The loss of HP in the reduction unit is not affected by engine accessories, or tuning errors or anything but the actual torque applied to the input shaft of the reduction unit.

There will be losses as reflected in the rise of oil (coolant) temperatures. Prop losses have no effect on reduction unit losses so long as all available HP is absorbed by the propeller. I suggest that losses are actually minimal. The format is the best choice for the job and the most efficient system,  (planetary). A loss of 10 to 20 HP would require

a very large cooler for just the reduction unit. This system is the first gear reduction from a Ford diesel truck with 450 to 600 foot pounds of torque. It would seem to be under little stress in an aircraft situation where a rotary engine is used as the torque output is low compared to piston engines. 160 HP at 5,500 RPM requires 152.78 foot pounds of torque. 160 HP at 6,000 RPM requires 140 foot pounds of torque.

 

Modern automotive applications now use up to 6 reduction speeds to achieve better fuel economy.So, adding planetary's to improve mileage tells me that planetary's are very efficient indeed.

 

Lynn E. Hanover 

 

 

 

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

 

Bill,

 

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

 

Mark 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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