2 stroke thread (with occasional F1 relevance!)

[manolis]

Hello all.

Here is the first OPRE prototype (not OPRE Tilting, just OPRE, more at https://www.pattakon.com/pattakonOPRE.htm) running on Diesel fuel at low-revs-idling:



Spot on the flywheel.

The heavy flywheel (made of steel, 400mm diameter, 50mm width, 48Kg weight) of the first OPRE prototype:



was used mainly for the manual cranking of the engine: a decopressor is pressed, the flywheel accelerates by hand, the decompressor is released and the engine starts; no electrical system, at all.


The second OPRE prototype engine uses a lightweight (around 5Kg) flywheel.
The OPRE engine is bolted on a flywheel / gearbox from a Nissan Micra 1,000cc first generation, as the following photo shows:



The following youtube videos show the low idling of the second OPRE Diesel prototype without a heavy flywheel:





The cranking is by an electric starter.
The shaft shown at left rotates with the revs of the differential (like a drive shaft).
You can easily count its rpm and multiplying by the overall transmission ratio you have the rpm of the engine.

The one engine is standing free on a desk, the other is standing free on the floor.

If you know a Diesel engine having better idling than the hand-made OPRE tilting prototypes, please post the video.

Thanks
Manolis Pattakos

[manolis]

Hello TokTokkie

You write:
"The H4 has 4 engines. Two per rotor. Yaw is achieved by slowing the one rotor slightly relative to the other. As seen in the video it gives very controlled yaw. The simple way to do it would be separate twist grips for the throttles of each pair of motors but it is not apparent how it is done from the video. The problem would be synchronising the rotor speeds before lift-off with such a system."


No.
Each rotor is powered by all four engines and not by the one pair of them.
Each engine is engaged by its own one-way clutch, so that at a stall of one or of two engines the Gen H-4 can still fly to land safely.

Yaw control (Wikipedia):
Yawing motion is produced and controlled by electronic gyroscopically-controlled differential electric braking of the main rotors.



I.e. in order to yaw, the Gen H-4 needs a differential, a battery and a control system; these parts add weight, cost and reliability issues.

The Portable Flyer uses the "aerodynamic control" to yaw (which is weightless, costless and reliable). The pilot uses his head / limbs (all in a high speed air stream) as ailerons).



More at https://www.pattakon.com/pattakonPatTol.htm

Thanks
Manolis Pattakos

[coaster]

Manolis, my friend in 1999 put a propellor on a vertical briggs and stratton, he mounted this on a bicycles rear pack rack and he cruised the streets.

For a little while,

The police radared him doing 65kmh on a main road, he turned suddenly to evade capture, the bicycles rear wheel folded in half a my friend lost a few teeth, but lived.

The force of the prop strike broke the engine in half at the base of the cylinder.

Imagine your arms hit this propellor?

[manolis]

Hello all.


The first OPRE Diesel engine arranged "vertically" and driving two aluminum propellers:



The engine is bolted on a lightweight tripod that stands free on the floor.

Manual cranking without the need of the heavy flywheel of a previous video / photo.

This GIF-video was made with a series of photos taken at even crank angles (same engine and propellers as before):





In this case (PatATi Opposed Piston engine, 800cc, "ATi": Asymmetric Transfer and intake):



the pilot cannot reach the propellers, no matter how hard he will try.

The same engine runnign on gasoline (fuel injection, spark ignition):





In this case (single OPRE Tilting, direct drive of propellers):



the frame, which is shown more clearly here:



is not allowing pilot's arm / hands to reach the lower propeller, no matter how hard he tries.



In this case (Portable Flyer with the two OPRE tilting engines leaning backwards):





the pilot cannot reach (with his limbs) the propellers.

• Can't a motorcycle or bicycle rider put his hand / fingers in the space wherein the spokes of the rear wheel spin? But he has to put a lot of effort to do this, and it is supposed he is not completely idiot.

While all the previous are significant for the safety of pilot's limbs, when he flies the top risk (the lethal danger) is to lose power (or control) and fall heating the ground.

