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hrs1(at)frontiernet.net
Guest

Posted: Fri Feb 23, 2007 7:47 am Post subject: Engines

List . . . please be patient while I ask a bunch of probably dumb 

questions re engines for my 701.  I always thought I would use a Rotax 

912 - 80 HP, but an awful lot of my buddies in my flying club are down 

on Rotax due to the continual AD's (is that the right word?).  I also 

see a lot of service notices in the EAA mags.  This sort of surprises me 

since they have been around a long time, and one would think the bumps 

would be smoothed out.



First dumb question - why do all of these engines for LSA and ultralites 

operate at such a high RPM, i.e. in the 5,000 RPM range?  I assume this 

5,000 RPM range has some sort of gearbox.  What are typical prop RPM's 

at cruise?



If I'm not mistaken the engines which powered the Aeronca, Taylorcraft, 

PIper Cub and the like were about 65 HP and were direct drive.  Why 

aren't such engines available for the 701, or are they?  Wouldn't these 

be much quieter (I"m  big on quiet)?  Those old classic birds just 

seemed to putt putt along.  My Piper Dakota of some years ago operated 

in the 2,400 range. 



Has anyone tried a 60HP HKS in a 701?  I've heard nothing but good 

things about the HKS's. Are cowlings and FWF packages available?  I've 

been impressed with the low 2 - 3 gph fuel consumption  of these 

engines.  Would the 701 fly ok with  60 HP?  It's my understanding that 

the 701 was originally designed for something like 55 HP, but I may be 

wrong about this.



Any other thought you might have will be appreciated.  Thank you.  

Robert Schoenberger 701 60%

larry(at)macsmachine.com
Guest

Posted: Fri Feb 23, 2007 9:04 am Post subject: Engines

Robert,

I share your concern with the Rotax engines. They are the most popular, 

but I'd be reluctant to use one because of company attitude and 

continuous "AD" notes. The latest requiring a waterless coolant didn't 

resolve a problem, but does acknowledge one. I'd have preferred they 

found a better fix. Most re-drives are nearly 2 to1, but 5000 rpm is 

only a number at which the peak HP is developed and it doesn't create 

more than the problem with having a re-drive in the first place. There 

are smaller engines that would perform just as well on a 701 and the HKS 

would, but for it’s light weight, is extremely reliable and well proven 

on trikes. Don't think a FWF kit is available at this time. The trend of 

putting the largest engine possible on these light Zeniths fails to 

realize the value of a "light aircraft". I'd also consider VW or the GEO 

aircraft conversions or Suzuki conversion engines. See link,



http://www.ultralightnews.com/sunfun2000/ravenredrivesnf.htm.



You might possibly find a Cont A-65 or a 75 hp Franklin that's 

available. Good engines! Simple! Somewhat Rare, as are some parts!



Larry McFarland - 601HDS at www.macsmachine.com



Robert Schoenberger wrote:

 	  Quote: 	
		   

 <hrs1(at)frontiernet.net>



 List . . . please be patient while I ask a bunch of probably dumb 

 questions re engines for my 701. I always thought I would use a Rotax 

 912 - 80 HP, but an awful lot of my buddies in my flying club are down 

 on Rotax due to the continual AD's (is that the right word?). I also 

 see a lot of service notices in the EAA mags. This sort of surprises 

 me since they have been around a long time, and one would think the 

 bumps would be smoothed out.



 First dumb question - why do all of these engines for LSA and 

 ultralites operate at such a high RPM, i.e. in the 5,000 RPM range? I 

 assume this 5,000 RPM range has some sort of gearbox. What are typical 

 prop RPM's at cruise?



 If I'm not mistaken the engines which powered the Aeronca, 

 Taylorcraft, PIper Cub and the like were about 65 HP and were direct 

 drive. Why aren't such engines available for the 701, or are they? 

 Wouldn't these be much quieter (I"m big on quiet)? Those old classic 

 birds just seemed to putt putt along. My Piper Dakota of some years 

 ago operated in the 2,400 range.

 Has anyone tried a 60HP HKS in a 701? I've heard nothing but good 

 things about the HKS's. Are cowlings and FWF packages available? I've 

 been impressed with the low 2 - 3 gph fuel consumption of these 

 engines. Would the 701 fly ok with 60 HP? It's my understanding that 

 the 701 was originally designed for something like 55 HP, but I may be 

 wrong about this.



