2 stroke thread (with occasional F1 relevance!)

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
NathanE
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Re: 2 stroke thread (with occasional F1 relevance!)

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manolis wrote:
Thu Sep 03, 2020 2:06 pm
Hello NathanE


As I understand it, what you think is that the problem is not the Portable Flyer but the pilot’s weak body.
Let’s suppose that we put the current “Olympic Champion on rings” to ride / fly the Portable Flyer.

With such a “superman” as pilot, please explain to the rest forum members, "in plain English", how he will fly keeping full control at all conditions.

Explain also . . .

Thanks
Manolis Pattakos
1) Weak body is the least of the issues.

2) I have absolutely no idea, to me it's physically impossible cos I don't know anyone who is both strong enough and bends in the right places to make it feasible apart from superman, and he doesn't need the pf cos he can fly anyway.

Manolis, I think folks stick around here cos they really love what you are doing and really want to help you make something that works. I went on from aero engineering into helping start businesses and then spent 20 years as a VC investor backing disruptive tech. I love it when the folks I work with are successful, it's the biggest rush I get. I genuinely think that's also what folks here are trying to support and encourage you with. There's folks on here with some much better technical chops than i ever had, let alone the rusty bits that I can still drag out of the dusty recesses of my noggin. Engage with them and ask them if they can help you and you might get to your destination quicker (and not risk your life in doing so :wink: )

gruntguru
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Re: 2 stroke thread (with occasional F1 relevance!)

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NathanE wrote:
Thu Sep 03, 2020 5:42 am
Manolis, thank you for your detailed explanation. I do however understand the basic principles, I am an engineering grad with a degree focus on fluid dynamics, thermodynamics and aerostructures. I learned my stuff in the labs where whittle built engines and Concorde was designed, and whist it is 30 years since I used this stuff in anger I haven't forgotten the basic principles.

My basic question is more about human dynamics than control system maths though.

When I bend forwards I can touch my toes. I went to the circus once and saw someone who could do the same bending backwards, but I sure as heck can't and I don't imagine many others on here can. Same side to side. Oh, and to be honest I can probably only do that by being assisted by gravity, if I suspended myself by the shoulders I'm not sure I could lift my legs at the hip in a precise and controlled enough way for flight quality control inputs.

Watch someone competing in gymnastics on the Olympic rings to see how hard it is going to be for anyone to put into practice the kind of control inputs you are thinking about.
Nicely put NathanE. (Mind if I call you Nathan?)
I have been around the block so many times with Manolis on this one but have come to a simple realisation.

When Manolis eventually puts his flyer to the test, it will have handlebars. (Forearms horizontal and upper arms vertical please Manolis.) Once the pilot and machine are sufficiently acquainted he can test the stability and control-ability with hands-off.

My opinion? I think the flyer could be developed to fly without handlebars. OTOH the stability and manoeuvrability will be far superior with them. Larger control inputs possible yet with finer precision - win win.
je suis charlie

Tommy Cookers
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Re: 2 stroke thread (with occasional F1 relevance!)

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manolis wrote:
Fri Aug 28, 2020 12:59 pm
The Gen H-4 is restricted to fly below 10m in the flying tests in Japan (this is their law).

Flying at 10m height in an open area, the ground effect on the Gen H-4 is negligible.

When the Gen H-4 flies at 10m height and when it flies at 1,000m height, where the difference in stability / controllability comes from?
there is a 'stability & control' benefit (of the H-4's large rotor coning) with motion outside ground effect ....
the aerodynamic moment eg opposing rotor axis tilt towards the direction of motion

manolis
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Hello Tommy Cookers

You write:
“there is a 'stability & control' benefit (of the H-4's large rotor coning) with motion outside ground effect ....
the aerodynamic moment eg opposing rotor axis tilt towards the direction of motion”



Quote from https://www.scinet.jp/english/ourbusiness/speciality/ (copyright 2009)

Image

GEN H-4 Specifications
Aircraft Height: approx. 2.4m (approx. 8 ft)
Rotor Diameter: 4.0m (13 ft. 1 in.)
Dry Weight: approx. 75 kg
Cruising Speed : 10 km/h to 40 km/h
Hovering is possible
Maximum Take Off Weight (MTOW) : 160kg when 600m above sea level;
180kg when at sea level (0m)

Engine Specification
Engine: Four GEN 125 engines
Type: 125cc, Two Stroke Boxer Twin
Output power: 10 HP per engine (40 HP total)
Ignition: Independent CDI for each engine
Fuel: 30:1 auto gas/oil premix

