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.
uniflow
uniflow
36
Joined: Sat Jul 26, 2014 9:41 am

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

Post

Sort of a pointless discussion now, Ive been blocked it seems, one guy is right, everyone else is wrong.
Not even about twostroke design, thats long gone.
Good luck with your personal flyer manolis, I hope it doesn't end in tears for you. Ive said what I need to.

NathanE
NathanE
2
Joined: Fri Mar 31, 2017 6:49 am

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

Post

Rodak wrote:
Sat Oct 24, 2020 2:32 pm
It is like the cloths / laundry hanged from a rope to dry. The wind keeps them away from vertical. The strong wind can keep them almost horizontal.
No it's not. Hang a person by their shoulders on a clothes line, have a storm with 60 mph winds come through, and see how horizontal they get.... And let's not even think about the L/D ratio.
This has got me thinking. Rotor diameter looks to be c1m (very small). Can someone with a bigger brain than mine work out the mass flow required to generate say 1.2g vertical lift for a 120kg pilot/flyer combo and translate this into airspeed for the 1.2m2 column of downward moving air that will result from the 2 intermeshing rotors?

I bet it is significantly higher than 20m/s. I can't imagine it will be much fun being in the middle of it. Given that probably 20% of this flow will immediately "hit" the pilot that will make the flow rate above an underestimate I guess.

manolis
manolis
101
Joined: Tue Mar 18, 2014 9:00 am

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

Post

Hello all.

Air hitting the pilot


The average speed of the wing-suiters is around 100mph (160Km/h, i.e. 45m/sec).

The speed of the air that "hits" the wind-dancer (video at page 238) is over 200Km/h (55m/sec), and she seems to enjoy it.

Mayman claims a top speed of 200mph (320Km/h, i.e. 90m/sec).

Yves Rossy does fly at 200mph (90m/sec):
  • His body is free in the air; 90m/sec air "hits" his body.

    With only an altimeter and timer, Rossy uses his skin and ears as airspeed indicators.

    "You feel very well, you feel the pressure," Rossy says, "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 Rossy says : "I am the fuselage, and the steering controls are my hands, head and legs"



See at 3:23 his hands, head and legs "steering" his Delta Wing JetPack.

Despite the high speed air that "hits" his body, Rossy feels very well and enjoys his flight.
Unfortunately, in less than 10 minutes he runs out of fuel, and the joy ends; then he has to use his parachute, again, “risking” one more landing.

Thanks
Manolis Pattakos

NathanE
NathanE
2
Joined: Fri Mar 31, 2017 6:49 am

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

Post

NathanE wrote:
Sat Oct 24, 2020 9:47 pm
Rodak wrote:
Sat Oct 24, 2020 2:32 pm
It is like the cloths / laundry hanged from a rope to dry. The wind keeps them away from vertical. The strong wind can keep them almost horizontal.
No it's not. Hang a person by their shoulders on a clothes line, have a storm with 60 mph winds come through, and see how horizontal they get.... And let's not even think about the L/D ratio.
This has got me thinking. Rotor diameter looks to be c1m (very small). Can someone with a bigger brain than mine work out the mass flow required to generate say 1.2g vertical lift for a 120kg pilot/flyer combo and translate this into airspeed for the 1.2m2 column of downward moving air that will result from the 2 intermeshing rotors?

I bet it is significantly higher than 20m/s. I can't imagine it will be much fun being in the middle of it. Given that probably 20% of this flow will immediately "hit" the pilot that will make the flow rate above an underestimate I guess.
Ok so this will embarrassingly show how far away I am from the days when, 30 years ago I got a decent degree in aero engineering and now I can't even do high school maths! I'm going to try to remember how to work this out from first principles. I will probably be wrong in how I calculate this but it will give others something to correct.

Upthrust needs to be c1500 N, or 1500 kgm/s2.

Density of air is 1.225 kg/m3. I'm not considering compressibility.

I'm thinking that in order to get the units balanced I need to multiply kg/s of mass flow by m/s of flow velocity. This is density x area x velocity2. (Kg/m3 * m2 * m2/s2 = kgm/s2).

So here V2 = 1500/(1.225* 1.2) and V = 32 m/s or 72mph.

