## 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.
manolis
manolis
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Joined: Tue Mar 18, 2014 9:00 am

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

Hello Gruntguru.

This “slide”:

is from the video wherein Browning breaks a world record (last page of this discussion).

At only 85mph (136Km/h) Browning is leaning by 30 degrees from horizontal.

His lower “wingsuit” (between his legs) makes big difference.

The same leaning (about 60 degrees from vertical, or 30 degrees from horizontal) was used in this drawing:

The aerodynamic drag is linearly proportional to both: the frontal area and the drag coefficient.

With 30 degrees ( sin(30deg) = 0.5 ) leaning from horizontal:
the drag coefficient (CD) drops a lot,
and the aerodynamic drag force reduces a few (say 3?, say 4?) times.

At 15 degrees ( sin(15deg) = 0.26 ) leaning from horizontal, say like:

the frontal area and the drag coefficient further drop, allowing high speed flights on small power (and fuel) consumption.

In the slide with Yves Rossy (or his partner?) flying upside – down:

with his arms and legs high above his body,

the center of gravity is well above the aerodynamic lift from the Delta Wing,
yet the “dynamic” stability appears, more or less, the same (the pilot seems taking pleasure in it).

Thanks
Manolis Pattakos

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

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

manolis wrote:
Tue Nov 26, 2019 6:05 am
In the slide with Yves Rossy (or his partner?) flying upside – down:

https://www.pattakon.com/Fly_files/Yves ... ubai_2.png

with his arms and legs high above his body,

the center of gravity is well above the aerodynamic lift from the Delta Wing,
yet the “dynamic” stability appears, more or less, the same (the pilot seems taking pleasure in it).
Hi Manolis. With respect, this is totally different. My concern is the flexibility of the join at the shoulders and the aerodynamic characteristics of the equipment forming the leading edge in horizontal flight. If the joint is rigid there is no problem. If the joint is movable you have a major stability/safety problem. Correcting the problem AFTER the first horizontal test flight, might include finding another test pilot. (To replace the dead one)
je suis charlie

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

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

Hello Gruntguru.

You write:
“If the joint is rigid there is no problem. If the joint is movable you have a major stability/safety problem.”

The slide with the pilot flying upside-down (last post), together with this one:

show how the Delta Wing is fastened with straps (strips / belts) on pilot’s upper torso (chest / shoulders / back).

With these belts:
on ground the Delta Wing is strapped from pilot’s body,
on air, pilot’s body is strapped from the Delta Wing.

There is no other connection.
• By the way:
while at flight the Delta Wing “hides” its weight, on the ground things get tough / heavy (see the posture of the three pilots entering in the “carrier” airplane); as for the aerodynamic lift from the Delta Wing, it appears substantially offset from the “connection” with pilot’s body.

The “connection” of the Portable Flyer with pilot’s body is not different.

Yves Rossy needs not handlebars to support or control his Delta Wing.
A big slack / “play” / flexibility of the connection between Rossy and his Delta Wing would create fluctuations / instability and would need handlebars.
But in practice it seems Rossy’s shoulders / torso can do a better job than any handlebars, leaving his arms / hands to deal with the aerodynamic and the weight displacement control.

Similarly the Portable Flyer pilot needs not handlebars to support or control it (the handlebars are optional).
The connection between Portable Flyer and pilot can be as tight as that between Rossy and his Delta Wing, or tighter:

This means the hands and legs of the Portable Flyer pilot are free to grasp (say, during a rescue) and hold and lift.
And with the downwash from the propellers being anything but hot, nothing below the Portable Flyer can get fire.

Compared the case with Browning and Zapata wherein the arms or the legs are “fixed” / occupied / not free, and wherein the red hot exhaust gas puts limitations to what can be “carried”.

Thanks
Manolis Pattakos

Pinger
Pinger
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Joined: Thu Apr 13, 2017 4:28 pm

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

Manolis - something I've just noticed and apologies if it's been mentioned before. You are driving the props at crank speed. Won't that limit your rpm to what the prop can handle (circa 3000rpm?) and will the engine produce enough power at a low rpm without being constructed larger and thus heavier?

gruntguru
gruntguru
456
Joined: Sat Feb 21, 2009 6:43 am

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

the aerodynamic characteristics of the equipment forming the leading edge (not the wing) in horizontal flight
je suis charlie

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

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

Hello Pinger.

