2 stroke thread (with occasional F1 relevance!)

[manolis]

Hello.

The PatPortLess engine



at http://www.pattakon.com/pattakonPatPortLess.htm fits with the updated thread title.

It is a port-less through-scavenged two-stroke engine.

With the cylinder-liner rid of intake and exhaust ports, this engine combines:
true "four-stroke" lubrication,
true "four-stroke" specific lube consumption,
true "four-stroke" scuffing resistance,
uniflow scavenging efficiency,
double valve-area and
some 30% longer piston dwell at the CTDC (Combustion Top Dead Center).

The vibration-free quality of the single cylinder PatPortLess (GIF animation in a previous post) is better than the vibration-free quality of the four-stroke two-cylinder TwinAir engine of FIAT used in several successful small and medium size cars.

Today most people would not even consider buying a medium size car having a single cylinder engine.

However,
if the two-cylinder four-stroke TwinAir of FIAT is good for the Alfa Romeo Mito,
and
if the VW TSI ACT (cylinder deactivation) is good for the VW POLO and the VW-Passat when it operates with only two cylinders,
the single cylinder PatPortLess is better.

Does anybody know another two-stroke through-scavenged (uniflow) having lower lubricant consumption than the best four-strokes?

Thanks
Manolis Pattakos

[uniflow]

Manolis, how many uniflow twostrokes ( running on petrol ) are out there. Plenty of concepts.
As you may have seen earlier in this thread I've made and run a uniflow twostroke in a boat, many hours of testing ( and fun ) . My idea was I wanted the lightest uniflow system possible so I stuck to crankcase scavange with two crankcases at one end of the engine feeding one cylinder and the two opposite feeding the second cylinder. As you can see in the video ( posted earlier in this thread) it was a success straight off the work bench. I learn't a lot from this engine and you are right it's a smooth concept having opposed pistons. Aim was to get fuel efficiency and good power to weight, tick that box.
Problem was I had no finance and everything was a compromise, home made CDI, cast iron sleeves, home cast pistons but it performed well dispite these short commings, could be run at full throttle, 9500rpm untill the fuel ran out.
Other problem is I want a more compact and more powerfull uniflow twostroke engine so I've gone off on the sleeve ( crecy ) track. Manolis, all my engines are crankcase charged so they will use oil.

[autogyro]

Hello Autogyro.

You write:
“Your flyer doubles any conversion losses by having two cranks.”


The PatATi is an opposed-piston two-stroke engine having compact combustion chamber and low mean piston speed (both crucial for the reduction of the total losses).

Compare it with the conventional (and very common in autogyros, ultralights etc) two-cylinder two-stroke Rotax 582.

The two crankshafts of the PatATi require, for their support on the casing, four roller bearings in total, while the single crankshaft of the Rotax requires – theoretically - only three, but in practice it has also four. Equity.

The PatATi has built-in asymmetric transfer and intake. The Rotax has not asymmetric transfer. The asymmetric intake of the Rotax requires an additional rotary valve, additional bearings and gearing to drive it (friction). Here the PatATi is clearly better.

The Rotax has two cylinder heads, the PatATi none. The thermal loss in the two cylinder heads of the Rotax decreases substantially the Brake Thermal Efficiency. Here the PatATi is way better.

The PatATi is perfectly balanced, the Rotax 582 suffers from inertia vibrations (second order forces, first order moments). In order to balance the inertia vibrations of the Rotax you need several bearings, balance shafts, gearing etc (which means friction). Here the PatATi is way better, too.

The basis of the PatATi (Portable Flyer) is rid of combustion vibrations, it is also rid of aby reaction torque. The Rotax cannot offer such things.


So, how the PatATi Opposed Piston doubles the conversion losses?

Thanks
Manolis Pattakos

I was not comparing your two crank through scavenged two stroke with the usual choice of a rotax for the amateur light autogyros now on the market Manolis.
I would never choose the rotax for the task anyway far to high an rpm range unreliable, noisy and thirsty.
If you look at the link to the W116 you will see its main world records were gained using a 60hp horizontally opposed four stroke with direct prop drive.
Actual world records Manolis not just ideas.

I was comparing your flyer with its two cranks with a similar opposed piston through scavenged two stroke with NO cranks or con rods, direct driving linear generators.
Converting energy from pistons to crank is no more of a loss and heavier than converting energy from pistons directly into electricity. The dual crank and gearing is also far more complex and cannot easily be used to include collective pitch rapid control for autorotation in the event of a mechanical failure.
A properly designed autogyro with electric VTOL would be far far safer and practical.

[gruntguru]

A strap-on autogyro? I'd like to see that.

[J.A.W.]

Agreed..
& if only A-G had the confidence to expose his ideas here.. ..to the level of criticism which he applies to others..

[manolis]

Hello Uniflow.

Correct me If I am wrong.

The crankshaft drives a piston.
The piston slides inside a sleeve that reciprocates inside a cylinder liner.
The combustion happens near the TDC with the sleeve valve covering the exhaust ports and with the piston and the sleeve covering the transfer ports.
The holes on the sleeve correspond to the transfer ports on the cylinder.
Later the sleeve valve opens the exhaust ports (at the top of the cylinder liner). Do you use rings for the sealing of the sleeve? Later the sleeve/piston open the transfer ports at the lower side of the cylinder. The compressed into the crankcase mixture scavenges the cylinder. Then, as the piston moves upwards, the intake ports close and then the exhaust ports.

