2 stroke thread (with occasional F1 relevance!)

[Tommy Cookers]

congratulations to those designing and making engines !

taking only the easy path of the spectator I found these Suzuki data from a site on 50cc racing motorcycles ....
https://www.classic50racingclub.co.uk/s ... acers.html
1964 single cylinder 40x39.5mm 9 gears 11 bhp @13000 rpm
1966 twin cylinder 32.5x30mm 12 gears 16.5 bhp@17000 rpm 20mm carbs (1967 14 gears 18 bhp@17300 22mm carbs)
1968 three cylinder (never raced) 28x26.5mm 16 gears 19 bhp@20000 rpm 20 mm carbs
these seem to imply with progression to more, smaller, cylinders the port areas increasing proportionately to support rpm
corresponding to stroke reduction ie based on piston speed (the engines being breathing limited not stress limited)
(the 3 was a rotary valve L-shaped 3 - there was a similar 125 L-3 as a conservative reserve for the 125 square 4)

imo the proliferation of gears between 1964 and 1968 was simple ....
the 1964 machine did maybe 80 mph - so needed a range of gears from eg a 40 mph hairpin to 80 mph
the 1968 machine did maybe 105 mph - so needed a range from 40 mph to 105 mph
ie the 1968 power band was relatively narrower than the 1964's but not narrower in rpm terms

from this do people think the port timing became more extreme over this period - or not ? .... and why (or not) ?

btw the 1969 rules yielded a Yamaha single 40x39.6mm 6 gears 15 bhp@15200 - not raced due to Bill Ivy's death


re. personal flyers ....
my TV showed a history of the jetpack (ex-rocketpack) flier rounding the Statue of Liberty
he nearly crashed from overbanking his turn and starting to 'fall' as the vertical thrust vector became increasingly inadequate
(he crashed his rocketpack into Sydney harbour that way)
does this tell us something about personal flyers ? - (spiral instability ?)

re. the recent upsurge in another thread of discussion on so-called 'Big Bang' engines (a bit like discussion of UFOs)
there is one kind of vehicle where any crankshaft rotational moments due to inertial effects clearly transmit to the load
it's the steam railway locomotive
their design (like M1 Yamaha's and URS's 40 years earlier) cancels said moments by the crank setting being 'crossplane'
however this ('quartering') is a fortuitous accident - quartering is there to enable starting (90% of locos having 2 cylinders)
99.9999% of 4 cylinder locos were 90 deg set ie had power strokes paired and acted as 2 cylinders (4 power strokes/rev)
there was debate by designers - whether more power strokes/rev was helpful or a hindrance to traction/controllability
c. 1960 I saw/heard at Basingstoke one of the 'Lord Nelsons' that were 45 deg set - giving the weird 8 power strokes/rev
(3 cylinder designs eg 'Flying Scotsman' were set for (roughly) 120 deg and 6 power strokes/rev)
regardless of the above and amusingly all the 2 cylinders at speed had ....
unbalanced primary inertia forces (vibrations) of many tons - enough to lift momentarily wheels from rails
even 3 and 4 cylinder designs weren't brilliant either - having wheel counterbalance weights (seemingly superfluous/wrong)
because a loco's wheels are fixed to the big-ends there's no crankshaft/case effect to 'as designed' sum/cancel the inertia forces

[manolis]

Hello Tommy Cookers.

For the “spiral instability” of JetPacks:


Mayman (left in the following picture) flies stable (so stable that his flight seems boring) and pure instinctively. He controls his flight by merely re-arranging his body relative to the force from the two or six jet-turbines, and by opening or closing the throttle. After 3 hours of tethered training (hanged flights in a controlled environment) a person is “ready” to start real flights.
Here is a recent video wherein Mayman flies with a partner in formation: https://www.youtube.com/watch?v=aTSssXt ... e=youtu.be




Zapata (2nd from left in the picture) flies instinctively, too, and stable, but it seems the pilot needs to have more “acrobatic” skills / capabilities and longer training as compared to Mayman’s JetPack. Also the take-off and landing requires a platform.


