Author Topic: Why schnuerle porting? (Read 9272 times)

Chris Wilson · « **on:** November 09, 2015, 06:47:00 PM »

Just trying to find realistic justification as to why schnuerle porting is so popular with stunt engines?

Originally lauded as a means to achieve higher efficiency and power 90 years ago, neither of which seem paramount for stunt, it seems like an overkill.

Witness the ever popular (and now discontinued) LA 46, good stunt run and wide spread between maximum torque and power and it does not have schnuerle porting!

(Disclaimer, I define schnuerle porting as directional around the cylinder and the LA 46 does not direct 'around' the cylinder.)

Is the popularity simply because other disciplines demand power and efficiency and so stunt gets the known technology hand me down?

Someone quipped on this site a while back "why wouldn't you have schnuerle porting?'

But really, why would you?

Thanks.

RandySmith · « **Reply #1 on:** November 09, 2015, 08:08:42 PM »

Quote from: Chris Wilson on November 09, 2015, 06:47:00 PM

Just trying to find realistic justification as to why schnuerle porting is so popular with stunt engines?

Originally lauded as a means to achieve higher efficiency and power 90 years ago, neither of which seem paramount for stunt, it seems like an overkill.

Witness the ever popular (and now discontinued) LA 46, good stunt run and wide spread between maximum torque and power and it does not have schnuerle porting!

(Disclaimer, I define schnuerle porting as directional around the cylinder and the LA 46 does not direct 'around' the cylinder.)

Is the popularity simply because other disciplines demand power and efficiency and so stunt gets the known technology hand me down?

Someone quipped on this site a while back "why wouldn't you have schnuerle porting?'

But really, why would you?

Thanks.

Chris

The OS LAs ALL have Schnuerle porting, as do most any modern engine, like the Super Tiger G34 and G51.
You have to go back to the ST46 and FOX 35 to find single bypass motors. Although there are others.
Schnuerle ported engines are more efficient both in fuel burn, and in power.
The LA 46 was just missing the boost port, which is not something that makes it "not Schnuerle ported"
Dr. Schnurle invented a system called "Loop Charging" as in the 180 degree opposed intake ports "loop" over each other at the top of the chamber.
Dr Schnurle designed this in 1926, but it took until the 1960s before it came to C/L Stunt, at least that was the first I saw, the first one that in my opinion worked well for stunt was the loop Charged HP-40 , They still run well today , and are a really great engine

You can get things with loop charging that you can't with single bypass, More power, torque, efficiency, and YES you can get a fabulous 4/2 , or a really great wet 2 . To try to come close some engine mfg.s added Perry ports, which was a ripoff on Loop charging, Even Super Tiger tried their spin... the "AirFoil porting" as seen on the G-21 35, another ripoff of Dr. Schurle's porting design.

Randy

Chris Wilson · « **Reply #2 on:** November 09, 2015, 09:42:35 PM »

Hi Randy, are you sure that the LA 46 directs the gas flow 'around' the cylinder?

All that I am seeing are two milled ports that direct gas straight across the cylinder with no angling at all.

And a recent article in Aeromodeller agrees with me, it likens it to Arden porting.

I know about the boost port not being part of the original design as it too doesn't angle flow around the cylinder walls.
(And I have read most posts by your good self over the years.)

Schnuerles defining trait is the angling around the circumference of the cylinder and vintage competitions here in Oz use exactly that as a separator for eligibility.

But definitions aside, single bypass is (obviously) not the only other port system either.

Best continued via PM?

RandySmith · « **Reply #3 on:** November 09, 2015, 09:55:31 PM »

Quote from: Chris Wilson on November 09, 2015, 09:42:35 PM

Hi Randy, are you sure that the LA 46 directs the gas flow 'around' the cylinder?

All that I am seeing are two milled ports that direct gas straight across the cylinder with no angling at all.

And a recent article in Aeromodeller agrees with me, it likens it to Arden porting.

I know about the boost port not being part of the original design as it too doesn't angle flow around the cylinder walls.
(And I have read most posts by your good self over the years.)

Schnuerles defining trait is the angling around the circumference of the cylinder and vintage competitions here in Oz use exactly that as a separator for eligibility.

But definitions aside, single bypass is (obviously) not the only other port system either.

Best continued via PM?

