Portable Flyer / PatATi Asymmetric Transfer & Intake 2stroke

[manolis]

Hello.

You may like to think (or dream) about this application:





It is an Opposed-Piston PatATi Portable Flyer having

80mm bore,

80+80=160mm stroke,

800cc,

540mm crankshaft axis to crankshaft axis distance (two directly-driven counter-rotating propellers, 1m diameter each),

perfectly "vibration free" and "reaction free" structure,

total weight less than 15Kp (33lb).


The second GIF is the one half of the Opposed Piston PatATi engine and shows the "internals".

The narrowing at the center of the cylinder of the OP PatATi engine enables a compact combustion chamber without spoiling the - loop - scavenging. The spark plugs are located more centrally. The narrowing causes the required squeeze during the combustion.

Without phase difference between the two crankshafts (yet, with asymmetric transfer and intake) and with the same instant pressure acting on the two piston crowns (common combustion chamber), the synchronizing mechanism (not shown) between the two crankshafts runs unloaded, so it can be lightweight and reliable, causing minimum power loss.

The two counter-rotating propellers act as the flywheels of the engine.

With the two oppositely moving pistons counterbalancing each other, the balance webs on the crankshafts have to balance only the mass of the crankpin and of the rotating part of the mass of the connecting rods (lightweight and compact crankshafts).

At 5,000rpm the speed of the blade tip of the 1m diameter propellers is 260m/sec.
With 0.5Kg reciprocating mass per piston (it includes the mass of the piston, of the wrist pin and of the "reciprocating part - typically 1/3 - of the connecting rod) the resulting maximum inertia force is 700Kp at the TDC (at the BDC the inertia force drops to 400Kp; con-rod to stroke ratio: 2). In comparison, with only 20 bar pressure inside the cylinder (20 bar is the BMEP - brake mean effective pressure - in the typical marine two-stroke supercharged engine), the resulting pressure force on each piston is 1,000Kp.




Application:

Imagine a pilot / rider wearing a wingsuit and having secured on his shoulders this Portable Flyer, flying only 2m above the sea (for safety) from island to island.

The pilot / rider can take off vertically, like a helicopter, and then he can progressively turn to horizontal fly, like an airplane, to cover the distance quickly and fuel efficiently (fast and cheap).
At landing he returns to "helicopter" mode to land vertically.

For more about the PatATi Aymmetric Transfer and Intake: http://www.pattakon.com/pattakonPatAT.htm

Thoughts?

Thanks
Manolis Pattakos

[manolis]

Hello.

As I wrote in the first post, the PatATi Portable Flyer is a:

perfectly "vibration free" and "reaction free" structure.


Let me further explain these terms.


The Wankel engine can be, "inertially", a perfectly balanced engine, however it cannot bet a "perfectly vibration free" engine / structure.

Consider the case wherein your paraglider (or your ultralight) is having a Wankel rotary engine driving a propeller.
At each combustion / expansion the propeller accelerates and the rest structure, including your body, inevitably receives a reaction torque pulse.
Think what happens at a sudden opening or closing of the throttle

Consider now that your paraglider (or your ultralight) is having a PatATi Opposed Piston engine driving two counter-rotating symmetrical propellers.
As happens with the Wankel rotary, the PatATi OP is, “inertially”, a perfectly balanced engine.
But it is also a "perfectly vibration free" structure.
During a combustion/expansion, each piston, through the respective connecting rod and crankshaft, accelerates its own propeller. The casing receives a "reaction" torque in order to accelerate the one propeller and an equal and opposite reaction torque in order to accelerate the other propeller. The two reaction torques cancel each other inside the casing of the engine. This way the basis of the engine, i.e. the rider / pilot / frame, remains perfectly rid of inertia and of combustion vibrations (common combustion chamber, same instant pressure acting on both piston crowns, zero phase difference between the two crankshaft).
The sudden opening or closing of the throttle cannot de-stabilize the structure any longer.



Consider now the PatATi Opposed Piston Portable Flyer.

With the two propellers (and flywheels) rotating at opposite directions (like two symmetrical gyroscopes), the structure has, according the theory and the experiments:
“no gyroscopic stabilization (acts just as if the gyroscopes were not spinning, ie., the gyroscopes fall over exactly as when they are not spinning - zero net angular momentum)” (quote from Physics Forums at http://www.physicsforums.com/showthread.php?t=173215 )

So, either the two big propellers (1m diameter each) rotate at 5,000rpm, or at 2,000rpm, or they are slow revving or they are completely stopped, the pilot / rider “sees” the same difficulty in order to change the direction of the Portable Flyer (and, so, the direction of the thrust force).
And this is quite important for a stable flight.

