2 stroke thread (with occasional F1 relevance!)

[coaster]

If a helicopter yoke is introduced, a rod along the spine to the hips, a weight reduction regime of magnesium, titanium, aluminum. A big hp increase and handlebars tied solid to the yoke pivot then im 100% onboard and a true beleiver.
Redbull stunt planes do a trick called a 'prop hang', big hp vertical climb deliberately stalled and caught again with power, 6 cylinder lycomi g turbocharged, 330kg ish airframe, this motor of Mr Patakos needs major dyno time and big hp gains.

[gruntguru]

Thanks. I believe the best method would be attachment via flexures which converge to a point above the powerplant.

As noted above this is what many of us have suggested investigating. To date there has been a consistent rejection of this idea based on the idea that control will be delivered by airflow redirection and cog shift purely based on hip flexion. Those of us with a concern about this are interested to understand how yaw and roll control will be managed on this basis and how positive (nose "up") pitch control is possible given restrictions of hip flexion (I.e. hips bend "forwards" much more easily than "backwards")

. . and coaster's video confirms it will take a lot more than legs in the slipstream to achieve control and stability in hover.

[Rodak]

. . and coaster's video confirms it will take a lot more than legs in the slipstream to achieve control and stability in hover.

.......I did suggest swim fins some time ago.

[manolis]

Hello Mudflap

You write:
“Well, if you sky-dive with a go pro attached to your helmet you can steer by moving your head to some extent.
Speaking of which, is it a coincidence that the flyer's maximum velocity is more or less the same as a sky-diver's terminal velocity ?”


The 300Km/h is, on one hand, attainable while, on the other hand, is affordable. At faster speeds the pilot will soon be tired.


Much more important, for this discussion, is the first sentence of your post.

When you sky-dive, your weight is the only thrust force, and your center of gravity is where this thrust force is applied.

By moving your head (or, in general, by varying your body posture) you cannot displace the thrust (i.e. your weight, i.e. the force by which the earth attracts you) offset to your center of gravity.
Being unable to offset the thrust force out of your center of gravity, you are unable for “weight displacement control”.

So, during a sky-dive, by moving your head you control your flight (your “falling flight”) exclusively by “aerodynamic control” (and not by “weight displacement control”).

So, by moving your head at a sky dive, you use pure “aerodynamic control” to steer (to some extent).

Regarding the “extent” of steering:

Using all the parts of your body, the extent of steering (we talk for pure “aerodynamic control”, nothing to do with “weight displacement control”) is more than anyone can ask:




The pilot of the Portable Flyer is, permanently, into a high speed air stream enabling full “Aerodynamic control” (even aerobatics, unless the above video is fake).

The Pilot of the Portable Flyer has also full “weight displacement control” (as the GEN H-4 and more, because in the Portable Flyer the pilot mass is about 80% of the total mass of the flying device:



while in the GEN H-4 (which has not the option of “aerodynamic control”):



the pilot mass comprises only 50% of the total mass.



The above reply to several suggestions.

• The philosophy behind the Portable Flyer is:
  to keep the weight the minimum possible,
  to simplify the structure using the human body as the basis,
  to exploit the available gimbal joints of the human body (the spine is just one of them),
  to use the brain, the eyes, the otoliths and the skin as the control system,
  to use the muscles and the bones of the pilot as the “servomotors”,
  to exploit both “weight displacement” and “aerodynamic” control,
  to improve safety by using two completely independent propulsion units,
  to focus on simplicity and on affordable cost.

Thanks
Manolis Pattakos

[Rodak]

Oh come on. The 'pilot' can't even move his/her body with your rig. How can they shift their weight to initiate control movements? Death machine. The thought experiment mentioned previously is right to the point; imagine strapping some sort of propeller device rigidly to a person and then ask them to control it by moving their body. Ain't gonna happen. Manolis, look at how a hang glider is controlled by shifting body weight. No way flapping your arms or legs will affect the flight path; as nz says, pissing off the bow of a ship to steer it. Again, build a model and test it. Easy and cheap to do. Words don't make it so no matter how much you believe them.