Hi Chris

Yes, by definition, the porting on the LA is Schnuerle ported. I think most all the variation in loop charging,, LIKE PDP Super Tigers AirFoil porting etc are all ripoffs on the Schnuerle porting design. I had even heard Super Tiger was not able to pass off their version of Schnuerle porting.

And the angle really doesn't matter and does not change it to NOT Schnuerle porting, since the charge is coming up from the bottom, along the sides of the case ports, it still goes to the top of the chamber and "loops" around each other.
The main ports are not in danger of flowing out the exhaust because of the location.. however look at most any "boost" port and you will see they are not cut square, and have an upwards angle, this is the one port that does have a problem if it is cut with just a straight edge
Not really any reason to not use loop charging in stunt engines, as the advantages are many.

Randy

Even the Cox 049 051 are Schnuerle ported.

Chris Wilson · « **Reply #4 on:** November 09, 2015, 11:46:37 PM »

Hi Randy,
just to be clear here, this is what defines Schnuerle porting to me at least -
The angling around the curved wall of the liner is being shaped by the liner and crankcase, just like in the patent.

GregArdill · « **Reply #5 on:** November 09, 2015, 11:47:58 PM »

The most obvious answer, Chris, is that Schnuerle porting is the industry standard and most if not all current engines used for (modern) aerobatics are in that configuration.

For most modellers it doesn't really matter if a particular engine is not technically Schnuerle ported, they'll simply put a prop on it and go fly. they'll discover by trial & error what makes an engine work better and under what conditions it fails to deliver expected results. They'll discuss these aspects with others and develop or dis-proove their theories, and move on until there is little extra to be gained.

Now if someone comes along with a new mousetrap then it'll take time to be accepted, and adapted to the current airframes. And of course if it provides more power from a given engine weight, then models will have to be adapted and new ones designed to cope with the extra power.

Fliers at the sharp end of flying will be first to take advantage of any new developments.

Tim Wescott · « **Reply #6 on:** November 10, 2015, 08:39:34 AM »

Quote from: Chris Wilson on November 09, 2015, 11:46:37 PM

Hi Randy,
just to be clear here, this is what defines Schnuerle porting to me at least -
The angling around the curved wall of the liner is being shaped by the liner and crankcase, just like in the patent.

That's one drawing from Wikipedia. Randy's been in this game long enough to write several books, if he cared to. I'd listen to Randy.

Besides, what he says makes sense.

RandySmith · « **Reply #7 on:** November 10, 2015, 12:14:55 PM »

Quote from: Chris Wilson on November 09, 2015, 11:46:37 PM

Hi Randy,
just to be clear here, this is what defines Schnuerle porting to me at least -
The angling around the curved wall of the liner is being shaped by the liner and crankcase, just like in the patent.

Hi Chris

You can define it however you like, but it would never beat a patent lawsuit, most every spin on loop charging I have seen is just that, a knock-off that the mfgs could not get past the original design and patent, however in answering your question about run in stunt, none of this matters, as they all do the same thing, so it a moot point.
this is from OS :

" 1973
The special O.S. designed machinery built for the complex high-precision machining operations essential to the success of the O.S. Rotary Engine, raised O.S. production technology to new levels. This proved invaluable in the manufacture of all subsequent O.S. engines, beginning with the high performance 6.5 cc Schnuerle-scavenged MAX-40SR of 1973.
"
OS even calls their porting scheme "Schnuerle" and the 1973 OS FSR has the same porting as their LA series , only less 1 boost port

remember Dr. Schnurle designed a charging system that eliminated the deflector baffle, and used the relocated ports to use the looping method to fill the chamber, doesn't matter what the cut angle of the port is 90 degrees , 30 , 60, 44 etc. I don't think you can bypass the patent by changing the machining angle of the top of the port, I know the PDP scheme did not get past it.

So if the question is one of getting past the definition, then that is a different one, other than , Why do people use it for Stunt.

Randy

RandySmith · « **Reply #8 on:** November 10, 2015, 04:32:21 PM »

Quote from: Chris Wilson on November 09, 2015, 11:46:37 PM

Hi Randy,
just to be clear here, this is what defines Schnuerle porting to me at least -
The angling around the curved wall of the liner is being shaped by the liner and crankcase, just like in the patent.

