2 stroke thread (with occasional F1 relevance!)

[Rodak]

I suggest the trunnion attached to the saddle located at the CoG position. This would provide for movement in pitch but constrain other degrees of freedom.

Good idea. I would suggest doing this with a scale model and electric motors. A large doll could be ballasted to simulate a human, and torque generated by legs, arms, head, etc measured; this would at least give some idea of practicality before full scale fabrication. To run a full scale test obviously requires a functioning power unit; what's the schedule manolis?

Edited to add: Was just looking at some uniflow info and ran across the Dair 100 aircraft engine with a mention of a centrifugal blower to aid scavenging. Uniflow, how well does that work?

[J.A.W.]

I suggest the trunnion attached to the saddle located at the CoG position. This would provide for movement in pitch but constrain other degrees of freedom.

Good idea. I would suggest doing this with a scale model and electric motors. A large doll could be ballasted to simulate a human, and torque generated by legs, arms, head, etc measured; this would at least give some idea of practicality before full scale fabrication. To run a full scale test obviously requires a functioning power unit; what's the schedule manolis?

Or, instead of a doll, a friendly housecat may be amenable to posture/harness evolution tests?

[J.A.W.]

Oh well, Honda is out of F1. That's the story of the day.

Thinking over your view quoted above for real topic relevance nzjrs...

I wonder if the publicly stated idea by F1 technical direction to consider a future F1 piston
engine in 2-stroke format riled Honda, given their openly established ethos of being anti-2T?

Perhaps for Honda, the need to prepare plans & design for such a future 2T F1 power unit were
'beyond the pale' philosophically, with resulting 'cognitive dissonance' making it a 'deal breaker'?

Between poor decisions in production car design/marketing/sales & Moto GP Championship failure,
Honda have been under a fair bit of self-generated stress lately, so IMO, it could well be a thing...

[manolis]

Hello Henry.

To support a Flying Device by trunnions cancels out its freedom, making it a pendulum.

The tethered tests (JetPack training schools) prevent the flying device from moving away from its initial position and from hitting the ground (if something goes wrong). For the rest, the rope is loose (See from 1’:30” to 1’:40”):





On the other hand, if you didn’t see the video “Part2 / RC Chinook” in page 212, take a look at it. It does what you propose to test, and more.

The following text is not mine, it is what the guy who made the RC Chinook and prepared / recorded the test says:

• 9:06
  
  Motor is then angled not quite vertical but it’ll be angled at a slight angle, or just to move the thrust line away from the center of mass, and the thrust line will come somewhere down here; now because the thrust line is not in line with the pivot point, there is a perpendicular distance here which, if there’s a force applied at perpendicular distance, will rotate the aircraft back to vertical position; so what’s done trying to get to, is that a mass hanging below a fixed point of thrust (you know a motor or propeller) DOES NOT RIGHT ITSELF LIKE A PENDULUM DOES, AND THIS IS KNOWN AS THE ROCKET PENDULUM FALLACY.
  
  I know it has “rocket” in the name, but it also applies to aircraft that hover such as helicopters.

In my last posts I explained analytically the recovery of the astronaut from a vertical dive by offsetting his center of gravity from the thrust axis (how? by simply varying his body posture, say from straight to fetal).

The specialists in this forum firmly refuse to admit "it can be done" or "it is according the physical laws" or "it doesn't violate any physical law".

Did you read any real objection in the specific explanation / problem for the recovery of the astronaut from vertical dive?

To analyze some forces and torques and calculate their affect on a body’s motion is what the 2nd year students in all university-engineering-schools apply for fun.


So, the tethered test will be with the rope loose and no trunnions as explained in the following quote from https://www.pattakon.com/GoFly/DTR_1.pdf :

• Tethered tests and training
  
  The top end of the hollowed pipes can be used for the tethered tests of the PORTABLE FLYER and for the initial training of the pilot (the PORTABLE FLYER can be hanged from a roof (or from a tree branch etc) by ropes tighten on the top ends of the hollowed pipes).

Thanks
Manolis Pattakos

[Rodak]

Oh my god, the feared

ROCKET PENDULUM FALLACY

again. manolis, do you actually read any of the responses? Does or does not your 'flyer' pivot about its c.g.?

[coaster]

You forgot the cinder block wall, its essential for the pilots sanity.

[nzjrs]

The specialists in this forum firmly refuse to admit "it can be done" or "it is according the physical laws" or "it doesn't violate any physical law".

