Foekema Symmetric twostroke after 10 years

FST a new twostroke design?

Forword
The first FST text was published on 19 january 2008. 2 month later on 16 March 2008 at 20.00hr the first FST engine was started in my home and my wife Hetty did make the movie on YouTube. One day later Jan Thiel called me to congratulate me, that was close before he went to Thailand.

First start of the engine March 16, 2008 [Vous devez être inscrit et connecté pour voir ce lien]

Now, more than 10 years later it is still not successful, yes it runs, but not in the way it should do. Partly due to the speed defined by the mixing of fresh and burnt gases, the fresh gases thus go too far directly into the exhausts. Therefore the temperature of the exhaust stays to low and so the speed can not increase further. It is therefore far from optimal cylinder filling and so it can have no power. Yes this was directly be heard during the first start and it was with adjustment, what I initially thought, not to get out. The solution must be sought in the process. The scavenging is also expected as very critical and needs to be improved in some way. And may be some day it will run, with new idees it is not impossible, I'm still working on it.

What do we know at this moment

1. In the 20s of the last century there were already engines with this system,

2. In the 50s there were Russian coxmotortjes model for this system,

3. In 1986 a patent for granted in England, but without a sequel,

4. Rotax has tested it expanded in 1989, without success

5. Frits Overmars has published his idee more than a month after my FST read here:

6. He still has only has a printed cylinders. While he wrote in his publication:
" Ideas only count when they are realized. That's why I would say, "Do your best, Luc. Show how good the system is that you and I have hought independently of each other. I hope my bike runs first. But if you are too quick for me, I hope that yours is running fast "

7. He called it FOS, but should have called it VDS, because he got the idea from Cees van Dongen in 1969, that's why he walks around with it 30 years, like he wrote. (read link for the order of publications)
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8. Ken Seeber 29 July, 2013 wrote he had the idea in 1984, but not 100% TA.


Dolf engine 1920
And what about those engines in the 20's of Dolf. The pricipal is the same, but those engines are not 100% TA and had no expansion exhaustpipes and therefore only runs in low engine speed with very low power. My prototype that runs after 2 months, had much more speed, but not enough, what it should be. Even without proper exhaust pipes like those Russian glowplug motors it can run for sure. However, in both cases, with much less port surface and therefore also with less engine speed and so very low power is available. What for me was the real reason to start this project.

What actions now?
All together it seems that it is never going to work. Does it still feel like there's still time to stabbing? From Frits I have not heard that he is going to stop it, much hurry he did not seem te have, after what is now known. Does it still make sense for me? No and Yes, No, because I do not have the impression that I could do it better than Rotax. Yes because I do have the engine, the cylinder and the exhaust pipes, so why not try something else? I am now 70 and still do not feel to be too old to learn. I'm looking for new idees to solve the current problems. Read below how it all started.


First publication of this new 2 stroke process
website not up to date, because I don't have access any more: [Vous devez être inscrit et connecté pour voir ce lien]

Original text of January 19, 2008
FST a new twostroke scavenging system. About 2 years ago I got the idea to change the way of scavenging of the twostroke engine. The current way of scavenging exist almost from the beginnng of the 2-stroke history and never changed, unless the many other systems which had been founded. But thinking to get more power you automaticly come to new ideas. So to me it came about two years ago, and that is the Foekema Symmetric Twostroke (FST).

It was not my intention to announce this new idea before making and testing it, but I was supprised when reading the magazine of Kickstart of january this year. Frits Overmars also got a new idea, which he called the FOS system. When reading, I thought: "I'm not sure, but it could be the same". Lucky for me he didn't explain the system, otherwise he would be the first. May be it is different, than we will have 2 new systems at almost the same time. The idea is not very difficult, but realising ideas like this is not that easy, because it has to be made very precisely.
Many things in two-stroke tuning has been made since the beginning of the two stroke. That is why I thought that someone else already did the same in the past. Till sofare I didn't want to spend time for this because there are many more important things to do when you wanted to be the fastest 50cc sprinter in the world on the 150 meter and the 1/4 mile.

The only thing I did was an announcement on the Kreidler.nl site, but without an explenation. Also I did tell it to some friends. But because in the current circumstances, I can't wait to explain my new system. That's why I like to introduce you the "Foekema Symmetric Two-stroke" (FST)
Who would be the first realising the idea in a working prototype is another question. Althought this system should produce more power than the current way, it still is the question, if in practice this will be prooven.

FST scavenging
Symmetric is one part to explain the system, but most important is the 100% Time Area. The whole scavenging will proceed in a symmetric way. After burning the gasses, when the piston goes down, the 4 exhaustducts opens first at the same time and the burned gasses leaves the cylinder. These ducts are fully symmetric around in the cylinder, so the gasses can flow into the 4 exhaustpipes very fast. After that, all symmetric transfers opens also at the same time and fresh gasses flows from all directions right over the piston to the center of the cylinder. This result in a flow of the gasses in the direction of the chamber, while pressing the last burned gasses to the edge of the cylinder. In the chamber the fresh gasses will turn around in the direction of the four exhaust ducts, behind the burned gasses.
So two rows of fully symmetric and 100% Time Area ports. The upper 4 ports are exhausts, the lower row are transfers. Which results in much maximum Time Area capacity, which is 100%. There is no more room left for ducts.

