Jump to content


Photo
- - - - -

Asymmetric Timing in the Two-Stroke engines


  • Please log in to reply
98 replies to this topic

#51 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 01 August 2014 - 04:17


Interesting stuff.
Are there actually any examples of the valved "loop-scavenged conventional two-stroke" in production or being proposed?

Advertisement

#52 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 01 August 2014 - 09:29

Interesting stuff.
Are there actually any examples of the valved "loop-scavenged conventional two-stroke" in production or being proposed?

Hello Kelpiecross.

Almost every company (Ricardo, Toyota, AVL, Denso etc) has proposed such a "loop-scavenged conventional two-stroke" (some proposed switchable 2/4 strokes versions).

However none of the proposals is in production.

It seems that instead of combining the advantages of the two-strokes (power density, lightweight, simplicity) and of the four-strokes (clean exhaust, low specific lube consumption, low specific fuel consumption, scuffing resistance etc), the "loop-scavenged conventional two-stroke" combines their disadvantages, too.

A big problem is the small valve time-area when all valves are on the cylinder head.

Take a look at the PatrPortLess uniflow two-stroke engine:

PatPortLess_Opposed_Cylinder.jpg

at http://www.pattakon....PatPortLess.htm

Compare the valve time-area of the PatPortLess to the valve time-area of the "loop-scavenged conventional two-stroke"

Take also a look at the PatMar:

PatMar.gif

that can replace the conventional giant marine two strokes keeping their top thermal efficiency (more than 50%), reducing substantially the specific lube consumption and the emissions, and increasing substantially the scuffing resistance / reliability.

Thanks
Manolis Pattakos

Edited by manolis, 01 August 2014 - 09:33.


#53 ray b

ray b
  • Member

  • 2,611 posts
  • Joined: January 01

Posted 01 August 2014 - 16:46

yes but can it run backwards ?



#54 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 01 August 2014 - 18:11

yes but can it run backwards ?


Hello Ray B.

If you mean if the PatMar can run backwards, yes it can.

Think that in the simplest case the intake valve on the piston of the PatMar opens and closes symmetrically with reference to the BDC, i.e. exactly as the intake ports of the conventional marine two-stroke.

In a more sophisticated version, with a system like the HyDesmo (at http://www.pattakon....akonHyDesmo.htm ) actuating the intake valve on the piston of the PatMar, the control over the engine operation / efficiency / emissions is better; for instance, at "slow steaming" the closing of the intake valve near (or at) the BDC increases the effective compression ratio (not possible in the current designs with the intake ports at the lower end of the cylinder liner)."

Thanks
Manolis Pattakos

#55 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 05 August 2014 - 18:03

Hello.

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

PatATi_OP_props.gif

PatATi_half_OP.gif

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 (not shown) 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.

PatATi_OP_flyer.gif


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.

Thoughts?

Thanks
Manolis Pattakos

Edited by manolis, 06 August 2014 - 06:34.


#56 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 14 August 2014 - 04:12

Hello.

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

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


It seems (from other forums) that only a few people understand the meaning of these terms, so let me further explain them.


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

Consider the case wherein your airplane (or your Electric Car Range Extender Module REM) is having a Wankel rotary engine driving a propeller (or an electric generator).
At each combustion / expansion the propeller (or the generator) accelerates and the rest structure inevitably receives a reaction torque pulse.
The NVH (Noise Vibration Harshness) of a Wankel REM cannot be as good as of an Opposed Piston REM (like the OPRE, for instance).
And this is not just theory: think what can happen in a light airplane at a sudden opening or closing of the throttle.


Consider now that your airplane (or your REM) is having a PatATi Opposed Piston engine driving two counter-rotating symmetrical propellers (or two counter-rotating electric generators).
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 (or its own electric generator). The casing receives a "reaction" torque in order to accelerate the one propeller (or the one electric generator) and an equal and opposite reaction torque in order to accelerate the other propeller (or the other electric generator). The two reaction torques cancel each other inside the casing of the engine. This way the basis of the engine 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 (I can further explain if there is interest) 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.physicsfo...ad.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.

Worth mentioning that at high revs the sudden change of direction of the PatATi Portable Flyer causes significant loads on the bearings of the two propellers / crankshafts and on the engine casing, however these loads cancel each other internally, with the rider / pilot feeling nothing.

Thanks
Manolis Pattakos

Edited by manolis, 14 August 2014 - 04:18.


#57 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 15 August 2014 - 05:34

I have no particular argument with your OP engine - but - I think your "backpack" portable helicopter (if you are actually serious)is a bit of a disaster. Mainly; two unducted (or even ducted) 1 metre diam. propellers could never lift anybody off the ground no matter what rpm or HP - the propeller disc efficiency is just too low. There have been many attempts at backpack helicopters - but, essentially none have worked - certainly not with 1 metre propellers. There was an interesting episode of Mythbusters where they built a backpack helicopter using two ducted fans of about 4 feet diam. and using 80+ HP - it didn't leave the ground.
Apart from this it would be fiendishly dangerous (for many reasons) both to the pilot and any bystanders.

#58 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 15 August 2014 - 14:54

I have no particular argument with your OP engine - but - I think your "backpack" portable helicopter (if you are actually serious)is a bit of a disaster. Mainly; two unducted (or even ducted) 1 metre diam. propellers could never lift anybody off the ground no matter what rpm or HP - the propeller disc efficiency is just too low. There have been many attempts at backpack helicopters - but, essentially none have worked - certainly not with 1 metre propellers. There was an interesting episode of Mythbusters where they built a backpack helicopter using two ducted fans of about 4 feet diam. and using 80+ HP - it didn't leave the ground.
Apart from this it would be fiendishly dangerous (for many reasons) both to the pilot and any bystanders.



Hello Kelpiecross.

What makes you think that it's not possible to lift a man with two 1m diameter propellers?


Take the MartinJetPack.

Its maximum weight at take-off is 330Kp (733lb).
It has a 2lt, 200bhp, V-4, two-stroke engine (some 60Kp heavy).
It has two ducted propellers of only 520mm diameter each.
And, the most important, it flies (see the several videos in the Internet).


Think about it a little deeper: the mission is a 70-75Kp man to vertically take-off, then to fly horizontally from a first point to a second point (fast if possible) and finally to vertically land.

Martin’s approach starts by increasing a few times the weight (the worst enemy when you try to fly).
The birds, bats and bugs fly because their weight relative to the power their body can provide is small.


Now take the PatATi Portable Flyer.

The total weight at take-off can be less than 100Kp (220lb): 70-75Kp the rider / pilot, 15Kp the complete Flyer and 10Kp the fuel (for a long range).

At 5,000 rpm the blade tip speed is well below the sound velocity, and the propellers near to their optimum efficiency.

The mission of the PatATi Portable Flyer is to lift the rider / pilot like a helicopter and then to allow him fly like an airplane (at high speed, fuel efficiently).


Wearing a wing-suit and falling at a 1:3 fall rate, you can fly with over than 150 Km/h.

Calculate the power:

The 75kp (750Nt) total weight lowers by (150Km/h)/3=13.8m/sec, which gives a power of 750Nt*13.8m/sec=10.4kW or 14bhp.

Imagine wearing a wing-suit and having the PatATi Portable Flyer above your helmet.
If the Portable Flyer provides this power (just 14 bhp), you can fly horizontally with 150Km/h for as long as the fuel tank has fuel.
With more power, you can go much faster.



Safety.

You can put a (removable) safety ring around the propellers for the take-off and landing (like those used in the paragliders). When you fly at high speed, say above 150-200Km/h, this ring should be removed (to avoid its aerodynamic resistance).


So, think again what (and why) is impossible and what not.

Much more important is to think how much the world can change with such a Portable Flyer.

Thanks
Manolis Pattakos

#59 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 17 August 2014 - 05:50


I remain unconvinced - two one metre (unducted) propellers will never lift anything useful.
The Martin device is interesting - but - 200hp? - a Robinson R22 is only 124hp - and has 2 seats, useful endurance etc. - and the Martin weighs almost as much as an R22 (hardly a walk-around backpack).
The backpack helicopter is an attractive idea - you can walk around, perform various tasks etc. - and then fly off into the distance. In reality this "anti-gravity suit" approach has no great advantages (unless you do have a genuine AG suit).
Some sort of very lightweight micro-helicopter is probably far better and more practical - and could even have 2 seats maybe.
It does make me wonder however if something with a layout like the Martin could be an idea. But with a proper weatherproof sit-down capsule (maybe for two) and with two decent-sized ducted fans (5-6 feet diam?) could be usefully practical. It would have the advantage (compared to R22 for example) of not having a giant whirling rotor whizzing around - so it would able to land in a much more confined space (like your own backyard) compared to an R22.
(But you would want to have a very effective ballistic parachute in case of problems).
An R/C electric-powered model could be interesting.

Advertisement

#60 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 17 August 2014 - 18:08

Hello Kelpiecross.