This intuitively feels low, but I guess thinking in "reverse" about skydive terminal velocity of 120mph maybe not. I guess the airflow is not columnar- more toroidal and if only 50% of the radius of the rotors gives true downdraft then this would be out by a factor of 4 so we could be talking up to c300mph which is going to be uncomfortable.

What have I got wrong?

J.A.W.
J.A.W.
92
Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

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

Post

uniflow wrote:
Sat Oct 24, 2020 8:22 pm
Sort of a pointless discussion now, Ive been blocked it seems, one guy is right, everyone else is wrong.
Not even about twostroke design, thats long gone.
Good luck with your personal flyer manolis, I hope it doesn't end in tears for you. Ive said what I need to.
Uniflow, do please continue to feel welcome to contribute here on 2-stroke matters,
- particularly including your own work - which is by any regard, very worthwhile.

Manolis can draw the flak, as you fly under the radar, surely?
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

Tommy Cookers
Tommy Cookers
539
Joined: Fri Feb 17, 2012 3:55 pm

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

Post

NathanE wrote:
Sun Oct 25, 2020 8:11 am
..... I guess the airflow is not columnar- more toroidal and if only 50% of the radius of the rotors gives true downdraft then this would be out by a factor of 4 so we could be talking up to c300mph which is going to be uncomfortable.
What have I got wrong?
fwiw I think that ......

you have the right concept (that the behaviour is equivalent to a column smaller than the prop disc diameter)
there's a term for the ('contraction' ?) factor driving the underlying velocity distribution of the jet
ie based on this factor an equivalent of your illustrative 50% might be ... 70 or 80% or something ?

manolis calculated a velocity - assuming a jet of uniform velocity ??

propeller maps (showing thrust over a full range of airspeeds etc ) seem as rare as unicorns
static thrust is low and thrust builds up during takeoff - this is poorly accounted
after 150 years competing propeller theories are still out there (some suggest that static thrust is infinite)

manolis
manolis
101
Joined: Tue Mar 18, 2014 9:00 am

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

Post

Hello NathanE

Here is an approach for the speed of the air that “hits” the pilot of the Portable Flyer at hovering.

Quote from NASA “Propeller Thrust” at https://www.grc.nasa.gov/WWW/K-12/airplane/propth.html :
  • Image

    Simple Momentum Theory
    Turning to the math, the thrust F generated by the propeller disk is equal to the pressure jump delta p times the propeller disk area A:
    F = delta p * A

    Etc, etc . . . (the link has the complete analysis)

    Substituting the values given by Bernoulli's equation into the thrust equation, we obtain
    F = .5 * r * A * [Ve ^2 - V0 ^2]
End of quote.


At hovering V0=0 (zero vehicle velocity), so the above formula becomes:

F = .5 * r * A * Ve ^2,
i.e. Ve=(2*F/ (r*A))^(1/2)

With your F=1,500Nt, r=1.225Kg/m3 and A=1.2m2,
the Ve (i.e. the speed of the air that "hits" the pilot of the Portable Flyer) is calculated at 45m/sec (100mph, 160Km/h).



Hello Tommy Cookers

NASA at https://www.pattakon.com/Fly_files/NASA ... Thrust.pdf gives a "formula" / relation for the Static Thrust of airplane propellers.

Image

For instance, a propeller having 42” (3.5ft) diameter, 30” pitch (the θ about 17 degrees at 0.75R, giving a K coefficient around 60,000), revving at 3,000rpm absorbing 30 bhp, gives a static thrust of:

T = 60,000 * 30 (bhp) / (3,000 (rpm) *3.5 (ft))=170lb = 780Nt (=78Kgf).

With smaller (into some limits) pitch, the power absorbed (same rpm of the propeller) decreases, but the coefficient K increases, giving, say, a similar Static Thrust.

Another reading of the above is: Keeping the propeller rpm constant, by varying the pitch what you can do is to reduce or to increase the power required for the "same" Static Thrust, but the change of the Static Thrust due to the variation of the pitch is small.

