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 [2 stroke] A better two stroke?

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AuteurMessage
Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: [2 stroke] A better two stroke?   Ven 6 Mar - 18:38

My MZ251 has been sold due to age.
I still dream of being the worlds best motorbike engine designer but have come down a little in size and scope.
Picture shows a concept study for a 24 *24 mm model aircraft engine with a single exhaust crank activated valve and a  counterrotating first order mass balance shaft.


[url=



Before You scream and ask me to leave this noble place my question is:

Is it absolutely impossible that a tuned exhaust pipe can work with an exhaust valve or only impossible?
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JanBros



Nombre de messages : 218
Localisation : Belgique
Date d'inscription : 05/12/2011

MessageSujet: Re: [2 stroke] A better two stroke?   Ven 6 Mar - 19:56

what will you use to scavenge ?
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Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: Re: [2 stroke] A better two stroke?   Ven 6 Mar - 20:02

For model aircraft engine the hollow crankshaft as shown is normal.
For a MZ erzats I think a membrane will be OK.
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JanBros



Nombre de messages : 218
Localisation : Belgique
Date d'inscription : 05/12/2011

MessageSujet: Re: [2 stroke] A better two stroke?   Sam 7 Mar - 21:33

but you are using the principles of 2-stroke diesels, and they need a blower to drive out the exhaust gases and fill the cylinder with fresh air/mixture.
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Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: Re: [2 stroke] A better two stroke?   Dim 8 Mar - 7:50

JanBros a écrit:
but you are using the principles of 2-stroke diesels, and they need a blower to drive out the exhaust gases and fill the cylinder with fresh air/mixture.

No I am not.
There was never a sidevalve two stroke diesel and there has been a lot of valveless ,crankcase scavenged,blowerless two stroke diesels made.
Slavia 1D90 TA is one and looks like a moped enginged doubled in all directions.
As two stroke racing is more or less dead,it is interesting to speculate why cubic displacement was used to determine racing classes.A modern racing two stroke somehow looks ridicuolus:You can hardly see the cylinder and the exhaust pipe is enormeous.
Cost of engine or mass would have been much more interesting and the racing just the same.
The sidevalve two stroke shown can be more compact than a normal 50 ccm due to lower piston length and fuel waste less due to bigger distance between transfer ports and exhaust.Biggest advantage is that I am inventor and apart from my dog nobody teels me what a genius I am.
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JanBros



Nombre de messages : 218
Localisation : Belgique
Date d'inscription : 05/12/2011

MessageSujet: Re: [2 stroke] A better two stroke?   Dim 8 Mar - 10:50

Niels Abildgaard a écrit:
JanBros a écrit:
but you are using the principles of 2-stroke diesels, and they need a blower to drive out the exhaust gases and fill the cylinder with fresh air/mixture.

No I am not.

you are correct in that there are crankcase scavenged 2-stroke diesels, but they have a cylinder-layout just like our beloved petrol 2-strokes : transfer and exhaust ports in BDC.

the 1D90TA cylinder :

http://www.nd-traktory.cz/1748-valec-holy-1d90ta.html



but you are using an exhaust valve in TDC, and without forced scavenging, you're engine simply will not run.
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Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: Re: [2 stroke] A better two stroke?   Dim 8 Mar - 15:18

You are wrong.
There is no difference if exhaust goes through a hole in the cylinderwall or a hole in top.
The first is covered by piston two third of the time and the hole i top is blocked by valve more or less the same time period.Valve stand heat and deformation better than aluminium piston.
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JanBros



Nombre de messages : 218
Localisation : Belgique
Date d'inscription : 05/12/2011

MessageSujet: Re: [2 stroke] A better two stroke?   Dim 8 Mar - 22:53

well, maybe it will run (barely). but you are not dreaming , you are having a nightmare

Citation :
I still dream of being the worlds best motorbike engine designer

lol! Wink
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JohnnyBurden



Nombre de messages : 1
Localisation : USA
Date d'inscription : 06/10/2015

MessageSujet: Re: [2 stroke] A better two stroke?   Mar 6 Oct - 4:36

Niels,
Are you still working on this design?  A tuned exhaust certainly will work with a poppet valve; the big question is how well it will work.  Poppet valves open and close so slowly compared to cylinder ports that I suspect the pressure signal delivered to and returned from the pipe will be very attenuated and thus much less effective than in a cylinder port arrangement.  Would be interesting to see it working!
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Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: Re: [2 stroke] A better two stroke?   Mar 20 Oct - 6:48

Hello Johnny and thank You for asking.I had lost interest but it comes back now in waves.
The scheme with a counterrotating balance shaft was never really the thing so I now opt for a V2 with a single common crankcase


 

https://i.imgur.com/kgeUWsJ.jpg
I have balancemodified an Ogar crank with two Vespa conrods and found some weedhacker pistons

https://i.imgur.com/U7ipN2S.jpg

The collaboration between a tuned pipe and highest possible acceleration exhaust valve in a two stroke is another question.This will be tested on a normal (sligthly modified) single cylinder two stroke and will be my next poject
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Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: Testing phantasies   Dim 8 Nov - 19:22

Have just celebrated my 70 year birthday,so will have to get going fast if  I am to make better two strokes.
There are two roads:

Compare simple,sv,ohv and ohc (without exhaust pipe and with.)8 combinations at 6000 rpm.
For this I will use a very cheap and very good engine.
I have had one and it ran first try.

http://fr.agmhobby.com/item/37hp-moteur-a-deux-temps-agm-30cc-moteur-a-essence-davion-p-127.html

When I have found the combination ,I like best, it is time to be serious and that is a 90 degree V2 with common crankcase.

As You can se from picture I have nearly everything needed for making a V2 crankshaft and if i spoil something, parts are very cheap.
The conrod pin can be made from a moped 12 mm piston pin.
https://i.imgur.com/ANSBe0X.jpg

https://i.imgur.com/hgCmLcg.jpg

Kind regards
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Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: Phantasy   Jeu 19 Nov - 13:55

Please find a two stroke proposal that can make chaisaw and mopeds less noissy and dirty (I think)



https://i.imgur.com/Iz3tD97.jpg

Kind regards

Niels
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Niels Abildgaard



Nombre de messages : 34
Localisation : Denmark
Date d'inscription : 26/02/2013

MessageSujet: Re: [2 stroke] A better two stroke?   Mar 19 Jan - 14:55

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xestv2



Nombre de messages : 2
Localisation : Barcelona
Date d'inscription : 10/08/2016

MessageSujet: Re: [2 stroke] A better two stroke?   Ven 12 Aoû - 23:19

My purpose is to forget carbs and start using direct injection, if we want cleaner 2stroke engines. next step, lubrication.
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