2 stroke thread (with occasional F1 relevance!)

[manolis]

Hello J.A.W.

The few exceptions confirm the rule (Aprillia is “still” selling a 2-stroke scooter, Java “still” sells 2T roadbikes in Britain).

Any clue why the Bombardier/Rotax E-TEC 600cc and 800cc were never used to propel a motorcycle or car?


Having one more member (the connecting rod) to control the gas flow in a 2-stroke, you have several additional design options, for instance.
For cleaner power by, say, starting the transfer at the end of the exhaust.
For releasing the 2-stroke from a tuned exhaust.
For turbocharged simple 2-stroke Diesels wherein the energy of the exhaust gas powers the scavenging.

Thanks
Manolis Pattakos

[manolis]

Hello Platinum Zealot.

You write:
“I notice the wrist pin is on the far side of the pistons. In theory this makes the piston more unstable and should increase side-load at the top of the piston. Did you notice this while running?”

No.

The piston is quite long for its stroke (84mm diameter and 84mm height for a 30mm stroke in the first prototype).
The lower side of the piston and the outer end of the cylinder bore run “cold” allowing smaller clearance and better lubrication.
The thrust forces are taken there (at the two ends of the cylinder).
The role of the distant top of the piston (or, more correctly, of the upper piston skirt that controls the exhaust and transfer ports) is auxiliary: it just abuts on the cylinder liner.


This is the Ducati Panigalle 1199 piston (cylinder bore 112mm):



and this is the piston of the supeleggera version:



The height of the piston skirt wherein the thrust loads are taken is only 30mm for a 112mm bore.

The lower piston skirt of the OPRE Tilting is just a little shorter (28mm) for a substantially smaller bore (84mm).

This means that if, for a specific clearance between the piston skirt and the bore, the piston of the Panigale Superleggera tilts for, say, 1 degree, the piston of the OPRE Tilting (same diameter, same clearance with the Superleggera) tilts for 0.8 degrees (20% less).

Besides, the piston of the OPRE Tilting is a crosshead piston: there is an upper piston skirt (below the piston ring) that controls the exhaust and transfer ports. This upper piston skirt reduces the tilting of the piston a few times with the upper piston skirt remaining almost unloaded.

Provided the Ducati Panigale Superleggera is OK, if you take under account and the smaller temperature difference between the lower piston skirt and the outer cylinder liner (both run relatively cold) of the OPRE Tilting, the OPRE Tilting is more than OK.


Take a look at the PatOP engine:



and listen at the youtube video:



It is a crosshead design, too: the thrust loads of the “combined” right piston are taken at the wrist pin side (scavenging side of the piston), with the piston skirt at the combustion side of the piston only slightly loaded (it just abuts on the combustion cylinder bore).

Thanks
Manolis Pattakos

[FW17]

Any clue why the Bombardier/Rotax E-TEC 600cc and 800cc were never used to propel a motorcycle or car?
Thanks
Manolis Pattakos

The Rotax Snowmobile options
E-Tec 800 produces 160 hp with a milage of 12L/100km on a trail
A 1200 cc 4 stroke with 130 hp also consumes 12L/100km on a trail

So on the road if the milage improves by 30% 8L/100km is not bad. Too bad we cant stick it into a golf and check it.

[J.A.W.]

Hello J.A.W.

Any clue why the Bombardier/Rotax E-TEC 600cc and 800cc were never used to propel a motorcycle or car?

Thanks
Manolis Pattakos

Manolis, AFAIK, the reasons ( which also apply to KTM not releasing their BMW developed DFI 2T Husqvarna bikes)
are not technical, but for marketing reasons, to do with the perceived conservative culture of motorcycle buyers..

Likewise Orbital has run a fleet of DFI 2T 1200cc cars on long-term test, but despite being a technical success,
GM marketing felt that potential buyers would perceive them as too 'alien' in their characteristics..

This, even though oddities such as the Smart powered by a small (but complex & expensive) 4T turbo have been sold..

[manolis]

Hello WilliamsF1 and J.A.W.

According my reasoning the problem cannot be just commercial (the majority of car and motorcycle owners neither know, nor care, how their engines operate; what they want is power and torque, reliability and low ownership / running cost).

Take the Rotax / Bombardier.
Their 800 E-TEC seems ideal for small airplanes. Lots of power, lightweight, simple, green, reliable etc, etc.
However, their offer for small airplanes is the Rotax 912 / 914 / 915 ( 4-stroke air/water-cooled boxers), and the old 582 2-stroke.

Any other guess?

Thanks
Manolis Pattakos

[FW17]

Maybe because they need a 2 stroke that works best between 500 and 4000 rpm

A 150 HP car will have about 125 nm torque at 1000 rpm
That Rotax probably will have 40 nm

Bikes OK but harder to ride, cars too heavy, probably OK for racing formula cars

[J.A.W.]

Hello WilliamsF1 and J.A.W.