First consider the case of MartinJetPack:
a pair or ducted fans of 520mm diameter each,
a 2,000cc, 200 bhp engine,
a maximum take-off weight of 330Kp,
a fuel capacity of 45 lt,
a range of 30Km,
a maximum airspeed of 74Km/h,
and a cruise speed of 56Km/h.

Now consider the case of the Ossprey (Bell Boeing V-22):
a pair of counter-rotating propellers of 11.6m diameter each,
a pair of engines providing 6,150 bhp each,
a maximum take-off weight of 27,400Kp,
a range of 1,627Km,
a maximum speed of 509Km/h.

Now consider the case of the Chinook (Boeing CH-47):
a pair of counter-rotating propellers of 18.3m diameter each,
a pair of engines providing 4,733 bhp each,
a maximum take-off weight of 22,680Kp,
a range of 741Km,
a maximum speed of 315Km/h.

And here is the estimation for the PatATi Portable Flyer:
a pair of counter-rotating propellers of 1m diameter each,
an 800cc PatATi Opposed Piston engine,
a take-off weight of 100Kp,
a range of 300Km,
a maximum speed above 200Km/h.

Consider the disk loading (weight to propeller area at take-off) for the three cases:
MartinJetPack: 330Kp/0.43m2 = 776Kp/m2
Ossprey: 27,400Kp/211.4m2 = 129.6Kp/m2
Chinook: 22,680Kp/526m2 = 43Kp/m2
PatATi Portable Flyer: 100Kp/1.57m2 = 63.7Kp/m2

The "disk loading" in the case of the PatATi is 50% more than Chinook's, but it is also half of the "disk loading" of the Ossprey and a dozen times lower than the "disk loading" of MartinJetPack.

If you still think that a pair of 1m diameter non-ducted propellers cannot lift a man, please explain your reasonig.


By the way, from the specifications you can see a serious problem of the JetPacks: their ducted fans and architecture may be good for hovering but not for cruising (power to cruising speed ratio); as for the fuel efficiency (lt/Km), the 45lt for covering 30Km is not good at all.


While its disk loading is closer to Chinook's, think of the PatATi Portable Flyer as a "small scale" Ossprey (it is capable for vertical take-off / landing and very good for covering long distances at high speed / low fuel consumption) wherein the sensors and the controls over the flight is the rider / pilot himself.

**********

Assuming the same “disk loading” with the Ossprey, the maximum weight of the PatATi Portable Flyer at take-off would be: (129.6 / 63.7)*100 = 203Kp (i.e. it lifts two heavyweight persons).

Simplifying things further by assuming the necessary engine power is proportional to the maximum weight at take-off, the power required by the 800cc PatATi engine in case of 203Kp total weight would be: (2*6,150*(203/ 27,400)) = 91bhp, while in case of 100Kp total weight at take-off it would be only: (2*6150*(100/27,400)) = 45bhp.

Thanks
Manolis Pattakos

Edited by manolis, 18 August 2014 - 02:44.


#61 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 14 September 2014 - 03:00

Hello.

The following youtube video ( https://m.youtube.co...h?v=bzbVwiIeM0M ) demonstrates the gyroscopic rigidity (or stabilization) of a set of "parallel" not coaxial flywheels in case they spin at the same direction and in case they spin at opposite directions:

bzbVwiIeM0M

According maths and physics (or, simply, according the above video) the pattakon Portable Flyers (at http://www.pattakon....pattakonFly.htm ) are rid of "gyroscopic rigidity": with the symmetric counter-rotating propellers (and crankshafts), the total gyroscopic rigidity is zero, i.e. the rider / pilot can "instantly" (as instantly as with the propellers stopped) vector the thrust to the desirable direction:

As aerodynamic "controls" the rider / pilot can use his feet, hands, head and body just like the wing-suiters do.

A wing-suit fits with the Portable Flyer, especially for long flights and "fast acrobatics".

Imagine a guy having a Portable Flyer on his shoulders and wearing a wing-suit competing in the Red Bull Air Race.

Flyers.gif

The birds and the bats and the bugs can fly only because their bodies can provide enough power for their weight.
The weight of a man cannot be decreased. In order to fly, a man needs more power than what his / her body can provide.

When I want to fly, what I need is neither a vehicle, nor sensors, nor transmission shafts, nor gearboxes, nor differentials, nor servomechanisms, not even a seat.
What I do need is more power provided in a perfectly "neutral" way.
My body is the vehicle and the sensors, and the servomechanisms and the landing system, just like the bodies of the birds, bats and bugs.


Objections?


Thanks
Manolis Pattakos

Edited by manolis, 14 September 2014 - 03:04.


#62 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 15 September 2014 - 07:35


Don't know about air races - the propeller pitch for static lift and fast forward flight are very different.

#63 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 15 September 2014 - 16:49

Aerobatics in a powered wing suit would be pretty tame. The L/D and max G would both be quite low.


Edited by gruntguru, 15 September 2014 - 16:50.


#64 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 16 September 2014 - 03:43

Don't know about air races - the propeller pitch for static lift and fast forward flight are very different.


Hello Kelpiecross.

It is a matter of optimization and of available power.

If you want the Portable Flyer for hovering (say as a "toy", for demos etc) a low pitch provides the necessary lift (static lift) requiring substantially fewer power by the engine (and consuming substantially less fuel per hour of hovering). The drawback is the limited cruise speed and range.

But if you want the Portable Flyer as transportation means, the high pitch optimizes the cruising (the fuel consumed per Km covered lowers, the cruising speed gets high, say more than 250Km/h; think of the small front area / aerodynamic resistance when the pilot / rider flies horizontal, think also how fast a motorcycle with similar power can go).
As for the static lift with the high pitch propellers: during the hovering, the required by the engine power increases substantially as compared to the case wherein the pitch is small; however the static lift / hovering (i.e. the take-off and the landing) is a very small part of the flight.

For specific uses (say for rescues of injured people / of near-drowning swimmers / of fire-trapped people etc) the variable pitch propellers are preferable for the Portable Flyer in order to get faster (at high pitch) to the incident and then to lift (at low pitch) a lot of weight.

Thanks
Manolis Pattakos

#65 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 16 September 2014 - 04:30

Aerobatics in a powered wing suit would be pretty tame. The L/D and max G would both be quite low.


Hello Gruntguru.

When a non-powered wingsuiter falls constantly at a 3:1 ratio flying with 150Km/h, the power consumed is about 15bhp (weight lowering).
This indicates a good L/D ratio.

And it seems that with a Portable Flyer providing more than, say, 70bhp, the top speed gets higher than what a wingsuiter - or a rider / pilot without a wingswuit - can stand for long.

Yet, more power is still useful during the accelerations ( G ) wherein both help: the redirection of the Portable Flyer (its gyroscopic rigidity is eliminated, so the thrust force can be redirected “instantly”) and the “aerodynamic controls” (the hands / feet of the rider wearing the wing-suit).

The precision at which the wingsuiters pass near rocks and though narrow openings (there are many videos in the Internet) indicates that the wingsuiters can, even without a power-unit, keep excellent control over their flight.

I think that seeing a guy taking-off and flying fast and controllably as a bird / helicopter / airplane will be, at first at least, spectacular.

Thanks
Manolis Pattakos

#66 TDIMeister

TDIMeister
  • Member

  • 265 posts
  • Joined: January 06

Posted 05 November 2014 - 15:08

Hello all after a long hiatus.

 

Asymetric port timing (within limits) in 2-stroke engines can also be achieved by a much simpler method.  The below was calculated using a stroke of 71.6mm, con rod length of 107.4mm and désaxé equivalent to 10% of the stroke.

 

Picture1_zps625b27f8.png

 

Granted, the relationships of the transfer and exhaust ports remain fixed, but it's another way to achieve asymetrical port timing in 2-stroke engines without fundamental redesign of the basic architecture.

 

As (possibly beneficial) side effects, true piston TDC occurs at 4.3° after crank TDC.  Over a large part of the actual heat release period between approximately 360° - 380°, the piston is physically closer to TDC than in the non-offset case, meaning that combustion takes place closer to the thermodynamically ideal isochoric heat addition process, see below.

 

Picture2_zps51a1c13f.png

 

Also, at the point where the cylinder pressure is highest at some point just after true piston TDC in each case, the Desaxé layout has the additional advantage that the crankshaft and connecting rods form a more advantageous lever arm to convert the very high cylinder pressure into useful torque and work.  Additionally, at this point of peak pressure, the connecting rod is more upright, leading to lower side forces on the cylinder walls, which result reduced rubbing friction.

 

A note about lever arm:  I'm not saying here that the lever arm in itself makes for a more efficient or higher torque engine -- not beating a long-dead horse.  It just changes the instantaneous torque plot and *may* result in benefits when the instantaneous torque is integrated over the complete 360° of crank rotation in combination with the potential thermodynamic and friction reduction effects noted above.