At what angle are the (large diameter) eccentric pins that drive the sleeve?

Isn’t it a problem the short stroke?

What is the resulting port timing?

Is there some animation (or drawings)?


By the way, here is the OPRE Tilting :



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

Thanks
Manolis Pattakos

[manolis]

Hello Autogyro.

In the PatATi Portable Flyer



each propeller is secured on its crankshaft, i.e. the crankshaft with the propeller is actually a single piece and needs only a pair of roller bearings for its support on the casing.

From a different viewpoint, you can regard the eccentric pin of the crankshaft as part of the propeller shaft.

In order to translate the reciprocation of each piston into rotation of the respective propeller, all you have to add is a connecting rod (that perform several other duties, like providing asymmetric transfer and asymmetric intake).

That is, you compare the complexity and the weight and the friction loss of a connecting rod with a set comprising a linear generator that provides electricity to some batteries, that provide electricity to some electric motors that drive the propellers.

Do I miss something?.

Thanks
Manolis Pattakos

[autogyro]

I dont think you missed anything Manolis.
Now turn off your engine in flight.
Your flyer plummets to the ground and kills the pilot.
My autogyro continues to fly with battery power alone.
If you then turn off the electric power supply my autogyro simply glides to a safe short run landing exactly the same as if the engine was on.

Have I missed anything?

[J.A.W.]

I dont think you missed anything Manolis.

Have I missed anything?

Well, A-G, apart from.. the plain facts on.. ..how you actually intend to fly, under what power,& for how long/far..
Yeah..
& some cogent stats on prevalence of fatal auto-gyro crashes vs any/every other microlight..

[manolis]

Hello Autogyro.


A safety option for the PatATi Portable Flyer is the ballistic parachute.

According Martin JetPack:
“A key safety system is the parachute system. This is a ballistic parachute system, with ballistic extraction and inflation of the chute. This leads to very quick chute opening, which enables the pilot to be saved in the case of a catastrophic failure down to a low height.”

Interesting reading: http://www.brsaerospace.com/files/brspa ... onders.pdf

Quote from the Internet:
“Through spring 2005, 177 lives were spared by real-time use of an installed BRS unit and zero life-threatening injuries were recorded.
The Cessna 150,172,182, Symphony 160 and Cirrus SR20, SR22 SRV and SRG-2 systems successfully met all FAA criteria for occupant protection (according to FAA's “Injury Criteria for Human Exposure to Impact”).”

A small size/weight ballistic parachute could be used for the lightweight PatATi Portable Flyer.


Another safety option for the PatATi Portable Flyer is the autorotation; it requires variable pitch / high inertia propellers, one way clutches, different synchronizing mechanism. In the future.


Another safety option is the pilot to limit his flight a few centimeters (a few inches) above the ground, or a couple of meters above the sea going from island to island.


Another option is to use the PatATi Portable Flyer as an assisting mechanism:

Think the case wherein the engine / propellers of the PatATi Portable Flyer are limited to provide only 80Kp (176lb) thrust, for a total weight of 100 Kp (220lb).

The pilot feels like weighing only 20Kp (44lb), so he can jump several meters high and then land on his feet safely, he can run “like the wind”, he can climb on mountains, he can cross roadless areas etc, etc.

Just imagine the potential for such use of the PatATi Portable Flyer.

Thanks
Manolis Pattakos

[J.A.W.]

Here is a 2-stroke powered US mil-spec Hiller mini-A-G from back in the day ..

http://www.alternatewars.com/SAC/XROE-1 ... y_1960.pdf

[gruntguru]

Cute little thing JAW - good find. (Its actually a helicopter.)

Did they make many of those things?

[J.A.W.]

Well observed distinction there, G-G,
& I stand corrected, since - it is indeed - a 'small but perfectly formed' - pukka helo..

As for having much of a service career, its doubtful, being a USMC project..

[uniflow]

Manolis, no, my twin cylinder uniflow engine ( in the boat ) has no moving sleeves just pressed in cast iron sleeves. Old tec and bad for heat flow ie cooling but it was all I could afford. Cylinders are near square bore and stroke.
I have many development engines on the go, you may be getting confused with the sleeve valve cylinder I also posted a picture of. This cylinder is awaiting a crank case to bolt it to, that's in the pattern shop now. Problem is I've got too many projects on the go at the same time. I've also got a fully variable rotary valve ( ECU controlled ) EFI twostroke engine in a bike frame that need to be finished as well. ECU controlled valve is also the throttle so other inputs will affect engine output. Should make this 70HP monster easier to ride / control.
Plus I too have a single seat autogyro that needs finishing. I'm a little fearful of small helicopters.
By the way, autogyro's can take off vertically but the rotor head becomes a little more complicated. In an engine out situation an autogyro can land with no wheel roll, so could be put in just about anwhere.
I would need to see AG's gyro flying on electric to take any notice, it would need to fly two hours on a charge to be anywhere near a petrol powered unit.

[gruntguru]

As for having much of a service career, its doubtful, being a USMC project..

Pity, I am sure there would be a huge demand if these were popping up in disposal stores.

I suppose there are modern equivalents in the kit or hobby markets? With current materials the weight could be significantly lower.