 Any other thought you might have will be appreciated. Thank you. 

 Robert Schoenberger 701 60%

zenith601xl(at)gmail.com
Guest

Posted: Fri Feb 23, 2007 9:49 am Post subject: Engines

The HKS is also geared and develops max power at around 6,000 rpm.



 On 2/23/07, LarryMcFarland <larry(at)macsmachine.com (larry(at)macsmachine.com)> wrote: [quote]--> Zenith-List message posted by: LarryMcFarland <larry(at)macsmachine.com  (larry(at)macsmachine.com)>



Robert,

I share your concern with the Rotax engines. They are the most popular,

but I'd be reluctant to use one because of company attitude and

continuous "AD" notes. The latest requiring a waterless coolant didn't 

resolve a problem, but does acknowledge one. I'd have preferred they

found a better fix. Most re-drives are nearly 2 to1, but 5000 rpm is

only a number at which the peak HP is developed and it doesn't create 

more than the problem with having a re-drive in the first place. There

are smaller engines that would perform just as well on a 701 and the HKS

would, but for it's light weight, is extremely reliable and well proven 

on trikes. Don't think a FWF kit is available at this time. The trend of

putting the largest engine possible on these light Zeniths fails to

realize the value of a "light aircraft". I'd also consider VW or the GEO 

aircraft conversions or Suzuki conversion engines. See link,



http://www.ultralightnews.com/sunfun2000/ravenredrivesnf.htm.



You might possibly find a Cont A-65 or a 75 hp Franklin that's 

available. Good engines! Simple! Somewhat Rare, as are some parts!



Larry McFarland - 601HDS at www.macsmachine.com



Robert Schoenberger wrote:

 	  Quote: 	
		   --> Zenith-List message posted by: Robert Schoenberger 

 <hrs1(at)frontiernet.net (hrs1(at)frontiernet.net)>



 List . . . please be patient while I ask a bunch of probably dumb

 questions re engines for my 701. I always thought I would use a Rotax 

 912 - 80 HP, but an awful lot of my buddies in my flying club are down

 on Rotax due to the continual AD's (is that the right word?). I also

 see a lot of service notices in the EAA mags. This sort of surprises 

 me since they have been around a long time, and one would think the

 bumps would be smoothed out.



 First dumb question - why do all of these engines for LSA and

 ultralites operate at such a high RPM,  i.e. in the 5,000 RPM range? I

 assume this 5,000 RPM range has some sort of gearbox. What are typical

 prop RPM's at cruise?



 If I'm not mistaken the engines which powered the Aeronca, 

 Taylorcraft, PIper Cub and the like were about 65 HP and were direct

 drive. Why aren't such engines available for the 701, or are they?

 Wouldn't these be much quieter (I"m big on quiet)? Those old classic 

 birds just seemed to putt putt along. My Piper Dakota of some years

 ago operated in the 2,400 range.

 Has anyone tried a 60HP HKS in a 701? I've heard nothing but good

 things about the HKS's. Are cowlings and FWF packages available? I've 

 been impressed with the low 2 - 3 gph fuel consumption of these

 engines. Would the 701 fly ok with 60 HP? It's my understanding that

 the 701 was originally designed for something like 55 HP, but I may be 


	


[b]

cffd(at)pgrb.com
Guest

Posted: Fri Feb 23, 2007 10:14 am Post subject: Engines

My direct drive Jabiru 2200 works just fine.

Chuck D.

N701TX



---

PatrickW

Joined: 27 Oct 2006
Posts: 380
Location: Fort Worth, Texas

Posted: Fri Feb 23, 2007 11:34 am Post subject: Re: Engines

Scroll down to the bottom page of http://www.zenvair.com/



If you decide you are interested in further research with the Corvair engine, look at www.flycorvair.com



- Patrick

billmileski

Joined: 07 Aug 2006
Posts: 68
Location: Ledyard, CT

Posted: Fri Feb 23, 2007 12:45 pm Post subject: Re: Engines

 	  Quote: 	
		  First dumb question - why do all of these engines for LSA and ultralites 

operate at such a high RPM, i.e. in the 5,000 RPM range? I assume this 

5,000 RPM range has some sort of gearbox. What are typical prop RPM's 

at cruise?