#67 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 06 November 2014 - 04:56

Hello TDIMeister.

The problem with the offset crankshaft (or with the offset wrist pin) is the “limited asymmetry” it introduces.

With the offset crankshaft the exhaust closes significantly after the transfer ports giving the time to a part of the charge to escape from the cylinder.

It is also the fact that the exhaust closes even later than in the case of the non-offset crankshaft.
If I had to combine the offset crankshaft with the PatATi system, I would use “negative” offset in order to open earlier and to close earlier the exhaust ports (but this way the other benefits – like the lighter thrust loads at high combustion pressures etc – are gone).

The PatATi offers, in comparison, an actually unlimited asymmetry.
In the PatATi Portable Flyer prototype we are preparing these days, the transfer continues several degrees after the exhaust closing (just as in the Primavis engine). If we want to decrease this angle (or make it zero, or make it negative), we have just to reduce the height of the asymmetric transfer ports.

It is also the asymmetric intake of the PatATi.
Without rotary, or reed, or drum etc valves, the intake is as asymmetric desirable:

PatATi_model1_timing.gif

With the three moving parts of the simplest two-stroke (crankshaft, connecting rod, piston) and the stationary casing, you can have the asymmetry you like. All you have to do is to “play” with the geometry of these parts.

Thanks
Manolis Pattakos

#68 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 18 November 2014 - 03:12

Asymetric port timing (within limits) in 2-stroke engines can also be achieved by a much simpler method.  The below was calculated using a stroke of 71.6mm, con rod length of 107.4mm and désaxé equivalent to 10% of the stroke.

 

Granted, the relationships of the transfer and exhaust ports remain fixed, but it's another way to achieve asymetrical port timing in 2-stroke engines without fundamental redesign of the basic architecture.

 

As (possibly beneficial) side effects, true piston TDC occurs at 4.3° after crank TDC.  Over a large part of the actual heat release period between approximately 360° - 380°, the piston is physically closer to TDC than in the non-offset case, meaning that combustion takes place closer to the thermodynamically ideal isochoric heat addition process, see below.

 

Of course port timing is the same in terms of piston position i.e. on a pv diagram. Same goes for ROHR. The désaxé  really only shifts the crankshaft position relative to piston position. Ultimately the only difference is the piston velocity profile and therefore the time spent sweeping various cylinder volumes.


Edited by gruntguru, 18 November 2014 - 03:15.


#69 TDIMeister

TDIMeister
  • Member

  • 265 posts
  • Joined: January 06

Posted 18 November 2014 - 03:21

Correct.  It's only a temporal shift.



#70 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 17 May 2015 - 06:37

Hello.

video-undefined-2895507200000578-400_636

Quote from http://www.thenation...ll-the-uae-home

“The key is Mr Rossy’s carbon-fibre wing, fixed to his back with a harness and mounted with four kerosene-powered jets, capable of a combined 88 kilograms of thrust.

It allows him to cover distances of up to 55 kilometres. He can achieve speeds of nearly 260kph – up to 177kph moving upwards at an angle of 35 degrees.

“It’s very effective. I can tell you, you feel it.”

Mr Rossy has taken his jetpack around the world, and in 2008 flew across the English Channel from Calais to Dover.

A typical day for him in Dubai includes two flights, beginning in the early hours of the morning to avoid the desert heat.

After examining his flight gear, harness, parachute, helmet, and a physical warm-up to get his legs prepared for a heavy landing, he gets into a helicopter that travels up to a height of about 1,800 metres.

He jumps out then turns on the jets and increases their thrust power with a small hand-held control.

“That’s the magic moment where you change from something that falls to something that flies,” he said.

Arching his body “like a banana” from head to toe allows him to fly horizontally; subtle movements from left to right will change his flying direction.

“I am the fuselage, and the steering controls are my hands, head and legs,” Mr Rossy said.

The flights last about 10 minutes, and include practising complex manoeuvres such as loops and flying in formation with small aeroplanes.

“Then back to reality, you open your parachute and you’re back on the ground, landing as good as possible.”

End of quote


Quote from http://www.futurecar...ng-dude-can-fly

Type: Jet-propelled wing

Manufacturer: Homemade by "FusionMan" Yves Rossy

Propulsion system: 4 Jet-Cat P200 engines of 48.5 lb (22 kg) thrust each

Top average speed: 124 mph (200 km/h)

Top ascent speed: 112 mph (180 km/h)

Top descent speed: 186 mph (300 km/h)

Vehicle weight (w/fuel and smoke): 121 lbs (55 kg)

Vehicle weight (dry): 66 lbs (30 kg)

Vehicle span: 8.2 ft (2.5 m)

Fuel(s): Mix of kerosene and 5% of turbine oil for lubrification

Flight time: 10 minutes

Parachute type: Parachutes de France "Legend R"

Canopy type: PD Spectra 230

Harness type: Cut-away system with engine shut-down and automatic opening of a rescue parachute for the wing

Price: NA

Availability: Not commercially available

End of quote



The video https://www.youtube....h?v=Czy0pXRRZcs with the two Jetmans in a “dogfight” over Dubai shows how easily and precisely the rider controls, with his body, the flight.
“I am the fuselage, and the steering controls are my hands, head and legs,” Mr Rossy said.


While spectacular, the Jetpack / Jetman / Flyer of Yves Rossi has significant issues to address, like:

take-off,

landing,

hovering,

range,

mileage.


Now take another read at http://www.pattakon....pattakonFly.htm and let me know your thoughts and objections.

Thanks
Manolis Pattakos

#71 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 22 May 2015 - 08:23

Hello.

Quote from “Physics Phorums”:

Each of the 4 engines is a JetCat P200, with specs as follows:
Thrust at full power 50 Lbs / 220N
Weight incl starter 4.8 Lbs / 2.2Kg
Diameter 5.1 inches / 130mm
RPM Range 33,000 - 110,000
Exhaust temp 670C
Fuel consumption 25.37 oz min at full power
Fuel Jet Al, 1-k kerosene
Lubrication 5% oil mixed in fuel
Maintenance interval 50 hours

End of quote.


According the specifications (above and in the previous post), the required power for the horizontal flight of the Jetpack / Jetman of Yves Rossy at 200Km/h speed is:

4*220 = 880Nt at 200Km/h (i.e. at 56m/sec) : 49Kw (67bhp)

with a fuel consumption at full load : 0.72Kg*4*60 = 173 Kg/h = 215 l/h (25.37*0.454/16 = 0.72Kg).

These figures agree with the 10minutes flight duration and the 25Kg of fuel.


The resulting overall efficiency is 3.97Kg / 173 Kg = 2.2%, i.e. less than 1/40 of the chemical energy of the fuel is eventually used to propel the Jetpack and the pilot.
(0.081Kg/kWh is the specific fuel consumption in case the engine runs at 100% fuel efficiency, and 49*0.081=3.97).

With ten times higher overall efficiency (a 22% is achievable with the right internal combustion reciprocating engine driving a pair of good propellers), the flight time becomes ten times longer (1.6hours) and similarly the range (from 55Km claimed by Rossy it goes to 550Km).
From another viewpoint, with 22% overall efficiency, Rossy would need only the one tenth of the fuel (2.5Kg instead of 25Kg) he is consuming now (same range, same flight duration).
Besides the pollution it is also the cost.


With the fixed / solid wing on his back, Rossy has to compromise, among others (like no take-off ability, no landing ability, no hovering ability) with the top horizontal speed of his Flyer.
A retractable wing would be preferable: smaller (and with less drag) at high speeds, larger at lower speeds to provide the required lift; isn’t this what a wingsuiter does by extending or retracting his hands and legs?


No matter how useless (as a transportation means) seems today the JetPack of Rossy, Rossy shows the way.
Rossy is doing a great and pioneering work.

Rossy proves in practice that the following quotation from http://www.pattakon....pattakonFly.htm

“What a man needs, in order to fly, is neither a vehicle, nor sensors, nor servomechanisms, nor control units, nor transmission shafts, nor differentials, nor gear-boxes, not even a seat.
What a man does need, in order to fly, is power provided in a true neutral and manageable way. The body is: the vehicle and the sensors and the control unit and the servomechanisms and the landing system, just like the bodies of the birds, bats and bugs.”

is absolutely correct.


If you look at a Personal Flyer as a serious transportation means, you will soon discover that the quantity of the mechanical energy (not power, energy) that eventually pulls or pushes the Flyer forwards (and needs to be carried at take off) is of vital importance.

Thanks
Manolis Pattakos

#72 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 23 May 2015 - 05:28


I think the Jetpack/Jetman flyers need a lot more wing area. The wing size is probably limited by what will fit in the launching helicopter.

#73 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 25 May 2015 - 05:22

Hello Kelpiecross.

Rossy doesn’t need to be inside the helicopter.
There are several other reasons a smaller wing is preferable, like maneuverability, top speed, portability, mileage etc.


