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WRT M3X prop boom measurements.
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by0ung(at)brigham.net
Guest

Posted: Thu Jun 04, 2009 8:57 am Post subject: WRT M3X prop boom measurements.

Boyd,

Thank you and others who have offered advice.Iam going to increase the pitch

this week-end and see if this will make go faster.

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>.


	


My thoughts were placed out there for theory.   Remember I have never run a

two stroke.   And I don't know what the changes will do to the engine /

jetting / temps / etc.



You mentioned that you were going to pull it back and run at  5300 rpm....

also know that in a go fast design  with constant speed prop, they set the

power level by using the manifold pressure gauge..     assuming that you run

at 5300 before and you increase the pitch and run again at 5300,,,  it will

require a bit more throttle ( increased manifold pressure )  to compensate

for the additional prop load..   it theory you should go faster and also

have a greater fuel burn  per hour,  but the fuel burn per mile may go down.

As you go faster there is also an increase in drag...  hard to know what the

trade off's will be.



If you make a good discovery, let us know.



Boyd Young

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 04, 2009 11:25 am Post subject: WRT M3X prop boom measurements.

The Rotax 912-S is designed to run at high RPM's, but the 5500 - 5800 RPM 

range is time limited by Rotax for a reason, and it will probably increase 

the engines life keep it at 5500 RPM and below and just not to try to get 

every last HP out of it.

 	  Quote: 	
		  

 Mike


	




The 912 series engines are designed to operate up to 5800 rpm for 5 minutes 

max.



5500 max contiuous.



To get the best overall performance with a fixed pitch prop (ground 

adjustable), prop it like you would a boat:  WOT, straight and level flight, 

just bump the red line - 5500 rpm.



75% power is about 5,000 rpm.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 04, 2009 11:38 am Post subject: WRT M3X prop boom measurements.

> BTW, this is also true of the 2-strokes but a bit higher degree than the 

912. It's a common misconception that they last longer running at 6000+ rpm 

continuously. Actually, the "sweet spot" for continuous operation with them 

is in the 5200 to 5500 range, at somewhere in the neighborhood of 2/3 

throttle.

 	  Quote: 	
		  

 LS


	




Max rpm for Rotax two strokes is 6800 rpm for 5 minutes.



Max contiuous is 6500 rpm.



5800 rpm is 75% power, the optimum rpm to operate a Rotax two stroke 

continuously.



5200 to 5500 rpm is the area the engine is trying to get "on the pipe", not 

the sweet spot for me.  The older two strokes were very unhappy in this rpm 

range.  They would either speed up or fall off.  The engine is not 

developing full efficiency below 5500 rpm.



Power settings are easier to describe using rpm rather than throttle 

settings.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jun 04, 2009 12:13 pm Post subject: Re: WRT M3X prop boom measurements.

 	  John Hauck wrote: 	
		  



Max rpm for Rotax two strokes is 6800 rpm for 5 minutes.



Max contiuous is 6500 rpm.



5800 rpm is 75% power, the optimum rpm to operate a Rotax two stroke 

continuously.



5200 to 5500 rpm is the area the engine is trying to get "on the pipe", not 

the sweet spot for me.  The older two strokes were very unhappy in this rpm 

range.  They would either speed up or fall off.  The engine is not 

developing full efficiency below 5500 rpm.



Power settings are easier to describe using rpm rather than throttle 

settings.



john h

mkIII 	




The 503 can handle 5800, but the TBO does come out a bit higher when it's kept in the region of 5400 or thereabouts.



Putting it another way, if 5400 continuous isn't enough to fly the plane as needed, it's probably underpowered.



5800 was high on my FSII, regardless of throttle setting (as it varied depending on my pitch setting) it also put the gas consumption above 3 gph without really substantially increasing my cruise speed.



5300 was spot on comfortable for the engine with no wandering rpm or sensitivity in the throttle setting that I ever noticed on any plane I've used the 503 on. With my FS II, gas consumption ran about 2.8 gph and I got about 65mph cruise at that RPM.



There was never a better match made between plane and engine than the FSII and 503. 



LS

_________________
LS
Titan II SS

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 04, 2009 12:33 pm Post subject: WRT M3X prop boom measurements.

> The 503 can handle 5800, but the TBO does come out a bit higher when it's 

kept in the region of 5400 or thereabouts.

 	  Quote: 	
		  

 LS


	




A 503 can operate continuously at 6500 rpm.



Optimum performance is 75% power, 5800 rpm.



TBO is established by the manufacturer who does not specify a particular rpm 

other than 6500 max continuous.



Where do you get your info reference extended TBO if you operate "in the 

region of 5400 or thereabouts"?



I don't pay much attention to TBO on two or four stroke engines established 

by manufacturers.  There is no guarantee the engines will go that long. 

Most will go well beyond manufacturers "suggested" TBO before performance 

degradation or failure.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jun 04, 2009 1:18 pm Post subject: Re: WRT M3X prop boom measurements.

 	  John Hauck wrote: 	
		  



A 503 can operate continuously at 6500 rpm.