You write:
“Manolis - something I've just noticed and apologies if it's been mentioned before. You are driving the props at crank speed. Won't that limit your rpm to what the prop can handle (circa 3000rpm?) and will the engine produce enough power at a low rpm without being constructed larger and thus heavier?”

This:

is an earlier single-engine design for a Portable Flyer.

The photo was used to show the Flyer tightly secured / strapped onto the pilot.

The engine architecture (OPRE Tilting, opposed-piston, pulling-rod, extra-over-square, spark ignition, more at https://www.pattakon.com/pattakonTilting.htm) allows a high ratio of capacity increase per lb of added weight.
A 1,000cc single-cylinder OPRE tilting (say, 120mm bore, 45+45=90mm overall stroke) would weigh around 15Kg / 33lb.
With 45mm piston stroke, at 4,500rpm the mean piston speed is only 6.75m/sec (i.e. as high as the mean piston speed the giant 2-stroke marine engines operate for weeks).

Propellers rpm:

The propeller revs (rpm) depend on propeller’s diameter.
A limitation is the tip speed (i.e. the speed at the ends of the blades) to remain below (or well below) sound velocity (for efficiency, for noise reduction, etc).

With propellers having 1m diameter (as in the photo) the tip speed at 4,500rpm is 70% of sound velocity.

Diesel engine:

Here the same propellers are driven "directly" by a direct injection OPRE Diesel engine:

The typical / conventional direct injection Diesel makes its peak power below 4,500 rpm; at 4,500rpm its efficiency is not good.

The OPRE direct injection Diesel provides some 30% additional piston dwell at the Combustion Dead Center (CDC) and can operate permanently and efficiently at 4,500rpm (and above, if necessary).

I.e. propellers directly driven by the crankshafts is not an unreasonable choice, with obvious advantages (simplicity, robust structure, no need for transmission etc) and drawbacks (propeller’s optimum revs are, typically, lower than engine optimum revs).

Here is the last version of the Portable Flyer:

It has two independent engines, each driving indirectly – at lower revs - its own pair of counter-rotating propellers.

The design optimizes independently the propeller revs and the engine revs.
More important, the design focuses on the safety:
at an engine stall, the other engine with its own pair of propellers enables a safe landing,
at a propeller (or transmission) malfunction, the other set of engine-propellers enables a safe landing.

Thanks
Manolis Pattakos

Pinger
Pinger
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Joined: Thu Apr 13, 2017 4:28 pm

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

manolis wrote:
Fri Nov 29, 2019 5:53 am

Propellers rpm:

The propeller revs (rpm) depend on propeller’s diameter.
A limitation is the tip speed (i.e. the speed at the ends of the blades) to remain below (or well below) sound velocity (for efficiency, for noise reduction, etc).

With propellers having 1m diameter (as in the photo) the tip speed at 4,500rpm is 70% of sound velocity.
You have it covered.

manolis wrote:
Fri Nov 29, 2019 5:53 am
I.e. propellers directly driven by the crankshafts is not an unreasonable choice, with obvious advantages (simplicity, robust structure, no need for transmission etc) and drawbacks (propeller’s optimum revs are, typically, lower than engine optimum revs).
Indeed. Many light aircraft operators insist on direct propeller drive - it does deny them the use of high(er) revving engines though. The absence of the weight of reduction gearing affords them a slightly larger engine and torsional (vibration) issues are easier dealt with - or absent.

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

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

Hello Gruntguru.

You write:
“the aerodynamic characteristics of the equipment forming the leading edge (not the wing) in horizontal flight”

In the case of the Portable Flyer the leading edge is the pair of the two OPRE Tilting engines:

Externally this pair is, more or less, a cylinder of ~130mm (~5 inches) diameter and ~0.5m (~20 inches) long.

A cylinder having its axis normal to the air flow is “aerodynamically” as neutral as a sphere.

Thanks
Manolis Pattakos

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

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

Thanks Tok_tokkie,

Initially it was called “Libellula / Portable Flyer” (Libellula is the Dragonfly), as in the following slide:

taken from the “exe” (for windows only) animation, wherefrom the gif animation at the top of the previous page was created.

But the name “Libellula” is widely used, so it was shortened to just “Portable Flyer”.