Quote from http://www.wired.com...ly-like-jetman/ (the article focuses on the actual flight; enjoy it).


Shore-Breitling-SA-51-660x440.jpg

Rossy flies with the grace of an eagle, and the subtle body movements he uses to maintain flight – and perform his loops, rolls, and other maneuvers – mimics a bird of prey.
. . .
“It was totally crazy,” he says of that first powered flight. After so many glide flights, the first time he flew straight and true without descending was like having someone pulling a giant handle on his back he says, “I can remember it very well, because it was so not normal.”
His wing has evolved over the years. He’s built more than a dozen and has destroyed a few. Though in an emergency, he can drop away from it during flight, and the wing has its own parachute.
. . .
To fly in the United States he had to register himself and his wing as an aircraft, N15YR is his identification number. He says he received an exemption for flying without a seat belt.

His flights have similarly evolved. . .

And all of the flight control is done with body movement. There are no ailerons or other flight control surfaces.


The four engines are mounted beneath the wing; eight gallons of jet fuel provide about 10 minutes of thrust. The only instruments are an altimeter and a timer mounted on his chest. The timer is his fuel gauge. The throttle control is a small dial mounted to a strap wrapped around his index and middle finger on his right hand.

. . .
Rossy performs a thorough pre-flight check with a crew chief who helps ensure the four engines are ready to go. The size of the wing keeps Rossy from actually getting inside an airplane or helicopter, so Rossy stands on the skid as it carries him to altitude. Less than a minute before getting to the proper altitude — 6,500 feet here in Oshkosh — Rossy and his assistant start the engines.
“I give an input on my little throttle, and that gives an electronic input to the engines for the startup process,” Rossy says. “Normally after 30-35 seconds all four engines are stabilized at idle with four green lights.”
Once the engines are running properly, the crew chief disconnects the monitoring equipment from the engines, Rossy makes a visual check to get his bearings, and then he drops into the void.
“I let go backwards,” he says of the backflip he makes away from the skid. “When I let go backwards, I give one turn of the throttle. There is a spool up of the engines and I am looking for speed.”
With only an altimeter and timer, Rossy uses his skin and ears as airspeed indicators.
“You feel very well, you feel the pressure,” he says touching his face and torso as he explains how the air feels during the flight. “You just have to wake up these senses. Inside an airplane we delegate that to instruments. So we are not awake with our body.”
As he freefalls, Rossy builds up extra speed as he flies nearly straight down to improve his control. Tests have shown he’s going about 160 mph during his descent. Once he feels he’s at the proper airspeed, it’s time to start flying.
“That’s the really good part,” he says.
At full thrust going almost straight down, Rossy raises his head and arches his back, shifting the airflow and transitioning him to horizontal flight. He describes flying his jet-powered wing with awed amazement of someone who still can’t believe he’s doing it.
“I am at full thrust, I arch, and lift is created on my wing and holds me in the air.”
Once in horizontal flight, Rossy can relax his head and back to fly straight and level. The throttle dial needs about two turns to go from idle to full power, and he’s typically at about 80 percent. That’s good for around 110 mph. Small changes in thrust allow him to fine-tune his position, something he must do when flying in formation with other aircraft.

. . .

I have to admit, I was a bit skeptical of the whole show. After following all kinds of aviation for many years, including Rossy’s exploits since he first started flying, I didn’t quite know what to think about seeing the Jetman in action.

But once I saw it, all I could do was laugh in disbelief.

Rossy flew all around us, passing underneath as he pulled up near the bomb bay doors, flying from the left wing to the right. He even backed off a few hundred feet to perform aerobatics. And he describes all of it with a continued sense of amazement, but at the same time as if he were just another aircraft.
“A roll is twist the shoulders,” he says making the simple motion in his chair, “and a little bit hands where you want to turn, like a ski jumper.”

Rossy says the movements are completely intuitive, “I can’t tell you what I’m thinking.” He compares it to skiing: Apply a little pressure here, a little pressure there and adjust your movements as needed.

Loops however are a bit more complicated. He has to enter the loop at more than 180 miles per hour.
“It’s full speed and you feel it. It’s like the sound barrier,” he says shaking around to show the buffeting of flying at top speed. “Okay, it doesn’t go faster than that, then arch, about the 3Gs, then it’s physical. You have to hold the arch.”
The biggest challenge comes at the top of the loop. As the airspeed slows down over the top, Rossy must reduce thrust to avoid getting in trouble.
“If not I have a pitch up moment and I’ll tumble,” he says, “that was my first looping experience, the tumbling.”

Rossy says he tumbled five or six times during the first attempt, and since then he has learned how to use his arms to change his center of gravity, helping to finish the loop (see video below).
Except for the top of a loop, most of the time Rossy keeps his arms at his side during flight – though during his formation flight with the B-17 he did extend his arms while flying level. He was just having fun.
“It was just to play superman,” he says laughing and humming the theme song to the movie with his arms stretched out again.

One of the more impressive aspects of Rossy’s flight is how quickly he can speed up and slow down during flight, “I have bad aerodynamics,” he says. “I am flying drag. As soon as I don’t have power, it brakes. When I give it power, it reacts.”

When the fuel timer approaches 9 minutes, 45 seconds, Rossy prepares to pull the ‘chute. Once he is lined up where he needs to be, he eases off the throttle to put the nose down. Then he cuts the engine, resulting in a bit more dive. When the engines are off, Rossy opens the parachute and begins his descent.

With nearly 100 pounds on his back, Rossy says he only attempts standing landings when the wind is at least 15 mph so he can come down vertically. Otherwise it’s a six point landing, “I brake maximum,” he says referring to the lines on the parachute, “then feet, then knees, then hands.”

At age 54, Rossy knows he probably won’t flying as Jetman forever. He already has his first student, a three time world champion skydiver who made his first powered flight earlier this month. Rossy says various militaries and other organizations have approached him about developing a jet wing for special forces, but for now he’s concentrating on his own flying and continues to explore the skies as Jetman, flying as birds do, and as we all wish we could.


End of Quote



"I have to admit, I was a bit skeptical of the whole show. After following all kinds of aviation for many years, including Rossy’s exploits since he first started flying, I didn’t quite know what to think about seeing the Jetman in action.
But once I saw it, all I could do was laugh in disbelief. "

"Rossy flies with the grace of an eagle, and the subtle body movements he uses to maintain flight – and perform his loops, rolls, and other maneuvers – mimics a bird of prey."


Thanks
Manolis Pattakos

#74 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 01 June 2015 - 08:52

Hello.

At http://www.pattakon....pattakonFly.htm it has been added a video (it is the First Run of the PatATi prototype engine; enjoy the sound).

Thanks
Manolis Pattakos

#75 bigleagueslider

bigleagueslider
  • Member

  • 992 posts
  • Joined: March 11

Posted 03 June 2015 - 01:48

Congrats on the first run of your "PatATi" engine. But as you likely understand it is just a small step towards demonstrating the viability of the concept for the application you intend to use it for.

 

While your website compares the "appearance" of this propulsion system to that of the V-22, in reality there is little similarity. The V-22 rotor system allows both collective and cyclic control, and your rotor system does not.



#76 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 03 June 2015 - 07:18

Hello BigLeagueSlider.

The closest thing to the PatATi Portable Flyer is the V-22 Osprey: they are quite similar in form and in flying ability (vertical take-off and landing capacity, hovering as a helicopter, horizontal flight as an airplane).

The PatATi Portable Flyer is quite different than the Osprey V-22 in that its fuselage and wings are anything but fixed.

Imagine an Osprey wherein the fuselage can change shape during flight, as a human body can.

Or think replacing the pilot of the PatATi Portable Flyer by a dummy; in such a case you do need cyclic and collective control over the pitch to control the flight.


With the human body being the fuselage, the control is quite easier.

As Yves Rossy / Jetman says: "I am the fuselage, and the steering controls are my hands, head and legs".

As they write: “He flies with the grace of an eagle, and the subtle body movements he uses to maintain flight - and perform his loops, rolls, and other maneuvers - mimics a bird of prey"


The four jets on the fixed wing at Rossy’s back, push him forwards. The direction of the thrust force is fixed relative to the wing; the strength of the thrust force is controllable: The throttle dial needs about two turns to go from idle to full power, and he’s typically at about 80 percent. That’s good for around 110 mph. Small changes in thrust allow him to fine-tune his position, something he must do when flying in formation with other aircraft.

See the video with the “dogfight” of Rossy with his partner above Dubai. Neither ailerons, nor cyclic or collective pitch control, nothing. All the control is based on the body of the pilot; and the precision is impressive.


As Rossy proves in practice, all we need in order to fly like birds is a thrust force to pull us forwards.

This is what the PatATi does: it provides the required thrust force in a perfectly neutral way. The body is: the vehicle and the sensors and the control unit and the servomechanisms and the landing system, just like the bodies of the birds, bats and bugs.


As you write, the V-22 rotor system allows both collective and cyclic control.