I've outlined my specific problems with your PF (not engine) several times. While you have no obligation to respond to me, I have offered to do some further analysis should you provide me with necessary information.

I do not understand how these discussions here have been going. Based on the earlier pages of this thread before it went off the rails, you appear to build physical, real and very impressive and novel 2T engines, test them in real life, document and describe them in sufficient detail to be granted patents, but do not want to do anything similar for the PF! I just do not understand why one field (Mechanical / engine engineering) is worthy of being taken seriously, but for the other (control systems, aeronautical engineering) it is not. It seems a joke - compared to the amount of testing you do of your 2T engines before patenting them, with the PF you basically seem to only do the most basic of analysis; 'Rossy does this in this video', the PF works like this hummingbird or lady in a bed, here is a RC stick, pendulim rocket fallacy, etc etc.

Why do you think 2T engines are worthy of being built and tested physically but your PF flight, controllability and stability can be evaluated from pictures of other flying devices and a few static pictures of your PF pilot in a few different orientations?

Once again.

Controllability and stability are dynamic processes which should not be reasoned about from static pictures of animals or ladies in the bed (or from other flying machines).

Thus you have not demonstrated neither controllability nor stability of your PF 'design'.

To stick to one specific example. If you believe c.g. shift from knee raises will provide sufficient control input then the details of this matter. You have not explained in sufficient detail the mounting mechanism and harness of the PF to the pilot. You have not answered Rodak specific question about the mounting - which as he said - the ease and ability to move the body depends on the harness and mounting type. As the pilot bends their knees, the magnitude of the c.g. shift (and other intrinsic features of the PF design, also not provided) will bound the flight envelope and constrain the time/space transition from hover to horizontal flight. (Maybe) pissing off the side of a cruise ship to turn it, as I like to say.

This is elemental analysis and something that I would recommend doing for your safety.

As mentioned, I think you could also learn some of these things by simply hanging in the harness and taking some photos of you moving about doing these maneuvers. I also think some form of tethered testing as suggested by henry is a good idea.

More generally, these concerns exist in (for example) roll and yaw in hover too. Sticking out the foot into the airstream might do something. Maybe it is offset by a hip c.g. shift in the other direction. Who knows, it depends on the mounting and other factors of the PF you will not disclose. Hang under the props and take some photos and measurements. Maybe it will also be pissing off the cruise ship to turn it.

You can also build a scale model to answer some of these questions as you wish.

I'm ignoring stability analysis in horizontal flight for now because most risk is in take-off and landing (proximity to the ground gives less room for error) so you should focus on that first.

Finally, by analogy - can an engine builder estimate the true performance and reliability of a 2T engine from diagrams, or photos of other engines? Or would the engine builder build their engine in stages, simulate it, test it on short runs, run it in different conditions and loads, etc, before trusting it? Surely you must think that is also the case with flying craft? Surely you must think this is even more important with flying craft because of the relative ease with which they can injure or kill you?

[gruntguru]

Oh well, Honda is out of F1. That's the story of the day.

I wonder if the publicly stated idea by F1 technical direction to consider a future F1 piston
engine in 2-stroke format riled Honda, given their openly established ethos of being anti-2T?

I don't think Honda are anti-2T.

They are anti-"crankcase-inducted, total-loss-lubricated, cylinder-ported, high-emission ICEs"

[Rodak]

Controllability and stability are dynamic processes which should not be reasoned about from static pictures of animals or ladies in the bed (or from other flying machines).

Great comment nz (the whole thing).

[J.A.W.]

Oh well, Honda is out of F1. That's the story of the day.

I wonder if the publicly stated idea by F1 technical direction to consider a future F1 piston
engine in 2-stroke format riled Honda, given their openly established ethos of being anti-2T?

I don't think Honda are anti-2T.

They are anti-"crankcase-inducted, total-loss-lubricated, cylinder-ported, high-emission ICEs"

Got a source for the quoted part, gg?

Old man Honda himself was anti-2T, & was frustrated that Honda really had to build them
to compete, & nothing has changed per that Honda ethos since, with bosses like Takeo Fukui
on record from 1984: "Honda views itself as 4-stroke company..." going on to on to decree
(in 2003) that Honda would eliminate the 2T from their product sales, (Honda duly did so)...