Rotor Specifications
Rotor type : Counter-rotating
Diameter: 4.0m (13 ft. 1 in.)
RPM: 800-900 rpm
Pitch: Fixed
Material: CFRP composite

Performance SPecifications
Weight - Airframe: 70 kg (155 lb)
Max. Takeoff Weight: 200kg (413 lb)
Endurance: 30 to 60 minutes
Cruising speed : 50 km/h (32 mph)
Ceiling: Projected at 1,500m (5,000 ft)
VNE (Max Speed): 90 km/h (60 mph)
Yaw control: Electronic

Safety Specifications
Engine: Four independent engines (capable of flying on three engines)
Parachute: Ballistic Parachute (optional)


Retail price (MSRP): US$85,000

End of quote


The upwards thrust is 150Kp to 200Kp (vehicle weight plus pilot weight plus fuel weight).
At 50Km/h cruising speed, a reasonable assumption for the horizontal air drag is one tenth of the upwards thrust (small frontal area, small speed), giving a leaning of only 6 degrees for the rotor axis.

The small leaning angle of the rotor axis combined with the wide (more-or-less 170 degrees according the drawing) angle between the two blades of each rotor, cancel the benefit from the “large rotor coning” in the case of the GEN H-4.


If, by a different hub, the angle between the blades of each rotor is reduced (say, from 170 to 120 degrees) the long (2m) blades, under the action of the centrifugal force, will either bend (increasing the angle between them) or will fall apart.

Thanks
Manolis Pattakos

manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all.


Question:

Can the average person apply the required “corrections” to keep the Portable Flyer under control?

or:

Has the pilot of the Portable Flyer to be as strong, lightweight and flexible as the Olympic champion on rings?



The Portable Flyer on the air is like a seesaw at equilibrium:

Image
  • Equilibrium in a seesaw comes when the moment of the weight of the one child times its horizontal distance from the central pivot equals to the moment of the weight of the other child times its horizontal distance from the same central pivot
Freeze the pilot and leave the Portable Flyer to fly on the air.

The set (Portable Flyer / frozen pilot) has no tendency to change its initial direction of flight (defined as, say, the direction of a propeller axis). This is what the “Pendulum Rocket Fallacy” says, and this is what the following image:

Image

demonstrates in practice (more at pages 212 and 213 of this discussion).
It doesn’t matter if the pilot is under the propellers or above or at the side of the propellers, it doesn’t matter if the center of gravity is higher or lower, the Portable Flyer with the frozen pilot tends to keep its direction of flight.
  • Worth to mention here:
    The Portable Flyer with the frozen pilot will slowly change its direction, but a significant change (say for 15 degrees) will take time το happen and will be at “random” direction; and without corrections the set will eventually hit the ground.

Back to the seesaw:

Take a seesaw at equilibrium, with two heavy adults (say, 100Kg each) seating at the ends of its 4m long board. In order to vary the angle of the board of the seesaw from horizontal to 10 degrees clockwise, what is required is a tiny torque (or moment).
Even with 1mN of torque, the seesaw will turn (suppose the central pivot is supported on roller bearings).
It is easy to calculate how long it will take the 10 degrees rotation.
  • EDIT
    Even with two elephants sitting at the ends of the seesaw board, the 1mN torque can turn the board.
    To take an idea of what 1mN of torque is: by leaning your head (it is about 5Kg / 50N) to the side, your neck is loaded by a torque of 50N * 0.1m = 5mN.
    I.e. just by leaning his head, the pilot of the Portable Flyer has 5mN of torque for corrections / control of his flight
    EDIT
The smaller the torque applied, the slower the variation of the board angle.
If the acting torque (control input?) doubles, the required time (for the same 10 degrees turn) halves.

So,
on one hand the Portable Flyer with the frozen pilot tends to keep its direction of flight, on the other hand in order to keep the direction of flight unchanged for hours what is required is a small torque that cancels out the small changes of the direction of flight before they become significant in amplitude (sorry for my “salad English”, but with a little dose of good will I am sure you will understand what the point is).

So,
if the pilot of the Portable Flyer is not going to make aerobatics or fast “changes” of the flight mode, any person – no matter how heavy or weak they are - can keep the control and make the basics on the air: i.e. to take off, to hover, to cruise at the desirable direction at affordable speed and to land safely (say, as an old or heavy person can stand and walk, but cannot run or make loops).