	




Don't mean to be contrary, but no it cannot. The chances of failure go WAY up if it's run at 6500 rpm all the time. Sometimes they make the specified 300 hour TBO run this hard, but failures are far more frequent (siezures and con rod failures are the most usual ones).



 	  Quote: 	
		  

Optimum performance is 75% power, 5800 rpm.



TBO is established by the manufacturer who does not specify a particular rpm 

other than 6500 max continuous.



Where do you get your info reference extended TBO if you operate "in the 

region of 5400 or thereabouts"?

	




Decades of field experience in a variety of planes by a very wide variety of pilots. I have about a decade under/in front of the 503 myself.



What we know from that is that when run in the region of 5200 to 5500 continuous, the 503 generally goes for about 450 to 500 hours (the original motor on my FS II had about 450 hours or so on it when I replaced it, it was still running fine at the time). The 447 commonly goes even longer than that. The 582 is the only weak one and that's in the area of the crankshaft. But even it commonly still has good compressions after over 400 hours of use



503's run at 6500 continuous may hit the factory 300 hour TBO but the failure rate is somewhat higher. drop 1000rpm off that cruise figure and 300 hours is cake.



 	  Quote: 	
		  

I don't pay much attention to TBO on two or four stroke engines established 

by manufacturers.  There is no guarantee the engines will go that long. 

Most will go well beyond manufacturers "suggested" TBO before performance 

degradation or failure.



john h

mkIII 	




I tend to go with field experience myself, especially when there's a lot of data like there is with the 503.



LS

_________________
LS
Titan II SS

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 04, 2009 1:36 pm Post subject: WRT M3X prop boom measurements.

> Decades of field experience in a variety of planes by a very wide variety 

of pilots. I have about a decade under/in front of the 503 myself.

 >>

10 years is a long time.  How does that equate to flight hours?



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jun 04, 2009 2:03 pm Post subject: Re: WRT M3X prop boom measurements.

 	  John Hauck wrote: 	
		  > Decades of field experience in a variety of planes by a very wide variety 

of pilots. I have about a decade under/in front of the 503 myself.

 >>

10 years is a long time.  How does that equate to flight hours?

john h

mkIII 	

I stopped counting at about 500, but there's some unaccounted-for trike hours and my 100 hours in my FSII since then.

Definitely enough to learn what a fine motor it is... I still have my toolset and a spare gasket set.....

PS: I'd be instructive to know how many hours you have running the 503 at 6500 continuous? I.e. I'm curious about how you arrived at your conclusion.

LS

_________________
LS
Titan II SS

zeprep251(at)aol.com
Guest

Posted: Thu Jun 04, 2009 2:34 pm Post subject: WRT M3X prop boom measurements.

Don't you believe manifold pressure or throttle position should also be a factor in determining % of power calculations? At full throttle my 503 pulled 2 inches of cable out of the housing and turned 6200 on climb out.But at cruise at 5500 it only pulled 7/8 of an inch of cable out of the housing.With no prop on it,it probably would turn 7000 slightly off idle but it would not be a good measure of power production.5800 could be 75% of allowable rpm but not power production it would seem to me.

   Just wondering,G Aman

 

   

 

   

 

 --

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jun 04, 2009 2:49 pm Post subject: Re: WRT M3X prop boom measurements.

 	  zeprep251(at)aol.com wrote: 	
		  Don't you believe manifold pressure or throttle position should also be a factor in determining % of power calculations? At full throttle my 503 pulled 2 inches of cable out of the housing and turned 6200 on climb out.But at cruise at 5500 it only pulled 7/8 of an inch of cable out of the housing.With no prop on it,it probably would turn 7000 slightly off idle but it would not be a good measure of power production.5800 could be 75% of allowable rpm but not power production it would seem to me.

   Just wondering,G Aman

    

  -- 	




Don't know about anyone else, but I do..... 



OTOH, it's hard to tell w/o a manifold pressure gauge which most 503 equipped planes don't have. There you have to approximate the power level based on the load and rpm, etc. So it's reasonable to guess that at a certain rpm you're running such-and-such throttle.



The torque/power graphs for the rotaxen are all done at WOT I believe, so those are max figures possible for each of those rpms. If you're turning those rpm's at more closed throttle settings, or flying at higher altitudes, the power output will be less than that stated on the graph.



Where I live, 3/4 throttle is all you can do unless you have a turbo or supercharger fitted......



LS

_________________
LS
Titan II SS

captainron1(at)cox.net
Guest

Posted: Thu Jun 04, 2009 4:49 pm Post subject: WRT M3X prop boom measurements.

There is no adventage at all to a single nlade prop. The parasitic drag and for that matter the induced drag will be the same. If all the props were designed for optimal effiecncey their total surface area would be almost identical, with probably the single blade prop having a bit more crosse sectional plane, and more parasitic drag as it has to be heavier to handle the root load on the single blade.. In other words to use up 100 HP all the props by deffinition will have pretty much the same total airfoil surface area and the same induced drag curve. 