If I'm not mistaken the engines which powered the Aeronca, Taylorcraft, 

PIper Cub and the like were about 65 HP and were direct drive. Why 

aren't such engines available for the 701, or are they? Wouldn't these 

be much quieter (I"m big on quiet)? Those old classic birds just 

seemed to putt putt along. My Piper Dakota of some years ago operated 

in the 2,400 range. 	




The small displacement is for high volumetric efficiency (hp per displacement).  Make a small displacement engine breathe well at high rpm to maintain torque, and inherit increasing hp with rpm. Small displacement equals low weight and small footprint.



Regarding the fear of Rotax..



The service bulletin history reveals the most active closed-loop development process of all the engine manufacturers. Rotax addresses engine issues, maintenance procedures, storage issues, etc etc etc, down to the detail level (e.g. size of vent hole in coolant overflow bottle), because they have a huge number of engines, and a stable installation configuration.  The "scary" bulletins are usually a proactive reaction to a small number of incidents. For example, there is a bulletin requiring mandatory inspection of cylinder bases for cracks. Lockwood Repair told me that this issue has only been seen by them (maybe the most experienced Rotax facility) in engines in towplanes seeing repeated, rapid heating and cooling (and I'm guessing all aircooled engines are at risk here too).  A lot of the service bulletins are there to report upgrades (e.g. reporting new clamps to hold carb sockets in place that automatically keep the 8mm gap, to prevent overtightening by the end user, which was the cause of some carb self-removals).



The 912S has the lowest prop speeds (5000rpm/2.43=2057rpm) and matches the power-to-weight of any engine.  Best floats or stol performance for 701.



Regarding fuel economy, I see 3.2-3.5gph at 4600rpm cruise (cruise pitch).  The HKS is better here, and this is probably a tie with the Jabiru, but the Jabiru requires 100LL, causing a 50% fuel cost addition.



Fuel type:  The 912S requires premium auto fuel.  The HKS has a similar compression ratio (11.3:1) and will be no different.  The Jabiru requires 100LL, and if you want to run 100LL this is a good choice -- the Rotax suffers reduced gearbox life if always using 100LL.  There may be an issue with 10% ethanol in auto fuel and the Rotax, but I am expecting them to say it's okay.



The Rotax is the LSA standard, with maintenance facilities adopting methods to deal with them, at a greater pace than other engines.  Cessna chose it for LSA proof-of-concept.  Also stand in the sidelines of the ultralight area at SNF, listen to the announcer talk about the planes as they take off.. "..powered by the Rotax 912S.." repeated as if a broken record.



All Lycomings, Continentals, and Franklins, and Subarus, exceed the max engine weight limit listed on my 701 plans.  Maybe the limit has been increased since I checked last, dunno.



Rotax powered airplanes are very likely installed in a standard firewall-forward package provided by a kit manufacturer, with standard results.  Insurance companies are most familiar with Rotax (of the non-certified engines).



Rotax has a very stringent documentation practice in order to support a certified engine (installed on lots of certified aircraft, by the way), and we inherit some of the benefit in the uncertified engine.  We get lots of detailed info on maintenance practices, operation in a variety of climates, etc. because of the wider variety of uses and conditions these omnipresent engines are exposed to.



Speaking of climates, the Rotax operates nicely with 200F/200F oil/water temps in my 701, whether it's 95F or -10F outside, as long as I tape over the coolers more as the temperature drops.  I am wondering how the aircooled engines manage.  And you only have to run Evans waterless coolant if you want to push water temps to 260F, otherwise 50/50 standard coolant is fine, and it actually provides better heat removal due to its higer heat capacity.



All the other engine manufacturers are dealing with their own design limitiations and review processes.. Jab with the cooling fin size changes and I think some valve train redesign, plus the current service bulletins on their web site..HKS with a total valve train redesign causing existing engines be replaced, the Subaru conversions with valve guide float and resultant growing pains..  I don't think you can assume their designs are happier just because their documentation is less feverish.



Manufacturer of conversions are even more likely to be playing catch-up with problems with their designs. They are small shops with limited resources, and each installation by their customers is likely very unique. The rate of customer feedback regarding issues is much slower because of the lower number of fielded engines.  Meanwhile Rotax is acquiring vast resources in the huge number of sales of these expensive engines, and further increasing their data gathering rate, and pumping more money into design improvements.