But this is not an option; it is a requirement, a need; otherwise the Osprey V22 cannot fly controllably.

Now think: does the PatATi Portable Flyer need such control over the rotors?

While the PatATi Portable Flyer does not need cyclic pitch, at all, the collective pitch is just an option.
With variable pitch propellers things can improve. For instance, it can be minimized the fuel consumption at hovering during a rescue (extending the flight duration), it can also be maximized the top horizontal speed and the mileage.

On the other hand, the fixed propellers are not that bad. Since the take-off and landing is a small percentage of the overall flight time, fixed propellers of pitch optimized for the cruising speed can be used (as in the small airplanes).

In case the propellers are designed to allow pitch alignment at standstill, the pilot can adjust the pitch before the take off. If he is to hover a lot, he needs small pitch. If he is going to cover a long distance at high speed, he needs to increase substantially the pitch (even if this overloads the engine during the take-off). If – during flight – he decides he need a different pitch, he lands, aligns the pitch and takes off again.

The use of variable – on the fly – collective pitch is an option for the PatATi Portable Flyer. The improvement of the fuel efficiency, of the top speed and of the functionality has to justify the added complication, cost and weight.

In comparison, the fixed propellers offer simplicity, lightweight and reliability.


Talking for variability,

the fixed wing of Rossy is a handicap at high speeds: the 200Km/h top horizontal speed with the 88 kilos of thrust from his four jets is small. As he puts is: at lower speed he would prefer a bigger wing, at higher speeds he would prefer a smaller wing.

The fixed wing is a compromise.

With the pilot of the PatATi Portable Flyer wearing a wingsuit and being disposed horizontal “hidden” behind the PatATi engine (reducing substantially the overall frontal area and the drag), the top horizontal speed and the diving speed get way higher.


You write: “Congrats on the first run of your "PatATi" engine. But as you likely understand it is just a small step towards demonstrating the viability of the concept for the application you intend to use it for.”

Thanks.

With the engine operating reliably (we are working on it), and with a set of good propellers, what other steps are required before demonstrating the viability of the Portable Flyer concept?

Learning how to fly with the PatATi Portable Flyer would be a challenge.

The PatATi with the two counter-rotating propellers is an absolutely neutral source of power (and thrust), equally neutral to, or more neutral than, the set of the four jets of Rossy.

Imagine the PatATi engine with its counter-rotating propellers secured not on the shoulders of a pilot, but on the front middle of the fixed wing of Yves Rossy jetpack (replacing his four gas guzzlers jet engines). Think how many more things Rossy could do this way.


To summarize:

The simplicity, the lightweight and the perfect symmetry of the PatATi Opposed Piston engine (with its built-in asymmetry of the transfer and of the intake, and its independence from a tuned exhaust) makes the difference.

Having a PatATi Opposed Piston Engine with a propeller secured per each crank, you actually have the simplest and the most "neutral" flying machine (airplane and helicopter) ready to fly controllably. And you need neither a fuselage, nor wheels, nor wings, nor instuments, not even a seat.

Thanks
Manolis Pattakos

#77 bigleagueslider

bigleagueslider
  • Member

  • 992 posts
  • Joined: March 11

Posted 08 June 2015 - 04:15

Let's be honest now. You cannot make a comparison between the V-22 and your PatATi concept. The V-22 has a MTOW of over 60,000lbs, has a max cruising speed of over 250kts, has a flight ceiling of 25kft, and can carry 32 troops.



#78 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 08 June 2015 - 10:31

Hello BigLeagueSlider.

You write:
“Let's be honest now. You cannot make a comparison between the V-22 and your PatATi concept. The V-22 has a MTOW of over 60,000lbs, has a max cruising speed of over 250kts, has a flight ceiling of 25kft, and can carry 32 troops.”


You can always make comparisons, provided you are not breaking the physical laws.


Post #60, for the Ossprey (Bell Boeing V-22):
a pair of counter-rotating propellers of 11.6m diameter each,
a pair of engines providing 6,150 bhp each,
a maximum take-off weight of 27,400Kp,
a range of 1,627Km,
a maximum speed of 509Km/h.

Post #60, estimation for the PatATi Portable Flyer:
a pair of counter-rotating propellers of 1m diameter each,
an 800cc PatATi Opposed Piston engine,
a take-off weight of 100Kp,
a range of 300Km,
a maximum speed above 200Km/h.

"Disk loading" of the PatATi : half of the "disk loading" of the Ossprey.


Imagine a scale-down version of the Osprey V-22, capable for carrying a single person.
Does it make the comparison "honest"?

Then eliminate the fuselage of the scaled-down Osprey; Yves Rossy / Jetman with his Jetpack proves in practice, beyond reasonable doubt, that the human body is a first class fuselage: functional and controllable, just like the bodies of the birds, bats and bugs. With a thrust of only 88 kilos, Rossy makes wonders in the air: the pilots of the conventional airplanes flying in formation with Rossy cannot believe what they see.

Obviously a Portable Flyer is for carrying a single person, or two during a rescue; nothing to do with the few dozens of the Osprey.

With the pilot of a Portable Flyer being into the air stream, a cruising speed above 300Km/h would be unpleasant (yet a 400Km/h speed for a few seconds, say at diving like a hawk or during an emergency, would be an interesting experience). It is still less than Osprey's.

Similarly for the take-off weight and the flight ceiling. The weight of the PatATi Portable Flyer is more than 200 times lower; and it does not need to fly at such altitudes.


For the rest, they are two substantially similar flying machines:
A pair of counter-rotating synchronized propellers provides the thrust in both of them; they both can take-off and land vertically lifting at least one person, they both can fly horizontally at high speeds and good mileage, they both can hover when required.


Take another look at the video with Rossy and his partner flying above Dubai and think what makes them fly so controllably.
Do they use some intelligent flight control equipment?
Nothing at all.
All they use is an altimeter (I suppose for the case wherein the clouds hide the land) and a clock/timer that rings when the fuel is near to end. The eyes, the brain, the ears, the skin, the body are their only sensing and control equipment. Nothing to do with the sensing and control equipment of an Osprey V-22.

So, let’s be honest: can a V-22 do in the air what Rossy with his Jetpack does, or what the PatATi Portable Flyer is expected to do?

As a wise man said “Everything is relative to everything else”.

Comparing the PatATi Portable Flyer with the Osprey V-22 is like comparing a motorcycle (or a sport convertible car) with a bus.
The bus is several times heavier. The bus carries dozens of passengers at longer distances. The bus is more comfortable. The bus is quieter. The bus is more fuel-efficient (fuel per passenger per mile). The bus is way safer. The bus is boring.

Many people who experienced the freedom and the advantages of a motorcycle, prefer (stick with) the motorcycle.

Imagine how much more freedom than the best sport cars and motorcycles will be offered by a PatATi Portable Flyer: while the best cars and motorcycles cannot help moving on one dimension (along the road) a Portable Flyer exploits all the three dimensions of the space in the sky.


Imagine flying from island to island of the Aegean sea, just 2 meters above the water. The dream of yesterday (Icarus), reality and useful tool of tomorrow.

With transportation means like the PatATi Portable Flyer the world will change dramatically.

Thanks
Manolis Pattakos

Edited by manolis, 08 June 2015 - 11:56.


#79 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 08 June 2015 - 23:02

I have just watched the Rossy video for the first time - amazing!

 

Manolis' portable flyer seems perfectly feasible to me. If successful it will be superior to the concepts of Martin and Rossy.



Advertisement

#80 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 09 June 2015 - 13:53

Thank you Gruntguru.

You write:
“If successful it (i.e. the PatATi Portable Flyer) will be superior to the concepts of Martin and Rossy.”


Let me explain it a little further.

Fuel Efficiency and weight.

The PatATi Portable Flyer (i.e. a PatATi Opposed Piston engine with the two counter-rotating propellers secured on the crankshafts) is not only "a true neutral propulsion unit" (neither vibrations, nor reaction torque, nor gyroscopic rigidity; only a force that can "instantly" and effortlessly be vectored towards the desirable direction), it is also a way more efficient and lightweight propulsion unit as compared to the set of Jets of Rossy / Jetman.

Why?

The propelling by Jets of a slow moving vehicle, like Rossy’s Jetpack (top speed 200Km/h), is highly inefficient:
From the chemical energy E1 of the fuel consumed, the Jets transform into mechanical / kinetic energy of the working gas only a small part E2.
And from this small part E2, only a small fraction E3 is actually used for the motion of the Jetman / Jetpack; the rest is gone with the high-speed exhaust gas.

With only 2.2kilos (5lb) per Jet, i.e. 8.8 kilos (20lb) for the four jets (for an 88kilos total thrust), the weight of the propulsion unit of Rossy’s Jetpack seems superior than any reciprocating engine.
But the Jetman has to carry both, the jets and the fuel to be used, i.e. 8.8 kilos for the jets plus 25 kilos / 55lb of fuel for just 10 minutes of flight.