Advantage of FST scavenging
The big advantage is that the whole scavenging will proceed much faster than in the current two-stroke way, because of the maximum TA capacity. That is why a much higher rpm is reacheable with the same or even a lower duration of exhausts and transfers.
Beside this there is another great advantage the symmetric scavenging keeps the temperature in the cylinder completely the same all arround. In the current way there are always risks that one side of the cylinder is more hot than the other side.

There is much more to read after 10 years
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The reason to post this is:
1. That the whole story should be known and not some details, incl. the truth about FOS
2. I did not work on the system for many years, but this doesn't mean that it stays that way.
3. I got hundreds of ideas from all over the world how to do, but I never saw one which was bright enough to try.


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After Ryger has won everything he races... a new concept to beat it!
Great...

Payment in friendly bitcoin.

Hello Luc,
Thank you for enlightening us on your work, with an honesty that honors you.
I am well placed to understand the amount of work required to develop such a project.
There are so many parameters to explore, that the task seems superhuman.
Reading your explanations, it would seem that the biggest difficulty is to prevent fresh gases from escaping through the exhausts.
It's a misfortune, since the original concept was to increase the permeability of the cylinder!
I congratulate you for having been able to advance the project, how far he is today.
I wish you, to put your finger on the solutions, which will direct you to new progress.

Friendly.
Francis.

fpayart a écrit:

Hello Luc,
Thank you for enlightening us on your work, with an honesty that honors you.
I am well placed to understand the amount of work required to develop such a project.
There are so many parameters to explore, that the task seems superhuman.
Reading your explanations, it would seem that the biggest difficulty is to prevent fresh gases from escaping through the exhausts.
It's a misfortune, since the original concept was to increase the permeability of the cylinder!
I congratulate you for having been able to advance the project, how far he is today.
I wish you, to put your finger on the solutions, which will direct you to new progress.

Friendly.
Francis.

Thanks Francis !
I'm glad there are still a few people who read it before ..... !

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Could someone here to explain this "100% time area" for me, as it isn't, and obviously not supposed to be 100%, because then the whole stroke area would be ported Ok, it's nearly 100% from the given port timing, but only for blow down and transfers. Nobody says anything about maximum timings, and blow down/transfers ratio they should have.

And even further, there is not a single explanation, how you should aim you time/angle areas, if you want to design your own FOS/FST cylinder. If you want your 50cc to have maximum power or torque at 12000, what do you need? How about if you want your 125cc to peak at the same RPM. I'm pretty sure, you shouldn't look for those timing or AA-tables from Blair or Jennings?

I've seen few graphs from LucF, where there is this maximum rpm/HP for different engine sizes, but how did you get to these values? What kind of time-areas you need, and how come these charts are so different to each other? For example other one says 12400rpm 12,6HP for 50cc, and other one was 17600rpm and 27,3HP. Latter was compared to Aprillia RSA125 level, and that other one I don't know where it was compared.

So, Mr Foekema (or someone else), could you be so kind, and give me something I can calculate. I don't want to do too many false assumption and plans

op76 a écrit:

Could someone here to explain this "100% time area" for me, as it isn't, and obviously not supposed to be 100%, because then the whole stroke area would be ported    Ok, it's nearly 100% from the given port timing, but only for blow down and transfers. Nobody says anything about maximum timings, and blow down/transfers ratio they should have.

100% area is on the given porttiming, in combination with as thin spacers as possible to guide the piston ring

op76 a écrit:

And even further, there is not a single explanation, how you should aim you time/angle areas, if you want to design your own FOS/FST cylinder. If you want your 50cc to have maximum power or torque at 12000, what do you need? How about if you want your 125cc to peak at the same RPM. I'm pretty sure, you shouldn't look for those timing or AA-tables from Blair or Jennings?

The total transfer timearea has been calculated to the max power rpm.
I never have read Jennings or Blair, but I think both does not have examples of transfers like FST.

op76 a écrit:

I've seen few graphs from LucF, where there is this maximum rpm/HP for different engine sizes, but how did you get to these values? What kind of time-areas you need, and how come these charts are so different to each other? For example other one says 12400rpm 12,6HP for 50cc, and other one was 17600rpm and 27,3HP. Latter was compared to Aprillia RSA125 level, and that other one I don't know where it was compared.

Sorry, it is impossible to explain all about it here again.
So read here and you will find the answers and read well the description of the different charts you mentioned.
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and here if the first didn't work [Vous devez être inscrit et connecté pour voir ce lien]