I like the Jabiru, the installation is cleaner, the engine is beautiful, I just wanted the stol the plane could achieve with the higher efficiency of a longer prop at lower rpm, and the few extra hp of the 912S might provide a little extra too.  The HKS is terrific, just forbids floats probably with only 60hp, and again stol suffers.  Everything else was too heavy in my opinion for the 701.



I flew into an airport to meet a friend (fellow builder) and the first words out of his mouth were "gee, I didn't hear you at all until you taxied up", and he was standing outside as I overflew at cruise power.  I have made and received cell phone calls in the cockpit at cruise without a headset adapter (can neither confirm nor deny I was PIC at the time). The noise is similar to a C152. Definitely not excessive.



In sum I would treat the active review process of the Rotax as a big advantage, it was one of the reasons I chose it.  I would look a little closer at the service bulletins if you think you see a lot of "fear" issues there. And browse the NTSB database to get a feel for Rotax related failures before discounting what might be a very good overall choice for a 701.  And none of the engines are perfect by any means.



Bill Mileski

Ledyard, CT

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Fri Feb 23, 2007 12:48 pm Post subject: Engines

By running an engine at a high RPM, you can get the same power out of  

a much smaller and lighter engine, even though you lose some of the  

weight advantage because of the need for a speed reduction unit. The  

tradeoff is a bit more complexity and a few more moving parts. These  

engines actually tend to be quieter than direct drive engines because  

the higher frequencies produced fade out quicker over long distances  

(the high pitched whine can be irritating up close though). In any  

case, most of the noise produced by an airplane is from the propellor  

not the engine. Speed reduction can be helpful here by allowing you  

to run a large prop at a relatively low RPM.



 	  Quote: 	
		   

 <hrs1(at)frontiernet.net>



 First dumb question - why do all of these engines for LSA and  

 ultralites operate at such a high RPM, i.e. in the 5,000 RPM  

 range?  I assume this 5,000 RPM range has some sort of gearbox.   

 What are typical prop RPM's at cruise?




	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

billmileski

Joined: 07 Aug 2006
Posts: 68
Location: Ledyard, CT

Posted: Fri Feb 23, 2007 12:57 pm Post subject: Re: Engines

 	  Quote: 	
		  All the other engine manufacturers are dealing with their own design limitiations and review processes.. Jab with the cooling fin size changes and I think some valve train redesign, plus the current service bulletins on their web site..HKS with a total valve train redesign causing existing engines be replaced, the Subaru conversions with valve guide float and resultant growing pains.. I don't think you can assume their designs are happier just because their documentation is less feverish. 

	




Just to clarify -- the problems with the Jab and HKS referred to, are the old problems, not new ones. I meant to say "All the other engine manufacturers HAVE DEALT with their own design.." instead of "are dealing with". I don't want to imply that the Jab or HKS are undergoing major redesign, just that they did.



Sorry for any confusion.



Bill Mileski

Ledyard, CT

p.mulwitz(at)worldnet.att
Guest

Posted: Fri Feb 23, 2007 12:57 pm Post subject: Engines

Hi Robert,



I have been following the responses to your engine questions, and 

noticed nobody seems to have answered your question about engine RPM 

being so high.



There are two different kinds of engines used in airplanes:  Ones 

that were designed for aircraft use and ones designed for another 

application that have been modified for aircraft use.



The big limiting factor in aircraft is the limit imposed by 

propellers.  A longer propeller generally works better than a shorter 

one, but propeller RPM is limited by the propeller length.  As RPM 

increases, the speed of the propeller tip also increases according to 

simple geometry.  As the propeller tip approaches the speed of sound 

it becomes inefficient, and if allowed to hit the speed of sound it 

can be destroyed.  So there is a trade off between RPM and propeller length.



Aircraft engines are designed to live with unusually low RPM limits 

because of the propeller trade off.  Engines designed for other 

purposes tend to use much higher RPM that is limited by engine design 

issues rather than propeller issues.  To become more compatible with 

propellers some sort of reduction gear or other reduction method is 

used to make the final RPM compatible with propellers.  Many use a 

PSRU (Propeller Speed Reduction Unit?) while some others use belt and 

pulley approaches.  In other cases, the engine is used in direct 

drive mode even though it is less efficient at the low RPM.