Browning (3rd from left in the picture) flies instinctively, too, and stable, too, but the pilot needs to have strong hands for the vectoring of the thrust force.



Quote from the above video wherein Richard Browing explains how things work:

1:00
“approaching this challenge of human flight leaning very heavily on that already pretty amazing machine (the human body) … there is one thing that’s missing, and that’s horsepower … we don’t have enough power versus our weight …”

6:32
“the brain and body is a quite awesome machine at being able to balance and control”



Quote from https://www.pattakon.com/pattakonFly.htm

“Control

When a child begins riding a bicycle, it progressively learns how to react properly to the signals from the eyes and the body (i.e. on how to keep the control).

Just like driving a bicycle, the eyes / body / brain of the rider / pilot of a Portable Flyer are the sensors and the control system: the rider soon discovers the way to react properly and to keep the control. For the Portable Flyer is a true neutral propulsion unit: neither vibrations, nor reaction torque, nor gyroscopic rigidity, only a force: a force that can "instantly" and effortlessly be vectored towards the desirable direction.

In a Flyer it is better to be used the body of the rider as the main sensing and controlling equipment (birds like), than developing and paying and carrying stabilizing and flight management systems.

The birds, the bats and the bugs fly because their bodies can provide adequate power for their weight. The power provided by a man's body is not adequate to lift its weight.

What a man needs, in order to fly, is neither a vehicle, nor sensors, nor servomechanisms, nor control units, nor transmission shafts, nor differentials, nor gear-boxes, not even a seat.

What a man does need, in order to fly, is power provided in a true neutral and manageable way. The body is: the vehicle and the sensors and the control unit and the servomechanisms and the landing system, just like the bodies of the birds, bats and bugs.”

[Pinger]

congratulations to those designing and making engines !

taking only the easy path of the spectator I found these Suzuki data from a site on 50cc racing motorcycles ....
https://www.classic50racingclub.co.uk/s ... acers.html
1964 single cylinder 40x39.5mm 9 gears 11 bhp @13000 rpm
1966 twin cylinder 32.5x30mm 12 gears 16.5 bhp@17000 rpm 20mm carbs (1967 14 gears 18 bhp@17300 22mm carbs)
1968 three cylinder (never raced) 28x26.5mm 16 gears 19 bhp@20000 rpm 20 mm carbs
these seem to imply with progression to more, smaller, cylinders the port areas increasing proportionately to support rpm
corresponding to stroke reduction ie based on piston speed (the engines being breathing limited not stress limited)
(the 3 was a rotary valve L-shaped 3 - there was a similar 125 L-3 as a conservative reserve for the 125 square 4)

imo the proliferation of gears between 1964 and 1968 was simple ....
the 1964 machine did maybe 80 mph - so needed a range of gears from eg a 40 mph hairpin to 80 mph
the 1968 machine did maybe 105 mph - so needed a range from 40 mph to 105 mph
ie the 1968 power band was relatively narrower than the 1964's but not narrower in rpm terms

from this do people think the port timing became more extreme over this period - or not ? .... and why (or not) ?

btw the 1969 rules yielded a Yamaha single 40x39.6mm 6 gears 15 bhp@15200 - not raced due to Bill Ivy's death

Was this not the period in which they were experimenting with very shallow transfer ports, a consequence of trying to maximise crankcase compression? For certain, that route led to razor thin power bands. And was reckoned to have come about after the success of full circle cranks significantly upping the power output of a Villiers engine when it replaced the standard T-crank.

[Pinger]

Manolis. Very likely you are aware of this >> https://www.theguardian.com/science/201 ... ou-by-2022 but on the off chance you aren't...

