[Technique] RossiGRM 2strokes boat engine

Passionnant topic que je n avais pas encore vu !! je ne peux m empecher de penser a Konig , Crescent , Zimmermann en lisant tout ça.

Puisqu' on est sur le pot ( ???) variable ou non, je rappelle aux rois de la rouleuse (de tôle) l' existence d' un petit programme GRATUIT qui m' a bien aidé : Cone Layout. Cherchez le avec Google ou avec votre moteur de recherche préféré.

Je résume : on rentre les diamètres d' entrée et de sortie, les angles, les longueurs et hop ! ça vous sort un développé aux petits oignons.

Après, yapuka reporter le tracé à l' échelle et c' est tout bon !

For correct information: Mr Thiel You was exactly right about my carburetor,without the pin it is impossible use it.I stop any test and go back to standard Dellorto, they are ok.
There are on these pages some info about clearence between main pin and conrod?
I start to have some problem for burned conrod...
Thanks

J'ai cherché en vain le topic où avait été évoquée la Monet-Goyon aux pots haricot.


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Gagnaire qui a construit cette réplique a fait des recherches sur un éventuel brevet concernant ces pots : rien, nada. Et à sa connaissance ce fut un one shot : jamais réutilisés après. D'ailleurs le tube de fuite est d'un diamètre +- égal à la lumière de sortie. Pour la petite histoire ces pots ont été refaits localement par un tôlier-formeur qui en a bien ch*é. Au toucher la finition est superbe !

Je recommande ce musée, à Melle (79) chez Batho/Ségolène : Musée Monet Goyon c'est à côté de la Poste.

Une précision pour Yves K et la sylviculture des ARBRAMOTEUR : Ils poussent aussi là bas :

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Renseignement pris, il a poussé il y a 13 ans pour des raisons de place disponibles dans le salon; et cette variété est motorisée !

Superbe  

J'en remets une couche sur la Monet-Goyon aux pots venus d'ailleurs avec les dessins (de Rebour ?) parus à l'époque :

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Précision : le cylindre a été tourné extérieurement pour diminuer les ailettes du bas; les grandes ailettes du haut de cylindre sont rapportées. Le goujonnage culasse/cylindre renforcé en + gros diam.

Les motos présentées dans ce petit musée sont dans un état remarquable et l'accueil est au top.

Intéressant ce sujet qui ressort de l ' ombre , dommage que RossiGRM ai disparu , le pot a longueur variable sur les hydroplanes a moteur 2 temps est assez ancien , vers le milieu des années 50 selon le témoignage d ' un de ses anciens pilotes.

Question aux spécialistes : de quand date la premiére utilisation de disques rotatifs sur un hydroplane ?

On sait que Dieter Konig les utilisaient déjà vers 1958/59 , mais avant ?..

ROSSIGRM a écrit:

For who likes to do experiment...Winter time is that...carburetor with Dellorto bottom parts, short as possible on the top: on my 500 engine 4 cilynders there are space problem...[Vous devez être inscrit et connecté pour voir cette image]" />

Hello everyone!!
Sorry I am so late to the thread. I am new to the forum, and am certainly grateful for the "intellectual capital" that Marc has gifted us here.

Mr Rossi, I see your carburettor idea and I wanted to offer you pictures of my own space saving modifications to a Mikuni TM34SS:
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Main jet extension. A soldered-over main jet is used as the nut. The idle jet gets a similar extension but is a simple tube.
And where are the floats?......
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Mikuni pump-around fuel pump is used. It is a delivery + scavenge system, like a 'dry sump' oil system. Fuel enters where the inlet is, but needle valve and floats have been removed.
Excess fuel is scavenged away by the brass fitting to the right. This sets the 'float height'
The uppermost brass fitting is for a large diameter breather pipe. You get a lot of bubbles in the scavenge line and any bowl pressure/vaccuum now affects 'float height'.
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Here is the double membrane pump used. The system is becoming popular in Karting and other high g-force applications. But use it to create a downdraft carburettor from a conventional carburettor.

Wow! it seems we have a new high level technician on board  

What about spending a few extra minutes to introduce yourself Nick?
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English will be fine of course  

Jarno a écrit:

What about spending a few extra minutes to introduce yourself Nick?

Hi Jarno. You are too kind. I have just posted a VERY brief intro on the Presentation page, and I will add some cool photos soon. Thank you for showing me the étiquette - it is a very good idea!

People laugh when they see this carburettor. Because it shocks them. Instead of saying "wow, what is going on there - tell me about it" they just laugh. It is a very strange world we live in where new ideas are terrifying. Keep them coming please !

I built this Vespa engine years ago for a competition. I just wanted to beat all the 'bolt-on-parts' guys. If I knew then what I know now from this forum, it would not look like this!

I'm pretty sure this carburettor has already triggered interest from PitLaners...
Feel free to post more pics abour your racing Vespa  

nick gill a écrit:

It is a very strange world we live in where new ideas are terrifying.

