[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked)

Nombre de messages : 39 Localisation : Australia Date d'inscription : 31/10/2012

Jan Thiel a écrit:

Manuel Rainer a écrit:

Jan Thiel a écrit:

Howard Gifford a écrit:: It is no secret what to use. DuPont makes a product called Vespel SP. I have used it and it works quite well at temperatures up to 500 degrees F and yes sir it is super expensive. SP-22 is the material of choice for pin plugs in that it has a thermal expansion rate that is identical to that of cast aluminum.
[Vous devez être inscrit et connecté pour voir ce lien]

Howard,

Are your plugs reliable?
Those made in Holland were not 100%.
I think they are not used anymore.
And most important: have you ever tested the difference they make on HP?
And where in te powercurve?
In Holland this was not done, so I am still curious!
And at 120$ apiece, so 240$ a piston, the plugs are too expensive
The welded piston pins made by Pankl in Austria were cheaper!
And 100% reliable.

hello

has some one tried to close the pin wit an aluminium rod?

I was thinking to press the aluminum rod into the pin and may set with loctite 648. after then work one it with the lathe.
can that work?

Manuel[left]

Yes, we tried that, and it worked.
First the pin was honed on the inside, and a piece of aluminium was pressed in.
The pin expanded a bit through the pressing-in.
So we fitted smaller needles.
Then it worked quite well, but it was a bit heavy.
We also tried magnesium, but that worked loose.
Then welding the pin was tried, that was lighter.
But sometimes there were reliability problems, the welded-on caps came loose.
This caused massive engine failure.
Finally we had our pins made by Pankl in Austria.
These were 100% reliable.

Hi,

I thought about the aluminium inside the pin.

How about shortening the pin by approximately 4mm. Then machining two aluminium caps 2mm thick and fitting those either side of the pin inside the clips?

Depending on how much the pin sits into the piston you may even be able to shorten the pin more for greater weight reduction.

What you think the minimum length the pin would have to fit into the piston in a GP engine.

Michael

michaelten a écrit:

Jan Thiel a écrit:

Manuel Rainer a écrit:

Jan Thiel a écrit:

Howard Gifford a écrit:: It is no secret what to use. DuPont makes a product called Vespel SP. I have used it and it works quite well at temperatures up to 500 degrees F and yes sir it is super expensive. SP-22 is the material of choice for pin plugs in that it has a thermal expansion rate that is identical to that of cast aluminum.
[Vous devez être inscrit et connecté pour voir ce lien]

Howard,

Are your plugs reliable?
Those made in Holland were not 100%.
I think they are not used anymore.
And most important: have you ever tested the difference they make on HP?
And where in te powercurve?
In Holland this was not done, so I am still curious!
And at 120$ apiece, so 240$ a piston, the plugs are too expensive
The welded piston pins made by Pankl in Austria were cheaper!
And 100% reliable.

hello

has some one tried to close the pin wit an aluminium rod?

I was thinking to press the aluminum rod into the pin and may set with loctite 648. after then work one it with the lathe.
can that work?

Manuel[left]

Yes, we tried that, and it worked.
First the pin was honed on the inside, and a piece of aluminium was pressed in.
The pin expanded a bit through the pressing-in.
So we fitted smaller needles.
Then it worked quite well, but it was a bit heavy.
We also tried magnesium, but that worked loose.
Then welding the pin was tried, that was lighter.
But sometimes there were reliability problems, the welded-on caps came loose.
This caused massive engine failure.
Finally we had our pins made by Pankl in Austria.
These were 100% reliable.

Hi,

I thought about the aluminium inside the pin.

How about shortening the pin by approximately 4mm. Then machining two aluminium caps 2mm thick and fitting those either side of the pin inside the clips?

Depending on how much the pin sits into the piston you may even be able to shorten the pin more for greater weight reduction.

What you think the minimum length the pin would have to fit into the piston in a GP engine.

Michael

This was also tried.
The aluminium caps quickly came loose inside the piston.

Nombre de messages : 39 Localisation : Australia Date d'inscription : 31/10/2012

Ok, scrap that idea!

I thought the pin rotating may chew out the back side of the disc.

It seems there is nothing that you haven't tried! lol!

michaelten a écrit:: Ok, scrap that idea!

I thought the pin rotating may chew out the back side of the disc.

It seems there is nothing that you haven't tried!

That was my job!

Nombre de messages : 39 Localisation : Australia Date d'inscription : 31/10/2012

Jan,

I have been looking for information about using unleaded fuel.

Information I am finding is saying that using unleaded the size of the silencer is important.

What did you find about silencer sizes when developing the RSA?

