Side-valved Two strokes for angels.

Discussion in '2-Stroke Aircaft Engines' started by Niels, Aug 18, 2019.

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  1. Aug 21, 2019 #21

    Niels

    Niels

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    Time- area is a way to control that wanted charge velocity is not going near to sonic somewhere.
    If Harley could get 40 horsepower past an exhaust valve of ca 40mm so can we.
    My concept needs that pistons are same mass but not diameter.
    The two exhaust valves and inlet porting belts can have different sizes and timings.
     
  2. Aug 21, 2019 #22

    pictsidhe

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    Charge and exhaust velocity need to be at certain levels to get good BMEP. 2 strokes just don't work well away fron those values. 4 strokes can get away with smaller valves for a smaller penalty as the piston pumps the charge in and out.
    You will have no problem with the transfer ports, the exhaust will be the limiting factor on your long stroke design. You'll need to run some numbers.
     
  3. Aug 21, 2019 #23

    Sockmonkey

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    You're gonna want forked connecting rods so you don't get that annoying rocking motion two-cylinder boxers have.
    [​IMG]
    Pretty much all V-twins use them.
     
  4. Aug 21, 2019 #24

    pictsidhe

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    Most Harleys, not most v twins by a long shot
     
  5. Aug 21, 2019 #25

    Sockmonkey

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    Why the heck wouldn't they?
     
  6. Aug 21, 2019 #26

    Niels

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    My phantasy engine use crankcase for charge pumping as do all desent two strokes.
    That means caged rollers between hard crankpins and rods.
    All V cylindered two stroke outboards do it by having cracked-parted connecting rods and a one piece crank
    Harleys had undivided conrods and made crank up from parts screwed together.
    For sizing of components we can do worse than study Yamahas V6 HPDI 250 outboard.
    Two of its 93mm bore cylinders make 83 horsepower at 5000 rpm and strokes 82 mm at a pme of 7 bar.
    They evidently have exhaust ports big enough to pass 40 horsepower per cylinder.
    If I double their stroke and run 2400 rpm they do what I want:ca 40 horsepower at 2400 rpm from a 92mm piston.
    From memory the crankpin diameter is 40mm and width of a conrod assembly is 20mm.
    If I chose 50mm diameter and 16mm width , this will be double as longlived as the Yamaha because I only run half as fast.
    Rigth or wrong I prefer undivided conrods and built up cranks.
    So be it.
    Single throw two stroke cranks are mostly made by pressing parts together.
    Cheap,heavy and also act as flywheel.
    Especially on Harleys.
    We do not need flywheel in a ungeared aeroengine.
    The propeller has lots of inertia.
    I will try to scheme the possibilityes tomorrow.
     
  7. Aug 21, 2019 #27

    pictsidhe

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    Their designers probably decided that it's not worth the hassle.
     
  8. Aug 21, 2019 #28

    pictsidhe

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    The outboard v engines have a seperate crankcase volume for each cylinder. Unless you copy that, you will have an unbalanced engine. A v-twin combined crankcase will also pump a low volume
     
  9. Aug 22, 2019 #29

    Niels

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    Last edited: Aug 22, 2019
  10. Aug 22, 2019 #30

    Niels

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    A 90 degree common crank V2 will pump half of what the present Yamaha arrangement does,that is twenty hp per cylinder or more than enough to get it started and feeding the turbo.
     
  11. Aug 23, 2019 #31

    Niels

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    The Hirth solution cannot not be easy to make.
    Picture shows five different solutions and the pink parts needs to be carburized and hardened in parts or total surface.
    If You wanted to make a fortune small by using a big to make V2 twostrokes and had the choise?
     
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  12. Aug 23, 2019 #32

    Sockmonkey

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  13. Aug 24, 2019 #33

    pictsidhe

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    Niels. A direct geared centrifugal supercharger would work for starting and running. You could then use a 4 stroke type bottom end. With turbo scavenging, an electric fan would work for starting. I think the crankcase pumping is the big flaw in your concept.
     