With its two pairs of ("counter-flapping"?) wings, the dragonfly / libellula is a flight-marvel, especially at hovering and at maneuvers, say, going backwards as in the video:

“wherein it uses its body to place the wings in the optimum orientation to do that”.

Only the colibri (hummingbird) can achieve such hovering quality, but its wing-flapping is too high for their weight (which may explain why it is an “energy-guzzler”).

“Your” video:

lasts 50 minutes and is worth seen it.

Thanks
Manolis Pattakos

J.A.W.
J.A.W.
91
Joined: Mon Sep 01, 2014 4:10 am
Location: Altair IV.

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

Hi Manolis, well done with your advancement to in-metal, with the 2T engine.

Here's a earlier 'personal flier' attempt - which had some of the issues - you have addressed.

http://www.douglas-self.com/MUSEUM/TRAN ... alheli.htm

(Ta coaster, for the site link).
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

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

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

Pinger wrote:
Thu Nov 28, 2019 11:46 am
Manolis - something I've just noticed and apologies if it's been mentioned before. You are driving the props at crank speed. Won't that limit your rpm to what the prop can handle (circa 3000rpm?) and will the engine produce enough power at a low rpm without being constructed larger and thus heavier?
higher 'propellor' (proprotor ?) rpm reduces the required pitch angle
helping reduce difficulties in horizontal flight ?
difficulties/inefficiencies due to the change of blade AoAs from the 'upgoing' and 'downgoing' parts of the rotational cycle

manolis
manolis
97
Joined: Tue Mar 18, 2014 9:00 am

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

Hello J.A.W.

You write:
"Here's a earlier 'personal flier' attempt...http://www.douglas-self.com/MUSEUM/TRAN ... alheli.htm"

Sewing the two wide “legs” of the pants of the guy in your “Internet-Museum” link, a “wingsuit” is formed (as that between Browning’s legs in the video wherein he breaks a world record).

• “The US army was experimenting with one-man helicopters . . . Extensive tests showed that mini-helicopters were almost as expensive to make and maintain as full-sized ones. . .”

By the way,
in the same “Internet-Museum”, at http://www.douglas-self.com/MUSEUM/POWE ... IC.htm#now it writes:
• “Another contemporary concept is the PatRoVa rotary valve. Like the Cross design it balances out the forces acting on the rotating valve.”
I communicated a few times with Douglas Self explaining how wrong his description about the PatRoVa rotary valve is, but he did not listen.

More about the PatRoVa rotary valve: https://www.pattakon.com/pattakonPatRoVa.htm

Thanks
Manolis Pattakos

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

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

Hello Tommy Cookers

You write:
“higher 'propellor' (proprotor ?) rpm reduces the required pitch angle
helping reduce difficulties in horizontal flight ?
difficulties/inefficiencies due to the change of blade AoAs from the 'upgoing' and 'downgoing' parts of the rotational cycle”

For a given horizontal speed,
the higher the leaning of the propeller-disk-plain from horizontal, the smaller the tip speed difference between the “advancing” blade and the “retreating” blade.

The counter-rotating propeller cancels out the moment created by the abovementioned tip-speed difference.

As a transportation means the Portable Flyer will take-off vertically and the soonest possible will turn to high-speed horizontal cruising till the destination wherein it will turn to hovering again, to land.

Therefore what counts is the optimization of the “high-speed-cruising”.

Thanks
Manolis Pattakos

manolis
manolis
97
Joined: Tue Mar 18, 2014 9:00 am

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

Hello all.

In his Internet Museum at http://www.douglas-self.com/MUSEUM/POWE ... alveIC.htm,
Douglas Self* writes:

“The Cross rotary valve: circa 1935

The "reaction bridge" shown in the picture at left absorbs the upward forces on the horizontal valve assembly, and is supposed to have reduced the gas forces on the actual valve. At the moment I'm not quite sure I understand how it worked.”

The “reaction bridge” of Cross “works” as follows:

The top half of the cylinder head is firmly secured to the crankcase by the “bridge” and the two strong pillars, i.e. the top half cylinder head and the crankcase form a rigid body.

The lower half of the cylinder head, together with the cylinder (the piece with the horizontal cooling fins) comprise another rigid body which is free to play for, say, 0.25mm (0.01”) up and down relative to the crankcase (the “spring” seal at the bottom of the cylinder pushes upwards the cylinder and the lower half of the cylinder head) .

