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.
tok-tokkie
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Re: 2 stroke thread (with occasional F1 relevance!)

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I am hugely impressed by Manolis's work. I look forward to the Personal Flyer being in the air. I expect it to work but I remain to be convinced that handle bars are not necessary. My expectation is they will make it much more controllable. Hang gliders have a trapeze which is essential whereas I expect handle bars will make the personal flyer easier.

I don't know if it was this thread which introduced me to the McCulloch 2 stroke engine for US WW2 gunnary target drones. Quite a lot in common with Manolis's design though his is very different in principle.

http://www.enginehistory.org/Piston/WW2 ... one2.shtml

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

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Hello NathanE

You are close to get it.

You write:
“lifting one's legs at the hip without bending one's knees will create a "control" input that will have a "downward" pitch effect enabling transition to forward flight.”


Let me explain a little further your “control input”.

Suppose that initially the Portable Flyer is hovering, with the thrust force vectoring upwards and passing through the overall center of gravity.

By lifting his legs at a normal angle relative to his spine, the pilot varies the eccentricity of the center of gravity relative to the thrust axis (actually, what the pilot does is to shift the thrust axis offset to the overall center of gravity).

With the thrust axis offset from the overall center of gravity, a torque (or moment) is generated (it equals to the thrust force times the offset of the overall center of gravity from the thrust axis); this torque accelerates angularly the Portable Flyer (including the pilot); even a tiny torque will accelerate angularly the Portable Flyer, however the smaller the torque the weaker the angular acceleration.

As the thrust force turns forwards (pitch effect), the horizontal component of the thrust force accelerates the Portable Flyer forwards (in order to keep his altitude, the pilot has to open properly the throttle).

If the pilot keeps his legs at normal angle relative to his spine, the Portable Flyer cannot stop turning (it will turn upside-down, with the thrust force pushing downwards), which is a problem).
So how things work?
When the leaning of the thrust axis is adequate (for the desirable forwards flight), the pilot restores his legs at their initial position / posture (say, in line with his spine), eliminating the torque.
But this is not adequate.
If he does so, the Portable Flyer stops accelerating angularly, but continues to turn at constant angular velocity; so, what the pilot has to do in order to stop the rotation of the Portable Flyer is to apply a decelerating toque (say, by bending his knees or by bending his spine).

To return to hovering, the pilot has to displace the thrust axis upwards, and he can do this by changing properly his body posture. Same reasoning as above.

To turn to backwards flight, the pilot has to vector the thrust axis backwards, and this can be done by, say, properly bending his spine and / or legs.

Similarly for side-wards flight: if the pilot lifts his left leg to the side, the thrust axis turns to the left etc.


And what about the yaw control?

The pilot of the Portable Flyer is permanently, from taking off to landing, into a high speed air stream. By deflecting a part of the air stream, a pair of forces causes the rotation of the Portable Flyer about its long axis.

Suppose the pilot turns for 15 degrees his left leg forwards and for the same degrees his right leg backwards. The reaction from the deflected - by his legs - air is a pair of forces that accelerates the Portable Flyer about its long axis. This is the yaw control. If the pilot turns his legs the other way (the left leg backwards, the right leg forwards) the Portable Flyer yaws at the opposite direction.

Do you know the following “paper toy”?

Image

If you throw it, it turns like a helicopter rotor.

The two wings of the toy are the legs of the pilot, the rest toy is the body of the pilot.

This is what the skydivers do in order to yaw:




According the previous analysis, if the pilot is lifting his legs at the hip without bending his knees, the torque (“control input”) will be so strong that the Portable Flyer will turn too fast.

More reasonable is the pilot to bend slightly his legs; this creates a “control” input and is easy for everybody.


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

Thanks
Manolis Pattakos

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

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More word salad Manolis. Build a model and do some testing and present some numbers. Anyone can just describe what they want to have happen but this is F1 Technical and actual analysis would be way more convincing. As I've suggested before, hang from a bar and do the exercises you describe; the pilot will have to be superman.

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

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Manolis, respect for your inventions and craftmenship but can't you put it in a project page? It seems like everything posted needs to be compared here to your ideas of what an engine should look like (with propellers). Perhaps it works brilliant but we won't know until you put it on a dyno.. So it's a bit a pointless discussion imo

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

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Argh!!!!! It's never ending.

Rodak
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nzjrs wrote:
Wed Sep 02, 2020 11:37 pm
Argh!!!!! It's never ending.
Yet we keep coming back. He has some neat mechanical ideas but his intransigence re control is .... odd. I can think of a number of ways of pretty easily testing some of his control 'theories'.

Hey nz, are you from New Zealand originally? I see Austria as your location but you certainly have excellent English....

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

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With that meat mincer above and no control, what could go wrong hey?

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

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Hello Brake Horse Power

You write:
“It seems like everything posted needs to be compared here to your ideas of what an engine should look like (with propellers).”


The comparison to existing engines / ideas is the shortest way.

