2 stroke thread (with occasional F1 relevance!)

[manolis]

Thanks PlatinumZealot

Quote from "your" link (Autoweek / Robin Warner):

“It was Rover, not Hyundai that did it first, and this video explains it.



Earlier this year, I wrote about the very first Continuously Variable Valve Duration, or CVVD, system from Hyundai. I claimed it to be the first production engine with the technology. As did Jason Fenske of Engineering Explained in his recent video about the technology. And, turns out, we were both wrong.

End of Quote


In the above video, at 4:16, Peter O’Tool (?) says for the VVC system: “looks extremely promising, so much that the design was patented to ensure it couldn’t be stolen”

In their patent, Rover does mention Mitchell’s patent as its closest prior art:



The conclusions are yours.


For the patVVD you write:
"I also have a question about the little arm beside the cam lobes. That peice may have to be separately manufactured, and pressed on."

The simplest way seems to have an integral arm on the camshaft (even one of the cam lobes can be used as such arm), drill it and secure a pin in it.

Thanks
Manolis Pattakos

[manolis]

Hello PlatinuZealot

You write:
"Whenever you guys are ready to get back to the portable flyer, I will be too. It is still unresolved."


PORTABLE FLYER

A useful improvement is the use of propellers having variable auto-adjusted pitch.

This way the necessary power for hovering will reduce substantially (and the hovering duration will increase substantially), while the maximum speed will increase substantially.

Also, in case of an engine stall, during the emergency landing the still functioning propulsion unit needs substantially less power.


For instance, suppose the Portable Flyer propellers have:

15" pitch until 3,500rpm propeller speed (which means 3,500rpm*2.4 = 8,400rpm engine speed),

while above 3,500rpm (propeller speed) the pitch increases (say, by exploiting the centrifugal force acting on the blades) becoming 40" at 4,000rpm propeller (9,600rpm engine), and 45" at 4,500rpm propeller (10,800rpm engine).



With all this research nowadays, and with so many propeller manufacturers around the world, I guess someone deals with this step ahead (I would say "breakthrought", but Hyundai changed the meaning of this word).


If the above are not clear, please let me know to further explain.

Thanks
Manolis Pattakos

[PlatinumZealot]

Manolis. OK.

This may have been posted before:

[Rodak]

Here's an even better video of the helicopter with some actual flying around.

https://youtu.be/sDC8Cs5gmqc

Notice, Manolis, that the pilot has a way to generate torque to tilt the rotor head. Let's modify this machine to make it like yours by removing the ability of the rotor/motor unit to pivot and attaching the pilot directly to the unit. Do a little mind experiment and tell me how on earth a machine like that would be controlled, with the pilot fixed to the motor and only able to move his legs about. Notice also how the pilot and fuel are locating the c.g. I'm curious to learn how the pilot in this video changes his rotational orientation. Pretty cool design.

[gruntguru]

I'm curious to learn how the pilot in this video changes his rotational orientation. Pretty cool design.

There are two possibilities.

1. The pitch of one or both rotors can be varied to obtain unequal torque in the rotors.

2. The speeds of the rotors can be different.

Probably 1.

[Dr. Acula]

I'm curious to learn how the pilot in this video changes his rotational orientation. Pretty cool design.

There are two possibilities.

1. The pitch of one or both rotors can be varied to obtain unequal torque in the rotors.

2. The speeds of the rotors can be different.

Probably 1.

It's actually solution 2.
They use a brake to slow down one rotor. The rotors are fixed pitch.

[Rodak]

They use a brake to slow down one rotor. The rotors are fixed pitch.

So there would need to be a brake on each rotor to allow rotation in both directions; good solution. This must mean that two of the engines drive each rotor as opposed to a collective drive unit. How are the rotor speeds matched?

[manolis]

Hello PlatinumZealot.

The GEN-H4 has been mentioned several times in this discussion.

It is also a basic reference in the "Device Technical Report" for the Portable Flyer in the GoFly /BOEING contest, wherefrom thefollowing quotes are (page 13 and 17 of https://www.pattakon.com/GoFly/DTR_1.pdf )

"Take-off, landing, hovering and cruising

The stability and the controllability at vertical take-off, landing and hovering of
the PORTABLE FLYER have no reason to be worse than in the GEN-H-4:



In the above GEN-H-4 the only control is the lever that displaces the center of
gravity relative to the rotation axis of the two big (13ft / 4m diameter) contrarotating rotors.
The PORTABLE FLYER looks like a symmetrical compact GEN-H-4"


"The PORTABLE FLYER besides the “weight displacement CONTROL” of the
GEN-H-4 (mentioned previously), has also the “aerodynamic CONTROL” of
Yves Rossy (Jetman, also mentioned previously).
Quote from https://www.thenational.ae/uae/jetman-h ... me-1.62201 :

• “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.

Similarly, the body of the pilot of the PORTABLE FLYER is the fuselage, and
the steering controls are pilot’s hands, head and legs.

The PORTABLE FLYER can be displaced, relative to the body of the pilot,
either by the shoulders / torso / back / spine of the pilot, or by pilot’s hands
pulling / pushing some handlebars. It is significant, at emergencies etc, the
pilot to be able to control the PORTABLE FLYER keeping his hands free. "

Thanks
Manolis Pattakos

[manolis]

Hello DrAcula

You write:
"They use a brake to slow down one rotor. The rotors are fixed pitch."