This is why a pair of independent propulsion units:



is so important.

Quote from https://www.pattakon.com/pattakonPatTol.htm :

• SAFETY
  
  As the Osprey, the Portable Flyer is capable for "vertical take-off / landing (like a helicopter), and for high-speed long-distance high-mileage flights (like an airplane).
  
  The malfunction of the one propulsion unit (due, for instance, to an engine failure, or to a rotor breakdown, or to a broken tooth-belt etc) is not fatal because the other (completely independent) propulsion unit, ALONE, is capable for the safe landing of the Portable Flyer.
  
  In the Osprey V-22 the malfunction / collapse / breakdown of the one rotor may turn out fatal, especially during a vertical take-off or landing.
  
  In comparison, the Portable Flyer with the two OPRE Tilting engines is safer.
  
  The breakdown of a rotor of a propulsion unit is not fatal: the other propulsion unit of the Portable Flyer (comprising an engine and two counter-rotating rotors) enables a safe landing or, if necessary, the flight to the closest safe landing place.
  
  Even in the case wherein both propulsion units fail, or in the case the Portable Flyer runs out of fuel, the Portable Flyer can still, using the rescue parachutes, land safely.

Thanks
Manolis Pattakos

[Brake Horse Power]

Has this been posted yet?

https://youtu.be/aULwM8-NRKw

Since my previous post was welcomed with such great enthusiasm

Here is a nice article about the engine

https://www.ust-media.com/ust-magazine/UST033/66/

[Rodak]

That's really difficult to read. Do you have a better link?

[Brake Horse Power]

You can zoom in and than it's OK? Here it is..

[Rodak]

It doesn't zoom; it has one enlargement step that is still difficult. I'll stop whining.... was just curious to read it.

[manolis]

Hello Brake Horse Power.

The article of your link has lots of technical information (nothing to do with the youtube video).

The REVolution engine is a supercharged 2-stroke (no crankcase scavenging) having a Bishop-like rotary valve at its exhaust (it is located after the exhaust port on the cylinder liner).

The rotary valve offers asymmetric timing:



The exhaust starts conventionally through the open exhaust port (on the cylinder liner) and through the open rotary valve.
Later the transfer (or scavenging) ports open. The supercharger feeds the cylinder, through the open transfer ports.
Later, and with the exhaust port still open, the rotary valve closes and the exhaust ends.
The compressed air from the supercharger has no way to escape to the exhaust. When the intake ports finally close (the exhaust ports are still open but the exhaust is blocked by the closed rotary valve), the cylinder pressure is substantially higher than the atmospheric pressure.

For the rest, they claim a lower lube specific consumption than the conventional 4-strokes (with ports on the cylinder, this is a strange), they also claim 177 gr/kWh peak BSFC (Brake Specific Fuel Consumption), which gives a 45% peak BTE (Brake Thermal Efficiency), they also claim 221gr/kWh at peak power (220hp from 578cc), which translates to 36% BTE.

The space between the exhaust ports and the rotary valve is a drawback. Another drawback is that the gas that passes through the Bishop-like rotary valves is “red-hot” (requiring a lot of cooling).



Now please take a look at the PatATE (Asymmetric Transfer and Exhaust) 2-stroke at https://www.pattakon.com/pattakonPatATE.htm and think if it does the same:







i.e. if it manages to end the exhaust several crank degrees before the end of the transfer.

If the crankcase of the PatATE is fed by a supercharger, or better by a turbocharger, the PatATE will work at the desirable MEP (Mean Effective Pressure).

The same can be achieved with the Opposed Piston engines wherein the exhaust ports can close substantially before the transfer ports.


While the REVolution engine does show the advantages of the early exhaust closing that allows the heavy supercharging of a 2-stroke, the same can be done without their rotary valves.

Thanks
Manolis Pattakos

[Rodak]

Yer gonna die. Really manolis, your control 'system' has no chance in hell of working. How is there torque applied to affect direction change? Good luck mate.