Thank you

Michael

michaelten a écrit:: Jan,

I have been looking for information about using unleaded fuel.

Information I am finding is saying that using unleaded the size of the silencer is important.

What did you find about silencer sizes when developing the RSA?

Thank you

Michael

We used the same silencers as before with unleaded fuel.
Only the 'restrictor' size went up by 0,25mm

Nombre de messages : 39 Localisation : Australia Date d'inscription : 31/10/2012

Thank you very much Jan.

It's fantastic to be able to ask questions to yourself and Frits

I appreciate it.

Michael

Howard Gifford a écrit:: Jan I will let you know how they stand up in a race situation. They seem quite good on the dyno but we do not do sustained runs on the dyno so I will find out shortly . I havent seen any big gains on the dyno either but with our auxillary exhaust communicatinbg with the transfewrs at tdc you would think that they can only help.
I tried machining two pieces out of aluminum that were bolted together by an allen screw. They had a locator pin and were curved on the belt sander to match the profile of the piston. They worked well also but they were heavier than I liked. The Vespel plugs weigh 4 grams each so weight is not a concern. I just wish I could give them a proper test on the track before I determine weather they are worth the bother.
Yes the cost is silly for the material and they are difficult to hold properly to machine so Im hoping they will become unnecessary. Especially since Frits promised to come to Canada to wring out some more «hp out of my motor.
BTW Frits the porsche actually belongs to my wife and she says it`s not for sale.

Hi Howard, I tried alluminium ones like you described back in 1999 on a rotax 250 single and allthough seemed good on the dyno they were rather unfreindly to the cylinder on the track. Especially when they came loose.
1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 584741

1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 584741

great stuff from Jan and Frits 1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 241515

1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 241515

Nombre de messages : 10 Localisation : italie Date d'inscription : 14/03/2012

Hi Howard, I tried alluminium ones like you described back in 1999 on a rotax 250 single and allthough seemed good on the dyno they were rather unfreindly to the cylinder on the track. Especially when they came loose.
1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 584741

great stuff from Jan and Frits 1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 241515

[/quote]

think you could use a system like that used in moto guzzi in the 60's on their gp? cap that worked even when stationary piston having beaten the piston and were placed inside the piston pin with interference .. sorry my bad English ettoiffi

Nombre de messages : 6 Localisation : usa Date d'inscription : 14/09/2012

Jan Thiel a écrit:

michaelten a écrit:

Jan Thiel a écrit:

Manuel Rainer a écrit:

Jan Thiel a écrit:

Howard Gifford a écrit:: It is no secret what to use. DuPont makes a product called Vespel SP. I have used it and it works quite well at temperatures up to 500 degrees F and yes sir it is super expensive. SP-22 is the material of choice for pin plugs in that it has a thermal expansion rate that is identical to that of cast aluminum.
[Vous devez être inscrit et connecté pour voir ce lien]

Howard,

Are your plugs reliable?
Those made in Holland were not 100%.
I think they are not used anymore.
And most important: have you ever tested the difference they make on HP?
And where in te powercurve?
In Holland this was not done, so I am still curious!
And at 120$ apiece, so 240$ a piston, the plugs are too expensive
The welded piston pins made by Pankl in Austria were cheaper!
And 100% reliable.

hello

has some one tried to close the pin wit an aluminium rod?

I was thinking to press the aluminum rod into the pin and may set with loctite 648. after then work one it with the lathe.
can that work?

Manuel[left]

Yes, we tried that, and it worked.
First the pin was honed on the inside, and a piece of aluminium was pressed in.
The pin expanded a bit through the pressing-in.
So we fitted smaller needles.
Then it worked quite well, but it was a bit heavy.
We also tried magnesium, but that worked loose.
Then welding the pin was tried, that was lighter.
But sometimes there were reliability problems, the welded-on caps came loose.
This caused massive engine failure.
Finally we had our pins made by Pankl in Austria.
These were 100% reliable.

Hi,

I thought about the aluminium inside the pin.

How about shortening the pin by approximately 4mm. Then machining two aluminium caps 2mm thick and fitting those either side of the pin inside the clips?

Depending on how much the pin sits into the piston you may even be able to shorten the pin more for greater weight reduction.

What you think the minimum length the pin would have to fit into the piston in a GP engine.

Michael

This was also tried.
The aluminium caps quickly came loose inside the piston.

Yes they do. Had alum in there for 2 months, or so Ithought. Took top end off and one was gone. I will never know how it did not cause major damage or how it made its way to the export.

Nombre de messages : 15 Localisation : Melbourne Date d'inscription : 22/12/2012

A quick question Frits and Jan,

I do hope this is not repeating a question asked previously in the threads but I do not recall it being asked.