Hi Chris

I pulled a 46 LA p/s and the intake ports in it are directed (angled ) toward the side or back of the sleeve...
however you would see it, that also makes the charge loop around each other, with more help from the curve of the sleeve, toward the opposite direction of the exhaust..
this also would definitely not by any stretch, distance it from Dr Schnulre's invention.
Did you know there was another attempt at this for use with or without a ring, by machining small directional "window ports" in a row around the sleeve. Lots of interesting take offs on the good DR. scheme :-)

Randy

Tim Wescott · « **Reply #9 on:** November 10, 2015, 04:39:11 PM »

And Cox dual-port cylinders are also Schnuerle ported, from an earlier patent.

Chris Wilson · « **Reply #10 on:** November 10, 2015, 07:07:34 PM »

Quote from: Tim Wescott on November 10, 2015, 04:39:11 PM

And Cox dual-port cylinders are also Schnuerle ported, from an earlier patent.

An earlier patent Tim?

Could you point me to it as I am interested.

Chris Wilson · « **Reply #11 on:** November 10, 2015, 07:23:10 PM »

Quote from: RandySmith on November 10, 2015, 04:32:21 PM

Hi Chris

I pulled a 46 LA p/s and the intake ports in it are directed (angled ) toward the side or back of the sleeve...
however you would see it, that also makes the charge loop around each other, with more help from the curve of the sleeve, toward the opposite direction of the exhaust..
this also would definitely not by any stretch, distance it from Dr Schnulre's invention.
Did you know there was another attempt at this for use with or without a ring, by machining small directional "window ports" in a row around the sleeve. Lots of interesting take offs on the good DR. scheme :-)

Randy

Hi Randy,
I did not know that there was a version with small directional ports, thanks for the info.

But definitions aside, the original question is still looking of "Just trying to find realistic justification as to why schnuerle porting is so popular with stunt engines?" is still there.

I kinda think that the answer maybe the old adage of "its easier to detune a race car for the street than it is to tune a street car for race."

Thanks.

RandySmith · « **Reply #12 on:** November 10, 2015, 08:24:01 PM »

The reason to use SP in stunt is because it is better, more efficient in power and fuel burn, no reason not to use it .

and the engines I am talking about using the muliti small ports isn't an OS

Randy

Chris Wilson · « **Reply #13 on:** November 10, 2015, 10:30:38 PM »

Quote from: RandySmith on November 10, 2015, 08:24:01 PM

and the engines I am talking about using the muliti small ports isn't an OS

Randy

Ah, I get your drift now - do the letters P and A come into it?

Tim Wescott · « **Reply #14 on:** November 10, 2015, 10:34:29 PM »

Quote from: Chris Wilson on November 10, 2015, 07:07:34 PM

An earlier patent Tim?

Could you point me to it as I am interested.

No I can't! I looked on the Internet and couldn't find anything but articles in motorcycling and model airplane magazines.

It's mentioned in Dave Gierke's book on glow engines in volume 1 -- if you don't have a copy you want one anyway, so go buy one.

Chris Wilson · « **Reply #15 on:** November 11, 2015, 01:05:57 AM »

Quote from: Tim Wescott on November 10, 2015, 10:34:29 PM

No I can't! I looked on the Internet and couldn't find anything but articles in motorcycling and model airplane magazines.

It's mentioned in Dave Gierke's book on glow engines in volume 1 -- if you don't have a copy you want one anyway, so go buy one.

I drew the same blank too Tim but I do recall seeing additional work by the good doctor years ago.

I have book 1 somewhere, so I will drag it out for perusal.

Thanks.

Randy Ryan · « **Reply #16 on:** November 17, 2015, 09:17:14 AM »

Perhaps it would be easier to describe this as porting that produces the loop charge motion Randy describes. The ports themselves are not the principal, the charge motion is. Any port then that produces this motion is a Schnuerle port because that was the purpose. The baffle piston engines allowed part of the fresh fuel charge to escape while at the same time failing to scavenge all the exhaust gases from the cylinder. The Schnuerle port principal essentially screws the charge upward through the exhaust gases into the cylinder directing it to the head from where it loops and pushes the remaining exhaust gases out.