Image

If something is not clear, please let me know to further explain.

Thanks
Manolis Pattakos
Last edited by manolis on Sat Sep 05, 2020 7:37 am, edited 1 time in total.

NathanE
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Re: 2 stroke thread (with occasional F1 relevance!)

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gruntguru wrote:
Thu Sep 03, 2020 11:46 pm
Nicely put NathanE. (Mind if I call you Nathan?)
I have been around the block so many times with Manolis on this one but have come to a simple realisation.

When Manolis eventually puts his flyer to the test, it will have handlebars. (Forearms horizontal and upper arms vertical please Manolis.) Once the pilot and machine are sufficiently acquainted he can test the stability and control-ability with hands-off.

My opinion? I think the flyer could be developed to fly without handlebars. OTOH the stability and manoeuvrability will be far superior with them. Larger control inputs possible yet with finer precision - win win.
Don't mind at all. Agree with you largely, although I still struggle with visualising control without handlebars - I'd be keen to understand how you envisage this?

It it strikes me as so simple to introduce some form of universal joint type arrangement between body harness/frame and motor mount, combined with "handlebars" to do highly leveraged, small input force control inputs that I struggle to understand Manolis' resistance to consider this.

There is also a bit of a question in my mind about the thrust/lift/stall situation in the acceleration to braking transition given his expectation in "horizontal" flight is that lift will come in no small part from the wing effect of the pilot's body. The motor going into full reverse thrust and the pilot flying feet first at negative angle of incidence into the incoming airsteram strikes me a a pretty effective stall environment, although I'd need to do a proper old fashioned force diagram to really get my head around it.

Rodak
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Re: 2 stroke thread (with occasional F1 relevance!)

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Now this is what I'm talkin' about!!!

https://youtu.be/TgACwfl6FBI

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nzjrs
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Re: 2 stroke thread (with occasional F1 relevance!)

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Rodak wrote:
Sun Sep 06, 2020 4:18 pm
Now this is what I'm talkin' about!!!

https://youtu.be/TgACwfl6FBI
I raise you ...... :lol: :lol:

Rodak
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Ah man nz, I fold!

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coaster
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Will try to hijack our way back to the topic here and ignore all the whirlybird nonsense.
Youtube has a channel, 'two stroke stuffing', the guy is a tinkerer trying to set a land speed record for 50cc class.

manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all.


Quote from https://newatlas.com/jetpack-aviation-f ... nce/56845/ (2018)

Image

For US$4950, you can spend a day learning how to fly the JB-10 with Mayman, the world's only FAA certified jetpack instructor (there's a nifty bullet point for the CV) and qualified pilot Boris Jarry. You'll do takeoffs, landings, hovering, forward, backways and sideways flight – Mayman says it's more or less a Segway in the sky and should be very intuitive for most people.
. . .
Total flight time will likely be around 20 minutes, and while it won't be enough to train most pilots up to the point where they could safely fly off tether, Mayman says successful pilots may have the option to come back and "take their training further."



In the above video, from 19” to 21” Mayman yaws, at 43” Mayman is leaning for more than 45 degrees from vertical.



Quote from https://www.aopa.org/news-and-media/all ... a-jet-pack :

Two flight control arms extend ahead of the pilot, each fitted at the end with a vertical hand grip similar to a motorcycle throttle. The right hand grip is the throttle, and the left grip controls ducts that direct the jet exhaust left or right. This twist grip is somewhat analogous to the pedals in a helicopter that control the tail rotor, in that it is used to create or counteract rotation around the vertical axis.

. . .


At altitudes below 10 feet, the engines are both breathing in a lot of their own exhaust, due to recirculation.

This, Mayman said, “degrades performance significantly.”

It might be counterintuitive for pilots of both fixed-wing and rotorcraft accustomed to a little extra lift in ground effect to discover that the jet pack gives exactly the opposite.

Once above 10 feet, “you get the power that you would expect,” Mayman said.

“I like to go straight up to at least 10 or 15 feet just to be sure that I have power before I transition forward,” Mayman said. He otherwise tries to keep some horizontal motion going. “It’s similar to a helicopter inasmuch as, if you can help it, you’re trying not to do a vertical climb/descent.”

Mayman said another concept familiar to most pilots and useful with a jet pack is to lead with power. Since forward motion is created by dividing vertical lift (produced by the jets) into a combination of horizontal and vertical lift, a jet pack pilot should add some power before vectoring the engines for a change in horizontal motion.

