2 stroke thread (with occasional F1 relevance!)

[Rodak]

I must be stupid, but what is that video showing? Rotary valves are certainly not new........ and (sorry for the racing content) banned by F1.

[manolis]

Hello Gruntguru

"Amazing" video, indeed.
They wanted to show something, but then they decided to not show it.


The following "rotary valve article / story" is from the page 151 of this thread.

Quote from https://markwalkermotorcycles.com/ :



Mark Walker:

“In the early 90’s I was travelling back from a Canberra Drag race and pulled into Bundanoon, I met a bloke in the bar, and he asked me what I had in the trailer, I said “My drag bike, a home built 2lt V-Twin” and he was very interested in my work and he happened to mention he was into Hot Rods and he said he had an unusual head at home, he said it had a cylinder in it, rotating and no valves, and I nearly dropped my coffee on the floor because at the time, I was building my own wooden models to build my own rotary valves,

so as you can imagine I was so keen to look at what this piece was,

so I followed him back to this old falling down weather board cottage, the house was chock with car parts and all around the yard and he directed me down to this old shed and he got up on an oil drum and lifted down this head wrapped in a blanket and he unfolded the blanket.

I wasn’t imagining much, but I went wobbly as it was a genuine Dunstan Rotary Valve, made in Melbourne by Dunstan himself, stamped no 29.

This changed my whole concept of cylinder heads, it was a cast aluminium head, water-cooled with a beautifully cast iron rotor cylinder down through the centre of it with slots both sides for the ports and floating bronze seals.


Since that awakening I have learn’t alot about David Dunstan and his heads.

The type of head I am using on Big Ned is a Roland Cross design valve, he started his work in the early 20’s in England.



2 Great Pioneers : Roland Cross and Aspen which you can research yourself.


I have spent my life working on, modifying and building Poppet Valve engines and then converted over to a new religion… “Rotary Valves”. When you realise the advantages of a Rotary Valve over a Poppet Valve are staggering…. They are an addiction.”



PS.
Still waiting for a reply on the stability of the Portable Flyer as compared to the Gen H-4.

Thanks
Manolis Pattakos

[Tommy Cookers]

it seems the Gen H-4 hasn't been higher than 30'

the Wright Flyer was unstable in pitch and also didn't go above c.30'
this for years ? after the supposedly definitive first flights in 1903

[manolis]

Hello Tommy Cookers.

You write:
"it seems the Gen H-4 hasn't been higher than 30'
the Wright Flyer was unstable in pitch and also didn't go above c.30'
this for years ? after the supposedly definitive first flights in 1903"


The Gen H-4 is restricted to fly below 10m in the flying tests in Japan (this is their law).

Flying at 10m height in an open area, the ground effect on the Gen H-4 is negligible.

When the Gen H-4 flies at 10m height and when it flies at 1,000m height, where the difference in stability / controllability comes from?

What I say is that the excellent stability / controllability of the Gen H-4 as shown in this video (from 0:14 to 0:18 and from 1:02 to 1:15):



remains the same either at 10m, or at 1,000m (provided there is no wind).


By the way,
the famous Osprey V22 (of Bell / BOEING) was initially unstable (dangerous at over-corrections).



A lot of electronics were added to make it stable / safe.

Thanks
Manolis Pattakos

[Brake Horse Power]

I must be stupid, but what is that video showing? Rotary valves are certainly not new........ and (sorry for the racing content) banned by F1.

It shows a 2-stroke, with conventional porting in the wall with a rotary exhaust valve. The crankcase doesn't need a fuel oil mix, I'm not sure how they lube the small and big-end and how the mixture flows. It's also equipped with a supercharger. This company is pretty serious about it if you just look at the quality of the parts. It's running on the testbench now so it's not a render.

I think the whole combination of parts and working on a 'clean' two stroke is pretty unique. There is some more on their website and social media but I'm to lazy to copy paste everything here.

[coaster]

I grew up near where the Dunstan rotary valve was conceived, Melbournes south east was thriving with manufacturing in the 1980's as there were 4 car manfufacturers at the time all getting their tooling made locally.
The Dunstan head predates 1990 by a long way, early 1960's, it was designed to fit the Holden grey motor which was similar to other GM motors of the 1950's. It ended up in a racing boat, maybe in a private collection now.

Pat Symonds hoped for a 2 stroke revival, so do I, his ideas followed Orbital engine companies ideas of direct injection with lubrication isolated from combustion.

Ralph Sarich held the patents in the 80's for direct injection 2 stroke, but it was underdeveloped and no auto maker took his patents.

Gosh, I would dearly love motorcyle manufacturers to bring back 2 strokes with direct injection, so much fun, you have not lived until you have riden a 2 stroke road bike, big fun.