[coaster]

I cant help myself, edited.

[manolis]

Hello Gruntguru.

You write:
“I believe the best method would be attachment via flexures which converge to a point above the powerplant.”


The powerplant of Browning JetPack comprises a central turbine fixed on pilot’s back, and two pairs of turbines fixed on pilot’s arms.
I.e. the powerplant is as fixed on pilot’s body as it gets.
Each pair of turbines has its own “gimbal joint”: it is the shoulder-joint of pilot’s arm whereon the pair of turbines is fixed.


In the Portable Flyer the powerplant is fixed / secured / tighten / fastened on pilot’s back / torso:



Back, torso and powerplant comprise a (fixed / inflexible) sub-assembly (grey color) shown at right-top in the above drawing.

All the rest parts of pilot’s body (beige color, bottom right), i.e. the hip, the legs, the arms and the head are completely free to move; these free to move parts comprise the big percentage of the human weight.



”Mobility” and Portable Flyer

A person wearing a Portable Flyer can move hip, head and limbs through their full range of motion.
I.e. the mobility of the head, of the hip and of the limbs is not at all restricted by the Portable Flyer.
If the wind tunnel dancer of the video of my last post was wearing a Portable Flyer on her back / torso, she could move her body parts (relative to each other) the same way.


Hovering, braking, backwards motion, forwards acceleration, high speed cruising

Hovering, vertiacal take-off and vertical landing:



During vertical take-off, vertical landing and hovering the pilot has to bend forwards (as in the drawing) in order to keep the thrust normal to the horizon and the overall center of gravity on the thrust axis.

Transition from hovering to backwards motion:



The pilot leans his head backwards, and bends his legs / arms backwards causing the displacement of the overall center of gravity aft the thrust axis. This causes the rotation of the Portable Flyer counter-clock-wise (above drawing). The horizontal component of the thrust accelerates the Flying Device backwards. When the thrust is at the desirable direction the pilot has to restore his initial posture in order to stop the rotation and continue moving backwards parallel to himself.
The same for the braking. The Pilot moves his head / limbs in order to displace the overall center of gravity aft the thrust axis; this causes a fast rotation of the device / pilot assembly creating the necessary horizontal backwards braking force. Soon after the pilot has to re-arrange his hip / head / limbs in order to displace the overall center of gravity on the thrust axis.

Transition from hovering to forward flight:



Being at hovering, the pilot bends his legs, hip, head and arms forwards. The overall center center of gravity is displaced fore the thrust axis creating a moment (torque) that rotates the device / pilot assembly clockwise. The more the thrust axis leans forwards, the stronger the horizontal component of the thrust force that accelerates forwards the Portable Flyer with the pilot:



If the pilot keeps his posture, the clock-wise rotation will continue (if the Portable Flyer is at a big altitute, it will perform loops as it falls).
When the pilot decides, he changes his body posture so that the overall center of gravity moves – initially – aft the thrust axis (in order to stop the rotation of the Portable Flyer) and then the pilot changes again his body posture in order to move the overall center of gravity on the thrust axis:



Now the Portable Flyer cruises at a velocity, with the pilot making “micro-alignments” in order to keep constant the direction of the thrust axis, with the overall center of gravity on the thrust axis. If he wants to cruise faster, he opens the throttle (this will also increase the altitude unless the pilot turns slightly forwards the thrust axis: this will increase the horizontal force without increasing the vertical lift).

All the above body postures are easy. Lying on a bed and turning to the side, one can replicate all the above posture.


In order to realize the previous modes of flight and the transitions mentioned, the weight displacement control is sufficient.
However the “aerodynamic control” is also available.
Combining the two methods, the control over the flight of the Portable Flyer goes to higher levels as compared to the existing JetPacks of Mayman / Zapata / Browning.


Worth to mention again:
It has nothing to do with a static equilibrium.
It is a dynamic equilibrium wherein the pilot feels and reacts to correct.



[You also write:
“. . and coaster's video confirms it will take a lot more than legs in the slipstream to achieve control and stability in hover.”