It is easy to tell that a Corvair or Subaru or VW engine is converted 

from automobile use for airplane use.  The Rotax is a little more 

difficult to guess.  This line of engines was originally designed to 

operate snowmobiles and modified for aircraft use.  It may well be 

that more Rotax engines are currently sold for aviation than 

snowmobile use, but that is their history.



Good luck with your engine hunt.  We all go through this since 

engines are a very significant part of the cost of a home built airplane.



Paul

XL Fuselage

At 07:41 AM 2/23/2007, you wrote:

 	  Quote: 	
		  



List . . . please be patient while I ask a bunch of probably dumb 

questions re engines for my 701.  I always thought I would use a 

Rotax 912 - 80 HP, but an awful lot of my buddies in my flying club 

are down on Rotax due to the continual AD's (is that the right 

word?).  I also see a lot of service notices in the EAA mags.  This 

sort of surprises me since they have been around a long time, and 

one would think the bumps would be smoothed out.



First dumb question - why do all of these engines for LSA and 

ultralites operate at such a high RPM, i.e. in the 5,000 RPM 

range?  I assume this 5,000 RPM range has some sort of 

gearbox.  What are typical prop RPM's at cruise?



If I'm not mistaken the engines which powered the Aeronca, 

Taylorcraft, PIper Cub and the like were about 65 HP and were direct 

drive.  Why aren't such engines available for the 701, or are 

they?  Wouldn't these be much quieter (I"m  big on quiet)?  Those 

old classic birds just seemed to putt putt along.  My Piper Dakota 

of some years ago operated in the 2,400 range.

Has anyone tried a 60HP HKS in a 701?  I've heard nothing but good 

things about the HKS's. Are cowlings and FWF packages 

available?  I've been impressed with the low 2 - 3 gph fuel 

consumption  of these engines.  Would the 701 fly ok with  60 

HP?  It's my understanding that the 701 was originally designed for 

something like 55 HP, but I may be wrong about this.



Any other thought you might have will be appreciated.  Thank you.

Robert Schoenberger 701 60%


	


---------------------------------------------

N601RT

Joined: 25 Feb 2006
Posts: 31
Location: Hillsboro, Oregon

Posted: Fri Feb 23, 2007 10:27 pm Post subject: Re: Engines

Robert,



Don't make your choice based on opinions from people that may not have real facts. Be careful to understand what are facts and what is rumor, possibly â€œfear of the unknownâ€. 



We all make significant investments (time and/or money) in our engines and therefore tend to think we have made the best choice. I think this can color our opinions.



I agree the reason there are "lots of ADs" on Rotax 9xx engines is because there are LOTs of Rotax engines in service. I was told that there are more than 20,000 9xx engines in service a year ago. I just read that Rotax is currently producing 5,000 9xx family engines per year. (Both figures from Eric Tucker who teaches a GREAT Rotax maintenance class and who is THE technical guru for Kodiak [North America Rotax distributor]. Lockwood is an example of a dealer who gets their engines from Kodiak.)



All engines have their pluses and minuses. My perspective on Rotax +/-



Minuses:

Expensive (compared to Corvair and Subaru conversion, I believe similar price to Jabaru)

Parts are relative expensive

18a alternator (which I think this is relatively low output)



Positive:

Reliable

Light overall installed weight for the horsepower

Quiet

Water cooled heads. (Different than water cooled engine, simpler)

Mine basically does not use oil. I assume this is typical

Nicasil plated cylinders, close tolerance pistons

Shock cooling is not a concern

Broad dealer network. (But your local A&P may not be familiar with it.)

Large corporation stands behind and supports the engine

LOTs of engines in service. Many examples of these have gone to TBO more than once.

Optional 2nd alternator available. (Corvair and Subaru conversions have option for a variety of alternators. Jabaru has relatively low output alternator as does 9xx series.)

Service and installation manuals available on line for download.

Service Bulletins (ADs) available on line. These ARE NOT required for engines that are not certified. Recommend that you carefully understand what and why they are published.

My local EAA chapter has done some noise testing. Richard VanGrunsven, his brothers and lots of other RV owner's are in the chapter. My plane was the quietest tested during climb out at the end of the runway and tied for quietest with the factory RV-10 for 1000 foot over flight at 90kts. The tests also include â€œproductionâ€ planes.

Paul's post to this thread has some misleading statements.



