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[166.248.68.167]) by mx.google.com with ESMTPS id n24sm5042803yhj.13.2012.03.01.05.43.00 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 01 Mar 2012 05:43:02 -0800 (PST) Subject: Re: [FlyRotary] Re: Throttle Back Bobble References: From: Tracy Content-Type: multipart/alternative; boundary=Apple-Mail-22-114864401 X-Mailer: iPad Mail (8F191) In-Reply-To: Message-Id: <4E8CB9FB-239F-4ADE-96C3-CEB8923768C9@gmail.com> Date: Thu, 1 Mar 2012 08:42:59 -0500 To: Rotary motors in aircraft Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (iPad Mail 8F191) --Apple-Mail-22-114864401 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii I don't think so but that's just my opinion. No one has had any trouble wi= th the snubber so far. It normally is not under load except during start up= because the input gear is hydraulically loaded against the thrust bearing b= y engine oil pressure. I do not know how much reverse thrust it would take= to overcome that pressure. Just cautioning against going to idle and point= ing the plane steeply down hill for the reasons already stated. Tracy Sent from my iPad On Feb 28, 2012, at 8:14 PM, Kelly Troyer wrote: > Tracy, > Does this problem warrant the addition of a thrust bearing in place o= f the nylon snubber (if this is even economically or > physically possible) ??... > =20 > Kelly Troyer >=20 > On Thu, Feb 23, 2012 at 7:03 AM, Tracy wrote: > What Lynn said. Most newer cars cut the fuel in that condition and it DO= ES eliminate the miss because the engine isn't even running. We don't want= to go there because of the lack of lubrication. =20 >=20 > But most of us pilots were taught to make all throttle changes smoothly an= d gradually anyway. Slamming the throttle closed is considered bad form in= an airplane. We do need to deal with the situation where we are going dow= nhill at the end of a flight and the engine can be windmilling for significa= nt periods of time. We are in a special situation for two reasons. First= is the lack of apex seal lubrication Lynn mentioned but also the limitation= of the gear drive. The nylon snubber in the drive is not designed to absor= b long term reverse thrust when the engine windmills. I'm always conscious= of maximizing the energy of altitude and descend with a small amount of pow= er rather than the drag of a windmilling prop. This maximizes fuel economy,= keeps the apex seals happy and keeps the torque going in the right directio= n in the gear drive. The number will be different for different airplanes b= ut for RVs a descent rate of around 300 fpm at 130 - 140 mph IAS works out w= ell. Plan ahead and watch the Vnav numbers on your GPS for when it's time t= o start down. If you have an autopilot, program it for the appropriate num= bers. We don't fly 747s so throttle control is still up to you. >=20 > Tracy >=20 > Sent from my iPad >=20 > On Feb 22, 2012, at 6:42 PM, Lehanover@aol.com wrote: >=20 >> Closed throttle at high revs makes a good fuel burn (idle mixture) unlike= ly. The effective compression ratio drops to near zero due to poor cylinder f= illing. >> =20 >> Fuel molecules are very far apart. The stock Renesis maps up to 44 degre= e of advance in this situation. The mixture burns very slowly requiring the a= dded advance (more time to burn). Popping and clicking is still burning mixt= ure lighting charges in the headers (turbo?) from chambers that didn't light= at all. (Misses). >> =20 >> In racing engines we didn't use the OMP and only premixed synthetic 2 cyc= le oil. So I jetted the idle mix real rich to keep the lube going in high re= v closed throttle moments. >> =20 >> The sheets of fire out the tail pipe was a crowd pleaser as well as the e= xplosions on gear changes. It didn't count against our 105 Db sound limit. >> =20 >> Lynn E. Hanover >> =20 >> In a message dated 2/22/2012 4:37:57 P.M. Eastern Standard Time, cbarber@= texasattorney.net writes: >> I had the same issue. I cut the fuel and added a bunch of advance for hi= gh-rev/low-MP operations. Cleaned it right up. >=20 >=20 >=20 > --=20 > Kelly Troyer > Dyke Delta_"Eventually" > 13B_RD1C_EC2_EM2 --Apple-Mail-22-114864401 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=utf-8
I don't think so but that's just my opi= nion.   No one has had any trouble with the snubber so far.  It no= rmally is not under load except during start up because the input gear is hy= draulically loaded against the thrust bearing by engine oil pressure.  = I do not know how much reverse thrust it would take to overcome that pressu= re.  Just cautioning against going to idle and pointing the plane steep= ly down hill for the reasons already stated.

Tracy<= br>
Sent from my iPad

On Feb 28, 2012, at 8:14 PM, Kelly Tr= oyer <keltro@gmail.com> wrote:=

   Tr= acy,
     Does this problem warrant the addition of a th= rust bearing in place of the nylon snubber (if this is even economically or<= /div>
physically possible) ??...
 
   Kelly Troyer

On Thu, Feb 23, 2012 at 7:03 AM, Tracy <rwstracy@gmail.com> wrote:
What Lynn said.   Most newer cars cut the fuel in that condition a= nd it DOES eliminate the miss because the engine isn't even running.   W= e don't want to go there because of the lack of lubrication.   

But most of us pilots were taught to make all throttle changes smoothly= and gradually anyway.   Slamming the throttle closed is considered bad= form in an airplane.   We do need to deal with the situation where we a= re going downhill at the end of a flight and the engine can be windmilling f= or significant periods of time.   We are in a special situation for two= reasons.   First is the lack of apex seal lubrication Lynn mentioned b= ut also the limitation of the gear drive.  The nylon snubber in the dri= ve is not designed to absorb long term reverse thrust when the engine windmi= lls.   I'm always conscious of maximizing the energy of altitude and de= scend with a small amount of power rather than the drag of a windmilling pro= p.  This maximizes fuel economy, keeps the apex seals happy and keeps t= he torque going in the right direction in the gear drive.  The number w= ill be different for different airplanes but for RVs a descent rate of aroun= d 300 fpm at 130 - 140 mph IAS works out well.  Plan ahead and watch th= e Vnav numbers on your GPS for when it's time to start down.   If you h= ave an autopilot, program it for the appropriate numbers.   We don't fl= y 747s so throttle control is still up to you.

Tracy

Sent from my iPad

On Feb 22, 2012, at 6:42 PM, Lehanover@aol.com<= /a> wrote:

Closed throttle at high revs makes a good fuel burn (idle mixture) unli= kely. The effective compression ratio drops to near zero due to poor cylinde= r filling.
 
 Fuel molecules are very far apart. The stock Renesis maps up to 4= 4 degree of advance in this situation. The mixture burns very slowly requiri= ng the added advance (more time to burn). Popping and clicking is still burn= ing mixture lighting charges in the headers (turbo?) from chambers that didn= 't light at all. (Misses).
 
In racing engines we didn't use the OMP and only premixed synthetic 2 c= ycle oil. So I jetted the idle mix real rich to keep the lube going in high r= ev closed throttle moments.
 
The sheets of fire out the tail pipe was a crowd pleaser as well as the= explosions on gear changes. It didn't count against our 105 Db  sound l= imit.
 
Lynn E. Hanover
 
In a message dated 2/22/2012 4:37:57 P.M. Eastern Standard Time, cbarber@texasattorney.net writes:
I had the same issue.  I cut the fuel and added a bu= nch of advance for high-rev/low-MP operations.  Cleaned it right up.



--
Kelly Troyer
Dyke Delta_"Ev= entually"
13B_RD1C_EC2_EM2
= --Apple-Mail-22-114864401--