So to answer the question, Schnuerle ported engines are more efficient and economical. More power in the same or smaller package. It is I think inaccurate to say that in stunt we're not worried about high performance. In reality we place tremendous demand on our power plants operating them in the various modes without any throttling. In vertical up an directions and complex maneuvers like the Cloverleaf we need a lot of power and reserve power as well as wind conditions change. Humidity changes effect them as well. As a matter of fact I've come to understand that a marginally powered model that does well in good conditions is susceptible to winding up on windy conditions because it was already running near peak in normal flight, it has no more engine breaking capacity when pushed past its optimum operating range. I hope I explained that right, but then again this is about porting. So Schneurle porting is definitely an advantage and when set up properly with a pipe, they "shift gears" like nothing else can all at the same needle setting. I suppose a cross scavenged engine could also benefit from a pipe but I really don't know.

Chris Wilson · « **Reply #17 on:** November 17, 2015, 03:58:12 PM »

Quote from: Randy Ryan on November 17, 2015, 09:17:14 AM

The ports themselves are not the principal, the charge motion is.

Bingo!

And what happens if you have schnuerle looking ports that do not produce a looping gas flow but rather collide from opposition?

Patent wise if it looks like a schnuerle then it must be one, but what if you were running a competition that specifically banned schnuerle ports due to advantage how would you troll throught the plethora of variations on the theme?
If you banned all engines based on the 'look' then you would have a comp at all.

RandySmith · « **Reply #18 on:** November 17, 2015, 06:32:14 PM »

Quote from: Chris Wilson on November 17, 2015, 03:58:12 PM

Bingo!

And what happens if you have schnuerle looking ports that do not produce a looping gas flow but rather collide from opposition?

Patent wise if it looks like a schnuerle then it must be one, but what if you were running a competition that specifically banned schnuerle ports due to advantage how would you troll throught the plethora of variations on the theme?
If you banned all engines based on the 'look' then you would have a comp at all.

Hi Chris
To add to some's confusion, I will point out the design from the good doctor Loops around the chamber ,and collides with each other.....

Randy

Chris Wilson · « **Reply #19 on:** November 17, 2015, 08:42:27 PM »

Quote from: RandySmith on November 17, 2015, 06:32:14 PM

Hi Chris
To add to some's confusion, I will point out the design from the good doctor Loops around the chamber ,and collides with each other.....

Randy

Yes, but not in direct opposition like the so-called Villiers porting.

RandySmith · « **Reply #20 on:** November 17, 2015, 09:54:31 PM »

Quote from: Chris Wilson on November 17, 2015, 03:58:12 PM

Bingo!

And what happens if you have schnuerle looking ports that do not produce a looping gas flow but rather collide from opposition?

Patent wise if it looks like a schnuerle then it must be one, but what if you were running a competition that specifically banned schnuerle ports due to advantage how would you troll throught the plethora of variations on the theme?
If you banned all engines based on the 'look' then you would have a comp at all.

That would not ban all engine.. it would just effectively means you would have a competition with single by pass baffle engines....
which is exactly what you would find in model airplane engines.
Randy

Chris Wilson · « **Reply #21 on:** November 17, 2015, 11:38:33 PM »

So my PAW 40 would be banned from a non schnuerle event?

I think that this thread has run its course, it (as usual) gets down to an argument about definition, thanks all for the mind candy!

Randy Ryan · « **Reply #22 on:** November 18, 2015, 10:38:36 AM »

Quote from: Chris Wilson on November 17, 2015, 03:58:12 PM

Bingo!

And what happens if you have schnuerle looking ports that do not produce a looping gas flow but rather collide from opposition?

Patent wise if it looks like a schnuerle then it must be one, but what if you were running a competition that specifically banned schnuerle ports due to advantage how would you troll throught the plethora of variations on the theme?
If you banned all engines based on the 'look' then you would have a comp at all.

In reality any charge motion of any multiple port system will eventually collide, this is not a negative condition because along with charging the cylinder and scavenging exhaust gas, charge mix and motion are important for economy and performance. Combustion in cylinder or rather combustion efficiency is dependent of fuel being exposed to free oxygen and the best way to ensure that to it's max extent is to keep the charge in motion whether it be swirl, tumble or a combination of both. These terms come mainly from diesel technology but apply to any power cylinder combustion system to some extent. It's true that in our engines the mixture is better homogenized than in a direct injected engine, but the motion does affect combustion efficiency and therefore efficiency and economy.