The Opposed Piston engines mentioned for comparison is not my idea:

The Junkers Jumo Opposed Piston Diesel engines (they were propelling airplanes in 1930’s) can offer a significant asymmetry of the timing of the exhaust and scavenge ports.
In the famous Deltic Opposed Piston engine:

Image

each two crankshafts run at 20 degrees phase difference.
With the exhaust ports closing several crank degrees before the scavenge ports, the supercharging of the engine can be as efficient as the supercharging of the REVolution engine.

The Achates Power Opposed Piston engines (a contemporary version of the old Junkers Jumo engines) can do the same.

The twingle engines of DKW can do the same.


The PatATE 2-stroke can, with one only piston, do the same and more.
It can put a significant phase difference between the exhaust and scavenge processes, with the exhaust starting several degrees before the scavenging and ending several crank degrees before the scavenging:

Image


If, as I wrote, the basic characteristic of the REVolution engine is the early closing of the exhaust that allows the efficient supercharging of this 2-stroke engine, the reference to the Opposed Piston engines (not to the pattakon Opposed Pistons, to the Opposed Pistons in general) and to the PatATE pattakon engine is well justified because they can do the same in a simpler way.


By the way, the Revolution “Bishop like” rotary valve in the "red-hot" exhaust needs oil (total loss lubrication), the cylinder liner (with its exhaust port opening) whereon the piston skirt slides and passes thrust loads, needs oil, too (again in total loss lubrication); these make the claim for specific lube consumption lower than the 4-strokes “strange”, at least.

I will be glad to read your objections to my “strictly technical” arguments.

Thanks
Manolis Pattakos

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

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manolis wrote:
Wed Sep 02, 2020 8:07 pm
Hello NathanE

You are close to get it.

You write:
“lifting one's legs at the hip without bending one's knees will create a "control" input that will have a "downward" pitch effect enabling transition to forward flight.”


Let me explain a little further your “control input”.


Thanks
Manolis Pattakos
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.

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

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Yep.

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

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manolis wrote:
Wed Sep 02, 2020 8:07 pm
With the thrust axis offset from the overall center of gravity, a torque (or moment) is generated (it equals to the thrust force times the offset of the overall center of gravity from the thrust axis); this torque accelerates angularly the Portable Flyer (including the pilot); even a tiny torque will accelerate angularly the Portable Flyer, however the smaller the torque the weaker the angular acceleration.

As the thrust force turns forwards (pitch effect), the horizontal component of the thrust force accelerates the Portable Flyer forwards (in order to keep his altitude, the pilot has to open properly the throttle).
Yes, this is basic. No one disputes this is how rigid body dynamics works. Now run the calcuations here precisely to tell you what the forces and torques invoved are, plug in the intertia and some aerodynamic values, and do the god damn modelling that was explained in step-by-step fashion in any of the papers I posted (or software). The H4 one was really a good introduction example for what you need to do.

Then you will know if your imaginary flight envelope is possible or not, or if you really will be pissing off the side of the cruise ship hoping it will turn.

On the other side, if the PF is as nimble as you say, maybe you will get rag dolled in increasingly unstable oscillations until your spine breaks and you are folded in two with your extremeties being cut to pieces in the blades. Who knows?

And ignoring if this thing is even controllable, I agree with the others here that doing a bunch of knee raises while hanging from the shoulders is not something I would consider easy for a 60 year old person
Last edited by nzjrs on Thu Sep 03, 2020 2:18 pm, edited 1 time in total.

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

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Comment removed.

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

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Hello NathanE

You write:
“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.”


It is nice to know you are an engineer with a degree on fluid dynamics, thermodynamics and aerostrucutres (all three relative with the Portable Flyer project).



You also write:
“My basic question is more about human dynamics than control system maths though.
. . .
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.”



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 the transition from hovering, to forwards fly, to high speed cruicing, to braking, to backwards fly etc:

Image

Thanks
Manolis Pattakos

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

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Rodak wrote:
Thu Sep 03, 2020 1:56 am
nzjrs wrote:
Wed Sep 02, 2020 11:37 pm
Argh!!!!! It's never ending.
Yet we keep coming back. He has some neat mechanical ideas but his intransigence re control is .... odd. I can think of a number of ways of pretty easily testing some of his control 'theories'.

Hey nz, are you from New Zealand originally? I see Austria as your location but you certainly have excellent English....
Yeah, I am from NZ and did my engineering studies in NZ. BTW I mentioned to Manolis that I was near the Martin Jetpack (NZ) when it was the new shiny thing, I've got a little first hand experience of 'crazy home made flying devices and the dreams of their founders'.

I have been in Austria for almost 10 years now. The timezone here certainly makes following F1 easier :wink: Im a huge fan of the ORF (Austrian broadcaster) coverage. They have Wurz as one of the commentators and he is excellent.

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

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manolis wrote:
Thu Sep 03, 2020 4:05 am
Hello Brake Horse Power

I will be glad to read your objections to my “strictly technical” arguments.

Thanks
Manolis Pattakos
I have no objections to your engine, nor am I claiming the Revolution is the most brilliant engine on earth. And honestly I couldn't care less. I just think the Revolution thing is a cool project. Just as regular expansion chamber 2 strokes are awesome but emission wise they suck 😉