you for all the attention you have given the Ryger engine.
My name is Harry and I have been working on two-strokes for about 45 years now.
Back in the year 2000 I was convinced that a clean two-stroke would be possible and I started thinking .. five years before the idea was finally there in the middle of the night, April 2005.
Then it all started… It took me 10 years of development and it was not much of an easy ride.
Nobody believed at first and there I was.. alone with some bits and pieces building the perfect engine.
Honestly I didn’t expect it was that good, I knew it was clean but the power was a nice present that came along with it !
The reason we introduce the Ryger step by step is simple: it is not meant for the big guys but for everybody.
Upgrading a conventional two stroke must be available to everyone before it is to late because of inescapable new emission regulations.

A few things to think about :
30.000 rpm ? easy….. it could do a lot more. How ? don’t let the piston touch the rings !
Port timing ? …not important !
Crankcase volume ? not important !

At last a big thank you to my dear friends Frits, Luc, Thijs and the lot from the Ryger team !

P.S. now and then I answer some questions but within my limitations, on my facebook via pm…Mcd Twist Ryger Engine.

Kind regards
Harry Ryger

[J.A.W.]

Bit of a tease there eh, Luc.. cryptic or what?

[J.A.W.]

Another glossy 2T site..

http://www.powerapt.com/sonicflow-engine.php

But again, a bit short on specifics, unlike Manolis..

[manolis]

Hello J.A.W.

You write:
“.. the Nippon makers were using reed valves that were good to ~13,500rpm..
& today, carbon fibre reeds are not expensive.. “


At 30,000rpm the inertia loads are 5 times bigger than at 13,500 rpm: (30,000/13,500)^2=4.94.


Wouldn’t it be better if, without limiting the functionality of the engine, you could eliminate / omit moving parts? (I mean moving parts like the reed valves and their associate limitations).

Here is the ArcticCat 600 reed-valve 2-stroke:



Imagine it without the reed-valves assembly (weight saving, packaging, noise, cost saving, reliability, high revving etc).



Hello LucF

Tell Harry Ryger that 30,000 rpm with 54mm piston stroke is not at all easy, at least according the Laws of Physics.

With 200gr total mass of the reciprocating assembly (including the piston, the piston pin and the upper 1/3 of the connecting rod(s)), it is required an average force of 5.5 tons (12,000lb) acting on the piston from 40 crank degrees before the TDC till 40 crank degrees after the TDC.



With only 23cm2 piston surface, in order to decelerate the piston assembly by the pressure into the cylinder, you need an average (not peak, average throughout 80 degrees around the TDC) pressure of 240bar.


By the way, the piston of the 2-stroke Yamaha DT200 (195cc) weighs alone (i.e. without its piston pin and without the upper part of the connecting rod) 200gr.

Thanks
Manolis Pattakos

[J.A.W.]

Again Manolis,

I think it is suggested that perhaps by dint of resonant gas flow inertia..
..the Ryger mill somehow cushion-voids such forbidding G force issues..

Whether some form of stepped/pre-compression sleeve valve ( "Twist"?) motion is involved.. we'll see, I guess..
With all the promised/mysterious hints/claims.. its getting to be.. a bit like a bloody kid waiting - at X-mas time.

I know that in everyday regular 2-stroke rpm range usage.. for decades.. reed valves have proven non-problematic.

With that pictured Arctic-Cat, the reed valves are incorporated as part of the crankcase air-intake/air-box complex,
..which are needful features of a practicable production mill.. ..so not too intrusive/space-wasteful functionality-wise..

& I doubt that they - per se - offer any kind of rpm restriction - while allowing asymmetric timing - in that application..

[manolis]

Hello J.A.W.

The Opposed Piston OPRE direct injection 2-stroke Diesel prototype engine of the following youtube video is based on reed valves.



At the right side of the photo you can see the “basis” (the pedals are not shown) of the two double reed valves it uses:



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


The single crankshaft Opposed Piston PatOP 2-stroke direct injection Diesel prototype engine of the following youtube video is also based on reed valves.