Ten minutes flight duration / 55Km rage is too short.

For a more serious flight duration, say half an hour, (or for a longer range, say 150Km) the Jetpack of Rossy (jets plus fuel) gets so heavy that it cannot fly at all.

With the PatATi Portable Flyer the fuel efficiency is several times better. With the same quantity of fuel the flight duration and the range will be several times longer.


Ownership and running cost.

According Yves Rossy, his Jetpack is expected to cost around US200,000$ when in mass production.
It consumes about one liter of fuel per mile (some 60lt/100Km).
The worst: it requires a helicopter or airplane for the initial lift at a high altitude (no take-off capacity).

Rossy’s Jetpack seems no more than an expensive toy.

In comparison,
a PatATi Portable Flyer is expected to cost no more than a motorcycle (because a motorcycle with a similar engine needs wheels, suspension, gearbox, steering, transmission etc, not necessary for a Portable Flyer).
Its fuel consumption will be comparable to that of a car.
It takes off and lands by its own, etc

Thanks
Manolis Pattakos

#81 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 09 June 2015 - 22:14

According Yves Rossy, his Jetpack is expected to cost around US200,000$ when in mass production.
It consumes about one liter of fuel per mile (some 60lt/100Km).
The worst: it requires a helicopter or airplane for the initial lift at a high altitude (no take-off capacity).

No landing capacity either - parachute required.

 

Manolis. I think you should start adding handlebars to your sketches of the flyer. They will greatly increase yaw and pitch control (particularly in hover) as well as providing a convenient location for the throttle control.



#82 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 10 June 2015 - 05:17

I have just watched the Rossy video for the first time - amazing!
 
Manolis' portable flyer seems perfectly feasible to me. If successful it will be superior to the concepts of Martin and Rossy.


"Perfectly feasible" are not words I would use to describe this proposed diabolical device.

If Rossy used two or three more jet engines (making six or seven altogether) he could possibly take off and land vertically from the ground.

#83 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 10 June 2015 - 06:20

No - Rossy does not have any control in a hover mode. Manolis' "device" uses the prop wash acting on the pilot's legs etc to control roll, pitch and yaw in the hover mode.

 

Adding handlebars would add significant pitch and yaw control (roll axis is along the pilot's body) by adjusting of the thrust angle.



#84 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 10 June 2015 - 07:45


I think I was mainly pointing out that these model jet engines have a very high thrust-to-weight ratio. A simple, light chair-like structure with (say) eight engines (with a bit of thrust vectoring for control) arranged around it would take off vertically like a rocket (so to speak).

#85 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 10 June 2015 - 12:12

Hello Kelpiecros.

You write:
""Perfectly feasible" are not words I would use to describe this proposed diabolical device."


Imagine this "diabolical device" flying above a shipwreck, lifting and transferring to a safe place (to the shore, to another nearby ship) those who need help.

Or imagine the PatATi Portable Flyer ridden by a first-aid doctor and landing besides an injured motorcyclist during a bottleneck, downtown.

Or imagine it rescuing people trapped on the roof of a burning skyscraper.

Or as a useful and affordable transportation means: just think what this means for those living in road-less areas, in small islands etc.


With transportation means like the PatATi Portable Flyer, the world can change dramatically.



Unless I am wrong, what you are afraid of, is the pair of rotating propellers above the head of the rider / pilot.

Things are not as you think.

When the PatATi engine with the propellers is secured onto your shoulders / torso, you cannot reach with your hands, legs and body the propellers, no matter how hard you try (just like you cannot put your hand into the rotating wheel of a motorcycle at motion).

So the danger is for the people around you.
Do you see any reason for being among or near people during a take-off or a landing?

From another viewpoint: What is the difference from a small airplane? If it moves among people, the rotating propeller can be fatal. Did you ever see people standing in front of an airplane during a take-off or landing?

So, please explain in details your objections.
What makes the PatATi Portable Flyer a "diabolical device"?


You also write:
"If Rossy used two or three more jet engines (making six or seven altogether) he could possibly take off and land vertically from the ground. "

and:

"I think I was mainly pointing out that these model jet engines have a very high thrust-to-weight ratio. A simple, light chair-like structure with (say) eight engines (with a bit of thrust vectoring for control) arranged around it would take off vertically like a rocket (so to speak)."


A big part of the fuel of the Concord is consumed during take-off (Concord is very inefficient at low speeds, say below the sound velocity). In a similar way, the jets are highly inefficient when they propel a vehicle moving at a relatively low speed (200Km/h is a low speed).

Obviously you can add several jets to Rossy’s Jetpack in order to make it capable for vertical take-off / landing, provided you remove equal weight of fuel (to keep the drivability acceptable).
During the take-off, you will spend a good part of the fuel.
During the landing, you will spend another good part of the fuel (unless a parachute is used, but then the additional weigh of the jets - the fuel is consumed - makes the landing more difficult and risky).
Reasonably the current 10 minutes of the flight duration of Rossy’s Jetpack will drop to some 5 minutes for the sake of the vertical take-off / landing.
5 minutes autonomy is not bad; it is a huge progress as compared to the Peroxide Jetpacks (wherein the flight duration is less than one minute), but it is still nothing more than a spectacular expensive toy.

By the way, the more Jets Rossy adds, the less the required wing area.

Thanks
Manolis Pattakos

#86 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 10 June 2015 - 15:49

Hello Gruntguru.

When handlebars are shown in the drawings, most people are confused thinking that the pilot is hanged, with his hands, by them.

Nor the gas cable needs a handlebar to be supported (as in Rossy’s Jetpack).

Having handlebars is easy (the casing is a kind of handlebars). But according the videos of Yves Rossy / Jetman, with the hands and the legs free, the control of the flight is excellent.

In the case of the PatATi Portable Flyer, holding the handlebars by your hands makes easier the displacement of the center of gravity relative to the propellers.
But with your hands free, you can better affect (with legs and hands) the air stream (either at hovering or at horizontal flight).

Both ways have advantages. Flight tests will show if handlebars are required.

Thanks
Manolis Pattakos

#87 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 10 June 2015 - 22:16

. . . according the videos of Yves Rossy / Jetman, with the hands and the legs free, the control of the flight is excellent.

 

My concern is hover mode. The system is not inherently stable.



#88 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 11 June 2015 - 05:46

Hello Gruntguru.

You write:
“My concern is hover mode. The system is not inherently stable.”

You are right.

With a dummy replacing the rider of a bicycle, the bicycle has stability issues requiring an intelligent control system.

Similarly, with a dummy replacing the pilot of the PatATi Portable Flyer, the Flyer cannot hover stable.

As a bicyclist reacts properly to the signals from the environment and keeps, by slight movements of his body, the control, similarly the pilot / rider of the Portable Flyer will intuitively displace slightly his hands, head and legs to achieve stable hovering.


Yves Rossy’s Jetpack cannot hover.
But the Peroxide Jetpacks can, as shown in the youtube video at https://m.youtube.co...h?v=E81KQ7u3-7s

0.jpg

With the PatATi Portable Flyer things are (more or less) similar, at hovering, with the Peroxide Jetpacks (see in the video how stable is the pilot).

In the Peroxide Jetpack, the pilot controls the direction of the two side rocket nozzles. The pilot cannot put his feet in the hot gas stream (they will be burned). That is, the only control is the direction of the two exiting (at some 1,000 m/sec) gas streams. Similarly for the water jetpacks, which are now in fashion.

In the PatATi Portable Flyer, with slight movements of his legs / hands / head the pilot displaces his center of gravity relative to the propellers and at the same time he affects the downwardly moving stream of air (his hands and feet act like flaps).
I think that in practice it will prove easier than walking, and that soon the reaction of the pilot will be intuitive (as in a hovering honey bird / colibri).


I keep writing that the PatATi OP with the two counter-rotating propellers secured on the crankshafts is a completely neutral propulsion unit.

Let me further explain.
Here is a cross radial PatATi engine:

PatAT4.gif

(more at http://www.pattakon....ttakonPatAT.htm )

It is as vibration free as the best V-8 four-strokes.
It is more lightweight than the Opposed Piston PatATi: the one has a single light crankshaft for four pistons, the other needs two heavier crankshafts for only two pistons).
If you put a propeller on the crankshaft of this cross radial, the resulting reaction torque (as the propeller rotates into the air consuming the power of the engine, and as the piston trust on their cylinder liners) is a great problem.

Imagine the cross-radial powering the wing of Rossy’s Jetpack; he could not avoid the rotation – about his long axis – at the opposite direction of the propeller, no matter how hard he would try.

Compare this with the case wherein an Opposed Piston PatATi driving two counter-rotating propellers replaces the four Jets of Rossy’s Jetpack. The only action will be a force forwards (i.e. nothing more than the action from the four Jets).