The pilot of the Portable Flyer has the option to use his limbs and head as ailerons to create the required torque for pitch / yaw / roll control.
The JetPacks cannot use this kind of control (i.e. the aerodynamic control) at hovering / low cruise speeds.

The extent of the “aerodynamic control” is analyzed in my last post.
Count how many times, during a second, the wind tunnel dancer changes direction and pose.
If she was sky-diving, she would do exactly the same aerobatics / dance during her fall.



I read several suggestions to add “gimbal joints”, subframes, fuselage, seat, landing gearing, “flexures converging high”, fins, electronic control systems, etc, etc.

However without all these, the Portable Flyer in its simplest form is fully functional and fully controllable.
For such an application the simpler, the lighter, the cheaper, the more reliable, the more responsive, is the better.


In engineering a big challenge is to do more with less.


Quote from https://www.pattakon.com/GoFly/DTR_1.pdf

This is what the PORTABLE FLYER is: it is like an extension of the human body and it is providing the required power in a true neutral way. The brain, the senses and the muscles do the rest.
. . .
The body, the eyes and the senses of the pilot/rider are available; why not to use them as the fuselage, the sensors and the control system?
Isn’t this what the birds are doing?
Relative to the birds, the low power to weight ratio of the human body is the only thing that restricts us from flying / hovering.
This lack of power is what the OPRE Tilting engines and the propellers are curing at a true “neutral” and efficient way.

Thanks
Manolis Pattakos

[nzjrs]

Good luck GG.

[Tommy Cookers]

... Redbull stunt planes do a trick called a 'prop hang', big hp vertical climb deliberately stalled and caught again with power, 6 cylinder lycomi g turbocharged, 330kg ish airframe, this motor of Mr Patakos needs major dyno time and big hp gains.

well it seems that .....

these engines sans props weigh 200 kg NA and have eg 315 hp
eg empty weight is 660 kg and single-seat operation MTOW is 820 kg
RB air race planes use standard engines from a Lycoming-run pool

most Lycomings etc now are 'angle valve' engines not 'parallel valve'
AV is 'semi-hemi' VIA (with/without a bit of compound angle ?) - not Detroit canted valves ie 2 small angles compounded
AV Lycomings have greater displacement and weight (than PVs) and they look very different

there's a large (non-OEM) market in engines 'improved' for use in planes licensed only in the 'experimental' category
(retro) AV fit is part of this - even Lycoming are in this 'crate motor' market


for stunts eg 'hover' ....

presumably a 315 hp 2 stroke engine could weigh 100 kg not 200 kg
giving correspondingly reduced airframe weight

Lycoming offer/have offered turbocharging or supercharging (and reduction drive)
turbocharging/supercharging is rather ineffective
there's far more thrust to be gained by having a freakishly large propeller-disc area (this would need reduction drive)
or by a twin-engined design (ie 2 engines and 2 props)
2 stroke of course

[coaster]

Hell may freeze before that motor makes 300hp, no expansion pipe, no reeds, its nothing more than a vintage lawn mower.
Besides, all this off topic head slamming the wall about directional stability without any controls has really gone past sensible and reasoning discussion.
Its bonkers, totally and utterly.

[manolis]

Hello all

Tommy Cookers writes:
“these engines sans props weigh 200 kg NA and have eg 315 hp
eg empty weight is 660 kg and single-seat operation MTOW is 820 kg
RB air race planes use standard engines from a Lycoming-run pool”


I.e. the power to weight ratio is well below 0.5hp/Kg for the Red Bull racing airplanes that can hover.

Does anybody understand why the Portable Flyer that weighs some eight times less than the Red Bull racing airplanes should have the same (~300hp) power output?

With 0.5hp/Kg specific power (power to weight ratio), the power output from each 340cc OPRE Tilting engine should be 25hp.

The actual power output of each OPRE Tilting engine is expected to be 2.5 times higher (it breaths efficienctly, it burns efficiently, it keeps the mean piston speed (and friction) low; at 10,000rpm the mean piston speed is only 10m/sec; at this rpm 62.5hp power output means 130mN/lit specific torque; the V-2 Ducati Panigale 1199 has 110mN/lit torque density and is a 4-stroke engine).