Whilst I've been designing the scaled up RSA cylinder, I've had people asking why I'm not using a 7 (transfer) port layout because 'apparently' they work better on larger bore motors than the 5 port layout.

My response has so far been that if the 5 port was most effective on the RSA, and my motor has the same bore/stroke ratio, then the 5 port will also be the most effective for my application.
I also state that perhaps the 7 port cylinders are more suited to large bore, short stroke motors such as those found in the aftermarket RZ350/banshee cylindere etc.

So I suppose my questions are:
-Why was the 5 transfer port layout chosen for the RSA over the 7 port?
-Will the same rules apply to my cylinder if the bore/stroke ratio is the same?
-under what conditions to the 7 ports become preferable?

Jeram a écrit:: Why was the 5 transfer port layout chosen for the RSA over the 7 port?

Every divider between two ducts acts as a heat exchanger: the mixture passing along them is heated by the heat in the metal. So what you would really want, is one large transfer port on each side of the cylinder. But then the ports would become too wide for the piston ring. And the directional stability of the transfer streams would suffer. Five ports is the best compromise.

Citation :: Will the same rules apply to my cylinder if the bore/stroke ratio is the same?

Yes.

Citation :: under what conditions do the 7 ports become preferable?

When the shape of the transfer ducts is inadequate for good directional flow stability, like in engines where the cylinder bores are too close together (overbored RD350/Banshee).

Nombre de messages : 15 Localisation : Melbourne Date d'inscription : 22/12/2012

Frits Overmars a écrit:

Jeram a écrit:: Why was the 5 transfer port layout chosen for the RSA over the 7 port?

Every divider between two ducts acts as a heat exchanger: the mixture passing along them is heated by the heat in the metal. So what you would really want, is one large transfer port on each side of the cylinder. But then the ports would become too wide for the piston ring. And the directional stability of the transfer streams would suffer. Five ports is the best compromise.

Citation :: Will the same rules apply to my cylinder if the bore/stroke ratio is the same?

Yes.

Citation :: under what conditions do the 7 ports become preferable?

When the shape of the transfer ducts is inadequate for good directional flow stability, like in engines where the cylinder bores are too close together (overbored RD350/Banshee).

Thanks Frits for your response, that answers all of my concerns and will make casting the cylinder much easier as we already have the permanent tooling to sand cast a 5-port 80x80mm cylinder, I just need to alter the transfer and exhaust ducts as per RSA.

As for the single transfer concept. If you can find an elegant solution for the directional stability of the transfer flows I will trial using rings with a high ferrous content and embed some electro magnets into the cylinder bore to replace the dividers by exerting a force on the piston rings as the approach the top of the transfer port windows.
Sadly I doubt it is that simple.

Thanks again

Jeram a écrit:: If you can find an elegant solution for the directional stability of the transfer flows I will trial using rings with a high ferrous content and embed some electro magnets into the cylinder bore to replace the dividers by exerting a force on the piston rings as the approach the top of the transfer port windows.

How about fitting a steel piston and using the magnets to pull it up and down, Jeram?
Then you can forget about the directional stability of the transfer.
(and you can start worrying about a very long extension cable) 1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 809516

1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 809516

Nombre de messages : 5 Localisation : UK Date d'inscription : 02/01/2013

Frits

If heat transfer from duct walls etc is a concern is there any value in coating ducts and cases in an insulator?

Nombre de messages : 6 Localisation : Italy Date d'inscription : 09/03/2012

Jan Thiel a écrit:

t0nix a écrit:: any of you know the diameter of rad shafts RSA?

Do you think for a motor 47x47, 5 with a shaft diameter of 62mm and width of 31mm, how could it be?

What do you mean by 'rad shafts'?

I mean the diameter of the crankshaft.

I 'm planing a crankshaft for engine 47x47,5. according the proportions with the crankshaft of the Aprilia Rsa( wich should be approximately 105mm) that my new crankshaft will have a diamter of the 62mm and a width of 32mm.

Do you think is correct?

Nombre de messages : 15 Localisation : Melbourne Date d'inscription : 22/12/2012

Frits Overmars a écrit:

Jeram a écrit:: If you can find an elegant solution for the directional stability of the transfer flows I will trial using rings with a high ferrous content and embed some electro magnets into the cylinder bore to replace the dividers by exerting a force on the piston rings as the approach the top of the transfer port windows.

How about fitting a steel piston and using the magnets to pull it up and down, Jeram?
Then you can forget about the directional stability of the transfer.
(and you can start worrying about a very long extension cable) 1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 809516

haha it was just an idea Wink

mj43 a écrit:: If heat transfer from duct walls etc is a concern is there any value in coating ducts and cases in an insulator?

