Foekema Symmetric Twostroke

[LucF]

Hello 2 stroke enthusiast,
 
Hereby I will inform you about my new 2 stroke system. About 2 years ago, I got the idea to change the way of scavenge of the cylinder. This idea is not very difficult, but realising ideas like this is not that easy, because it has to be made very precisely.

Till so fare I didn't want to spend time for it, because there are many more important things to do when you want to be the fastest 50cc sprinter in the world on the 150 meter and the 1/4 mile.

But I was very surprised when reading the magazine of Kickstart of january this year, that someone else also got also a new idea about that, he called it 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. May be there will come more new 2T systems at this moment, because I heard from good friends, that there are more young people in action with new systems!

That's why I don't want to wait any longer and introduce you the "Foekema Symmetric Two-stroke system" (FST system)

Read all about it on my website
http://uk.geocities.com/racing50cc/FSTsystem.html

Or read the text below. 

Kind regards,
Luc Foekema

Text of the website page


A new twostroke scavenging system the FST system
About 2 years ago I got the idea to change the way of scavenging of the twostroke engine. The current way of scavenging is almost from the beginnng of the 2-stroke history never changed. But thinking to get more power you automaticly come to new ideas. So to me it came about two years ago, and what the name already suggest that is a symmetric working scavenge system.

It was not my intention to announce this new idea before making and testing it, but I was supprised when I read the magazine of Kickstart of january this year. Frits Overmars also got a new idea, which he called the FOS system. When reading it, 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. That is why I thought that someone else already did the same in the past. Because many things in two-stroke tuning has been made since the beginning of the two stroke. 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 system" (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

Symmetric scavenging
The word only seems to be enough. The whole scavenge will proceed in a symmetric way. After burning the gases, the the piston goes down, the 4 exhaustports opens first at the same time and the burned gases leaves the cylinder. These ports are fully symmetric and around in the cylinder, so the gases can flow into the exhaustpipes very fast. After that, all symmetric transfers opens also at the same time and fresh gases flows from all directions right over the piston to the center of the cylinder. This result in a flow of the gases in the direction of the chamber, while pressing the burning gases to the edge of the cylinder. In the chamber the fresh gases will turn around in the direction of the four exhaust ducts, behind the burned gasses.
Symmetric system already exist for a kong time. But not full around the cilinder, with full 100% TA capacity. So two rows of fully symmetric ports, the upper 4 ports are exhausts, the lower row of ports are transfers. Which results in much more time area capacity.

Advantage of the symmetric scavenging
The big advantage is that the whole scavenging process will proceed much faster than the current two-stroke system because of the much higher 100% TA capacity. That is why a much higher rpm are 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.

Realising an operating Symmetric system
Realising this system is not that easy, because it has to be made very precisely, because otherwise the scavenging does not proceed symmetric. Each small deviation in transfers or exhausts has a negative influance in this process.
There are still some more details of which some very important to keep in mind. But that I will keep for me, till the system has been ready for operation later this year.

A pitty !!!
Yes a pitty for me, because I did prefer to appear one day on an event unespected, with an engine operating with this symmetric system. Altought the news has gone, a well operated system will be the next challence to realise.

Several forums
These subject is to find on next forums:
1. www.kreidler.nl
2. www.scootertuning.net
3. www.2stroke-tuning.nl
4. www.RD350.nl
5. http://zundapp.messageboard.nl
6. www.apriliaforum.

On some of them there is also written about the FOS systeem, in which is clear that nothing of the system has been explained.

[bak189]

Zeer interessant voor de tweetak motor.......veel succes......en laat onz weeten of het werkt.........

[Stan Back]

Easy for you to say.

[1212FBGS]

are you using piston rings? with all of that port area i think ring controll and flutter might be a problem...
kent

[LucF]

On Dutch forums there are many questions and ofcourse advises.
The piston ring is no problem, the pistonpen more, but can also be solved.
I will keep this forum updated with the results

Greetz,
Luc

[Dean Los Angeles]

I had that same sort of thought in 1968 when I was racing karts. I realized there was no where near enough exhaust area on the McCulloch kart engines. So I drilled 18 exhaust holes above the intakes. Vented to the atmosphere. After some experimentation I discovered that at low speeds the intake charge went directly out the exhaust, so there was no such thing as low end torque. Since is was ported directly outside, at low speeds, like at starting, it blew fuel out of everywhere and gave the distinct sound and visual impression of a blown head gasket.

Once it came up on the pipe, it produced glorious amounts of power. It was named the Holey Wonder, not only for the holes, but for the unworldy sound it made at full pop. The conventional ported McCulloch would wind up to 12-13,000 rpm. This thing made 18,000 rpm. Won quite a few races with it.

The rod wasn't up to the task I soon found out. It would last about 3 short races and break. Always at the top end of the rod. And then it would transform itself into an 18,000 rpm buzz saw. I still have scars from one of the grenade jobs.

Piston ring life on an extreme ported engine is not long, but you live with the trade offs.

[LucF]

Thanks Dean,
This is the answer where I was looking for. But when reading again I realise that there are some differences. Dean uses an existing cilinder, with ofcourse an exhaustport which is full open at bottem dead center. This will disturb the symmetric way of scavening.
But unless this, it is a way which comes close to my idee. Remember my idee is 100% transfers round the cilinder and als 100% exhaust full arround. So totaly 100% input  and output. May be also 100% horsepower?? Wait for the prototype !! 
 