The OPRE Tilting needs not reed valves

A basic characteristic of the OPRE Tilting engine is the elimination of the reed valves and of the conventional rotary valves of the 2-strokes.
The tilting valves (that comprise part of the small ends of the connecting rods) do more than the reed valves and the rotary valves can do.



But it is not easy to get how they work.



The analysis at https://www.pattakon.com/tilting/pattak ... s_FLow.htm is a good start for discussion.

Thanks
Manolis Pattakos

[Rodak]

All the above body postures are easy. Lying on a bed and turning to the side, one can replicate all the above posture.

Sure, it's also easy to do in a swimming pool, but so what? No one is suggesting the positions are impossible to achieve; now try them repeatedly while hanging in a 'flyer' frame.....

[nzjrs]

Manolis, would the PF be possible with any other engine?

[manolis]

Hello all.

Is the body of the pilot of the Portable Flyer overstressed?

The positions / postures shown in the drawings of my last-but-one post are for fast transitions (say, for aerobatics).

For normal flights the required eccentricity of the overall center of gravity from the thrust axis is several times smaller.
That is, for the “basics” (smooth take off, hovering, smooth transition to medium speed cruise, cruise, smooth braking, smooth landing) the pilot’s body remains unstressed / relaxed (even old people will be able to fly it).

Normal flight versus making aerobatics is like walking versus fast running.

At hovering (say for surveillance) the posture is relaxing.
Even more relaxing is the position / posture at medium speed cruising (see the drawing): the pilot is literally lying on an air mattress and needs to make only “micro corrections”.


Can other engines replace the OPRE Tilting engines of the Portable Flyer?

Here are the characteristics of the Portable Flyer:

• Zero vibrations, zero gyroscopic rigidity, zero reaction torque:
  
  The symmetry of the engine, the zero phase difference between the two synchronized and counter-rotating crankshafts, the common combustion chamber (same instant pressure on the piston crowns of the two opposed pistons, same (and opposite) instant torque on the two crankshafts), and the symmetrical load (two counter-rotating symmetrical propellers) rids the saddle (and the pilot) of all kinds and orders of vibrations (zero free inertia forces, zero free inertia moments, zero free inertia torques, and zero combustion vibrations of all kinds). This is an absolute requirement when a powerful high revving engine is to be tightened to the body of a person.
  
  The reaction torque is also permanently zero: no matter how wide the “throttle” is opened, or how abruptly the “throttle” opens or closes, there is no reaction torque (the only that happens is the increase or the decrease of the thrust force provided by the propellers).
  
  The symmetry and the counter-rotation of the propellers and of the crankshafts maintains the gyroscopic rigidity of the PORTABLE FLYER zero. Even when only the one engine is running (for instance due to a malfunction of the other engine), the gyroscopic rigidity is zero. Zero gyroscopic rigidity means that the pilot “instantly” and “effortlessly” can vector the engine/propellers (i.e. the thrust force) towards the desirable 4 direction, which is an absolute requirement for a safe, accurate and instantaneous control of the flight.
  
  Without zero inertia and combustion vibrations, without zero gyroscopic rigidity, and without zero reaction torque at the changes of the “throttle”, the control of the flight becomes slow, inaccurate, unsafe, uncomfortable and exhausting.
  
  Two independent propulsion units are required, for safety, with each of them capable – alone – for emergency landings.
  
  The total weight of the Portable Flyer is crucial: above 25 - 30Kg it is not wearable and the legs of the pilot are not strong enough to be used as the landing gearing.

If there are engines that comply with the previous, then yes, they could be used.

Thanks
Manolis Pattakos

[coaster]

Most postal companies limit packages to 25kg, some 20kg.
Chinese acdc tig welders weigh 22kg, the large mailbox looking ones with 8 potentiometers.

Ever lifted one?

Now balance it on your head, try some aerobic movement.