[Technique] RossiGRM 2strokes boat engine

Marc..how does one post pictures?

Here are the explainations, but in french...

[Vous devez être inscrit et connecté pour voir ce lien]

Frits Overmars a écrit:

But I would take great care in making sure that there are no leaks at the joints.

I remember a french dealer of moped parts named RGDiffusion made a variable length exhaust and the two parts were sealed as follow:

[Vous devez être inscrit et connecté pour voir cette image]

An other way to fight the leaks is the graphite braided packing but you will need a "presse-étoupe" (I don't know the english word) to compensate the wear of the packing.

[Vous devez être inscrit et connecté pour voir cette image]


PS: thank you all for sharing your knowledge

I have included pictures of our rotary valve motor and the 24/7 cylinder. My good friend Bruce Nicholson does all the machine work.

Sorry to disturb you, guys, but now, i am very curious to learn more about Mr Rossi's work...

[Vous devez être inscrit et connecté pour voir cette image]

Any link?

Marc...go to [Vous devez être inscrit et connecté pour voir ce lien]

Dtenney a écrit:

For those of you that do not know Giusseppe, he is a boat racing legend and many time world champion and is truly a wondeful person.

For those of us who can use a lesson in modesty now and then (and that certainly includes me)..... Respect, Giuseppe!

Dtenney a écrit:

And because of the Forum we are building a 24/7 cylinder...that was an eye opener. I will try to post pictures.

It feels great to see those pictures, Dtenney. But you have got two names mixed up. Your pictures show the FOS-cylinder with symmetric scavenging. The name 24/7 refers to the opening hours (24 hours a day, seven days a week) of an other idea I had: an induction control that acts as a reed valve when the engine has to be started, but swings out of the way when the engine runs in the power band and the exhaust suction takes care of the scavenging.
You'll find a picture + info about the 24/7 here: [Vous devez être inscrit et connecté pour voir ce lien]

gau a écrit:

Apropos sliding pipes:
In Uk a lambretta's tuner named Kegra made a pneumatic system for change pipe length in his speed record lambretta, he called his system KPS.... I don't have informations about what kind of "logic" he used in this system, probably a pressure valve on the handlebars...

[Vous devez être inscrit et connecté pour voir cette image]
With this pneumatic activation I suppose the pipe is either long or short, without the possibility of intermediate lengths.
Giuseppes intended approach with a windshield wiper-motor probably offers better control.
It also makes a difference whether you slide the initial small-diameter part of the pipe, or the belly.
Lengthening the small-diameter part not only lengthens the path for the resonance waves, but also lowers the Helmholtz frequency more effectively than lengthening the belly.
And I like the simple sealing in Maneton's pictures. I like simplicity anyway; that is why I like two-strokes .

Frits...thanks for the correction. My mind hit the rev limiter!

Dtenney a écrit:

I have included pictures of our rotary valve motor and the 24/7 FOS-cylinder. My good friend Bruce Nicholson does all the machine work.

Here are some pictures to keep Bruce busy 8):
[Vous devez être inscrit et connecté pour voir cette image]

thank you Frits

Dtenney a écrit:

On the race course we run with wide open throttle all the time and control speed by varying the length of the pipe.

And beacuse of the Forum we are building a 24/7 cylinder...that was an eye opener. I will try to post pictures.

WOT with a 24/7, controlling speed with the exhaust pipes, that seems quite unbelivable at first glance. Dtenney & Rossi i'll bet you're opening interested eyes.

and

onboard camera to test grm 250
visual....... carburetor.........
[Vous devez être inscrit et connecté pour voir ce lien]

And why not an intake pipe length varying according to engine speed and throttle opening? I am currently working on this project.

Impressionnant. je ne savais même pas que ça existe le drag boat..
et j'ai l'impression que ces types sont encore plus fou que les motards....



sur ce moteur , on voit que la lumiere d'échappement est tres basse par rapport au PMH . quels sont les diagrammes utilisé sur ce genre de moteur ??

In fact all should be variable ,
the exhaust system lenght , the intake lenght , the squish of course the ignition point , + the 24/7 inlet (F.O.S )etc...
In order to obtain a great result one life would not be enought isn't it ?A good software and hours and hours on dyno.
Far from being the best forum i ever seen , thanks once again To Marc.

Good night and nices dreams to all 2 strokes lovers.

Frits Overmars a écrit:

Giuseppes intended approach with a windshield wiper-motor probably offers better control.
It also makes a difference whether you slide the initial small-diameter part of the pipe, or the belly.
Lengthening the small-diameter part not only lengthens the path for the resonance waves, but also lowers the Helmholtz frequency more effectively than lengthening the belly.

Thank you for your explanation Frits.

Frits Overmars a écrit:

And I like the simple sealing in Maneton's pictures. I like simplicity anyway; that is why I like two-strokes .

We are using a copy of Aprilia cylinder, sure not the last one... I modified the exaust many times, to find a good compromise between bottom torque and top rpm...
With my dyno,it is a home made water brake effect,(the design is from KONIG ) , the power of the 125 is 38 hp at 10000 rpm goig up to 46 at 13500. I understand that the bike engine are a lot better in hp , but this is the best wich we have.
The 250 2 cylinder is with one crankcase volume togheter: always the bottom cyl is more rich than the top one. We use different main jet size for reduce the problem.
In next week a Aprilia pipe will be ready for a test on my 125...[img][Vous devez être inscrit et connecté pour voir cette image][/img]
[img][Vous devez être inscrit et connecté pour voir cette image][/img]

Could you show the design of your exhaust colar