“You need to lead with power … it’s like any other aircraft,” Mayman said. “If you’re going to lose lift, you need to introduce power. Before you do an aggressive change in direction … you want to lead with power.”

The reverse is true when reducing horizontal velocity and transitioning into a hover, such as during approach and landing: Anticipate the extra vertical lift that will result as less thrust is directed horizontally, and reduce power accordingly.

As for controlling the motion vectors, roll, and rotation, “it’s nearly instinctive to do that,” Mayman said.

Thanks
Manolis Pattakos

Brake Horse Power
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Re: 2 stroke thread (with occasional F1 relevance!)

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coaster wrote:
Sun Sep 06, 2020 9:21 pm
Will try to hijack our way back to the topic here and ignore all the whirlybird nonsense.
Youtube has a channel, 'two stroke stuffing', the guy is a tinkerer trying to set a land speed record for 50cc class.
Ha you beat me, just wanted to post this. This guy has some awesome and radical ideas. 👌 That intake and crankcase is soo cool 😎 also the exhaust channel is interesting.

J.A.W.
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Re: 2 stroke thread (with occasional F1 relevance!)

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Brake Horse Power wrote:
Tue Sep 01, 2020 4:24 pm
Brake Horse Power wrote:
Thu Aug 27, 2020 9:42 pm
Has this been posted yet?

https://youtu.be/aULwM8-NRKw
Since my previous post was welcomed with such great enthusiasm :roll:

Here is a nice article about the engine

https://www.ust-media.com/ust-magazine/UST033/66/
Ta for posting that link B.H.P., but how far a 'bold claim' like reliable running at "25 bar" stands scrutiny
with such apparently scanty heat-rejection capabilities, then boosts into 'marketing hype' of "6-cycle"
operation, leaves a certain credibility issue to be resolved - IMO.

Furthermore, this effort appears to be yet another example of 'reinvent the wheel' 2T type of work,
since if the design engineering team had done 'due diligence' they'd have used a 120 degree triple
crank arrangement, with its superior dynamics in both synergistic gas-flow & torque harmonics.
"Well, we knocked the bastard off!"

Ed Hilary on being 1st to top Mt Everest,
(& 1st to do a surface traverse across Antarctica,
in good Kiwi style - riding a Massey Ferguson farm
tractor - with a few extemporised mod's to hack the task).

manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello Gruntguru

Handlebars

As explained in my last-but-one post, for the “basics” (hovering, smooth take off, smooth increase / decrease of horizontal (cruise) speed, smooth landing) the required torque for the control of the Portable Flyer is weak (the pilot can “freeze” his rest body and move only his head to control his flight).

Having his limbs free, the Portable Flyer pilot can do much more than what Browning, Mayman and Zapata can do during a, say, rescue, or during an emergency (like a fire on Browning’s JetPack, with his arms busy to vector the jets providing a significant part of the overall thrust).

And when things get too hard (like, say, during aerobatics, during harsh weather etc ) the pilot of the Portable Flyer has the handlebars to hold and control his flight.

Thanks
Manolis Pattakos

manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all

Negative Ground Effect of JetPacks

As Mayman explains (second quote of my last-but-one post), at take-off and landing the ground effect on his JetPack is negative due to recirculation of the exhaust gas in the intake.

Browning’s / gravity JetPack has the same problem:

Image

The problem is worse for Zapata’s JetPack wherein the jet turbines are located under the feet of the pilot. This explains why Zapata needs a special structure (an elevated wire-net) in order to take-off and land:

Image


And why the negative ground effect of the JetPacks is a problem?

Take the case of a vertical landing of Mayman JetPack. At 10ft height the thrust from the jets is substantially stronger than at 1ft height. In order to compensate for the negative ground effect, the pilot has to open properly the throttle; if not, he will have a hard landing.
During landing (i.e. when the most accurate control over the thrust is required), the pilot has to feel (and react instantly) on the reduction (and variations / oscillations) of the available thrust.
If, near the ground, the thrust oscillates due to variations in the percentage of the exhaust gas in the intake, the safety gets at big risk.


On the contrary to the JetPacks, the Portable Flyer (just like the Osprey V22 and the helicopters) has “positive ground effect” (the lift (or thrust) increases as the height reduces), important for soft / easy / controllable landings and take-offs.

Thanks
Manolis Pattakos