Here you can see the two, of the four, reed valves it uses (also the 130mm diameter cylinder of the 850cc piston-type scavenging pump; the engine capacity is 635cc):



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


The Opposed Piston PatATi 2-stroke spark ignition prototype engine of the following youtube video is rid of reed valves and of rotary valves.



It uses its connecting rods, pistons and cylinder to realize a substantially asymmetric intake and a substantially asymmetric transfer (the exhaust closes before the end of the transfer).



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


Why to use reed valves if you can do a lot more without them?

I know, in theory and in practice, some advantages and some drawbacks / limitations of the reed valves.

Think of the “Connecting Rod Valves” of the PatATi architecture and let me know their disadvantages and your objections.

Thank you
Manolis Pattakos

[fredric21]

The problem with the piston cooling in the Crecy was one of uneven oil flow and distribution between pistons. Air became entrapped in the hollow con rods at higher rpm's as the oil within them was flung out under centrifugal force and caused a partial vacuum which drew in air from beneath the piston. We are using jets directing oil to the under-piston in our sleeve-valve two-stroke developments.
As has been said, the Ricardo V-twin ran reliably with little problem in piston cooling or sleeve overheating.

[fredric21]

Any two-stroke that drags oil across cylinder ports with the piston rings can never be a "clean" motor. The claims for the Ryger engine are unfounded, I would say. Also, all the suggestions for "improved" two-stroke designs suffer from the same fateful flaws.
I will make no stupid claims for my own two-stroke engine (which is being developed right now) until I have some genuine proofs of its efficacy.

[J.A.W.]

F, one of the Ryger 'claims' is the discrete use of sealing functions..
.. that separates the piston from rings, so obviating the concern you note.. ( yet to be seen, or explained)..

I note the 'Sonicflow' mill ( linked further above - on this page) also claims to have dealt with the oil issue..

& Manolis,
- thanks again for your daringly-openly shown, well explained, & thoughtful design presentations..

Uniflow, anything new to report?

The lively & interesting developments shown( or hinted) here in this thread.. are encouraging to the 2-stroke enthusiast..

[manolis]

Hello Fredric 21

You write:
"Any two-stroke that drags oil across cylinder ports with the piston rings can never be a "clean" motor. The claims for the Ryger engine are unfounded, I would say. Also, all the suggestions for "improved" two-stroke designs suffer from the same fateful flaws."

Did you see the PatMar 2-stroke uniflow cross-head port-less desing at http://www.pattakon.com/pattakonPatMar.htm ?



Its lubrication is true-four-stroke.
According theory (there is no prototype yet) it has a lower specific lube consumption than a good four stroke of similar power.


Did you see the PatPortLess 2-stroke uniflow pull-rod design at http://www.pattakon.com/pattakonPatPortLess.htm ?



As the PatMar, it also uses true-four-stroke lubrication. Its specific lube consumption is lower than the best 4-strokes of similar power.

With its "Pulling Connecting Rod" architecture it achieves some 30% longer dwell at the Combustion Dead Center.
This simply means that with the PatPortLess operating at 30% higher revs than a conventional Diesel, the same time is given to the fuel to get prepared and burned efficiently at high compression (or, more correctly, at high expansion) ratios.


Worth to mention that a 2-stroke fits better with compression-ignition (Diesel), because a Diesel is, by definition, a lean-burn engine.

Thanks
Manolis Pattakos

[tok-tokkie]

Manolis,

I really appreciate and enjoy your contributions with their lovely easy to understand CAD models. I am fascinated by your portable flyer and look forward to when it is in operation.


The portable flyer http://www.pattakon.com/pattakonFly.htm

I particularly like the concept of the opposed piston with reed valves and uniflow combustion chamber. There was one with squish but it is not in that link.