** It would be interesting to know if all the four jets of Rossy are rotating at the same direction.


It seems that the PatATi portable flyer combines the take-off / landing / hovering capacity of the Peroxide Jetpacks with the flight / aerobatic capacity of Rossy's Jetpack and with the flight duration and range of the conventional airplanes.

Thanks
Manolis Pattakos

Edited by manolis, 11 June 2015 - 05:54.


#89 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 11 June 2015 - 06:33

The issue I see with hover mode (and no handlebars) is the hinge joint where the power pack joins the pilot at the shoulders. At first glance one might think that the lift vector tends to keep this joint straight and the shaft(s) vertical but this is not so. The thrust vector passes through the centre of the hinge regardless of orientation so the power pack will tend to flop to one side or the other under self-weight and thrust does not provide a restoring force to return the shaft to vertical.

 

Handlebars will allow the pilot to control this hinge joint and thus control pitch (and to a lesser extent yaw) in a much more positive and precise fashion than merely bending his body at the waist.

 

Instantaneous pitch control is largely via moving the CG away from the thrust vector whereas angling body parts in the prop wash is a slower, more delayed effect. Shifting the CG away from the thrust line is best achieved by flexing a hinge joint located as close to the propellors as possible.



#90 Kelpiecross

Kelpiecross
  • Member

  • 992 posts
  • Joined: October 10

Posted 11 June 2015 - 06:55


I agree about the handlebars for control - and it would give somewhere to put the throttle control as well.
I still think the device would be deadly dangerous and very lucky to be able to lift itself of the ground.
I hate to say anything in support of this device - but I would have thought that hanging the weight of the pilot underneath would add stability. ("Pendulum stability" I think they call this in aeronautical circles).

If I were the injured motorcyclist I would volunteer to wait for the ambulance - at least you would have some chance of survival then.

#91 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 11 June 2015 - 14:33

Hello Gruntguru

Is a hinge required?

The PatATi Opposed piston engine with the two counter-rotating propellers is secured onto the torso of the rider / pilot:

PatATi_Timing_Belt_arrangement_b_1.jpg

in a way similar to the way the torso of Yves Rossy is secured to the wing of his Jetpack (see the photo at the beginning of post #70).

In the PatATi Portable Flyer there is no need for a hinge joint.
You don’t need to hold the engine.
The engine tighten on your torso becomes, in a way, a part of your body.

When you are on the ground, you can walk with the engine / propellers on your shoulders (operating or stopped).
You can even run or sit on a chair.
There is no need to support the engine with your hands. It is secured onto your torso / shoulders and it stays there.


The propellers are your wings; they are mounted on (and are powered by) the PatATi engine that "comprises" a part of your torso.
It reminds the way the wings of an insect are mounted on (and are powered by) its thorax.


After the take-off, you keep control over the flight by moving / displacing your head, hands and legs (even by changing a little the position of your torso / shoulders) and by opening / closing the throttle valve (which needs not a handlebar to be secured; see how Rossy keeps between his fingers the "throttle pedal", actually a rotating rheostat).


For instance, if, during hovering, you feel you are leaning forwards, you relocate / shift you hands and / or legs a little backwards.

For instance, if, during hovering, you want to roll about your long (perpendicular) axis, you extend the one leg slightly forwards and the other slightly backwards.

For instance, if, during hovering, you want to start flying / moving forwards, you just shift / relocate you legs and / or hands forwards.


It is like describing to someone how to drive a bicycle or how to walk.
The truth is that after an initial short period, the "pilot" / "rider" gets so familiar that he starts reacting intuitively keeping the control without thinking of it.
I bet that, even during his aerobatics, Yves Rossy / Jetman can talk through his cell phone for serious matters.


I think the best way to get familiar with the control of a Portable Flyer is to leave your brain to experiment and learn how to react to the signals it receives from the environment (say by a few hours of tethered hovering / fly).

Thanks
Manolis Pattakos

#92 bigleagueslider

bigleagueslider
  • Member

  • 992 posts
  • Joined: March 11

Posted 12 June 2015 - 05:01

Manolis-

 

The photo you posted above illustrates the issues your concept has with regards to control, stability and hover efficiency.

 

First, it has long been understood that the hover efficiency of fixed pitch, high speed, small diameter rotors with high disk loading is extremely poor. Here's a video of a one man, recip engine, counter-rotating, coaxial rotor helo that has a much greater disk area (and lower disk loading)  than you are using.

 

Second, the primary method of attitude (pitch/roll) control your concept has is by the operator shifting his lower body to alter the mass center relative to the rotor aero center of lift. The helo shown in the video above uses a similar technique to control pitch/roll, but the helo uses differential speed regulation of the coaxial rotors for yaw control. It does not rely on aerodynamic forces resulting from rotor downwash flows over the operator's body parts for primary control of pitch/roll/yaw.

 

Lastly, I did not see any free-wheel capability in your rotor system to allow even a minimal auto-rotation function in the event of an engine failure. Are you familiar with the "dead man's curve" in relation to helicopters?



#93 gruntguru

gruntguru
  • Member

  • 5,761 posts
  • Joined: January 09

Posted 12 June 2015 - 06:30

 

Is a hinge required?

I just assumed that the connection to the pilot would have some flexibility (human flesh is flexible). Looking at your photo it does look like you have extended a rigid frame some distance below the shoulders so I accept the joint is not very flexible.

 

Advantage of a hinge. A stable hover requires the CG to lie on the thrust axis. If not, a counteracting aerodynamic moment is required. Without a hinge, the location of the CG with the pilot hanging relaxed is determined by the geometry of the harness. If this location is not on the thrust axis, the pilot will need to apply a constant correction - bending the torso, hips or legs. It would be better to provide a hinge which the pilot can adjust with a small movement of the hands, either towards or away from the body rather than hold an uncomfortable pose to maintain a stable hover.

 

The hinge could be arranged so that the instant centre was above the rotors with the thrust tending to return the hinge to the centre position. Imagine a pair of linkages converging above the rotors. The linkages could be flexures - again providing a restoring force.



#94 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 13 June 2015 - 02:47

Hello Bigleagueslider.

You write:
"The photo you posted above illustrates the issues your concept has with regards to control, stability and hover efficiency.
First, it has long been understood that the hover efficiency of fixed pitch, high speed, small diameter rotors with high disk loading is extremely poor. Here's a video of a one man, recip engine, counter-rotating, coaxial rotor helo that has a much greater disk area (and lower disk loading) than you are using."


The question is whether a pair of intermeshed counter-rotating propellers of 1m diameter each, can provide a static thrust above the take-off weight of the PatATi portable Flyer (100Kp / 220lb).

It can, according both: theory and practice.


The next question is how much power this pair of intermeshing propellers requires in order to provide the above static thrust, and if this amount a power can be provided by an 800cc two-stroke engine directly driving the two propellers and operating at revs wherein the rotors tip speed is significantly lower (say M0.75) than sound velocity.

The power required depends on the pitch.
An 800cc two stroke revving at 5,000rpm can easily provide this power for a pitch good for both, take-off and high speeds flight.


Regarding the disk loading:

The disk loading of the PatATi Portable Flyer at take-off is half than the disk loading of the Osprey V-22 at take-off / fully loaded.
Using the same disk loading with the Osprey V-22, the take-off weight of the PatATi Portable Flyer doubles.
That is, in case of emergency and with disk loading not higher than the disk loading of the Osprey, the PatATi Portable Flyer can take-off with the pilot and a passenger and some luggage (or extra fuel).


The GEN personal helicopter of your link (youtube video) is better for take-off / hovering.
The PatATi, just like the Osprey, is better for high speed / high mileage horizontal flights (both are capable for vertical take-off / landing and hovering).

It is like comparing the Chinook helicopter with the Osprey. Despite its advantages (for instance: auto-rotation, substantially lower disk loading etc), the Chinook is phased out and is progressively replaced by the Osprey (that achieves almost double cruising speed, more than double range etc, etc).

A lower disk loading is advantageous at vertical take-off / landing and hovering, but it becomes a serious drawback at high-speed flight, at bad atmospheric conditions etc.


By the way, here are some of the GEN helicopter specifications (world’s smallest helicopter with coaxial counter-rotating propellers):

Cruising speed: 100Km/h
Weight: 75Kp (165lb) empty
Time (flight duration): 30 to 60 min

Rotors: 4m diameter
Fuel: 19lit
Altitude: 3,000m
Power: 40 bhp (four 125cc two-stroke boxer engines)
Steering: by pivoting the rotor-head on a gimbal using a control handle

Price (self assembly kit): US35,000$

No autorotation capacity (the rotors are of fixed pitch)


You also write:
"Second, the primary method of attitude (pitch/roll) control your concept has is by the operator shifting his lower body to alter the mass center relative to the rotor aero center of lift. The helo shown in the video above uses a similar technique to control pitch/roll, but the helo uses differential speed regulation of the coaxial rotors for yaw control. It does not rely on aerodynamic forces resulting from rotor downwash flows over the operator's body parts for primary control of pitch/roll/yaw."