(I did my apprenticeship for a guy who had a prototype of Sarichs orbital gathering dust, kept from unpaid bills. The 'orbital' was essentially a hydraulic vane pump with peripheral ports and spark plug, simple idea. That prototype is long lost to time now)

[NathanE]

The h4 controllability appears totally different from what I understand the pf design to use. It looks like there is a ball joint between the motor/rotor unit and the seat. This is significantly higher than the cog of the lower body (seat and pilot). The handlebars are rigidly mounted to the motor/rotor. The distance between pivot and lower cog is probably 4 to 5 x the distance between the pivot and col giving substantial leverage to control inputs. Like a hang glider this allows for relative motion at small displacement angles to be used as control inputs.

The h4 lift, including in forward motion comes from the very large rotors which like a helicopter remain in a largely horizontal aspect with a very low ratio of horizontal rotor thrust to lift (please don't post a picture of airwolf doing acrobatics it's not relevant to the point). This means the angle of incidence of the pilot remains roughly vertical throughout maintaining the ability to make control inputs. It's not clear if the rotors have a swash plate arrangement and gearboxes to vary relative rotor speed that could also be critical control mechanisms.

It's not impossible for you to design aspects like these into the pf, but I still don't believe you will find it easy with your current design to transition from full on superman horizontal flight to stationary, unless maybe you make the rotors go into reverse thrust? - now that would be fun to watch!

[manolis]

Hello NathanE

You write:
“The h4 . . . The distance between pivot and lower cog is probably 4 to 5 x the distance between the pivot and col giving substantial leverage to control inputs.”


If by “col” you mean “center of lift”:


In the Gen H-4 there is no “col” (center of lift).
What there is, is an axis of lift (aol?), or thrust axis, which is the axis about which the two contra-rotating rotors spin.
The control of the Gen H-4 is pure “weight displacement control” and is realized by displacing the axis of lift (“aol”) relative to the center of gravity (alternatively, you can think of it as displacing the center of gravity relative to the axis of lift).

In simple words, the pilot controls the flight by revectoring the thrust (as in a rocket wherein the flight is controlled by revectoring the thrust).

This is what the “Rocket Pendulum Fallacy” says and explains (page 192). Try to get it.


The Portable Flyer has also an axis of lift (aol) and its control is either “weight displacement control” (as in the Gen H-4 above), or “aerodynamic control” (wherein the limbs head of the pilot – being in the high speed air stream – are used as ailerons) or both.



Thanks
Manolis Pattakos

[nzjrs]

God damn it don't encourage his pendulum rocket fallacy fallacy bollocks.

I was hoping that this thread might stay on engines for a while while manolis was off doing some modeling of the controllabilty of the pf, similar to the h4 stability, modeling and controllability paper I posted.

[coaster]

Relax NZ, this thread has been off topic for a really long time.

[manolis]

Hello NathanE, again.

Here is an old Flying Platform:



Oppositely to the Gen H-4, the lift in the Flying Platform is generated substantially below the center of gravity.

Similarly to the Gen H-4, the axis of lift (aol, in my last post) in the Flying Platform is displaceable around the center of gravity, giving instinctive "weight displacement" control.


A kind of Flying Platform is the Zapata Flying_Board_Air:



with the lift well below the center of gravity.

Thanks
Manolis Pattakos

[coaster]

Those are shrouded propellors with the weight shift above, yours is opposite to this arrangement.
I might buy this machine for my wife,
https://www.amazon.com/dp/B00LEWUTBS?ot ... c|[ch|[lt|
It has steel blades spinning fast and reduces vegetables to a puree, but I'm getting off topic now.

[NathanE]

God damn it don't encourage his pendulum rocket fallacy fallacy bollocks.

I was hoping that this thread might stay on engines for a while while manolis was off doing some modeling of the controllabilty of the pf, similar to the h4 stability, modeling and controllability paper I posted.

sorry messed up again, I couldn't help myself.

[NathanE]

Hello NathanE, again.

Here is an old Flying Platform:

http://www.airvectors.net/avplatfm_02.jpg

Oppositely to the Gen H-4, the lift in the Flying Platform is generated substantially below the center of gravity.

Similarly to the Gen H-4, the axis of lift (aol, in my last post) in the Flying Platform is displaceable around the center of gravity, giving instinctive "weight displacement" control.


A kind of Flying Platform is the Zapata Flying_Board_Air:

https://steemitimages.com/640x0/https:/ ... zqruu.jpeg

with the lift well below the center of gravity.

Thanks
Manolis Pattakos

Manolis, I love the pictures. None of them address the issues I raised which have nothing to do with the pendulum fallacy.

Like I said before I love the engine work you are doing, but I think your PF test flight video is going to be hilarious to watch. Please, please make sure you incorporate a quick release for the flyer and a parachute in your design.

[tok-tokkie]

It's not clear if the rotors have a swash plate arrangement and gearboxes to vary relative rotor speed that could also be critical control mechanisms.

The H4 has 4 engines. Two per rotor. Yaw is achieved by slowing the one rotor slightly relative to the other. As seen in the video it gives very controlled yaw. The simple way to do it would be separate twist grips for the throttles of each pair of motors but it is not apparent how it is done from the video. The problem would be synchronising the rotor speeds before lift-off with such a system.