Ironic too, since a 1/4 century ago, Honda itself had developed their EXP-2 'clean-green' 2T,
by which - although still a basic "crankcase-inducted, total-loss-lubricated, cylinder-ported..."
2T - they'd overcome the efficiency issues of such "high-emission ICEs", & had also proved it reliable
in enduro competition both as a factory race bike (Paris-Dakar) & via a production dual-purpose
(road-legal) dirt bike (the CRM 250) - only to be shelved - due to that 'Honda is 4T!' ethos.

See cited items in this link: https://www.dirtbikeplanet.com/future-of-two-strokes/

[manolis]

Thanks Nzjrs

You write:
“you appear to build physical, real and very impressive and novel 2T engines, test them in real life, document and describe them in sufficient detail to be granted patents, but do not want to do anything similar for the PF! I just do not understand why one field (Mechanical / engine engineering) is worthy of being taken seriously, but for the other (control systems, aeronautical engineering) it is not.”



The “time sequence” is different than what you describe.

First is the invention (say, the discovery of the basic idea), then it comes the detailed design of it, then it is the application for a patent and substantially later it is the proof-of-concept prototyping (based, in most cases, on the drawings used in the patent application).

• The four stroke VVA’s inventions, the V-belt CVT’s, the VCR’s, the PatVRA (whose Search Report was posted a couple of days ago) and the rest projects presented at https://www.pattakon.com followed the above time sequence.

To prototype and test before patenting is risky; “the first who applies for an invention is the owner of the patent” (at least in the USA (US-PTO)).


The same was done with the Portable Flyer.
The basic idea was ready from a dozen of years ago and a patent application was filed for it (you can read it at https://www.pattakon.com/Fly_files/VTOL ... achine.pdf ). The only significant improvement came with the compact / lightweight OPRE Tilting design which allows the use of two complete, yet independent, propulsion units for safety.

• When the theory (the thinking, the principles) behind a new idea is correct (solid, strong), practice cannot help confirming it.

The control over the Portable Flyer is quite simple.
The discussion in the forums is to see how the others think about it, and if someone – around the world - can “see” some flaw.
So far the project survived.
And the various JetPacks that appeared in the meantime, confirm that the basic idea is correct and that it will work.

So the way we are following is to make full scale Portable Flyers and test them by flying them (initially with tethered tests: the Portable Flyer will have the freedom to move (at all directions) 1m from a central position located 1.1m above the ground; say, by a rope holding the Portable Flyer from above and by another rope holding the pilot from below and anchored to the ground; no matter how hard the pilot will try, he cannot strike the ground).

The human body is the most important part of the Portable Flyer, making meaningless the idea to make a scale model for tests.

• The control over the Portable Flyer seems intrigued, however it is quite simple.
  
  This is why I insist in the “recovery of an astronaut from vertical dive”.
  
  All it takes is to deal with a mass and an eccentric force.
  
  It is a dynamic, yet simple, problem.
  
  If an astronaut can move just one part of his body (his head? a hand? a foot? a finger? his tongue?) and has a thrust force (say a pair of rockets at his sides) “secured” on his “frozen body” (frozen except the movable part mentioned), then the astronaut has full control over his flight because he flies controllably and he can go at any destination he likes.

Is there a disagreement, an objection, to this?
If you can fly in the space and go to any destination you like, your flight is controllable.

So I am confident (because the physical laws say so) for the effectiveness of the control of the Portable Flyer by the body of the pilot; more confident than I am about the engines of it.


So we do have a simple case to examine and use it as the basis for the full analysis of the Portable Flyer Control: it is the “frozen astronaut that recovers from a vertical dive” and has full control over his flight even by moving only his tongue (I imagine the “clever” comments, however this is the truth: a “paralyzed” astronaut can control his flight by just moving his tongue; this is what the maths and physics predict, and, as a wise man said: “nobody can argue with mathematics”).

However this requires some minimum “good will”.
It requires listening to what the other says, before advising him to “make and test one”.

Thanks
Manolis Pattakos

[manolis]

Hello all.

Quote from another forum discussion about the PatVRA:




Thanks Gruntguru.

You write:
“In removing the "inertia torque" from the drivetrain, the eccentricity of your mechanism would obviously be chosen to produce constant speed at the flywheel when motored. The crankshaft will now have an increased angular speed variation (compared to the case of the same engine without your mechanism). The effect will be faster rotation around TDC and BDC (reduced piston "dwell").
Have you considered the effect on the thermodynamic cycle?”



Let’s put some numbers to calculate the variation of the angular velocity of the crankshaft (case with no flywheel secured on the crankshaft).