Both methods are functional (yaw control).

The one (yaw control by slight displacement of legs / hands) is the simplest possible (as well as the most lightweight, the most reliable and of zero cost); the other (that of GEN "helo") requires a differential, an electronically control break etc.

By the way: the strongest air wash happens on the central part of the PatATi engine wherein the cooling fins are (cooling).


You also write:
"Lastly, I did not see any free-wheel capability in your rotor system to allow even a minimal auto-rotation function in the event of an engine failure. Are you familiar with the "dead man's curve" in relation to helicopters?"

According GEN’s specifications, its propellers are of fixed pitch, which means that autorotation is not possible. Imagine the case the fuel ends at 50m altitude during a vertical landing. Or the case of a malfunction of the control over the differential (yaw control). Or any problem in the transmission / propellers.

Neither Osprey V-22 is designed for autorotation (it would require heavier and bigger propellers which would pose significant limitations in the “airplane” characteristics of the Osprey, like top speed, range etc).

Nor in Martin’s JetPack (again in fashion: a couple of months ago Martin achieved some 20 millions stock funding) the autorotation is possible. See their recent advertising youtube video at https://www.youtube....h?v=i8gncCih7Js
Quote from Martin’s web site:
"Martin Jetpack has been designed with safety in mind and for easy adoption, with pilot qualifications easy to obtain. The Jetpack is "fly by wire" so unlike other aircraft including helicopters it is relatively easy to operate and with its ballistic parachute system that can safely recover the aircraft from a few meters above the ground it will be one of the most safe light aircraft on the market."


A redundant injection and ignition (four fuel injectors independently controlled, one per intake port, two high voltage ignition systems, one per spark plug) can substantially increase the reliability of the PatATi engine and the safety of the PatATi Portable Flyer. Also the low mean piston speed of the engine: 13.3m/sec at 5,000rpm (say at take-off), 10.6m/sec at 4,000rpm (say at cruise).

Alternatively or complimentary a ballistic parachute could safely recover the PatATi Portable Flyer from a few meters above the ground in case of emergency (as in Martin Jetpack).

Alternatively or complimentary a second independent PatATi engine driving its own pair of counter-rotating propellers would increase a lot the safety factor (this is preferable than GEN’s approach wherein the safety is based on multi-engines all sharing the same transmission system and propellers).

Alternatively a parachute like that used by Yves Rossy / Jetman during landing.


On the other hand, imagine the case wherein you fly with the PatATi Portable Flyer (without additional safety means like the abovementioned) at very low altitudes (say no more than 2m above the ground, or, even better, no more than 3m above the sea water). Is the motorcycle safer?

Thanks
Manolis Pattakos

Edited by manolis, 13 June 2015 - 03:08.


#95 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 13 June 2015 - 04:03

Hello Gruntguru.

If you look at the PatATi Portable Flyer not as a toy but as a transportation means, you will see that the hovering covers only a tiny percentage of the flying time.

Actually, only during a rescue you need to hover immovable above someone or something; if the pose of the body is not comfortable, it is not a significant issue.

On the other hand think how much simpler and lightweight and reliable (and more comfortable during a long flight at high speed) is to have the PatATi engine / propellers secured on your torso, leaving your hands free.

It seems way safer and way more fuel efficient if, immediately after the take-off (say in 2 seconds) you turn progressively to horizontal flight at very low altitude (say 2-3m). When your speed gets adequately high, then you can safely go to higher altitudes.
Similarly for the landing: you approach the ground flying almost horizontally (as the conventional airplanes at landing) and progressively turn your body perpendicular, decelerate and land. Hovering time: 2-3 seconds.

For the emergency landing, a skateboard (or wheeled shoes) can make it safer.

In youtube videos they are shown wingsuiters landing without parachute on a pile of paper boxes and on a lake surface.

That is, if you get a high horizontal speed before leaving the safety of the ground (say while below 3m altitude), you have the opportunity of an emergency landing if something goes wrong.

In comparison, think what if at only a dozen meters above the ground the engine of Martin Jetpack has a major malfunction and the thrust is completely lost. Can the ballistic parachute safe the pilot?

All the effort with the Portable Flyers is to make them as simple, reliable and lightweight as possible. Everything redundant (without functionality issues) better be omitted.

On the other hand, it is the simplicity of the PatATi engine that makes the Portable Flyer safer. The mechanical simplicity combines with redundant injection and ignition (four injectors –one per intake port – independently controlled, two spark plugs with independent high voltage circuits)

Thanks
Manolis Pattakos

#96 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 23 June 2015 - 14:40

Hello

At http://www.popsci.co...ctual-hoverbike

under the title: “The US Army Wants Its Own Hoverbike, Again”

it is presented the last version of Malloy’s HoverBike:

532x800xP2.jpg.pagespeed.ic.g0s4U_CMVC.j

Two pairs of counter-rotating propellers, with the pilot / rider seating above the engine (as in a motorcycle). Below is an electric version:

malloyhoverbike.jpg?itok=pRvfcbKK

Quote from the above link:

"The Department of Defense is interested in Hoverbike technology because it can support multiple roles. It can transport troops over difficult terrain and when it's not used in that purpose it can also be used to transport logistics, supplies, and it can operate in both a manned and unmanned asset. It can also operate as a surveillance platform."


Recently various personal flying machines like:

Yves Rossy’s Jetpack,
Martin’s Jetpack,
Malloy’s Hoverbike,
Aerofex Hoverbike,

gain increased interest.

Thanks
Manolis Pattakos

#97 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted 30 June 2015 - 03:04

Hello.

Today it was granted the GB2,515,369 patent (United Kingdom Patent Office) for the Tilting Valve (more at http://www.pattakon....akonTilting.htm and http://www.pattakon....pattakonFly.htm )

Flyer3a.gif

Here is the first running OPRE Tilting prototype:

OPRE_tilting_prot_1.jpg

333 cc, bore 84mm, stroke 30+30=60mm
(same bore to stroke ratio with BMW's boxer R1200GS of 2013)
weight: 8.5Kp (19lb) without the exhaust pipe and the carburetor
height: 250mm

The lightweight,
the perfect balancing (vibration-free),
the longer dwell at the Combustion Top Dead Center
the reaction-free frame,
the reliability (low mean piston speed even at extreme revs, rid of reed valves etc),
are among the characteristics that make the OPRE Tilting an interesting choice.

PatTilt_Flyer_Frame.gif

PatTilt_Flyer.jpg

Thanks
Manolis Pattakos

#98 MatsNorway

MatsNorway
  • Member

  • 2,154 posts
  • Joined: December 09

Posted 30 June 2015 - 07:51

I think you will find more HP with the intake port further down and perhaps a flat (or closer to it) compressor valve. You will get a better emtying of the chamber if so.



#99 manolis

manolis
  • Member

  • 529 posts
  • Joined: May 03

Posted Yesterday, 01:32

Hello MatsNorway

A drawing of the "flat compressor valve" would be useful.
If you mean to make flat the outer (i.e. away from the crankshaft) side of the tilting valve, you can alternatively “shape” properly the (immovable) "covers" of the compressor.
On the other hand, a very small dead volume of the compressors consumes power (like, say, the pumping loss).

The scavenging of the OPRE Tilting is strange / unconventional.
You can call it "cross uniflow".
The transfer and the exhaust ports are arranged at opposite sides of a particularly shallow cylinder (84mm bore for a piston stroke of 30mm in the prototype).
The narrowing at the middle of the cylinder is not affecting the scavenging; besides, it allows a compact combustion chamber and creates two squeeze areas (the same narrowing would be a problem for a through scavenging opposed piston).

As the prime mover of a Portable Flyer, or of a paraglider, or of a small airplane etc, the OPRE Tilting needs optimization / tuning only at specific revs / heavy load.
The "tuned" intake makes questionable the need for a heavy / expensive tuned exhaust.


For more HP, another way is to increase the capacity.

The OPRE Tilting architecture allows extremely lightweight, really compact and true-vibration-free engines to be made.

A 10Kp / 22lb weight for an injected 0.6lt OPRE Tilting seems attainable:
Bore: 101mm, Stroke (36.5+36.5)=73mm (i.e. bore and combined stroke as in the BMW R1200GS), capacity: 585cc, total engine height: 300mm / 12 in.


Think the difference the OPRE Tilting can bring to:

Martin's Jetpack (as it is now, the unique crankshaft of their V-90 4-cylinder 2-stroke 2,000cc 200HP has to drive a pair of counter-rotating ducted fans),

or to Rossy's Jetpack (an OPRE Tilting driving a pair of counter-rotating propellers and secured on the wing),

or to Malloy's hoverbike (a front and a rear OPRE Tilting engines, each driving a pair of counter-rotating propellers, with a central ECU controlling / coordinating the two engines).

Thanks
Manolis Pattakos

Edited by manolis, Yesterday, 01:39.