Quote from wikipedia:

" Yawing motion is produced and controlled by electronic gyroscopically-controlled differential electric braking of the main rotors"

End of Quote


The transmission to the two rotors of the GEN-H-4 is like the final transmission in cars: a differential shares (not equaly) the power allowing the drive wheels to rotate at different speeds. If a brake decelerates slightly the one rotor of the GEN-H4, the other rotor spins a little faster, and the GEN-H4 together with the pilot yaws about the vertical axis.

While it seems a good solution,it is not because it adds weight, faults, complication and cost (you need a battery, servomotors etc). It is also slow.

In comparison the Portable Flyer has "built-in" yaw control because the pilot is permanently in the highs peed downstream of the small-diameter high-disk-loading propellers: using his limbs the pilot has simpler and faster control over the yaw:



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


By the way:

The GEN-H4 is one more Flying Device that proves that your:

• "If you wanna properly overcome this issue, you will need at least 3 thrust sources, each with individually adjustable thrust and thrust vectoring."

is wrong.
Because the GEN-H4 with one only adjustable thrust, does everything being stable and controlable.

Thanks
Manolis Pattakos

[manolis]

Hello Rodak.

You write:

“Notice, Manolis, that the pilot has a way to generate torque to tilt the rotor head. Let's modify this machine to make it like yours by removing the ability of the rotor/motor unit to pivot and attaching the pilot directly to the unit. Do a little mind experiment and tell me how on earth a machine like that would be controlled, with the pilot fixed to the motor and only able to move his legs about. Notice also how the pilot and fuel are locating the c.g. I'm curious to learn how the pilot in this video changes his rotational orientation. Pretty cool design.”


Think what the pilot of the GEN-H4 does.

When he displaces the control lever, the only that happens is the displacement of the axis of the thrust force relative to the center of gravity of the device (the pilot included) .

With the lever the pilot vectors the thrust force towards the desirable direction.

The pilot of the Portable Flyer does the same, but without needing a control lever: by bending his spinal cord and by displacing his limbs and head, he displaces the axis of the thrust force relative to the overall center of gravity.



And because the pilot of the Portable Flyer is – from take-off, to landing – permanently into the high speed downstream of the propellers, besides the “weight displacement control” of the GEN-H4, he has also “aerodynamic” control.

Thanks
Manolis Pattakos

[Rodak]

...by bending his spinal cord and by displacing his limbs and head....

Good luck with that; the old stomach muscles might get tired after a bit. Really, Manolis, you need to seriously think about control stuff. And while 'displacing his limbs' he is also controlling the throttle et al? How does that work? And how is rotational direction controlled? Stick with the motor stuff, that's pretty good.

[manolis]

Hello Rodak.

You write:
"And while 'displacing his limbs' he is also controlling the throttle et al? "

Easier than Zapata.



At his right hand Zapata (riding his Fly-Board-Air JetPack) has not only the throttle control, but also the yaw control.

So, where is the difficulty you see?


You also write:
" the old stomach muscles might get tired after a bit."

At hovering the engines/propellers hold the pilot, not the opposite.



At high speed cruising, the pilot is actually lying on an a relaxing air mattress.

Thanks
Manolis Pattakos

[Tommy Cookers]

isn't the GEN H4 yaw control rather by inertial reaction ? (to the 'braking' torque)
of course any electrical machine/device already driven by the shaft is a simple means of generating such +- torque(s)


regarding the previously-mentioned automatic adjustment of 'propeller' (or 'proprotor') pitch .....
isn't this what has been the normal way of propellers for 80 years ?

(how/why ?) is something desired beyond this existing range of capabilities ?

(as I said a year ago) today (for 'recreational' aircraft anyway) there's (some anyway) such capability without moving parts
by suitably 'tailored' propeller structural properties available from use of composite materials

proper propeller maps seem irritatingly rare ...

oddly the standard 'public teaching' still seems to be 150 year old Froude 'actuator disc' propeller theory ....
which (saying efficiency at zero forward speed is zero) seems to show that propellers can't move aircraft (or boats) from rest
though non-flyers all convince themselves (wrongly) that full thrust is applied from rest

many assumptions about propeller blade 'stalling' are wrong
due to stream 'inrush' - and blade sections/Re No that develop LE bubble but resume high Cl at high AoA

using the term engine stall is unhelpful - it is seemingly impossible and so regarded
though I have done it (stalled the engine at touchdown - presumably by wrong-footing the pitch regulation)
also I have HOGE'd fixed-wing aircraft (maintaining c.65 deg pitch attitude and height)

[PlatinumZealot]

@Manolis.

The JetMan is extremely strong and fit. The average person with weak core strength will find it hard to last more than a few minutes.

Why not use the Gen-H4 method? It seems easy to operate.

[tok-tokkie]

@Manolis.

The JetMan is extremely strong and fit. The average person with weak core strength will find it hard to last more than a few minutes.

Why not use the Gen-H4 method? It seems easy to operate.

I must say I agree about using the H4 method. As I recall it was included in your early proposals.