[Tommy Cookers]

given that the human-carrying EFV is now possible (like the 'model' drone but larger) .....

isn't a similar ICEFV (eg powered by multiple Wankel-type or 2 stroke engines) more capable in real-world situations ?
one such project c. 20 years ago was backed by afaik a former Senior Scientist (boss) of NASA Langley
a man who was famous for attacking convention in aeronautics (as I witnessed at one of his lectures)
the real-world situation identified was development in undeveloped areas without eg needing to cut roads through jungles

55 years ago RR 'lift-jets' ie turbofans gave 40 lb of 'lift' per each 1 lb of weight (for a VTOL SST)

btw
I met someone (a civilian) who had made hundreds of USMC Harrier flights but never left the hover training 'tennis court' (cage)
he hover-trained officers (formerly fast jet pilots) - afaik officer deaths/other training failures were costing too much
NCOs were former helicopter pilots - their deaths/training failures were usually outside the hover and anyway cheaper
this someone having been a hovercraft test pilot eg on the MC/SRN5-type? hovercraft evaluation program
he once broke the hovercraft into 2 pieces (though beaching fully-manned through 5' waves often went ok)

[manolis]

Hello Pinger.

Thanks for the link wherefrom the following is quote:

“Alice’s giant battery alone accounts for more than half its weight. For eVtols then, Bar-Yohay warns: “The least efficient way you can take someone through the air is vertically. It’s impossible to build [an eVtol] certified in today’s regulatory environment that will have a proper, real-life mission and makes economic sense.”


Quote from https://www.pattakon.com/GoFly/DTR_1.pdf :

“The EHANG184 (at http://www.ehang.com/ehang184/specs/ ) is an indicative example of such a battery powered personal flying device: 260Kg net weight, 100Kg payload, 100Km/h speed, 25 minutes autonomy and ~25miles (40Km) range."


There is no eVtol today having a sufficient range (say 100miles / 160Km) or a satisfactory flight duration (say, an hour).

Compared to the electric cars (wherein the heavy batteries are carried by the wheels at low friction loss, i.e. at low energy loss), an eVtol has to lift its batteries into the air.


Quote from https://www.pattakon.com/GoFly/DTR_1.pdf :

“Starting with the same energy content (315MJ), the total take-off weight (including the pilot) of the electric flyer is 2.5 to 3 times higher than that of the PORTABLE FLYER, which means it requires a few times more power to hover and fly (especially when the maximum dimension is limited and the noise penalty is high), which means a many times smaller range. The many times smaller range is a crucial disadvantage for the usefulness of the personal flying device and for the safety: even if the path (that the personal flying device is to follow) is full of battery recharging stations, to land and take off several times in order to go to a destination where the PORTABLE FLYER goes “non-stop”, is by itself very risky (the safest part of a flight seems to be the cruising). When there are not recharging stations (like when going to an island) the battery personal flyer is useless.”

The energy density of the current batteries (say, in MJ per Kg of weight) is, still, several times smaller than that of the gasoline (or Diesel) fuel.

Here:



are three “fresh” OPRE_Tilting blocks with their liners “thermally” inserted but not yet machined (the external diameter of the cylinder liner is more than 0.1mm bigger than the bore of the block liner).

Thanks
Manolis Pattakos

[Rodak]

Maybe a bit off topic, but Manolis, once the personal flier takes off vertically how does one rotate to horizontal flight? It seems the 'flier' would be stable in a vertical position; there is no way to apply torque to start a rotation to horizontal flight, and no way to control attitude and direction. For example, if the flier takes off vertically the system would be stable in that position from pendulum forces; the weight of the pilot tends to keep the props facing upward. Even if horizontal velocity can be achieved, how does the pilot control this thing? Your depiction of 'high speed' shows the pilot being pulled along by the motor unit, but for the pilot to have any control they would have to be an aerodynamic component of the system and be attached in a rigid manner to the motor unit. Otherwise the pilot is just sort of hanging out there in space being dragged along with no control input. Maybe I'm not seeing something, but this looks impossible to control. Hang gliders are a good example of control forces by body action, as the pilot can shift the center of gravity by pushing against the control bar, causing the craft to go nose up or down or generate turning forces; I see no ability to do so here.