Thanks
Manolis Pattakos

[autogyro]

The idea of a through scavenged opposed piston supercharged two stroke worked well in the Commer knocker and the Deltic engines just after WW2 but why bother with crankshafts in the 21st century

Oh and why use props?
I am currently playing with vectored thrust for small lift systems, props are a PITA in that field.

[manolis]

The idea of a through scavenged opposed piston supercharged two stroke worked well in the Commer knocker and the Deltic engines just after WW2 but why bother with crankshafts in the 21st century

Hello Autogyro.

Ecomotors (Bill Gates with 23 million dollars is one of their famous investors) and Achates Power (some 100 millions invested so far, Wal Mart is their main investor) are both dealing exclusively with Opposed Piston Engines.

An Opposed Piston engine has several advantages as they are presented in my previous posts.
For instance (and with divided load on the two crankshafts) its basis can be perfectly rid of vibrations (imagine to secure at your shoulders a heavily vibrating engine).
Also it has reduced surface to volume ratio (important for high thermal efficiency).
Also it can drive directly two big propellers without any gearing.
With the asymmetric transfer and the asymmetric intake it can be tuned for fuel efficiency, for power etc.
Etc, etc.

Which is the "modern" engine of the 21st century you propose?

Oh and why use props?
I am currently playing with vectored thrust for small lift systems, props are a PITA in that field.

Weight? Efficiency? Lift per bhp?

Is the "vectored thrust" used in some airplane or helicopter so far?

Thanks
Manolis Pattakos

[autogyro]

Vectored thrust is not as efficient as rotors for lift and rotors are not as efficient as unloaded (autogyro) rotors.
Small diameter props are not as efficient as slow turning larger diameter rotors but require gearing to match the usual 3 to 4 thousand operating rpm of IC engines. 4,000 rpm takes the tip speed of a small diameter prop to the speed of sound.
It is the cranks, crank cases, gearing etc that at least doubles the weight of an opposed piston engine compared to a design that needs non of these.
For small lift devices the props or rotors are a distinct disadvantage because they can snag things very easily and cause damage and injury.
Vectored thrust eliminates this problem.
I cannot say much more at present.

[mep]

Good points there by autogyro.
Btw. how are your two crancshafts synchronised to each other because at the moment there is nothing seen on your animations. Without synchronisation they won’t work.

[manolis]

Vectored thrust is not as efficient as rotors for lift and rotors are not as efficient as unloaded (autogyro) rotors.
Small diameter props are not as efficient as slow turning larger diameter rotors but require gearing to match the usual 3 to 4 thousand operating rpm of IC engines. 4,000 rpm takes the tip speed of a small diameter prop to the speed of sound.
It is the cranks, crank cases, gearing etc that at least doubles the weight of an opposed piston engine compared to a design that needs non of these.
For small lift devices the props or rotors are a distinct disadvantage because they can snag things very easily and cause damage and injury.
Vectored thrust eliminates this problem.
I cannot say much more at present.

Hello autogyro.

For the weight of the Opposed Piston,
please take a look at the OPRE Opposed Piston prototype Diesel engine:



at http://www.pattakon.com/pattakonOPRE.htm ,

and at the PatOP Opposed Piston prototype Diesel engine:



at http://www.pattakon.com/pattakonPatOP.htm .

The one is 502cc the other 635cc, both are single cylinders opposed piston.
The mass of each one is 20 Kg (44lb) and can be lower.

The 800cc PatATi we are currently building (spark ignition) is expected to have a mass of 15Kg (33lb).
The perfect balancing (vibration free) is one of its characteristics.
Do you know a conventional 800cc, single or twin, comparable to the PatATi in mass (and smoothness, and thermal efficiency etc)?

An Opposed Piston engine is rid of cylinder heads, it needs lighter balance-webs on the crankshafts (because the two oppositely reciprocating pistons counterbalance each other) etc.

Thanks
Manolis Pattakos

[manolis]

Good points there by autogyro.
Btw. how are your two crancshafts synchronised to each other because at the moment there is nothing seen on your animations. Without synchronisation they won’t work.

Hello Mep.

In the PatATi Opposed Piston engine of the Portable Flyer the phase difference between the two crankshafts is zero (yet the intake and the transfer are quite asymmetric), which means the synchronizing mechanism runs unloaded (common combustion chamber, same instant pressure acting on the two piston crowns).

This way even with chain and sprockets we can reliably synchronize the two crankshafts with the minimum weight.

The synchronization mechanism we plan to use is quite unconventional. This is why it is not yet published in the http://www.pattakon.com web site.

Thanks
Manolis Pattakos