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Engine basics => Engine set up tips => Topic started by: Paul Taylor on February 19, 2017, 08:56:46 PM
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I have heard the term for some time and I'm not sure what it means.
Can someone please explain the difference is?
Thanks
Paul
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See https://en.wikipedia.org/wiki/Schnuerle_porting (https://en.wikipedia.org/wiki/Schnuerle_porting).
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I have heard the term for some time and I'm not sure what it means.
Can someone please explain the difference is?
Thanks
Paul
Schnuerle Porting
Schneurle porting means the engine has multiple ports in the cylinder allowing fuel into the combustion chamber. Non schnuerle ported engines or 'loop scavenged' engines have only one port opposite the exhaust port which may allow fuel to pass over the piston and exit out through the exhaust port. The multiple ports of schnuerle engines causes fuel to flow from different directions to converge at the centre of the cylinder allowing more fuel to be burned and therefore more power. Most modern engines use schnuerle porting.
Source: "https://web.archive.org/web/20090616071821/http://www.doddington-kent.org.uk/Planecrazy/schnuerle.htm (https://web.archive.org/web/20090616071821/http://www.doddington-kent.org.uk/Planecrazy/schnuerle.htm)"
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You must be referring to the crank shaft as single by pass. My schnuerle engines have several passage ways up beside the cylinder. also flat top pistons.
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I have heard the term for some time and I'm not sure what it means.
Can someone please explain the difference is?
A cross-flow/"baffle piston" engine usually (but not always) uses a vertical fence on the top of the piston to deflect the incoming charge up along the side of the cylinder towards the top, and hopefully pushing the exhaust from the previous cycle out the exhaust port.
A schneurle engine counts on aiming the charge up towards the top of the cylinder as it comes through the intake ports (originally just the fore/aft ports, later with the "boost port" added), and pushing the exhaust out. One interesting feature of this arrangement that matters for stunt is that acceleration along the cylinder axis can greatly alter the way the scavenging works, so maneuvering can cause the engine to run differently on inside and outside maneuvers when the cylinder is upright or inverted.
Brett
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I have heard the term for some time and I'm not sure what it means.
Can someone please explain the difference is?
Hey Paul:
Does it make sense now? Or would you like us to talk at you more?
The only thing to add is that in general Schnuerle-ported engines are designed to run at higher RPM than baffle-piston engines. To my knowledge a Schnuerle-ported engine could be made that would be quite happy at lower RPM, but Schruerle porting gives an engine a higher RPM potential and thus a higher overall power potential for the same displacement.
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Noted C/L Speed flier Glenn Lee wrote an excellent article on 2-strokes: http://www.airplanesandrockets.com/motors/inside-the-two-cycle-engine-feb-1968-aam.htm
You may also want to dig into the history of Walter Kaaden's contribution to the development of the modern high performance 2-stroke engine.
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To help a bit to identify them, OS FP, HP 40 , LA , ST G51 ST G34 are all Schnurle ported motors
Fox 35 Older OS 35 S , 40 H older Merco 35 are cross flow baffle engines
The typical port arrangement for Loop Charged motors are 2 intakes front and rear, 90 degrees from the exhaust port, and added is a boost port that is across from the exhaust port, So you ,most times . have 3 or more intake ports, 1 exhaust port
Randy
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Noted C/L Speed flier Glenn Lee wrote an excellent article on 2-strokes: http://www.airplanesandrockets.com/motors/inside-the-two-cycle-engine-feb-1968-aam.htm
You may also want to dig into the history of Walter Kaaden's contribution to the development of the modern high performance 2-stroke engine.
Thanks for the post, Bob. That is an excellent article. It's interesting that, written in 1968, Mr. Lee starts the article by talking about electrics and that he has switched to electric motors completely.
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Thanks for the post, Bob. That is an excellent article. It's interesting that, written in 1968, Mr. Lee starts the article by talking about electrics and that he has switched to electric motors completely.
Important to note: the article has an introductory paragraph written by someone ELSE, not Glenn Lee! It is in that introductory paragraph where the author claims to be going electric.
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Thanks for the post, Bob. That is an excellent article. It's interesting that, written in 1968, Mr. Lee starts the article by talking about electrics and that he has switched to electric motors completely.
That's not Glenn Lee. That's the usual author's introduction to a letter from Lee. BTW, electric was *entirely impractical* for virtually any performance modeling competition category in 1968. It didn't become practical for stunt until the late 90s, and is more or less still only practical for stunt and non-performance applications. Maybe other people were doing it, but the triggering event for stunt was Mike Palko taking his electric to the NATs - that's when the capability was made obvious to everyone.
Brett
p.s. Bill and I do not have a private communication channel over which we consult...
Note also that scavenging example D might look pretty familiar - because it's more-or-less how a Cox Olympic 15 works. There is no accident that the Olympic and its rotary-valve descendent, the Tee Dee, was a remarkable breakthrough that put a widely-available consumer engine ahead of anything in the world. The Tee Dee 049 wasn't surpassed in a production engine until the 80's, and then it was limited-production engines like the Shuriken that were in very short supply - not something you could buy at the corner drugstore with a modeling corner. Go back and read things like the Peter Chinn reviews of the Tee Dee and Olympics - they were amazed and hadn't believed that any glow engine could outdo a .15 diesel!!! And this one ran at nearly full speed straight out of the box with nearly no break-in.
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Can I still call this a Schnürle..? :)
L
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Schnuerle porting uses the back cylinder wall curvature as a deflector, so in a way most engines use a deflector of some sort, but the genius shown by Adolf is that he used what was already there.
In effect it is a simpler, lighter design that uses a looping gas flow described by the upward and rearward angled ports, curving around the cylinder wall and the normally bowl shaped head and exiting out of exhaust - all in a circular motion or "Loop."
There is no need for internal geometry to promote gas flow as distinguished by baffles, conical piston crowns etc.
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Important to note: the article has an introductory paragraph written by someone ELSE, not Glenn Lee! It is in that introductory paragraph where the author claims to be going electric.
Thanks for pointing that out. I was talking about it with my brother and commented that back then, you'd have to have a lawn mower battery onboard!