User-Agent: Microsoft-Entourage/10.1.4.030702.0
Date: Wed, 21 Apr 2004 22:39:03 -0400
Subject: Re: [FlyRotary] Re: Performance Props
From: Bulent Aliev <atlasyts@bellsouth.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Message-ID: <BCACA887.B956%atlasyts@bellsouth.net>
In-Reply-To: <list-3183448@logan.com>
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> 
> Tell me:
> your engine HP at X RPM sealevel

My guess is 260 HP at 6300 RPM

> redrive ratio

Tracy's 2.175:1

> cruise RPM, and desired cruise speed at that RPM

5500 rpm 180 knots

> number of blades, 2 or 3 (probably 3)

3 blade

> prop diameter (limited by rotation angle on a pusher)

68"

Here is a discussion on John Slade's propellor with about the same engine
setup:
> 
>> > called Tracy and picked his brains A summary of our conversation
>> > follows:
>> > 
>> > 
>> > Drive bushing dia: 5/8
>> > Drive bushing depth: 9/16
>> > Pilot boss Dia: 2.25
>> > Pilot boss depth: 1/2 (I measured this at 3/16 but Tracy advised me
>> > to allow
>> > a little extra and specify 1/2
>> > Bolt Circle Dia: 4.75 (SAE 2)
>> > 
>> > 
>> > We discussed the other specifications and my requirements. Tracy
>> > agreed that
>> > a 3 blade was the obvious choice. I want best possible cruise, so
>> > Tracy
>> > recommended a Max prop RPM of 2850 and a cruise rpm of 2500. This
>> > will run
>> > the engine at around 6100 and 5450 respectively. He says that above
>> > 6100 the
>> > power rises in a linier fashion while stress on the components
>> > rises
>> > logarithmically. I'll be able to "dial in the power I want" by
>> > adjusting the
>> > turbo boost. The calculations of max power were interesting. Tracy
>> > asked my
>> > maximum boost and, following what I remember about Greg Richter's
>> > installation, I said 7 - 8 PSI. This is half an atmosphere and,
>> > apparently,
>> > power rises in direct proportion to boost. So, if I have a 200HP
>> > engine
>> > boosted at 1.5 atmospheres, I should get 300HP which aligns with
>> > Gregs
>> > numbers. This assumes no power lose due to intake temp rise and
>> > exhaust back
>> > pressure. Allowing 5% or so for looses due to these issues Tracy
>> > estimated
>> > 280 HP as a reasonable target. Next came the question of speeds and
>> > altitudes. After some discussion and considering the norm for the
>> > Cozy IV we
>> > ended up at a target of 220 MPH at sea level which would give much
>> > higher
>> > TAS at optimum cruise altitude of 12,500.
>> > 
>> > I called Greg Richter and ran Tracy's numbers by him. He agreed that
>> > they
>> > seemed reasonable based on his experience with his turbo 13B Cozy
>> > III, and
>> > mentioned that he's also planning on getting a prop from
>> > performance.
>> > 
>> > Performance were very quick. I had the prop in about 3 weeks. Clark
>> > Lydick
>> > settled on a 68 diameter, 84 pitch prop, so I'm a bit puzzled that
>> > it
>> > measures 33 1/8 from center to blade tip. Anyway, I started fitting
>> > the
>> > spinner by copying the curves of the prop with one of those metal
>> > things
>> > with pins that move in and out. I transferred the curve to the prop
>> > and cut
>> > out the shapes with a dremel. The carbon fiber is fairly flexible. I
>> > think I
>> > could have got away with cutting both curves and bending the spinner
>> > as it
>> > went on the prop. This way I could have got a better fit. Later
>> > Clark
>> > confirmed that my prop is a 66 x 84 with a blade area of 312.3. "

> 
> I can work up some numbers for you to build to, blade pitch and chord.
> 
> Perry
> 

Thanks Perry
Bulent