[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked)

Daniel A. a écrit:

Hello.

I've got a little question to brokedown, Ian Harrison, Dave Pearce and all the others who might have experiences with it.

Could you please tell me something about the durability of Devcon Aluminium Putty when used in transfer / exhaust ports? (several years?)

Thanks. Regards.

well im certainly no expert with epoxy. but at my house i have devcon F and green stucco that jan has mentioned before but i havent used either one yet. but in the last few days i have prepared a cylinder with green stucco in the trans ports but it may be several weeks before i can run the engine. you can have a look at the photos. i think it will hold up well. the data sheet says it works good for gasoline and jet fuel and methanol and its not brittle when cured so i think that might be good also.  
[Vous devez être inscrit et connecté pour voir ce lien]

hey ian or frits or someone else with experience maybe you can comment on my cylinder photos and say if theres something i should do different, i know alot of you guys dont like T style ports and i dont either but it was sitting around the garage so i wanted to make it run better. besides i have several other cylinders with aux exh ports to work on when im done with this one. i have tried to use logical thinking with the whole project  . i only increased the blowdown area and left the lower portion of exh small.  

original specs
exh 78% bore
exh timing 180*
trans timing 124*
A port 15* upward
B port 25* upward
C port 62* upward

modified specs
exh 95% bore
exh timing 200*
trans timing 130*
A port 20* upward, and width was increased a couple mm forward
B port 12* upward, and width was increased 2mm rearward, and green epoxy putty added
C port 62* upward

[quote="Jan Thiel"]

lodgernz a écrit:

Manuel Rainer a écrit:

Hi
One question to the RSW Disc Valve


and have you ever tried to cut the closing part of the disc like in the photo? the timing is the same but der is a improvemend of opening area

thanks Manuel

I tried this in 1970, but it did not give any advantage.

Thanks Jan

In the PDF from Aprilia called "Tracciatura e taglio valvola rotante" there is how to cut and set the disc valve of the RSW. the timings (Opens: 142,5 before T.D.C. Closes: 88 after T.D.C) are different then the (Opens: 146 before T.D.C. Closes: 93 after T.D.C) from RSA.
are this only old informations, or where they always differend settings? and why?


Thanks Manuel

hi guys. does any of you have a link where i can buy good diamond bits to cut through nikisil ? all mine is carbide and i think it will just chip the plating. starting a new project soon.   

Hi, for diamond burrs give a look at ccspecialtytool.

Does anyone know where to buy a bellmouth like this?
[Vous devez être inscrit et connecté pour voir cette image]

Those ones were made by FPE, so you could try asking them... but it was machined from a solid bar of plastic, so probably not cheap.

Hello GrahamB:
Do you have a e-mail address or contact info for FBE? Thank you.

P, not B... as in Francis Payart Engineering. Francis is on pitlane as FPayart, you should be able to find one of his contributions to this thread to send him a PM

Thank you both GrahamB and Marc. I sent him a PM thru this site.
Jeff

Hello,
As said Graham, the bellmouth used on our carburetor is our own design and is made ​​in small batches, for this reason the price can probably look very expensive: 65.00 Euros.
The attachment is intended to our carburetor, centering Ø 63 mm.

brokedown a écrit:

hi guys. does any of you have a link where i can buy good diamond bits to cut through nikisil ? all mine is carbide and i think it will just chip the plating. starting a new project soon.    

I usually cut the plating out of the area I'm porting with diamond impregnated bits, and then go back after I'm safely through the plating with a carbide bit.  I layout the parts I want to cut with layout fluid and scribe lines where cutting.  I don't get too close to the line until the final stages of the job though.  I ordered a lot of my tools from [Vous devez être inscrit et connecté pour voir ce lien] - the same place that Filandro suggests.

I hope this helps!

Cheers,

~Josh

do you do a final pass with abrasive stone on the plating or is the diamond bits sufficient ?

fpayart:
Thank you very much for your response. Yes the 65 euro is alot but the dia of 63mm is wrong for me.
I'll have to make my own.
Jeff

My little APx cylinder collection.

From left to right: APB, APC, APC newest generation, APE and finally APF
[Vous devez être inscrit et connecté pour voir cette image]

Mic a écrit:

My little APx cylinder collection.

From left to right: APB, APC, APC newest generation, APE and finally APF
[Vous devez être inscrit et connecté pour voir cette image]

Like!!!

Hello Mic:
Would you describe the differences between the different cylinders other then what we can see?
Thank you.
Jeff

jfn2 a écrit:

Hello Mic:
Would you describe the differences between the different cylinders other then what we can see?
Thank you.
Jeff

Yes, that would be great!  

I read with great interest about the transfer ports shaping a coloum of air that moves up the centre of the cylinder and you try to shape it run uo the back wall. That all makes sense but how do you do that.
Do you angle the c port down low to push the base of the coloum across towards the exhaust trying to topple it over ?
Every thing I could think off with the a and b ports wasgoing to push it towards the exhaust port.
I can understand that the coloum will start where you aim the transfer ports but I cant understand how you lean it back.
having the coloum start closer to the c port instead of the exhaust does this change the characteristics of the engine at all. Is one way better for high rpm than the other.

Thank you

Wax, did you take a look here? [Vous devez être inscrit et connecté pour voir ce lien]

Jan you mentioned that the thinnest ring you had known of was 0.4mm thick, what size bore was this used in ?

RAW a écrit:

Jan you mentioned that the thinnest ring you had known of was 0.4mm thick, what size bore was this used in ?

It was used in a Kreidler with a 40mm bore.

Yes frits I did,
Either I couldnt understand or it wasnt there about how to make the coloum lean back. And I was not sure on what length down the centre line of the piston was better for top end versus low end power

Ok I just re readit and made more sense of it regarding the tower of pisa,

The b-ports are left flat and push out colide and head up the bore axialy. The a ports angled at 20 degrees push the coloum to the back wall to stop it short circuiting out the exhaust port.
You then go on to say "Then we will also see that short-stroke engines require smaller axial angles."
Im struggling to understand that as to why they need a smaller axial angles.

How do you determine the best radial angles for a certain power delivery.
Thanks for answering my questions I really am trying to get my head around this

wax a écrit:

....You then go on to say "Then we will also see that short-stroke engines require smaller axial angles." Im struggling to understand that as to why they need a smaller axial angles.

Let's assume that we want to aim the flow from an A-port at the opposite cylinder wall at a height halfway between BDC and TDC. That means: if we shorten the stroke, the axial angle of that port must be made smaller.

Citation :

How do you determine the best radial angles for a certain power delivery.

I think that the optimum radial layout is rather constant, irrespective of the kind of power that you want and also irrespective of the cylinder capacity. The picture below shows what I have in mind.
But there may be practical problems and the main problem will probably be that the leading flanks of the A-ports cannot be aimed backward nice and straight because of the cylinder layout (stud positions, coolant cavities).
This may force you to apply a twist in the A-duct and a bevel at the exhaust side of the port roof, which will weaken the kinetic energy of the flow.

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