Edited to add: Nice to see a running machine, but why is it drifting along a floor without restraints? I would have fitted this into a test bench. Just asking.

[Tommy Cookers]

Richard Browning's 75 sec flight between England and the Isle of Wight was on my TV 2 days ago
his trousers seemed to have a panel spanning the legs (roughly like a long skirt) to give aerodynamic forces and moments

adding in translational flight to the 'body' some useful lift and control moments and 'stability' moments
useful but (as with some other rudimentary ways of flying) not a complete set IMO

[Pinger]

Manolis: my post was only in case you hadn't seen the other proposed flyers - but you have it seems!
Agree re fuel density and range, but the article I read (or the way I read it) seemed to be about short hop city use where range isn't such an issue and,crucially, it is emission (at point of use at least) free. This, as we banish ICE cars and trucks from cities will favour those over yours - for city use that is - if it ever catches on.

If you believe there is a market for your flyer outside of that niche market, then keep going.
Congrats on the progress so far. There really aren't very many who have designed and built their own engine. Let alone one so novel. Very impressive.

[manolis]

Hello Rodak.

The brown “saddle” is secured onto the shoulders / torso of the pilot:



and the Portable Flyer is secured to the saddle.

I.e. the pilot is not hanged by the Portable Flyer; the pilot is secured to the Portable Flyer, and the Portable Flyer is secured to pilot's shoulders / torso; in other words, the Portable Flyer is like an extension of pilot's body :



This enables “weight displacement control” as in the GEN-H-4, but instead of pulling / pushing some lever to displace the center of gravity relative to the thrust force (i.e. relative to the rotation axis of the rotors), in the Portable Flyer the pilot displaces his head / limbs relative to his shoulders / torso (and so relative to the Portable Flyer), as in the following animation:



Besides the “weight displacement control”, in the above animation it is also illustrated another kind of control, the “aerodynamic control”, used (in the specific case) for the rotation about the vertical axis.

Quote from https://www.pattakon.com/GoFly/DTR_1.pdf :

“The heavy disk loading (thrust to disk area) of the PORTABLE FLYER (similar to that of the OSPREY V22) causes a high downwash velocity, with the pilot inside it. Either at take off / landing, or at hovering, or at cruising (low / medium / high speeds), pilot’s limbs and head are in a high velocity air stream, which allows the control over the flight in a way similar to the way the skydivers control their flight / fall. 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)”

End of quote.

Back to the animation:
in order to turn to the left about the vertical axis, the pilot moves his left leg forwards and his right leg backwards; pilot’s legs interact with the high speed air from the propellers, a torque is generated, etc, etc.

…

The OPRE Tilting engines in the videos are standing free on the floor to demonstrate their “vibration free quality”.
An interesting video would be to secure the one piston (of the two opposed pistons) at its TDC, crank the engine as it stands free on the floor and try to follow it as it jumps and moves around uncontrollably...

Thanks
Manolis Pattakos

[Rodak]

I posted this earlier but it didn't appear so will try again,

One problem with this motor unit is horizontal flight. When the motor is vertical all the energy is lift; as soon as there is a transition to some horizontal component of flight the lifting force is lowered. For example, at 0° (vertical) lift = 1. If the motor is rotated to 45° the vectors of lift and horizontal thrust are equal, cos(Θ), 0.707 in both the X and Y directions. If the motor is tilted at 75° the vertical component is about 1/4 of the horizontal; most of the energy is being used for horizontal flight. The power of the motor would have to be about 4X that required for vertical flight just to stay aloft, assuming there is no lift generated by the pilot, which seems pretty true. In fact there is a huge amount of drag from the pilot being pulled along hanging in the air stream. Up and down maybe, high speed horizontal flight not much chance; despite your explanation of control motions manolis, I have grave doubts of their efficacy.