The “horizontally” arranged cylindrical rotary valve (the typical Cross rotary valve) abuts, at its top side, on the upper half of the cylinder head.
The body comprising the cylinder and the lower half of the cylinder head abuts on the lower half of the rotary valve.

For as long as the pressure inside the cylinder (above the piston) is small (which happens during the induction cycle, during the exhaust cycle, and during most of the compression cycle, i.e. during some 70% of the total time) the cylinder with the lower half of the cylinder head are pushed upwards by a weak force; the only who prevents the cylinder with the lower half of the cylinder head to move upwards is the lower half of the rotary valve whereon they abut; and the only who supports the rotary valve from not going upwards it the upper half of the cylinder head whereon it abuts.
So, the weak force mentioned passes to the rotary valve, then to the upper half of the cylinder head and, through the pillars, to the crankcase.

During the last part of the compression cycle and during the combustion and expansion cycle, the high pressure in the cylinder translates into a heavy force onto the “cylinder and lower half of the cylinder head”, and another heavy force onto the part of the rotary valve surface whereon the high pressure gas acts through the “window” of the combustion chamber. The sum of these two heavy forces equals to the force the gas applies to the piston top. The rotary valve passes this total force to the upper half of the cylinder head whereon it abuts.

I.e. during the last part of the compression and during the combustion – expansion the rotary valve receives a strong force that deforms / flexes it, and it passes all of it to the upper half of the cylinder head.

But this heavy loading happens only during the, say, 30% of the total time. For the rest 70% of the time the rotary valve runs almost free of loads (no need for heavy preloading).

But even for the 30% during which the rotary valve undergoes strong forces, the lighter the load the engine runs, the lighter the forces on the rotary valve.

This way Cross achieved to reduce the, otherwise, necessary heavy preloading between the rotary valve on its “bearings”, improving the reliability and longevity, and reducing the specific lube consumption.

One side effect is the “side support” of the “free” / “sliding” cylinder in order to receive the thrust loads from the piston and the leaning connecting rod.

Another side effect is the significant increase of the maximum force acting on the rotary valve and its bearings: it equals to the gas pressure times the piston area.
In the conventional Cross rotary design, the force on the rotary valve and its bearings equals to the gas pressure times the “window” area.

Note: the “self-adjusting reaction bridge”, top-right in the image, may be used to reduce the “hammering” from the “oscillating cylinder”.

Quote from my last reply to J.A.W.:

“in the same “Internet-Museum”, at http://www.douglas-self.com/MUSEUM/POWE ... IC.htm#now it writes:
• “Another contemporary concept is the PatRoVa rotary valve. Like the Cross design it balances out the forces acting on the rotating valve.”

End of Quote

While the bearings of the Cross Rotary Valve receive all the gas pressure acting on the piston,
the PatRoVa rotary valve:

runs permanently unloaded as the following quote from https://www.pattakon.com/pattakonPatRoVa.htm explains:

The high pressure inside the cylinder "sees", though the chamber ports, the two fronts and loads them heavily. The rotary valve receives the two strong forces. With the one force counterbalancing the other (through the body of the rotary valve), the overall "pressure" force acting on the rotary valve is from small to zero, leaving its bearings unloaded.

That is, in order to bear the heavy forces applied by the cylinder pressure on its fronts, the PatRoVa "disk rotary valve" needs not the support of a bearing and avoids, this way, both: the inevitable clearance / "play" a bearing introduces and the associated friction / wear.

What the rotary valve does need is a very strong "body" to "connect" the oppositely acting fronts; so strong that the heavy loads applied on the fronts to cause no more than an insignificant deformation of the rotary valve and thereby to keep into the required strict limits the clearance between the chamber ports and the rotary valve fronts (wherein the sealing happens).

Thanks
Manolis Pattakos

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

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

Further to this recent test appraisal of 2T suitability as a race engine, in both skills & costs terms:

https://motocrossactionmag.com/two-vs-f ... ur-stroke/

MotoGP journalist Matt Oxley reports that KTM Motorsports Director Pit Bierer also agrees:

"We want to make cheaper racebikes... we want to try putting 2T engines in this (RC4R/'Moto3')chassis...
this is not only for riders who are trying to make it to the top, it is also for riders who race for fun.
We want to reignite this part of the sport."

Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"