Yes, very much so. Most surfaces that are in contact with fresh mixture should be coated. Many people also think that coating the piston crown, the inside of the combustion chamber and the inside of the exhaust duct is a good idea, but it is not. An insulating coating there will pick up combustion heat, store it (because it is not carried off to the underlying metal) and then put this heat back into the fresh mixture, provoking detonation.

The picture below shows a coated crankcase. This coating ([Vous devez être inscrit et connecté pour voir ce lien] can simply be applied with a brush and its insulating quality is amazing: a piece of aluminium sheet covered with it can be held directly above a flame and the upper side never gets too hot to touch.
[Vous devez être inscrit et connecté pour voir cette image]

Hi, I have a lil bit different problem with designing than you guys, I want to make a 230cc motor that will be used as trial engine (loads of torque at low rpm about 3000 to 4500 rpm). Bore is 71mm and stroke is 59,5mm carb 26-28mm (this cannot be changed because it's a vintage engine), I have a problem with finding a suitable portmap, I was thinking about old trial engines like Bultaco or Ossa and copy thier layout of ports because I can afford all information about them (port map , duration of ports ect), maybe You could help me with this . And I have a dilemma about expansion chamber angles , I have no idea how to start with it , I have never done this kind of low rpm tuning before, they should be all mild like 3,5 then 5 and the reverse cone 8 degrees ? Any help is appreciated :) Regards Dawid.

Sorry Dawid, I have no experience with trial engines.

Nombre de messages : 15 Localisation : Melbourne Date d'inscription : 22/12/2012

Frits Overmars a écrit:

mj43 a écrit:: If heat transfer from duct walls etc is a concern is there any value in coating ducts and cases in an insulator?

Yes, very much so. Most surfaces that are in contact with fresh mixture should be coated. Many people also think that coating the piston crown, the inside of the combustion chamber and the inside of the exhaust duct is a good idea, but it is not. An insulating coating there will pick up combustion heat, store it (because it is not carried off to the underlying metal) and then put this heat back into the fresh mixture, provoking detonation.

The picture below shows a coated crankcase. This coating ([Vous devez être inscrit et connecté pour voir ce lien] can simply be applied with a brush and its insulating quality is amazing: a piece of aluminium sheet covered with it can be held directly above a flame and the upper side never gets too hot to touch.
[Vous devez être inscrit et connecté pour voir cette image]

Very interesting, if memory serves me correct that was originally Russian home insulation paint!

Another question Frits, with the benefits of graphite pistons in two strokes demonstrated by Honda in the final years of 250 racing, was it ever considered feasible to use these on the aprilia?

Jeram a écrit:: with the benefits of graphite pistons in two strokes demonstrated by Honda in the final years of 250 racing, was it ever considered feasible to use these on the aprilia?

What graphite pistons? Did you see them? Did anyone see them?

Pistons with a bisulphide coating . . . . perhaps?? I never saw them. 1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 55116

1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 55116

Ian

Jan Thiel a écrit:

Howard Gifford a écrit:: It is no secret what to use. DuPont makes a product called Vespel SP. I have used it and it works quite well at temperatures up to 500 degrees F and yes sir it is super expensive. SP-22 is the material of choice for pin plugs in that it has a thermal expansion rate that is identical to that of cast aluminum.
[Vous devez être inscrit et connecté pour voir ce lien]

Howard,

Are your plugs reliable?
Those made in Holland were not 100%.
I think they are not used anymore.
And most important: have you ever tested the difference they make on HP?
And where in te powercurve?
In Holland this was not done, so I am still curious!
And at 120$ apiece, so 240$ a piston, the plugs are too expensive
The welded piston pins made by Pankl in Austria were cheaper!
And 100% reliable.

I have a different perspective on piston pin plugs that some may disagree... 1. for starters they are difficult and expensive to make... 2 ... We have tried many designs without noticeable gain.. 3 ...A highly stressed race motor already has enough liability issues without adding another possible cause for catastrophic failure . 4 When you plug the ends there is no chance for cooling to the pin and without an escape route for the heat it might cause detonation late in a race when you least need it.. Food for thought ... mike

Frits Overmars a écrit:

Jeram a écrit:: with the benefits of graphite pistons in two strokes demonstrated by Honda in the final years of 250 racing, was it ever considered feasible to use these on the aprilia?

What graphite pistons? Did you see them? Did anyone see them?

You know , there is a kiwi saying that .... and if i tell you , i'll have to kill you lol!

but except on a deutsch website , i've never seen any 1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 116295

1973 - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked) - Page 31 116295

» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4)
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