[NathanE]

But the pendulum rocket fallacy clearly shows that you don't need to apply any kind of torque to generate a control inputs.

Actually I can see that lifting one's legs at the hip without bending one's knees will create a "control" input that will have a "downward" pitch effect enabling transition to forward flight. It looks like Manolis has abs of steel from the photo wearing the frame, so this might just be possible for a highly tuned athlete like him. For a lard bucket like me, maybe not so easy but I guess not everyone is built to fly.

What will be funny to watch is that unless I'm unusual as well as overweight, my hip flexion means it would not be possible to reverse this motion, so transition to braking will have to come via a 270 degree "somersault" input.

How you do yaw and roll control I have no idea.

[coaster]

That gif of the 2 steel blades counter rotating makes me wide eyed with the fear of death.

[manolis]

Hello all.

The demonstration of the OPRE Diesel (that with the aluminum propellers) in the youtube video points to airplane application:

• Replace the “lightweight tripod that stands free on the floor” (where the OPRE Diesel of the video is bolted on) by the nose of a lightweight airplane, and you have an interesting combination.

Bore: 80mm,
Combined stroke: 50+50 = 100mm,
Total height: 505mm,
Direct Injection compression ignition with “pulling rod” architecture,
17:1 compression ratio.

Here are the parts of the prototype engine:



A lot of metal can be removed without affecting functionality.

0.5lt (30 cu.in) capacity,
built-in piston-type scavenge pump,
direct drive of the counter-rotating propellers (each one directly bolted on its own crankshaft),
high-pressure pure-mechanical fuel-injection (no electrical system, at all),
overall weight, including the propellers: 20Kg (after the removal of the unecessary material from the prorotype),
perfectly balanced (no vibrations on its basis),
zero reaction torque on the basis.

Besides its weight, the only loading of the frame of the airplane by the above propulsion unit is a forwards thrust force. Nothing else. Elastic mounts are not necessary.

The last characteristic (no reaction torque) is important for the safety of lightweight (and ultralight) airplanes wherein an abrupt opening or closing of the “throttle” (or a missfiring) may cause destabilization (even upside-down turn).

Important for the safety is also the Diesel fuel which is less flammable than the gasoline.

The absence of high voltage electrical system is also important for the safety / reliability (think of the twin ignition systems and of the two spark plugs per cylinder used in spark ignition air engines). Without electrical system, no short-circuit can happen (even running under water).


Cranking safety:
With the engine bolted on the nose of an airplane, the manual cranking is as safe as the manual cranking of any other airplane engine.

Weight saving and cost saving come from:
the lightweight propulsion unit,
the “unloaded” frame of the airplane (no vibrations, no reaction torque, lightweight engine),
the better thermal efficiency of the compression ignition engines which calls for less fuel for a specific distance,
the even better thermal efficiency of the specific compression ignition engine (increased dwell at the combustion dead center: pulling rod engine architecture) which calls for even less fuel weight,
the smaller fuel tank etc.

Quality / Feeling:
With the airplane fuselage rid of inertia vibrations of all kinds and orders, rid aso of power-pulse vibrations of all kind and orders, this single-cylinder propulsion unit seems better in feeling / quality than any Wankel rotary and than any multicylinder piston engine.

Thanks
Manolis Pattakos

[NathanE]

Hello all.


Thanks
Manolis Pattakos

I love seeing this, huge respect that you have made it.

[nzjrs]

Hello all.


Thanks
Manolis Pattakos

I love seeing this, huge respect that you have made it.

Absolutely 1000% agree. His craft and dedication to mechanical prototyping is truly impressive.

If he spent even 2% of the effort on any sort of quantitative analysis on the stability and controllability of the PF as he does with his engine, this thread would be less farsical.

The portable flyer part contributes to the impression that he is a crank - an impression that would not be possible if he just posted about 2-stroke engines and his engine construction project. The crazy pendulum rocket stuff and rediculous stick person flying diagrams really ruins the impressiveness of the entire project IMO.