"guys" would have been better

avec ce système de boite à clapets les pertes par pompage dans les hauts régimes sont théoriquement moindres! Quelle belle idée!

Thanks for the reply and sharing so genius ideas with us Frits.
It’s very funny, because before two years I had a bit similar experience with an turbocharged scooter engine. Its got an central rotaryvalve taken from an italsytem (SV31 not100% shure) kart engine,and at the dyno by full throttle the belt popt off,the rotary valve also stopt at the right moment and the engine was taken even more RPM.
But I was thinking all the time it was the turbocharger who did it possible.The funny thing about it is that on page 6 in this topic is a picture from this engine and they think it was never working .:-)

Concerning your idea with the reed valve with one side that moves is as great than simple. I even think it would take no really long time to realize it, but to find the right exhaust chamber design will take some time,or not?. I will try to build such a reed valve and than i will tell you how it works. Thanks for this great idea.

Thats great:-)
i will construct some kind of reed valve and show it next week in this topic.

really nice design Frits and thanks for sharing...
yesterday I was looking at intake mach numbers (flow velocity) on my freshly designed 100cc and noted how the reed valve phase lasts 300° degrees of crank rotation.
in the remaining 60° degrees there is a negative wave travelling through the inlet that shuts the reeds closed.
probably with further intake lenght tuning the intake phase would last slightly less than 360°... then why have a reed valve, that is an obstacle to the flow?

So Frits, nice idea.

Hello ,

very impressive and interesting way of seing things of two stroke. Photos and your knowledge Frits you are my (our with Boogie = Burgard) hero .

@ Boogie pour le système de boite à clapets au niveau emcombrement ça serait idéal sur du piaggio avec les "dentures" vers le cylindre et à l'extérieur pour voir comment agissent les lamelles .étancher le système et voir ce que ça donne en terme de perf.

Juste une question concernant le ressort , ne va t'il pas s'affoler à MI régimes (avant que ceux ci ne restent ouverts à hauts régimes) ? Sont ils supposés être en constante tension ?

Si le deux temps n'a pas vraiment évolué ces dernières années , il semblerait que certaines idées ingénieuses de ce type puissent changer la donne .

En tous cas merci pour les rêves.

Hello @ all,

Here my construction idea :

What do you think about, Frits ?

Hallo Michael,
I see only one hinged reed in your drawing but I get the impression that you are planning to use two reeds, like I did in my original design.
Keep it simple and use only one reed, and shape the duct so that the flow is optimal when the reed is opened.

With todays cheap programmable ignitions this idea could be quite easily driven off a servo or solenoid and be throttle position/rpm dependent. I would look to have a central splitter (to direct flow at the reed tip) incorporated in the design.

Bon marché programmable allumages cette idée pourrait être chassés un servo ou solénoïde et être accélérateur emplacement/rpm contrôlée,très facilement. J'aimerais examiner d'avoir un répartiteur central (à directement à la clappets astuce) sont incorporées dans la conception.

Hello Frits,
thanks again for the information,now i think i can way better imagine the construction you think about.I will show as soon as possible some new drawings.

The part between starting and coming into resonance is utterly unimportant compared to the flow when the engine is running in the power band.
You cannot say that the lowest pressure is under the rising piston; any pressure differences in the crankcase move with the speed of sound (well, not quite but almost, if you consider the laws of gas dynamics). The piston is only moving at about 10% of that speed so any difference that it might cause, is immediately evened out. And anyway, not the piston but the exhaust pipe is doing the major part of the suction.

In theory enclosed cranks are good. Jan Thiel did some experiments at Aprilia with a kart engine that had its reed valve at the front: the incoming mixture had to move against the direction of crank rotation. And although the crankcase stretched over the crank webs, reversing the direction of rotation brought another HP. So the crankshaft does have an influence.
But in practice, if you reduce the distances between crankshaft and crankcase walls to less than 1 mm, the viscous friction of the mixture between the surfaces really costs power at high rpm. And if you make the clearances so tight that lubricating oil can no longer reach the big-end and crankshaft bearings, it will also cost engines
Another negative aspect: any volume with a narrow 'entrance' between the crankshaft and crankcase surfaces acts as an hydraulic damper on the Helmholtz-resonance in the crankcase.
Aprilia has avoided this by making the space between the crank webs as wide as the big-end bearing. As a result the crankcase volume of the 125 cc RSA engine at TDC is about 650 cc, so the exhaust pipe really has some volume to breathe from.
So much for the fairy tale of high crankcase compression

By the way, Jan Thiel also measured the influence of the exhaust pipe on engine power. A good engine produced 52 hp then. Then the pipe was removed, and carburation and ignition were meticulously
re-optimized for the pipe-less engine. Its best power was 17,5 hp...
So you can say that a good exhaust pipe adds 200% extra power to a racing two-stroke :lol:

This is not mathematic!
17,5 + P = 52
Means the pipe without engine produce 34.5 hp...

OK

Nice logic, Marc! OK, the engine produces 52 hp. But if you remove the spark plug, it produces zero hp. So the spark plug alone produces 52 hp? Let's build twin spark engines then! Or triple spark. Or quadruple spark. Or ..... what comes after quadruple ?

you have the right to whip Marc


he likes this

Frits

Hello Fritz, thank you for your participation in this forum. A quick question, have you ever used ceramic bearings on your crankshaft, and what do you think of this application.