[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5)

Bien sûr, je considère que le vilo tourne à vitesse constante, que les accélérations positive et négative sont égales, ce qui n'est pas prouvé , mais les temps sont tellement petits : de 0 à 90° c'est 1/2000ème de sec. et aussi que ces accélérations sont continues, ce qui n'est pas rigoureusement exact ( angle de la bielle, longueur de celle -ci inconnue., position angulaire...etc). Ce qui me donne une valeur moyenne, un ordre d'idée réaliste. Je parts d'une vitesse linéaire max de piston de 90m/s pour une vitesse moyenne de 54m/s ( course 54mmx2 par tour et 30000 rpm; 500 r/s). aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 980796

aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 980796

Dan

Nombre de messages : 27 Localisation : nancy Date d'inscription : 25/06/2014

Je cite Frits OVERMARS

" Port timing - not important "

and blowdown, as a consequence, neither ??

Nombre de messages : 12 Localisation : Hellas Date d'inscription : 02/03/2014

Frits,
you've said that lower comp ratio 'feeds' exhaust pipe with more energetic pulses,thus bigger suction-scavenging.
Did Jan try a low full stroke cr,like 10:1?
I think some dozens of pages ago you said you're testing a 9:1 cr engine..who did it work?
Should I prefer a low cr in an engine with good flow and a well-working pipe?

No, at Aprilia we used 1:16 on the dyno.
Sometimes lower ratios were used on track, depending on the atmospheric pressure.
But never lower than 1:15

To your question: No

Lef16 a écrit:: I think some dozens of pages ago you said you're testing a 9:1 cr engine..who did it work?

The 9:1 won German 50 cc championships in 2014 and 2015, with a 110 kg rider, so it's not doing too bad Wink

.

Nombre de messages : 57 Localisation : DFW,Texas Date d'inscription : 15/11/2013

What's with all the rioting farmers in Brussels ?

Looks like they've got their race faces on....

That's a LOT of tractors blocking the fast line !

Nombre de messages : 362 Localisation : Belgique Date d'inscription : 05/12/2011

ambike a écrit:: What's with all the rioting farmers in Brussels ?

Looks like they've got their race faces on....

That's a LOT of tractors blocking the fast line !

they don't get enough paid for their milk and pork-meat in order to continue racing tractors aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 809516

aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 809516

Hello everyone

While we hope the secrets of the Ryger Engine could be revealed and we imagine their innovations ...
I have a question, if not has been treated before, there are many pages.

At the time of make the cylinder cast, through what system you get a cast of better quality.
With mold made of sand?
Or with steel shell mold?

It seems obvious that a prototype is cheaper sand mold.
And for long series the shell mold is cheaper.
But as to the quality of the cylinder?

And going further, what is the best aluminum alloy for the cylinder?

What systems have been used for casting GP cylinders?

Again, thanks a lot to Jan, Frits and others for share their knowledge.

Regards

I just let you know that Ambike has been banished for an indefinite while...

aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 324787

aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 324787

_________________
Un p'tit clik vaut mieux qu'une grande claque; c'est Harry qui l'a dit! [Vous devez être inscrit et connecté pour voir cette image]

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Sand casting gives the best quality in my opinion.
And we had our castings 'hipped' to eliminate any porosity.
Steel molds have a tendency to produce very porous castings.
The material we used was GAlSi9

Thank you very much. aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 101130

Nombre de messages : 56 Localisation : Austria Date d'inscription : 02/03/2014

Frits, it's been a long time but I do would like to come back on this one.

Frits Overmars a écrit:: It takes only very little fouling to create a conductive path over the insulator of a surface gap plug, and once that happens, the electrons can migrate without even having to create a spark. I tend to agree with Bob:

The thing with these plugs is that the sparks run along the insulator and burn off the carbon deposit every time the ignition sparks. This way they prevent that from happening.

That is also why they are used in 2stroke boat engines. They are also used in F1 but this is for space saving and reliability.
Jacobs' book also provides the dyno results for surface discharge plugs against normal plugs and this proves that they only improve horsepower when the ignition system is down on power.

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

Can someone please tell me how to remove an unwanted message that I wrote?
Thanks,

Bob

Nombre de messages : 956 Localisation : France Date d'inscription : 02/04/2015

You go to the message you want to remove, you click on "Edit" (upper right corner of your message), you erase the text of your message, you click on "envoyer". It's done.

Microstructure is finest with gravity die casting. It's the reason why mechanical properties are better with gravity die casting than sand casting. Lot of very stressed parts are manufactured with gravity die casting: it's the best casting process to do that.

Sand casting is OK to performed very large or complexe pieces. If highest mechanical property is needed, steel parts are added to the pattern and the mold to improve the coolig rate and reduce localy the microstructure size.

HIP is useful in case of little porosity or shrinkage. If the casting is OK, no improvment due to HIP.
If the defect is too large, or exposed to air (oxyd), the hip has no effect.

aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) 771973

When you say "gravity die casting", is it a gravity casting + application of pressure, or injection molding ?

I spoke about casting without pressure.
You can apply low pressure (around 1b) in sand or gravity die casting. It doesn't change a lot.
Then we spoke about low pressure die casting. The most common application is wheel.
When you apply high pressure (around 1000b), it's high pressure die casting. Useful for high volume production : gear box housing, engine block...
The mechanical property are too bad because of oxides. During pouring, aluminium is sprayed and squeezed in the mold. it's a mixture of air, aluminium and oxides.
It's the reason why parts are very difficult to weld and heat treated.

Nombre de messages : 56 Localisation : Austria Date d'inscription : 02/03/2014

Jan, Frits,
What is actually the difference between late APC cylindes and APE cylinders of the same year?
I see the differences on the outside (different cylinderhead,...) but what about ducts/ports?

The ducts and ports were exactly the same.
The APE was only made to make a quicker removal of the head possible.
To make it easier to take a look at the piston.

Nombre de messages : 56 Localisation : Austria Date d'inscription : 02/03/2014

Thanks a lot Jan!

Nombre de messages : 12 Localisation : Hellas Date d'inscription : 02/03/2014

Jan,
from what material was the crankshaft made?

Some kind of cromium-nickel steel I suppose.
It was not something that was of my competence.

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

[quote="Jan Thiel"]Some kind of cromium-nickel steel I suppose.

Typical crankshaft materials : 15CrNi6 and 16CrMn5.

I suppose: the crankpin in case hardening matérial treated for 62 Hrc ( surface hardness), and the webs and shafts will be good in 35CrMo4 treated for 1000/1100 Mpa.
Dan

Nombre de messages : 38 Localisation : valencia Date d'inscription : 03/03/2015

you think of this? rotary valve system for exhaust. With this system, which is able to close the outlet of gas entering cool.
I want to do, but I think someone before I would have thought the same, there is something? somebody has tried?

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