Suppose you have a straight-four even-firing four-stroke having a ratio of the rotating mass to the reciprocating mass equal to 4.

Why 4?

• Real figures from existing engines:
  0.5Kg mass of a piston with its wrist pin and with the ~1/3 of its connecting rod
  2Kg rotating mass at crankpin eccentricity (crankpin mass, plus 2/3 of the connecting rod mass, plus the 1/4 of the overall mass of the crankshaft).

If at the TDC (and at the BCD) wherein the reciprocating masses have zero speed, the angular velocity of the crankshaft is ω, and at the middle stroke (90 degrees after the TDC, wherein the center of the crankpin and the reciprocating mass move at the same speed) the angular velocity of the crankshaft is ω’, the conservation of the kinetic energy gives:

4*ω*ω = 5*ω’*ω’, i.e. ω/ω’ = SqruareRoot(5/4)=1.12

I.e. at the TDC the angular velocity of the crankshaft is 12% higher than it is 90 degrees later.

I.e. at the TDC and at the BDC the angular velocity is 6% higher than the mean angular velocity of the crankshaft, while at the middle stroke (90 degrees after the TDC) the angular velocity of the crankshaft is 6% lower than the mean angular velocity.

With a typical flywheel secured on the crankshaft these percentages reduce, say by 50% (from 6% to 3%).

So, in comparison to an existing four-cylinder car engine, the modification to PatVRA will give a 3% higher speed of the crankshaft at the TDC (and BDC) and a 3% lower speed 90 crank degrees later.

That is, if the conventional engine is running at 3,000rpm mean angular velocity, with the patVRA the combustion (which happens around the TDC) feels as if the conventional engine was revving at 3,090 rpm, while the expansion (around middle stroke) happens as if the engine was running at 2,910 rpm.

In the previous we took only the peaks.

But the combustion duration is several degrees (say from -30 to 50 degrees from the TDC), the same for the expansion.

So the above +/- 3% reasonably reduces to +/- 2%

Conclusion:

The increased rotational non-uniformity of the crankshaft affects the thermodynamics only marginally (and not necessarily in a negative way).

Thanks
Manolis Pattakos

[coaster]

With full power the pilot hangs below the flyer, with low or no power the centre of mass would suddenly rotate. Nose down, unrecoverable without altitude to re apply power and to direct the thrust downwards again, since most personal flyers are low altitude device this leaves you only one option.
Centralise the mass, park that motor midway on the pilot, the belly button is near perfect point of reference for centre of mass.
Extend those props with light driveshafts above the head, add a swashplate for 2 props.
Swashplates, trust me, they work.

[Rodak]

So we do have a simple case to examine and use it as the basis for the full analysis of the Portable Flyer Control: it is the “frozen astronaut that recovers from a vertical dive” and has full control over his flight even by moving only his tongue

So I would understand from this that the 'flyer' is not stable at all, as something as simple as a tongue movement can affect a change in attitude..... Manolis, stability was discussed a while ago; do you know what it is? Things like center of pressure and c.g. location stuff? Have you attempted to examine the 'flight' characteristics of the human body, lift, drag, etc. in different positions and relate those to the control forces required to control your 'flyer'?

For example, in horizontal flight at 100 mph what would be the attitude of the pilot's legs vs the attitude of his upper body? How would the differences affect flight? Can the pilot force his legs into a position to aid in horizontal flight? For how long? For that matter, what is the minimum speed for horizontal flight, as you assume the pilot's body is providing lift? Is this lift kite lift or wing lift? Basic question, what is your flight envelope? What is the maximum angle of attack before stalling? Do you have any information about power required to sustain flight at different attitudes? What about the loss of lift from the power unit as the pilot approaches horizontal flight? What would be the actual angle of attack in steady horizontal flight at different speeds? The list goes on. Tongues don't do it.

[Jolle]

The 2-stroke vrs. 4-stroke dilemma was pretty much settled in the early 2000's MotoGP. IIRC 2-stroke engines were allowed up to 1000cc and 4-stroke engines up to 500cc.

I remember the Pons Honda from Alex Barros using 2-stroke with higher CC's, while other teams including official Honda team using 4-stroke engines.

It was shown back then that the 2-stroke cylinders had much better torque but the 4-stroke offered much better power curve and above all driveability and top end speed.

you have that backwards. the 2 strokes were 500s the 4 strokes were 900s

990 cc to be nitpicking