According my reasoning the problem cannot be just commercial (the majority of car and motorcycle owners neither know, nor care, how their engines operate; what they want is power and torque, reliability and low ownership / running cost).

Take the Rotax / Bombardier.
Their 800 E-TEC seems ideal for small airplanes. Lots of power, lightweight, simple, green, reliable etc, etc.
However, their offer for small airplanes is the Rotax 912 / 914 / 915 ( 4-stroke air/water-cooled boxers), and the old 582 2-stroke.

Any other guess?

Thanks
Manolis Pattakos

Sorry Manolis, but I think you'd be wrong about bike buyers & conservatism.. In the '80s - Yamaha, then Suzuki..
.. built 2T 500cc G.P. roadbike 'race replicas' - but didn't find as many buyers as they'd hoped, due to
most potential buyers being too fearful of the perceived 'hard edge' riding needed to do them justice..

Needless to to say, they are both high priced sought-after 'classics' - today..

Much the same thing happened with Bimota's late`90s effort to sell a 2T 500cc DFI roadbike, & was compounded by
Italian small-time maker industrial issues - such as using buyers as defacto development testers..

As for Rotax/Bombadier & no ETEC for flight - well, I'd reckon it is , in fact a marketing matter, since the
ability to generate more profit from expensively complex yet hard flown 4T mills, plus potential liability
issues from introducing new to market high performance ETEC 2T mills for flight purposes - is not in their business plan..

Same for KTM sitting on their DFI 2T tech.. they could be selling a clean green efficient 900 roadbike triple based
on their longstanding, proven 60hp 300cc enduro cylinder, a 180hp/130kg sports machine..
..but that would undercut their existing ( & profitable) 4T line-up..

[manolis]

Hello WilliamsF1.

As they do with their 4-stroke airplane engines (Rotax 912, 914 and 915), they can use a propeller speed reduction gearbox in the 800 E-TEC to optimize both, the engine revs and the propeller revs at cruising.

While in the conventional car you need flat torque curve, good response at partial loads over a wide rev range, low emissions at all conditions etc, etc, in an airplane things are different.

An airplane engine optimized at a short range of revs and loads (wherein it operates at cruising) is OK. This fits with the 2-strokes, even the old ones.

Thanks
Manolis Pattakos

[manolis]

Hello J.A.W.

It seems we have to agree on the definition of the terms technical, marketing and commercial.


The peaky torque of the old 2-strokes, their poor mileage, their response at partial loads, their emissions, their reliability issues etc were strictly technical problems; these problems were solved (at least in a degree and obviously with compromises in other fields) by their 4-stroke competitors which dominated in the market.


Case of the Bimota 500 DFi :

It was a dangerous / lethal motorcycle with several deaths encountered before they were recalled and phased-out (bankrupt of Bimota).

The power was delivered in an unpredictable way.

A technical explanation was that the temperature of the top of the piston crown (wherein the fuel was injected on) was crucial for the following combustion. A few seconds with closed throttle were adequate for a big change of the temperature of the top surface of the piston crowns.

Imagine an engine delivering at 5,000rpm with half open throttle 50bhp and which, after a few seconds with closed throttle, is delivering at the same 5,000rpm and with half open throttle 20 bhp initially which, without any change of the throttle, turn to 50 bhp a couple of seconds later. It is like playing the Russian roulette.

The problem was never solved.

It took years until to decide to replace the DFi with carburetors in order to sell the stock of Bimota 500 DFi.
A pure technical problem ended up with a commercial disaster.



For the case of the Rotax E-TEC 800, I would agree with you if Rotax – Bombardier was the only engine maker (or aviation engine maker) of the world.
They are not.
And they know from inside their E-TEC technology and its limitations.
This is why they invest on the 4-stroke technology for the future, even if powering small airplanes is the ideal application for the 2-strokes.

Thanks
Manolis Pattakos

[J.A.W.]

Indeed Manolis - the story of the Bimota 500 2T Vdue is a sorry tale.. Bimota went bust attempting too much, too soon..
& sadly poisoned the ground for any potential new 2T road bikes.. even though the technology is now well seasoned..

As for Rotax, see https://www.rotax.com/en/products/rotax ... -takt.html

The ETEC 600 snowmobile mill is tuned to nearly twice the specific output of their equivalent aero-engine..
You could approach them & ask why they do not utilize the ETEC for flight purposes, & if they've tested them as such..

Looking at Rotax 4T aero-engines, well, the cost & complexity/profit of their newly turbocharged 4Tmill is of course..
..something Honda would love to do - to build a competitive 4T chainsaw, but the economics/market simply wont add up..

[uniflow]

Autoflight 700 twin, designed for aviation use. Water cooed, case reed, internal gear reduction. Uses a balance shaft. This is the prototype, two more engines are now available for test. New engines have the balance shaft internal, water pump in a different place, electric start. Future development to become semi direct injection with oil less top end, all proven technology, just needs to be applied.