There is no need to guess the history of the Rotax 912, 914 engine series. The Rotax 912, 914 series of engines are clean sheet, modern design aircraft engines. Yes Bombardier (parent company Rotax) makes snowmobile engines, but the 9xx series IS NOT related to the snowmobile engines. Before Bombardier created the separate Recreational Products division, the company who owned Rotax also owned Learjet. Maybe the 9xx was derived from a Learjet.   



Propeller tips that are supersonic lose efficiency. They can be destroyed, but there are many propellers that go supersonic regularly. Not saying this is recommended, just not a certain disaster.



Regards,



Roy



N601RT: CH601HDS, nose gear, Rotax 912ULS, All electric, IFR equipped, 681hrs, 802 landings

btucke73(at)yahoo.com
Guest

Posted: Sat Feb 24, 2007 9:05 am Post subject: Engines

 	  Quote: 	
		  > As RPM increases, the speed of the propeller tip

also increases >>according to simple geometry.
	




True.



 	  Quote: 	
		  >  As the propeller tip approaches the speed of sound


	


 	  Quote: 	
		  >it becomes inefficient, 


	


True.



 	  Quote: 	
		  >and if allowed to hit the speed of sound it can be

destroyed.
	




I would love to see your reference on this one.  The

Texan I fly on weekends has the tips go supersonic

just about every flight.  I haven't done the math, and

don't care to, but you can hear the difference when it

takes off.  When I take off, I pull back the prop as

soon as I get the gear up, and it purrs by.  Most of

our pilots leave the prop up until at altitude.  The

sound is a high pitched whine.  The difference in RPM

is only 100 - 200.  You can often hear the same thing

on Bonanzas and others if the prop is left up.  



R/



Brandon

601 HDS / TD / Corvair

70 hours

 

Never miss an email again!

Yahoo! Toolbar alerts you the instant new Mail arrives.

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naumuk(at)alltel.net
Guest

Posted: Sat Feb 24, 2007 9:37 am Post subject: Engines

Or physics, depending on how you look at it.

                    do not archive

Bill Naumuk

HDS Fuselage

Townville, Pa

---

p.mulwitz(at)worldnet.att
Guest

Posted: Sat Feb 24, 2007 11:22 am Post subject: Engines

Hi Brandon,

No, I don't have a specific reference on the supersonic prop tips.  I 

wonder if your Texan tips are actually going supersonic or if they 

are just transonic.  Do you get a sonic boom?

There is a nice prop tip speed calculator on the Culver prop web 

site.  You can plug in the RPM and prop diameter to get an estimate 

of the mach number for the tips.  Of course, mach number varies a 

great deal with air conditions, but it still might be interesting to see.

I am amused by the responses I am getting to a post I didn't think 

would be at all controversial.  I was merely trying to help Robert 

understand the answer to his question of why some engines run at such 

high RPM.  Your question about tips going over mach 1 was also 

mentioned by Roy while he strongly defended the ancestry of the Rotax 

engine design.  I guess I am just an irritating guy . . .

Paul

At 09:00 AM 2/24/2007, you wrote:

 	  Quote: 	

 >> As RPM increases, the speed of the propeller tip

also increases >>according to simple geometry.

True.

 >>  As the propeller tip approaches the speed of sound

 >>it becomes inefficient,

True.

 >>and if allowed to hit the speed of sound it can be

destroyed.

I would love to see your reference on this one.  The

Texan I fly on weekends has the tips go supersonic

just about every flight.  I haven't done the math, and

don't care to, but you can hear the difference when it

takes off.  When I take off, I pull back the prop as

soon as I get the gear up, and it purrs by.  Most of

our pilots leave the prop up until at altitude.  The

sound is a high pitched whine.  The difference in RPM

is only 100 - 200.  You can often hear the same thing

on Bonanzas and others if the prop is left up.

R/

Brandon

601 HDS / TD / Corvair

70 hours

Never miss an email again!

Yahoo! Toolbar alerts you the instant new Mail arrives.

http://tools.search.yahoo.com/toolbar/features/mail/

---------------------------------------------

Paul Mulwitz

32013 NE Dial Road

Camas, WA 98607

---------------------------------------------

n801bh(at)netzero.com
Guest

Posted: Sat Feb 24, 2007 4:56 pm Post subject: Engines

 	  Quote: 	
		  >and if allowed to hit the speed of sound it can be

destroyed.

