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[70.209.0.95]) by mx.google.com with ESMTPSA id 48sm46883417yhq.11.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 07 Oct 2013 14:49:18 -0700 (PDT) Subject: Re: [FlyRotary] Re: Prop and PSRU efficiency References: From: Tracy Content-Type: multipart/alternative; boundary=Apple-Mail-FF49A306-A608-4BA8-A01D-52E400C0F9FE X-Mailer: iPad Mail (10B329) In-Reply-To: Message-Id: <94369886-A42A-4105-9B69-F321B1B970F6@gmail.com> Date: Mon, 7 Oct 2013 17:48:53 -0400 To: Rotary motors in aircraft Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) --Apple-Mail-FF49A306-A608-4BA8-A01D-52E400C0F9FE Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Wikipedia is generally a pretty good source for info. They put planetary l= osses at around 3%. That sounds about right to me. A simple spur or helic= al gear set is around 2% loss and I would expect the planetary to be a bit h= igher due to the higher number of gears in mesh. Tracy Sent from my iPad On Oct 7, 2013, at 17:42, "Bill Bradburry" wrote:= > Based on the below statement, where would Tracy=E2=80=99s planet gear syst= em fall? > =20 > PSRUs have losses inherent in their gearsets or belts. Lay people have oft= en speculated that these losses are up to 40 hp in the case of a 200 hp clas= s drive. This is absurd as it would represent about 30,000 watts being dissi= pated as heat. If this was in fact true, the case or belts would melt in jus= t a few minutes. Typical losses for single mesh spur and helical gears is ar= ound 2-2.5%. HTD belts run at 3-4%. Twin mesh helical gearsets would then ha= ve perhaps a 6% loss as worst case including bearing losses. >=20 > The statement came from: > =20 > http://www.sdsefi.com/air51.htm > =20 > B2 > =20 > From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Be= half Of Bill Bradburry > Sent: Monday, October 07, 2013 3:42 PM > To: Rotary motors in aircraft > Subject: [FlyRotary] Re: Prop and PSRU efficiency > =20 > Mark, > =20 > They would be included if the engine was tested on a dyno, so I consider t= hem to be part of the engine. But not so the PSRU if measuring from the fly= wheel. > =20 > Ernest, > =20 > I don=E2=80=99t know what you mean by .98 to .99?? Certainly you don=E2=80= =99t think it would only be a loss of 1 or 2%!?? It would have to be in the= range of 10 to 20 HP or even greater. That is 5 to 10% in our HP range. J= ust the loss due to prop efficiency is in the range of 30 HP! > =20 > Bill > =20 > From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Be= half Of Mark Steitle > Sent: Monday, October 07, 2013 1:26 PM > To: Rotary motors in aircraft > Subject: [FlyRotary] Re: Prop and PSRU efficiency > =20 > Bill, > =20 > While you're at it don't forget to account for the water pump and alternat= or(s). > =20 > Mark S. > =20 >=20 > On Mon, Oct 7, 2013 at 12:18 PM, Bill Bradburry = wrote: > I have asked this question a couple of times and no one has hazarded a > guess. >=20 > How much HP is lost from our engines due to the PSRU? I have been > interested in determining what the HP output of my engine is and that info= > would be needed for that estimation. >=20 > They tell me that most props are about 80-85% efficient, so to calculate t= he > hp, you take the difference between your climb rate and your glide descent= > rate at the same airspeed, multiplied by the weight, and then divided by > 33000. >=20 > Wt * V / 33000 =3D HP >=20 > This would be the prop HP, so to get the prop flange HP, you would divide b= y > the prop efficiency, between .8 and .85. >=20 > To get the engine flywheel HP, you would have to add something for the los= s > of the PSRU. >=20 > Is anyone willing to take a shot at that number?? Third or forth chance! > :>) >=20 > Bill B >=20 >=20 >=20 >=20 > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List= .html > =20 --Apple-Mail-FF49A306-A608-4BA8-A01D-52E400C0F9FE Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Wikipedia is generally a pretty good s= ource for info.   They put planetary losses at around 3%.  That so= unds about right to me.   A simple spur or helical gear set is around 2= % loss and I would expect the planetary to be a bit higher due to the higher= number of gears in mesh.

Tracy

Sent from my= iPad

On Oct 7, 2013, at 17:42, "Bill Bradburry" <bbradburry@bellsouth.net> wrote:
=

Based on the below statement, where wou= ld Tracy= =E2=80=99s planet gear system fall?

 

PSRUs have losses inherent in their gearsets or belts. Lay people have often speculated that these losses are up to 40 hp in the case of a 200 hp class drive. This is absurd as it would represent about 30,000 watts being dissipa= ted as heat. If this was in fact true, the case or belts would melt in just a fe= w minutes. Typical losses for single mesh spur and helical gears is around 2-2.5%. HTD belts run at 3-4%. Twin mesh helical gearsets would then have perhaps a 6% loss as worst case including bearing losses.<= /font>

The statement came from:

 

http://www.sdsefi.com/air51.htm

 

B2

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironli= ne.net] On Behalf Of Bill Bradburry
Sent: Monday, October 07, 201= 3 3:42 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Prop= and PSRU efficiency

 

Mark,

 

They would be included if the engine wa= s tested on a dyno, so I consider them to be part of the engine.  But not= so the PSRU if measuring from the flywheel.

 

Ernest,

 

I don=E2=80=99t know what you mean by .= 98 to .99??  Certainly you don=E2=80=99t think it would only be a loss of 1 o= r 2%!??  It would have to be in the range of 10 to 20 HP or even greater.  That is 5 to 10% in our HP range.  Just the loss due to prop efficiency is in the range of 30 HP!

 

Bill

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironli= ne.net] On Behalf Of Mark Steitle
Sent: Monday, October 07, 201= 3 1:26 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Prop= and PSRU efficiency

 

Bill,

 

While you're at it don't forget to account for the water pump and alternator(s).

 

Mark S.

 <= /font>

On Mon, Oct 7, 2013 at 12:18 PM, Bill Bradburry <bbradburry@bellsouth.net> wrote:

I have asked this question a couple of times and no one has hazarded= a
guess.

How much HP is lost from our engines due to the PSRU?  I have been
interested in determining what the HP output of my engine is and that info would be needed for that estimation.

They tell me that most props are about 80-85% efficient, so to calculate the=
hp, you take the difference between your climb rate and your glide descent rate at the same airspeed, multiplied by the weight, and then divided by
= 33000.

Wt * V / 33000 =3D HP

This would be the prop HP, so to get the prop flange HP, you would divide by=
the prop efficiency, between .8 and .85.

To get the engine flywheel HP, you would have to add something for the loss<= br> of the PSRU.

Is anyone willing to take a shot at that number??  Third or forth chanc= e!
:>)

Bill B




--
Homepage:  http= ://www.flyrotary.com/
Archive and UnSub:   http://mail.lancaironline.net:81/list= s/flyrotary/List.html

 

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