[Tommy Cookers]

as I wrote (at the top of this page) we saw Mayman nearly die in Sidney harbour (and telling us about it)) because .....
the 'lift' vector falls so quickly when the 'lean angle' becomes rather large eg in turning
producing unintended descent tending to accelerate itself - also the turn tends to tighten itself

[Rodak]

Yeah. Here's the same effect except with a fixed wing aircraft.......

https://youtu.be/0HJ4z1jGEcA

[manolis]

Hello Rodak.

Quote from Wikipedia:

“On 25 October 2009, in Lahti, Finland, Visa Parviainen jumped from a hot air balloon in a wingsuit with two small turbojet engines attached to his feet. The engines provided approximately 160 N (16 kgf, 35 lbf) of thrust each and ran on JET A-1 fuel. Parviainen achieved approximately 30 seconds of horizontal flight with no noticeable loss of altitude.”

Quote from https://www.dropzone.com/articles/news/ ... ight-r601/ :

The exit was stable and on-heading, after attaining normal bird-man flight, Visa requested full power from the engines, which responded smoothly in horizontal acceleration. After checking the altimeter several times, it was apparent that there was no appreciable loss in altitude for this period of time. Visa next changed his angle of attack by redirected the thrust and changing his body position to attain vertical climb. This caused a loss in horizontal speed, and stalled (the body?). Recovering from the stall was made easy because of the agility of the human body to change flight profile easily.





End of quote.


Each of the state-of-the-art JetPacks (Mayman’s, Zapata’s and Browing’s) has a huge power output (around 1,000bhp) and consumes the fuel in a respective / relative rhythm; but as regards the thrust force, they are “underpowered”: the total thrust force is not too bigger than the total take-off weight (pilot weight plus engines weight plus fuel weight).

In comparison, the Portable Flyer has several times smaller power output (and “proportionally” lower fuel consumption), but substantially stronger thrust (with both engines running, the thrust force is more than twice the total weight, enabling an upwards acceleration of 1g (10m/sec2): at full power take-off, the pilot feels as “falling” towards the sky).

Besides its substantially better “thrust” and its several times lower fuel consumption, the Portable Flyer has an additional control not available / attainable in the JetPacks (at least in the low / medium speeds): it is the aerodynamic control; the pilot of the Portable Flyer is inside the downwash and so, by deflecting (by his limbs / head) the surrounding high speed air, he has not only the typical “weight displacement control” of the JetPacks, but also true “aerodynamic control” (the JetPack pilots cannot be into the red-hot exhaust gas flow).


Back to the first powered wingsuit of Visa Parviainen:

At 100mph (160Km/h) all he needs in order to sustain a horizontal flight is 32kg (70lb) of thrust. This means a power of less than 20bhp (the power required equals to the force times the velocity).


With the pilot of the Portable Flyer wearing a wingsuit, he/she can fly horizontally at 100mph with his engine(s) running at light / partial load (hopefully at lean burn / HCCI) and the propellers’ axes near horizontal. The required thrust (say 30 – 40kg) pulls the pilot / Portable Flyer forwards, while the wingsuit provides the required lift.
In such a case the Portable Flyer needs not to provide any “direct” (verical) lift.


Without a wingsuit:
the pilot can sustain the same (100mph) horizontal speed by changing his body pose to keep the propellers more upwards, opening at the same time the throttle as required,



or
the pilot can increase the cruising speed to, say, 200mph (300Km/h) wherein his body (without a wingsuit) can provide the required lift, with the propellers’ axes looking only slightly upwards.



Thanks
Manolis Pattakos

[Rodak]

A wing suit, flown very well, has a glide ratio of about 2.5:1 This is NOT an effective alternative to a wing for generating lift. Almost all your lift will have to be from engine power.

Edited to add: From your drawing of 'high speed' the inclined angle is about 10° from horizontal; you would need about 6 times hover power to fly at this attitude, neglecting lift from the body.