I'm afraid it has always been like that, Nick, and I am even more afraid it won't change any time soon. Just when people think they have finally understood something, you come and take away their 'certainties'. You are pushing them into a sort of midlife crisis! You should be grateful that you don't get burned at the stake because of your witchcraft .

Hi Frits,
While I have your attention, I want to talk about Pulse Jets and your 24/7 valve. Should I PM you? or ask here?

nick gill a écrit:

Hi Frits,
While I have your attention, I want to talk about Pulse Jets and your 24/7 valve. Should I PM you? or ask here?

I blocked forum-PMs to save my life, so we will have to do it here, Nick.

Let us consider the 24/7 reed valve you have proposed:
So when a 24/7 valve is operating in it's specified range, about peak power, then given that the entire system is resonating, interrupted only by the piston to detonate and extract some work, is it not otherwise considered a pulse jet at this point?
If so, then might we find we are tuning the port timing to keep combustion in the cylinder and not allow it to drift into the chamber. May this combustion location become the operating limit of such a system perhaps?
- Given your love of model aircraft and two stroke gas dynamics, I'd be shocked if pulse jets aren't your hidden talent

Also, years ago I read about a man injecting a little water spray into the expansion chambers of his NSR250. He talked about the steam altering the pressure in the chamber, and therefore the resonance, but maybe the drop in temperature was a more likely a factor? I never could picture it clearly. Could this be worth trialing for these hydroplanes?

When the engine is operating in the powerband, the 24/7 reed valve has disappeared - well, it is still there, but out of the way of the inlet flow. So I would not formulate it as 'a 24/7 valve operating in it's specified range' but rather as 'a 24/7 inlet system operating... etc.'
If you would take the piston out of the equasion, then it would be a proper pulse jet. But the piston does a couple of things. It compresses the fresh charge, making it easier for the spark to ignite it. It makes for intermittent combustion, allowing higher peak temperatures without the engine melting, it governs the system's frequency and it drives the crankshaft.

If you mean combustion confined to the cylinder forms the operating limit, I tend to say no. A true pulse jet will have a certain resonating frequency that may be slightly influenced by mixture strength, but I think it will be impossible to synchronize it with a piston thus that there will be positive pressure during its downstroke, if that piston is not governing the combustion frequency.

Using the pulse jet to generate exhaust gas driving a turbine would be a lot simpler, but its efficiency would be mediocre. That is why free-piston engines are employed to generate exhaust gas: because of their intermittent compression and combustion their efficiency can be a lot better than that of a pulse jet.

Water injection into exhaust pipes in order to lower the exhaust gas temperature and thus the system's resonating frequency has been tried over and over. It works, but it does nothing to protect the engine from detonation.
Therefore I wanted to inject water into the combustion chamber, exchanging temperature for steam pressure. I even had a water reservoir designed around the exhaust tail pipe in order to heat the water to just below its boiling point before it was injected.
I also tried to hit the piston crown with the injected water but a steam cushion would form, preventing most of the water from wetting the piston crown. Breaking through that steam cushion would require a huge (for that era) pressure and a very thin water jet, or the engine would drown. I could not get it realized back then (in 1992, when I was working for Rumi) so there are no test bench data.

Talking about hidden talent: I once told a friend about pulse jets. He immediately wanted to build one, so I prepared some drawings and lent him a 34 mm Mikuni carb. It worked, but he was not prepared for the two meter long flame - he almost burned his shed down. And the noise was incredible  - lovely!

First of all,THANKS to everyone for the shared knowledge about motors.
My question is this:
What can be the minimum distance from the centerline of the wrist pin to the top edge of the piston 54
Why some pistons are 28 mm and Aprilia is 24 mm ?? Has anyone tested 21 mm ??
Sorry if this subject has been already discussed on the forum
Thanks in advance for the help

ROSSIGRM a écrit:

What can be the minimum distance from the centerline of the wrist pin to the top edge of the piston ?

I think the minimum distance will be limited by the temperature of the wrist pin bearing, Giuseppe. The nearer it is to the underside of the piston crown, the hotter it will get.
Apart from this temperature issue, it will be a good idea to put the wrist pin as high as possible. The bulk of the piston mass is above the pin, so the higher the pin, the lighter the piston.

Thanks Mr. Overmars, I have made some test with the 21mm with a long rod and have seen some evidience of wear on exhaust port at top and on intake boost port at top and bottom.
The standard piston with 28mm and a short rod not have this type of wear.
Thanks again

Big pleasure: someone can indicate any information on this Forum about transfer channel?
which one is better: 130° or 140°??
Thanks a lot for help

ROSSIGRM a écrit:

Big pleasure: someone can indicate any information on this Forum about transfer channel?
which one is better: 130° or 140°?? Thanks a lot for help

130°. We haven't heard from you for a long time Giuseppe. Have you been building something nice?

Thanks Mr Overmars, the only work has been on carburetor for have quick setting during free practise, adjustable main jet save time. Next photo is our carburetor 40 mm , still testing, but it give more trouble for a good setting...
We done a new cilynder...copy of the Aprilia

We would like to see the rest of the bike...

By the way, don't you think about injection ?