I would love to see your reference on this one.  The

Texan I fly on weekends has the tips go supersonic

just about every flight.  I haven't done the math, and

don't care to, but you can hear the difference when it

takes off.  When I take off, I pull back the prop as

soon as I get the gear up, and it purrs by.  Most of

our pilots leave the prop up until at altitude.  The

sound is a high pitched whine.  The difference in RPM

is only 100 - 200.  You can often hear the same thing

on Bonanzas and others if the prop is left up.  

R/

Brandon

601 HDS / TD / Corvair

70 hours

I have had my prop at 1.2 mach. In fact it gets over mach everytime I fly. 76" three blade inflight adjustable Ivo. 160+ hours and the tips look as good as the day I installed them. 

do not archive

Ben Haas

N801BH

www.haaspowerair.com

-- Brandon Tucker <btucke73(at)yahoo.com> wrote:

--> Zenith-List message posted by: Brandon Tucker <btucke73(at)yahoo.com>

 	  Quote: 	
		  > As RPM increases, the speed of the propeller tip

also increases >>according to simple geometry.

True.

 	  Quote: 	
		  >  As the propeller tip approaches the speed of sound

 	  Quote: 	
		  >it becomes inefficient, 

True.

 	  Quote: 	
		  >and if allowed to hit the speed of sound it can be

destroyed.

I would love to see your reference on this one.  The

Texan I fly on weekends has the tips go supersonic

just about every flight.  I haven't done the math, and

don't care to, but you can hear the difference when it

takes off.  When I take off, I pull back the prop as

soon as I get the gear up, and it purrs by.  Most of

our pilots leave the prop up until at altitude.  The

sound is a high pitched whine.  The difference in RPM

is only 100 - 200.  You can often hear the same thing

on Bonanzas and others if the prop is left up.  

R/

Brandon

601 HDS / TD / Corvair

70 hours

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   [quote][b]

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Feb 24, 2007 6:15 pm Post subject: Engines

I'm only going to tackle one question you asked.



About the high RPM of the newer engines.  Horsepower is a factor of many

things a few of which are the displacement of the engine and the number of

power pulses per minute.  Increase the number of power pulses and you

increase the horsepower.  Of course there is a level of diminishing returns

on this or we would all be driving cars with thimble size engines turning 5

million RPM. And producing 500 hp..  Older engines were designed for the

props they would be turning.  Those props were most efficient below 3000 RPM

so the engines were designed to have a max RPM of below 3000.  They

increased their power by adding cubic inches.  Basically bigger cylinders

and more cylinders.  Quite a few of the radial engines had planetary

reduction gearing in the nose that allowed than to max out at around 5000.



A few things to consider are the improvements in engineering and materials

in the last seventy years.  Newer bearings, cylinder walls and better

cooling methods allow much higher revving engines.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

badbob

Joined: 07 Jan 2007
Posts: 8
Location: Willamina, Oregon

Posted: Sat Feb 24, 2007 11:26 pm Post subject: Engines

Â¨I have had my prop at 1.2 mach. In fact it gets over mach everytime I

fl

y. 76" three blade inflight adjustable Ivo. 160+ hours and the tips look

 as good as the day I installed them.Â¨

do not archive

Ben Haas

N801BH

www.haaspowerair.com



WOW!!! At 70 degrees F that is 3400rpm for Mach 1.0 and at Mach 1.2 that

is around 4100rpm! I am surprised that the prop can take that!



Bob from Oregon.

_________________
Bob Johnson
601XL scratch built.
badbob0007(at)earthlink.net

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sun Feb 25, 2007 6:53 am Post subject: Engines

Those numbers will come down a bit when  you take into account the  

forward speed of the airplane. But still, that would be one noisy  

airplane. Ben's neighbors must really  love him. 



On Feb 25, 2007, at 6:24 PM, BadBob wrote:

 	  Quote: 	
		  

> On Feb 25, 2007, at 12:53 AM, n801bh(at)netzero.com wrote:

>

> ¨I have had my prop at 1.2 mach. In fact it gets over mach  

> everytime I

> fl

> y. 76" three blade inflight adjustable Ivo. 160+ hours and the  

> tips look

>  as good as the day I installed them.¨

> do not archive



 WOW!!! At 70 degrees F that is 3400rpm for Mach 1.0 and at Mach 1.2  

 that

 is around 4100rpm! I am surprised that the prop can take that!



 Bob from Oregon. 