[manolis]

Hello Uniflow.

Is the 700 twin based on sleeve valves?





Provided the following info is not confidencial,

what is the bore and stroke?

what is the timing used?

what is the distance of the intake and exhaust ports?

Any drawing / blue-print of the kinematic mechanism?



Hello J.A.W.

You write:
"The ETEC 600 snowmobile mill is tuned to nearly twice the specific output of their equivalent aero-engine..
You could approach them & ask why they do not utilize the ETEC for flight purposes, & if they've tested them as such.."

I could approach Rotax - Bombardier.
Yet I bet they would never really answer.
This is why I asked if anybody has a clue / guess.

Thanks
Manolis Pattakos

[uniflow]

Ha Ha, you joke, drawings? I just build stuff, don't need no drawings
No the 700 is a standard case reed twostroke but it can be semi direct injected (as I have done on the YZ250T and F9 350 Kawasaki using delayed injection principal) and now with Ryger technology it can run a oiled bottom end with a dry top end, no oil burn, imagine that.
Can't remember the timings off hand on the sleeve engine, I think the exhaust is around 190 degrees open, transfers at approx 130 degrees. There is no leed on the sleeve drive with the sleeve and piston arriving at TDC together. Piston stroke is 54mm, sleeve stroke is 24mm. Relying on the exhaust doing a lot of the pumping work for me, like a normal twostroke. I'll try out of phase later on. I'm working on an FOS and an FOS / Ryger hybrid at the moment, also an HCCI test engine. All the parts are cast I'm just trying to find time to machine them up. All these cylinder options run on the same crankcase as the sleeve engine, interchangeable for quick testing.

[manolis]

Hello Uniflow and thanks for the info.

I still cannot find a patent application publication for a 2-stroke engine under the name of Ryger.

And, unless I am wrong, there are no drawings of the Ryger engine in the Internet.

From the writings of LucF (previous posts) the biggest advantage Ryger claims for his 2-stroke engine is the 80% reduction of HC in the exhaust “as compared with a similar racing 2-stroke engine”; however, looked in absolute numbers, the HC in the exhaust of the Ryger 2-stroke are some five times above the limits set for the old (made before 1986) non-catalytic 4-stroke engines.

So let me ask: when you say “dry top” and “no oil burn”, do you mean absolutely or in comparison to a similar 2-stroke?

To put it differently:

Suppose you upgrade your 700cc conventional 2-stroke according Ryger’s technology.
Are the piston rings gonna slide on an absolutely dry cylinder liner?
If not, what is the estimation for the specific lubricant consumption? (gr of lubricant per kWh provided)



For aero engines the overall weight (including both, the engine and the fuel required for a specific range) is crucial.


I think the following design for a turbocharged direct injection 4-cylinder 2-stroke even-firing PatAT Cross-Radial:





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

which without any balance shaft is better balanced than the best 8-cylinder 4-strokes,
which, by means of a turbocharger, uses the energy of the exhaust gas to power the scavenging,
which shares the same crankpin and bearing among the four pistons (the crank which is the heaviest part of the engine is made several times lighter),
which uses 4-stroke lubrication in the crankcase and controllable lubrication of the compression rings (at the TDC the oil scrapper ring lubricates the cylinder liner just below the ports, at the following BDC the compression ring abuts on the top end of the lubricated area of the cylinder liner),
which achieves asymmetric transfer (the transfer can end after the exhaust) without adding parts in the simplest 2-stroke design,

brings several advantages to the technology even if, for the moment, it is just a drawing / a design.

For instance, imagine it as a lightweight turbocharged 2lit direct injection Diesel (more than 200bhp at 2,500 rpm for a weight estimated at 35Kg / 80lb) directly driving the propeller (without a propeller reduction gearing the overall weight and the loss of energy in the transmission are further reduced), with BSFC and emissions lower than the state-of-the-art direct injection 4-stroke Diesels (reduced mechanical friction per kWh provided).

By the way, while the lubricant consumption (gr of lubricant per kWh provided) can be comparable with (or even less than) that of the four strokes, it cannot be zero.

Thanks
Manolis Pattakos

[uniflow]

I don't know what Ryger has up his sleeve, although I think I have a fair idea, with there being for want of a better decription a large valve guide between the bottom and the top end. With this guide it's possible seal off the oil into the bottom of the engine, crank etc, with the top ends piston not touching the bore ( microns close but). Yes the piston ring? How is the top ring on a fourstroke oiled as the oil scraper should keep it dry. Lubed buy fuel and deposits of oil in the bore cross hatch (that stay there). The Ryger type twostroke could have a fuel lubed ring also (petrol is a real thin oil) and an oil type lube embedded in the crosshatch finish of the bore.
By the way, I don't think the Ryger has a conventional ring anyway, how the hell is a standard ring going to seal on a 54mm stroke at 30,000 RPM on the crank? My Ryger development engine has a different piston sealing method that has no inertia problems, it stays put.