Based on the below statement, where would Tracy’s 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 dissipated
as heat. If this was in fact true, the case or belts would melt in just a few
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.
The statement came from:
http://www.sdsefi.com/air51.htm
B2
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Bradburry
Sent: Monday, October 07, 2013
3:42 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Prop and
PSRU efficiency
Mark,
They would be included if the engine was
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’t know what you mean by .98 to
.99?? Certainly you don’t 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. Just the loss due to
prop efficiency is in the range of 30 HP!
Bill
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mark Steitle
Sent: Monday, October 07, 2013
1:26 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Prop and
PSRU efficiency
While you're at it don't forget to account for the water pump and
alternator(s).
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 = 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
of the PSRU.
Is anyone willing to take a shot at that number?? Third or forth chance!
:>)
Bill B
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