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

n801bh(at)netzero.com
Guest

Posted: Sun Feb 25, 2007 7:02 am Post subject: Engines

I should clarify that the 1.2 number was from my 84" blades at -31 f here in Jackson Hole. Take 4700 motor rpm , redrive ratio of 1.43-1 = 3216.78, Whats that mach number ??  I haven't seen 70 degrees since last oct.. <G> 

do not archive 

Ben Haas

N801BH

www.haaspowerair.com



-- BadBob <badbob0007(at)earthlink.net> wrote:

--> Zenith-List message posted by: BadBob <badbob0007(at)earthlink.net>



Â¨I have had my prop at 1.2 mach. In fact it gets over mach everytime I

fl

y. 76" three blade inflight adjustable Ivo. 160+ hours and the tips look

 as good as the day I installed them.Â¨

do not archive

Ben Haas

N801BH

www.haaspowerair.com



WOW!!! At 70 degrees F that is 3400rpm for Mach 1.0 and at Mach 1.2 that

is around 4100rpm! I am surprised that the prop can take&nbsp================================================sp;    - The Zenith-List Email Fp;List utilities such as the Subscriptions&nbsp================================================      - NEW MATRONICS WEB&n========================================================   [quote][b]

n801bh(at)netzero.com
Guest

Posted: Sun Feb 25, 2007 7:19 am Post subject: Engines

Thats why I don't run the 84" blades anymore at those speeds.   Close neighbors to the airport are mostly motorheads so the engine itself is music to them. The real issue is JAC is the only airport located in a National park and us locals do try to keep the racket down to a mininum. 

do not archive

Ben Haas

N801BH

www.haaspowerair.com

-- Bryan Martin <bryanmmartin(at)comcast.net> wrote:

--> Zenith-List message posted by: Bryan Martin <bryanmmartin(at)comcast.net>

Those numbers will come down a bit when  you take into account the  

forward speed of the airplane. But still, that would be one noisy  

airplane. Ben's neighbors must really  love him. 

On Feb 25, 2007, at 6:24 PM, BadBob wrote:

 	  Quote: 	

> On Feb 25, 2007, at 12:53 AM, n801bh(at)netzero.com wrote:

>

> ¨I have had my prop at 1.2 mach. In fact it gets over mach  

> everytime I

> fl

> y. 76" three blade inflight adjustable Ivo. 160+ hours and the  

> tips look

>  as good as the day I installed them.¨

> do not archive

 WOW!!! At 70 degrees F that is 3400rpm for Mach 1.0 and at Mach 1.2  

 that

 is around 4100rpm! I am surprised that the prop can take that!

 Bob from Oregon. 

-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

<========================         - The Zeatronics List Features Navigator to browse

_-= the many List utilities such as sp;  --> http://www.matronics.com/Navigator?Zenith-Lis========================sp;          - NEat content now also available via the&nbsp=========================================   [quote][b]

n801bh(at)netzero.com
Guest

Posted: Sun Feb 25, 2007 7:46 am Post subject: Engines

My bad,,,,  the real speed is 106%, 

let the flame wars begin........ 

do not archive

Ben Haas

N801BH

www.haaspowerair.com



-- "n801bh(at)netzero.com" <n801bh(at)netzero.com> wrote:

 

I should clarify that the 1.2 number was from my 84" blades at -31 f here in Jackson Hole. Take 4700 motor rpm , redrive ratio of 1.43-1 = 3216.78, Whats that mach number ??  I haven't seen 70 degrees since last oct.. <G> 

do not archive 

Ben Haas

N801BH

www.haaspowerair.com



-- BadBob <badbob0007(at)earthlink.net> wrote:

--> Zenith-List message posted by: BadBob <badbob0007(at)earthlink.net>



Â¨I have had my prop at 1.2 mach. In fact it gets over mach everytime I

fl

y. 76" three blade inflight adjustable Ivo. 160+ hours and the tips look

 as good as the day I installed them.Â¨

do not archive

Ben Haas

N801BH

www.haaspowerair.com



WOW!!! At 70 degrees F that is 3400rpm for Mach 1.0 and at Mach 1.2 that

is around 4100rpm! I am surprised that the prop can take ================================================sp;    - The Zenith-List Email Fp;List utilities such as the Subscriptions ================================================      - NEW MATRONICS WEB&n========================================================[quote]



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