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  14. Aug 25, 2019 #34

    Niels

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    The Argus As10 inverted V8 engine from 1934 was120mm bore and 140mm stroke.

    My SV inverted V2 two stroke will have 100mm bore and 150mm stroke and run at MEP of 6.2 bar to make 80 hp at 40 rps and be built with comression ratio of 7,5 to 1 allow use of oktane 92 petrol.

    (The Belgian SV Dmotor has 100 mm pistons as well and tolerate 92 oktane in 8 to 1 compression at MEP 10 bar.)

    It is possible to make a better combustion chamber with only a single side exhaust valve with than both inlet and exhaust side by side.

    I therefore think that Maximun pressure in my V2 running compression ratio 7,5 and MEP 6.2 will be somewhat lower than the Comp 5,9 times MEP 8,5 from the old Argus. 7,5*6.2=46,5 (Angelina) and 5,9* 8,5= 50.2(Argus)
    The Argus was/is 15.2 kg/litre so my 2,4 litre Angelina can be surely be 37 kg dry and probably less.

    The argument for my original 92mm pistons was to reduce knock incidence and with present day 95 oktane it seems not a problem.100mm pistons make clearance between conrod and liner more easy.

    The Dmotor is sold with Compressio 8 and Mep of 10.2 and is 21.5 kg per litre giving some sense of credibility to the other estimates.
     
    Last edited: Aug 25, 2019
  15. Aug 25, 2019 #35

    pictsidhe

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  16. Aug 25, 2019 #36

    pictsidhe

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    Something along the lines of the May Fireball combustion chamber could be worth looking at. Probably not that extreme, but an assymetric passage to the combustion chamber may help. With a sidevalve, new heads are easy to make...
     
  17. Aug 27, 2019 #37

    Niels

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    It is not easy to make a nice looking design for side-valves actuated direct from crankshaft,and maybe not nessecary.

    40 horsepower per human is a good number for flying.
    A bore stroke ratio of 1.5 from 12m/sec piston speed looks about right.

    Noise is very dependent on tip speed and that make following sizes desirable
    Hp Bore/stroke RPM MEP in Hp ,mm and bar

    40 80/120 3000 5
    80 100/150 2400 6.5
    160 120/180 2000 6
     
    Last edited: Aug 27, 2019
  18. Aug 27, 2019 #38

    Niels

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    Next step is to make a comparison seen from front with a VW half,A Rotax and a Lycoming O320.
    If it can be within the envelope with overhead valve(s) it is maybe worth some phantasy.
     
  19. Aug 27, 2019 #39

    Niels

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    A dimensional sketch
    The horizontal line from cylinder corner to cylinder corner will be 425mm for the 40 hp version
    If You superimpose on an aircraft or another engine please let us see.
    425 mm corner to corner gives 40 hp.
    540mm gives 80 and 640 makes 160 hp
     
  20. Aug 28, 2019 #40

    AJLiberatore

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    Neils,

    I think you are not alone w/ the concept of a side valve for a 2 stroke. It has been in my head now for years, and I bet others here as well. I can't say who, but I have ran this by some engine types, one was no, 2 strokes are dead, the other ya It's been in head, I want to try it. Another a 2 stroke guy couldn't make a case for it via the flow in the head. Research University of Alabama if my memory is correct, a number of students for their graduation added DI to a flathead, and even patented it. 2 exhaust valves and a centrifugal supercharger blowing through the uniflow ports is what I envisioned, for a flat four. Trying it first on a Briggs & Stratton with making both valves the same size, modifying the cam and both valves are exhaust. IMHO maybe there is a case for some sort of stratified charge in the head depending on FI or DI timing. Eon's ago if my memory is correct, there was a flat 2 @ OSH that might have been essentially a Bourke Scottish Yoke 2 stroke w/ flat head valves (a Reed Valve below the Carb for the Crankscase IMMIC). It was smooth as silk, I put my hand on it while it was running on it's stand (with a flywheel) it was like nothing you'd ever experienced. They showed up one year and then gone.

    Good Luck sir!
    My best,
    Anthony
     
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