ESE's works engine tuner

[wobbly]

The reason there might be no "real " flow till the Aux open is because the mains roof timing is way too low, ie they are virtually the same .
Thus a large amount of Hp bandwidth is lost , as stagger , where the main port is higher - gives rise to a much more intense amplitude wave front exiting into the duct, increasing both leftward and rightward wave action.

As it stands , due to the huge disparity in Blowdown path lengths the initial wave front will be reduced in amplitude and also severely smeared out in time.
In a conventional 3 port, if all are opened concurrently , big power losses occur on both sides of peak.
This shows the inherent limitations of using flowbench data to drive development strategy.
Edit - this is why the Aux are square , as the flowbench ( and the designer ) knows nothing about upward short circuiting from the A port.

[Flettner]

A useful thing just turned up. Heat treating at home.

[Niels Abildgaard]

UK postal service dream of serving remote locations with drones that can move 100 kg 1000km.
Their first versions are driven by Briggs and Stratton Vanguard twin 38 cui lawn mover engines and we all can think of better ways.
UK Flying Post Angels will need plus 200 engines per year if these can be low mass,reliable and frugal.

[URL="https://www.dieselprogress.com/news/Vanguard-powered-UAVs-bring-aid-from-above/8013169.article"]

An inverted single cylinder two stroke direct drive with exhaust valves as a Honda Cub (More than 100 millions made)
will be better for making 30 horsepower at 60 rps.
76 mm bore and stroke 112mm.



More words and maybe a working link can be seen here

https://www.homebuiltairplanes.com/f...p.36052/page-5


https://drive.google.com/drive/folde...XM_g0HQ9pOxbmv

https://windracers.org/

[Niels Abildgaard]

A know it all ESE user can do valuable deeds for humanity etc.
Tuned exhaust pipes as we know them does a good job of converting blowdown kinetic energy to suck and blow back.
The blowback is not needed in this aero aplication as a MEP of 7.5 bar will do and exhaust closing timing is done by camshaft.
How long aproximately shall pipe be?



My beloved MZ301 had a pipe of ca 1.2m length and came on at cirka 50 rps (3000rpm)

[andreas]

Seems like you are talking about a two stroke uniflow, to my knowledge the honda cub engine is not one of those. How long a diffuser only, pipe shold be? Of course all the usual input: rpm, ex open etc is required.

[Niels Abildgaard]

Seems like you are talking about a two stroke uniflow, to my knowledge the honda cub engine is not one of those. How long a diffuser only, pipe shold be? Of course all the usual input: rpm, ex open etc is required.

Different wording for another fellow scandinavian

"with a cylinder head like a Honda Cub with two exhaust valves "

I really have not the faintest idea of best timing and asume that a clever guy with a good programe can optimize timing and pipe simultaineously

Input parameters are ca 76 mm bore,112mm stroke, 30 horsepower and 60 rps.

[andreas]

Ok, I understand now. Someone probably could do that, just prepare for a less than significant increase in power, because the poppet valves don't give nearly as high wave amplitude as an ex port, and there is only the expansion wave doing work.

[Niels Abildgaard]

Ok, I understand now. Someone probably could do that, just prepare for a less than significant increase in power, because the poppet valves don't give nearly as high wave amplitude as an ex port, and there is only the expansion wave doing work.

The holy and perfect Aprilia was once run without any pipe and inlet resonater etc by Jan Thiel and it gave an Mep of 6 bar.
We need 7.5 and has much better trapping due to longstroke uniflow.
Pipe are not asked to make miracles

[andreas]

I like the altruistic agenda, and it doesn't seem unrealistic for it to work.

[Flettner]

Haha, popet valves are for toilets.

[Niels Abildgaard]

I like the altruistic agenda, and it doesn't seem unrealistic for it to work.

Two counterrotating ,synchronized single cylinder engines give cargo and airframe an easy ride as torque reactions cancel.
When one engine quits it is not a disaster,but slower mail.

[ceci]

UK postal service dream of serving remote locations with drones that can move 100 kg 1000km.

They are already working, and more than 100 Kg, I am not sure but I think I have seen some, since their fuselage is different from that of light aircraft (the double rudder is not usually common in common light aircraft)

https://dronedj.com/2021/07/14/franc...ansport-drugs/

https://english.elpais.com/spain/202...m-morocco.html

[peewee]

guys let me ask something about the divider between main exh and secondary on a cylinder with iron liner. 1mm wide should be fine i think but what about .75mm. the liner is thick so it should be strong enough just to keep the ring in the groove. it might wear down faster but i dont care

[wobbly]

Depends how close to 70% the main port is.
At this width the ring absolutely does bulge out into the port , and the bridges are heavily point loaded when pushing the ring back into the groove.
Having an oil hole drilled thru the piston directly over the bridge will help , just as it does for T port bridge wear issues.

[peewee]

its slightly under 70% if i recall. i may put a bit of arc on the roof to be safe. when i was punching the new windows into the liner i fucked up and grinded the secondaries closer to the main than i wanted. to some what match the liner to the main its going to leave a thin divider of 1mm or so