With the portable flyer I assume the pilot will have a reserve parachute on his chest but will there be enough height to deploy it should the engine stop? (I assume it will not be able to autorotate to bring the pilot down safely – is that correct?) That made me wonder if a autogyro version would not have advantages of both safety and extended range.

[J.A.W.]

T-T, I understand that it it is the point of Manolis' flyer to allow individual flight..
..sans all that needless fuselage/landing gear 'copter-type stuff..
& with an additional winged (bat-like aero-membrane) flight suit - if desired.. depending on operational requirements..

( I suggest you check his site for particulars..).

[uniflow]

F, one of the Ryger 'claims' is the discrete use of sealing functions..
.. that separates the piston from rings, so obviating the concern you note.. ( yet to be seen, or explained)..

I note the 'Sonicflow' mill ( linked further above - on this page) also claims to have dealt with the oil issue..

& Manolis,
- thanks again for your daringly-openly shown, well explained, & thoughtful design presentations..

Uniflow, anything new to report?

The lively & interesting developments shown( or hinted) here in this thread.. are encouraging to the 2-stroke enthusiast..

Keep an eye on Kiwi Biker forum, ESE works tuner thread, lots of speculation going on there and a few test parts been made.

[manolis]

Hello Tok-Tokkie and thanks.

The emergency parachute is a reasonable solution.

Yves Rossy uses a parachute at every landing.
(do see the video:

[youtube]http://www.youtube.com/watch?v=Czy0pXRRZcs[/youtube]

and focus on the perfect flight-control he and his partner achieve using exclusively their bodies)


Another solution is to fly near the ground.
Imagine flying from island to island of the Aegean Sea, just 3 meters (10 ft) above the sea level.


Another solution is to take-off and land as an airplane:



all you need is three wheels and a wing-suit.
In this case a significant horizontal speed is required (say 160Km/h, 100mph) during take-off and landing, just like in a normal airplane.

Being at a small altitude (say lower than 100m, 300ft), the pilot lands exploiting his horizontal speed.

What if the Portable Flyer hovers (zero horizontal speed) at a high altitude?
Being at a high altitude, the pilot exploits the gravity to gather speed (think: the dynamic energy of a mass at 100m altitude equals with its kinetic energy in case it moves with 160Km/h or 100mph; differently speaking: without aerodynamic resistance, if you leave an object from 100m height, it hits the ground with 160Km/h, 100mph).
As the Portable Flyer approached the ground. the pilot turns the flight to almost horizontal flight and lands.

Worth to mention here that the Osprey cannot autorotate safely; in case both engines stop (say, after running out of fuel), or in case the one engine stops and the transmission system is inoperable, or in case a propeller is destroyed, the Osprey does an emergency landing as any normal airplane.


Another solution is a secondary (emergency) engine-propellers set, operating only at small altitudes. In case the main engine fails, the landing is still safe.



AUTO-ROTATION

For auto-rotation you need bigger/heavier propellers and pitch control.

Suppose you have a Portable Flyer based on the compact OPRE Tilting engine, like:



(more at http://www.pattakon.com/pattakonTilting.htm )

With the two propellers at slightly different height (say 5cm / 2in) to avoid collision in case of desynchronization) and with free-wheel mechanisms and pitch control, you have auto-rotation.

If the engine stops at small height, the propellers continue to rotate for an emergency landing.

If the engine stops at a big altitude, the pilot selects the proper pitch to accelerate the rotation of the propellers during the fall. At the right altitude the pilot changes the pitch, uses the energy stored in the two propellers and lands safely (as a helicopter).


PS.
The engine shown in your post is the PatATi prototype, which is rid of reed valves.
The following OPRE Diesel uses reed valves:

[youtube]http://www.youtube.com/watch?v=64TY-x2Cj6Y[/youtube]

The distance of the two crankshafts does not limit the diameter of the propellers.
With big propellers, pitch control and a free-wheel between each propeller and its mate crankshaft, a “Portable Flyer” based on this arrangement can auto-rotate.

Thanks
Manolis Pattakos