This is the reasoning behind the PatPitch:

Image

At hovering ("medium" engine (and propeller) revs), the PatPitch keeps the propellers at a lower pitch; at high cruise speeds ("high" engine (and propeller) revs), the PatPitch keeps (with the heavier centrifugal forces acting on the blades) the propellers at a larger pitch, allowing substantially higher top speed.



Hello J.A.W.

I can't get what you mean by "Manolis can draw the flak, as you fly under the radar, surely?"

Thanks
Manolis Pattakos

manolis
manolis
101
Joined: Tue Mar 18, 2014 9:00 am

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

Post

Hello all.


Air speed and human body leaning (from previous posts):

This photo shows Richard Hammond in a wind tunnel:

Image

In the following photo, Browning is wearing, between his legs, of part of a "wind-suit".

Image

The above two photos (actually slides from videos) are not fake.


If the following photo and video (from 00:37 to 00:45) are not fake, they are impressive:

Image




Does anybody have some better photos or videos showing the relation between the speed of the hitting air and the leaning of a human body?

Thanks
Manolis Pattakos

Rodak
Rodak
28
Joined: Wed Oct 04, 2017 2:02 am

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

Post

Ok so this will embarrassingly show how far away I am from the days when, 30 years ago.....
You're not alone. I started looking at this using the helicopter lift equation (here's a good site on helicopter flight): https://www.intechopen.com/books/flight ... ht-physics

L = 1/2pv²ACL (sorry, couldn't find the ASCII for rho) where p = air density, v = velocity, A = rotor area, and CL = coefficient of lift. It's unclear to me where velocity is measured; at the tip, at the middle of the rotor, rpm? CL has to be determined experimentally but can be estimated.

nzjrs
nzjrs
93
Joined: Wed Jan 07, 2015 10:21 am
Location: Austria

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

Post

It's seems all of us here who are blocked here by manolis can have a nice conversation.

Rodak
Rodak
28
Joined: Wed Oct 04, 2017 2:02 am

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

Post

I didn't see manolis posted the same equation....

nz, not sure what you mean about blocking, I'm seeing everything.....

nzjrs
nzjrs
93
Joined: Wed Jan 07, 2015 10:21 am
Location: Austria

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

Post

Rodak wrote:
Sun Oct 25, 2020 7:14 pm
I didn't see manolis posted the same equation....

nz, not sure what you mean about blocking, I'm seeing everything.....
Like uniflow said, by way of manolis never answering our questions, I assume we are blocked/ignored by manolis (so he doesn't see our posts).

Was a bit of a joke tbh :wink:
Last edited by nzjrs on Sun Oct 25, 2020 9:16 pm, edited 1 time in total.

uniflow
uniflow
36
Joined: Sat Jul 26, 2014 9:41 am

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

Post

[/quote]
Uniflow, do please continue to feel welcome to contribute here on 2-stroke matters,
- particularly including your own work - which is by any regard, very worthwhile.

Manolis can draw the flak, as you fly under the radar, surely?
[/quote]

Happy to, thanks for the vote of confidance. One issue I do have is I must be careful on what I disclose, manolis is watching and might run off and patent my ideas. Thats his end game after all, make money out of something he has secured via patent for himself. Thats life I guess.

I still havent organised a photo server, I must do that.
By the way JAW, how is that LC , 750 Kawasaki hybrid going?
Last edited by uniflow on Sun Oct 25, 2020 10:12 pm, edited 1 time in total.

Rodak
Rodak
28
Joined: Wed Oct 04, 2017 2:02 am

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

Post

Manolis can draw the flak, as you fly under the radar, surely?
I did work on the B-2 Stealth bomber, so I just evade the radar. Funny how that flak statement paints pictures of WW2.....

gruntguru
gruntguru
465
Joined: Sat Feb 21, 2009 6:43 am

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

Post

uniflow wrote:
Sun Oct 25, 2020 8:57 pm
One issue I do have is I must be careful on what I disclose, manolis is watching and might run off and patent my ideas.
Really? I haven't seen anything that might suggest that behaviour.

Of course disclosure on a public internet forum exposes you to the full spectrum of personality types. If you post information that could be misused for profit - it will happen.

As for patents - once you make an idea public - it can't be patented - by you or anyone else.
je suis charlie