The problem with the single blade prop using 100 hp will be a tremendous wieght disadventage to boot. so not only it will have the same parasitic ( or more ) drag but also the same induced drag and then it will weigh X times more (lets start with a counter weight that does nothing, then add to that a very thick crank to stop the bending moment on the crank, overbuilt engine mounts and frame, not to mention a very likely resonance that will be impossible to stop as the airframe has to deal with that big asymmetrical load frequency. Look we have two legs, not one. A kangaroo has two hind legs not one. Dogs run faster because they have four legs. Birds have two wings not one, dragon fly has 4 wings not one. If there is a case where one propelling surface with his inherent imbalance was better some creature somewhere would have taken advantage of it.  

Sometimes I think that the original progenitor of the single blade prop was a Jokester.





=================================================================================

---- Richard Girard <aslsa.rng(at)gmail.com> wrote: 



=============

http://www.ultraligero.net/Cursos/varios/helice_de_una_pala.pdf

<http://www.ultraligero.net/Cursos/varios/helice_de_una_pala.pdf>Rick



On Wed, Jun 3, 2009 at 6:35 PM, b young <by0ung(at)brigham.net> wrote:



 	  Quote: 	
		   

 For aircraft like ours, I agree that there wouldn't be much if any

 measurable advantage to a one blade prop, and the associated problems would

 outweigh any slight advantages.  However, they have been used to advantage

 on some model airplanes... control line "speed" ships that can do 200mph,

 with engines turning around 30,000 rpm.  With such tiny props turning so

 fast, the blades ARE close enough together that going to one blade helps.



 -Dana

 >>>>>>>>>>>>>>>>>>.



 Dana



 For a 1 blade to do its job effectively I would think that it should be

 installed on a slick go fast plane.  The cruise would be in keeping with

 the

 large pitch angle needed to use up the HP. And less of the HP being used up

 as parasitic drag.  To put it on a slow aircraft the prop would use up the

 hp but be stalled,  therefore not creating the thrust that it could do on a

 faster craft.



 And as for the 1 blade design being the most efficient,,  I should have

 clarified it by saying in cruise,  and in a tractor configuration, where it

 is not slapping the large pitch against the disturbed air,,   climb would

 probably not be as good even with the pitch reducing coning angle.



 Boyd Young




	


--

kugelair.com

jbhart(at)onlyinternet.ne
Guest

Posted: Thu Jun 04, 2009 5:48 pm Post subject: WRT M3X prop boom measurements.

At 08:49 PM 6/4/09 -0400, you wrote:

 	  Quote: 	
		  

...............
	


If there is a case where one propelling surface with his inherent imbalance was better some creature somewhere would have taken advantage of it.  

 	  Quote: 	
		  Sometimes I think that the original progenitor of the single blade prop was a Jokester.




	


May be a fish?



Jack B. Hart FF004

Winchester, IN

captainron1(at)cox.net
Guest

Posted: Thu Jun 04, 2009 7:05 pm Post subject: WRT M3X prop boom measurements.

Yeah thought about that too, even a shark has two balanced fins to his tail. I suspect Bob Young (?) could be the same troll I bounced off the flygeo list twice, each time with a different name. 



=======================================

---- "Jack B. Hart" <jbhart(at)onlyinternet.net> wrote: 



=============




At 08:49 PM 6/4/09 -0400, you wrote:

 	  Quote: 	
		  

...............
	


If there is a case where one propelling surface with his inherent imbalance was better some creature somewhere would have taken advantage of it.  

 	  Quote: 	
		  Sometimes I think that the original progenitor of the single blade prop was a Jokester.




	


May be a fish?



Jack B. Hart FF004

Winchester, IN

--

kugelair.com

sky-king(at)inbox.com
Guest

Posted: Fri Jun 05, 2009 3:13 am Post subject: WRT M3X prop boom measurements.

Thanks for the info,my main concern is that to make 65-70 mph in cruse Iam wot,6500 rpm and 4.5 gph.I want to increase my flight time,so need to get the fuel burn down into the 3gph range.



[quote] --

by0ung(at)brigham.net
Guest

Posted: Fri Jun 05, 2009 6:34 am Post subject: WRT M3X prop boom measurements.

Don't you believe manifold pressure or throttle position should also be a factor in determining % of power calculations? At full throttle my 503 pulled 2 inches of cable out of the housing and turned 6200 on climb out.But at cruise at 5500 it only pulled 7/8 of an inch of cable out of the housing.With no prop on it,it probably would turn 7000 slightly off idle but it would not be a good measure of power production.5800 could be 75% of allowable rpm but not power production it would seem to me.

   Just wondering,G Aman  

   

 	  Quote: 	
		  >>>>>>>>>>>>>>>>.  

   
	


Manifold pressure is the best way,, and the only way on a plane with a constant speed prop.   But with a fixed pitch prop rpm does extremely well .   and once the relationship between the two is determined,  they are interchangeable.    At least they would be interchangeable as long as the prop is pitched correctly.  

   

Boyd  Young  

   

       [quote][b]

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Thu Jun 18, 2009 7:43 pm Post subject: Re: WRT M3X prop boom measurements.

After reading all the posts I really don't know anything about props.

I think the next prop I buy will be another 2 blade ground adjustable IVO.

It is just so easy to adjust.

I have a Firestar II with a 503 DCDI

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

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