Low noise Two stroke?

[Niels Abildgaard]

Shown here is a proposed 24 times 24 mm engine that is different.

[Roger B]

Are you using the poppet valve for the exhaust like the GM two stoke diesels?

[Niels Abildgaard]

Are you using the poppet valve for the exhaust like the GM two stoke diesels?

Most two stroke diesels to day have exhaust valves,but not actuated directly from crank and not as sidevalves.
Pistons are not really good at controling unsymetric exhaust.

[Allen Smithee]

An interesting concept Is it intended to have rear disk/drum valve induction - if so what is the reason for the hollow crankshaft? I'm not sure you'd get away with the short piston at these sizes; it ma need a longer skirt.

My only other thought would be that the exhaust valve looks rather small compared to the sort of size exhaust port you'd typically see on an engine like this.

AS

[Niels Abildgaard]

The hollow crank is a leftover from having normal crankwindov inlet.
Away with that.
The Piston guiding length is around 20 mm compared to 24 mm diameter.No standard car pistons are more I think.
The valve is half bore diameter.
The normal two stroke exhaust port is going down to piston edge at lower dead point mostly to avoid burning.It is the blowdovn area that is important.

[lohring]

You are throwing away a good combustion chamber shape with the flat head design.  It's tough to beat the rapid opening and high flow of piston controlled ports, especially with the high frequency of cam operated valves.  Poppet valve engines have mostly been used on lower speed engines.  The double piston engine has more potential for high power in a uniflow design. 

The sleeve valve two stroke has many of the advantages of a double piston in a single cylinder uniflow design, but was never fully developed.  See http://www.modelenginemaker.com/index.php?topic=4395.0  I wouldn't think a two stroke sleeve valve would be harder to make than a poppet valve with its cam.  The sleeve can be operated with an eccentric on the crankshaft with a link to give the sleeve a rotary and reciprocating motion like the dummy piston on the Crecy.  Ricardo used this mechanism on his single cylinder test engines.  See http://www.amazon.com/High-Speed-Internal-Combustion-Engine/dp/B001TGPTGE/ref=sr_1_1?s=books&ie=UTF8&qid=1420998982&sr=1-1&keywords=ricardo+high+speed+internal+combustion+engine  For a detailed description of the test program that lead to the Crecy.

Lohring Miller

[Niels Abildgaard]

Hello Lohring

Easy, it is just a game and nobody has been robbed yet.
Your arguments about chamber design  is surely Right but are Briggs and Stratton sidevalve engines copies still being made in big numbers?
A two stroke of this kind can maybe be better than B&S SV engines.
Let us compare
Both have 4 bearings
2 for crank and either 2 for camshaft(B&S) or two for balanceshaft.
Two gearwheels .Crank and either cam or balanceshaft two cams and valves versus one of each
Exhaust noise equal as same amount goes through exhaust valves.
If the new can use 1% oil /fuel , real oil pollution will be less.
I was visiting a Chinese homepage that offered two stroke moped cranks for 2$ (and for BMW FS650 for Fifteen.)
If the new one can be lighter and  much less harsh, lawnmover engineers will raise their hands in joy.

[Niels Abildgaard]

Hello Allen and Lohring

If You see a two stroke cylinder as a volume between two restrictions ,inlet and exhaust,it will be obvious that the exhaust shall be smaller than inlet to reach max charge.What the valve does is most likely to make tuned exhaust strategy valueless.It is the very violent blowdown that keep tuned pipes going energywise.It is also the very same violence that makes port exhaust noissy.On the plus side for an exhaust valve is that timing can be unsymetric.
I still think it looks lovely.
Some belgians make sidevalve aircraft engines and claim better fuel consumption than Rotax 912.

http://www.d-motor.eu/nl/fuel-consumption-110.htm

[lohring]

I'm obviously trying to get someone to build a sleeve valve two stroke.  I was inspired by Ricardo's book in the late 1950s.  There have been several model four stroke sleeve valve engines built, a much more difficult problem.  Briggs and Stratton engines are designed for low cost, not high performance.  The flat head Ford V8 is similar.  You can't get  the high compression and large valves that high performance engines need in a flat head.  If you aren't worried by performance, any number of designs will run.

Lohring Miller

[Allen Smithee]

If you aren't worried by performance, any number of designs will run.

...most of them built and sold by Vauxhall

 

AS

[dieselpilot]

Lohring, I've been throwing around the sleeve valve two stroke idea for a while. It would be just for fun though.

[Niels Abildgaard]

Hello Lohring

I have the RR Crecy two stroke sleeve valve book.It could be heard in Lands End when being tested in Derby.
British sleeve valve development was a dead end and probably a rather expensive one.
Nothing that was done by Bristol sleeve valves was not  equalled by normal valves and the napier things where grounded soon after war end.
My two stroke sidevalve proposal can surely have a higher compression ratio than Harleys as there is only one valve.
A belgian 60 kW sidevalve aircraft engine claim 260 gram per kWh and weigh 1 kg per kW.This is on par with the top of the pop Rotax 912 that uses 280 gram.The watercooled Continental that circled the world was more mass but used only 240 at best point.
My sidevalve two stroke is better than your sleevething.

[Niels Abildgaard]

Mass produsable singlesidevalvesingle.
The camcrank is not for amateurs

[Allen Smithee]

Why not?

AS

[lohring]

It's ironic that I'm building an engine of almost exactly your same design.  It's a two stroke, but it is a flash steam engine.  That layout has become almost standard in "modern" flash steam engines.  See http://www.modelenginemaker.com/index.php?topic=2760.0  Here, compression isn't as much of a factor and simplicity is.  Low valve train inertia helps at 10,000 rpm.  A long valve stem is also a plus to seal the 1000+ psi steam.  The piston and materials are much different.

The last big aircraft piston engine designs mostly used sleeve valves, even in the US.  Most were never built and the turbine made them obsolete in any case.  There were a lot of advantages, especially in cylinder wear and combustion chamber design.  The sealing problems were solved, even in air cooled cylinders.  Except in aircraft piston engines, there was never much incentive to explore radical new designs after the 1920s.  All the engines actually used in WW II were 1930s designs at the latest.  Today you get a lot bigger benefits from electronic engine management.  The cost to change engine manufacturing lines is huge.  Some of the push rod V 8 engine designs date from the mid 1950s.

Good luck

Lohringh Miller