Ofcourse I'm not drilling 18 holes around the cilinder, because a 2stroke engine needs a well calculated exhaustpipe to produce good power.
Also the max rpm will be kept under controll with the right exhaustpipe.
The best conrods for a Kreidler can run till 20.000rpm.
The one I do use now can do it to about 17.000 rpm

Low speeds also are espected to gave some problems, but that was also the fact with the 1965 Honda 50cc twocilinders under the 10.000rpm.
Racing engines normaly works at high rpm, so no problem.
And the last point the sound I was wondering for.
I will made it with 4 exhaust ports which comes together in 2x2 exhaustpipes.

Greetz,
Luc
 

[wolbrink471]

has anybody figured out how to quantify the point a rod will let loose?

maybe something like....

stroke * rpm equals foot per second which compared to the 'terminal velocity' of cast metal x

Mark

jeez, i reread the post and not sure if it would be more appropriate ont he 'star trek/ batllestar gallatica' forum?!?

[dwarner]

Usually happens when the car noses over at about 4.5 miles.

DW

[Stainless1]

has anybody figured out how to quantify the point a rod will let loose?

Usually happens when the car noses over at about 4.5 miles.

But only when you are on a record return and you just qualified a little over in the last mile... 

[LucF]

I had that same sort of thought in 1968 when I was racing karts. I realized there was no where near enough exhaust area on the McCulloch kart engines. So I drilled 18 exhaust holes above the intakes. Vented to the atmosphere. After some experimentation I discovered that at low speeds the intake charge went directly out the exhaust, so there was no such thing as low end torque. Since is was ported directly outside, at low speeds, like at starting, it blew fuel out of everywhere and gave the distinct sound and visual impression of a blown head gasket.

Once it came up on the pipe, it produced glorious amounts of power. It was named the Holey Wonder, not only for the holes, but for the unworldy sound it made at full pop. The conventional ported McCulloch would wind up to 12-13,000 rpm. This thing made 18,000 rpm. Won quite a few races with it.

The rod wasn't up to the task I soon found out. It would last about 3 short races and break. Always at the top end of the rod. And then it would transform itself into an 18,000 rpm buzz saw. I still have scars from one of the grenade jobs.

Piston ring life on an extreme ported engine is not long, but you live with the trade offs.

Hi Dean, Can you tell me something about that McCulloch engine,
bore, stroke and horsepower?


Kind regards,
Luc

[Loose Goose-Terry#1]

Dean, did you have a MC91 or MC91A? I ran both sprint & enduro with the old McCulloch engines. Loved it. 91, 91A, 91B & 91B/1s.

  McCulloch MC7 (1962) through MC93 (1977) were the same bore and stroke at 2.165 bore x 1.635 stroke at 6.05 cubic inches.
A stock McCulloch would produce, I think around 12 to 14 hp (but who knows what was really "stock". IKF had a lot of rules and some people found ways around them in the American Reed class. 
If I remember correctly, mine dyno’ed around 21 to 24 hp on alky and Klotz. 

Rods were week and when you got that under control the pistons would let go or the block would come apart. Wiped out several stuffer plates and third carb setups. 

“They” say you can't balance a single cylinder two stroke engine, so I removed all the weight from the flywheel and ground ALL the counter balance off the crank. It was Hell on sprint tracks around the Midwest. Set a lot of track records and won a lot of races. Several sprint tracks started making me run with the B-Opens and Duels. We called it “The Shaker”! Boy was it fun. 0 to 60mph in two seconds!

Remember Luc, Jack would say, Theoretical engines produce theoretical horsepower!
Have fun designing but remember it has to be able to be built. There are a lot of designs out there but when it comes to the actual fabrication that is when the plans go up in smoke.

[Dean Los Angeles]

Mc 8, 9, 91, 100, 101 you name it, I ran it. And blew it up. I ran sprint, enduro and 1/8 mile dirt oval. I rarely ran stock, it wasn't as much fun. I did help other guys with stock. We used to push the center out of the flywheel and advance it 4 degrees. It's only illegal if you get caught.

I don't remember the horsepower. Spent lots of dyno time but it's been a long time ago. Ran methanol and Klotz too! As well as nitromethane, hydrazine and a wide variety of other chemicals. 

Ran a lot of rotary valve engines too. Parilla, Komet, B-Bomb. Wicked amount of horsepower for 100 & 125CC. Also ran twin engine and a FKE III class with a Kawasaki A7R 350CC.

[JackD]

Now you begin to understand his preferred riding position on the LSR bike.

[LucF]

Thanks guys,
I wanted to judge that 18.000rpm in relation to ... cc engine, that seems to be 100ccm
Now I understand that the rods break. When driving a 54mm bore piston (160 gram), (normaly 12-13K) with 18k, than the piston weight twice the normal weight. From about 1000kg to about 2000kg and that is to much.

I do racing and sprinting 50cc and 90cc.  90cc with about a bore of almost 54mm. 
In 1968 we raced Kreidler 50cc with about 15hp at about 15.000rpm
Today the same engine with better ignition and better chamber runs 17hp at 16.000rpm.
The best 50cc I have is 18.5 hp at 16.500 rpm and the best 90cc is 25hp at 14.200rpm
HP's on rearwheel for good understanding.

The new FST system which I am making, first in 50cc, will run about 18.500rpm
It is only the question how much HP advantage will I have in comparing the current 2T system.
It is not a question if I make this FST design, only when I am ready.
By the way, I am not the only one who is making it. There is another one Frits Overmars who is making a HRC 125cc in this system. He started is making it very professional, which cost more time.
For me it is also a challenge to be the first.

The reason why I put this new system on several forums is that I like to know if someone else did exactly the same as the FST system. Till sofare nobody came up with is, only Dean came close to it.  But it is only about 2 weeks from January 19th when I did announce it, so we are waiting ............

Notice that this FST system allows 100% Time Area for exhaust and 100% for Transfers. No other system before does have this.
 
Kind regards,
Luc