ESE's works engine tuner

[wobbly]

Very well done Frits, thinking rationally like that obviously comes naturally.
Sadly my immediate reaction only accounts for the obvious proven 54 bore at a 70% chordal, where 2.5mm is commonplace - so yes 2.6mm is too big.
Also in my opinion anyone saying a 65% chordal is happy with 2mm ( even if it is a 40mm bore ) simply means its closer to a lawnmower than a race engine.
Some might opine that Im so narrow minded it could fit between the blocks at Giza - and no a credit card wont go, been there , tried that.

[Wos]

Very well done Frits, thinking rationally like that obviously comes naturally
Sadly my immediate reaction only accounts for the obvious proven 54 bore at a 70% chordal, where 2.5mm is commonplace - so yes 2.6mm is too big.
Also in my opinion anyone saying a 65% chordal is happy with 2mm ( even if it is a 40mm bore ) simply means its closer to a lawnmower than a race engine.
Some might opine that Im so narrow minded it could fit between the blocks at Giza - and no a credit card wont go, been there , tried that.

Frits! Are the winner bikes in liedolsheim lawn mowers

Fact is...bidalot has only main cordal 65...max 66...and 2mm bridges to the boosts...
Not the optimum as nearly everybody knows ! ��

But these zylinders are strongest in this competition...untouched Ducts... 21 -22 hp/ crank
Very fast lawnmowers.

Frits! Once you were involved in liedolsheim...supported jan schäffer with a simson...and he did second place inthe 8h race!!


https://www.youtube.com/watch?v=1X4N3BJwoT0

Can you give us a idea, which power the engine made?



Think it was before bidalot sold its rf 50 wr and before its problems with their original pistons were solved...

Lap times are nowdays at low 1.54

Thanks

Grüße Wolfgang

[Wos]

Wob, you're underestimating me. On the job you learn words from your colleagues that you won't find in a dictionary. I think back fondly on Miguel Sauca, the Spanish draughtsman who came with Jan Thiel from Bultaco to Garelli. So now I can also swear perfectly in Italian and Spanish. And in Dutch of course, and a little in French, and even in Finnish.
Come to think of it, I cannot swear in Japanese. I wonder it that's a flaw in my upbringing or a testimony of Japanese civilization.

OK, back to the harsh reality.
I try to answer this type of questions with a universal answer that is independent of bore, stroke, etc.
In this case my answer would be that the width of a vertical bar between two ports must be at least 5° of center angle.
Example: a cylinder with a 54 mm bore has a circumference of Pi x 54 mm = 169,65 mm.
That circumference comprises a total center angle of 360°. One degree center ⁶angle has a cordal width of 1/360 x 169.65 mm = 0.47 mm. And a bar with a width of 5° center angle is therefore 5 x 0.47 = 2.36 mm wide.

Now would be the time to say that you can forget most of what I wrote above. I can simplify it to:
The minimum bar width must be 0.044 x the cylinder bore diameter.

Thanks Frits for the Formula!

Is the Formula independent from width of main ex or made for the known sturdy and effektiv 70 percent cordal width?

Think the narrower the main...the higher is life span of every involved part there.

Conclusion could be that it is possible to use narrower bridge bars, if main is under 70 percent?? Right or wrong??

Thanks again Frits! 😉

Grüße Wolfgang

[Frits Overmars]

Are the winner bikes in liedolsheim lawn mowers?

Engines for eight-hour races are prepared for reliability rather than power. They do not nearly reach the piston speeds that Wobbly is use to and in this respect I can understand Wobbly's remark.

Fact is...bidalot has only main cordal 65...max 66...and 2mm bridges to the boosts. Not the optimum as nearly everybody knows !

A port width of 70% of the cylinder bore in combination with the optimum port shape will give the optimum blowdown angle.area. But making the main exhaust port narrower yields more place for auxiliary exhaust ports, in which case the 70% main port width is not sacred and keeping it narrower may give a better total blowdown angle.area.

Frits! Once you were involved in Liedolsheim...supported Jan Schäffer with a Simson...and he won the 8h race! Can you give us a idea, which power the engine made?

Sorry Wolfgang, I don't even remember what year it was; I would have to look it up in the Langtuning dyno-computer but that computer is not online for security reasons and at the moment I am not even in the same country.

EDIT: I overlooked your link ( https://www.youtube.com/watch?v=1X4N3BJwoT0 ). Now I see that this particular race was 12 years ago.

Thanks Frits for the Formula! Is the Formula independent from width of main ex or made for the known sturdy and effective 70 percent cordal width?
Conclusion could be that it is possible to use narrower bridge bars, if main is under 70 percent?

That formula is only dependent on the factors mentioned in it, as should be the case with any formula. Do you see any port width mentioned?
The bridges between the ports in a cylinder have more than one function. They must guide the flow but they must also keep the cylinder together. And they do not always succeed, as you can see below. So do not make them too narrow.

[Wos]

Thanks for answers and lot of input from you Frits! Top!

Yes for sure, the mecanical and thermal stress is a factor and it may depend from material and quality of cast methods...

Dont be afraid...in case of endurance reliability counts 😉 level a bit under freetech50...

Liedolsheim Engines peak at about little over 14 000...reso begin about 10 000...overrev to 17 000...

The year you were involved should be 2013 😉

Grüße Wolfgang