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I agree, Bill, a prop is a prop, but even
there - there is at least one rather radical prop design, that came out within
the last year or so which is reportedly such an improvement that
the small class type air racers are seeing remarkable increases in
airspeed at the same rpm.
This is the strange looking Ellippse race prop
designed by Paul Lipps and reportedly gives tremendous increase in airspeed for
the same prop rpm. I mean considerably more that 5-10 MPH increases have
been reported - and while I am not aware of any publish data on testing, they
apparently are dominating their class in air races.
Report on Reno Air Races
The Gold Biplanes, which didn't race Friday due to high winds, were dominated
by Californians Tom Aberle and Jeff Lo, with their unusual propellers, designed
by Paul Lipps.
So my point is new ideas are out there - some may pay
off in better props, better prop controllers all lighter, better (and
hopefully cheaper {:>))
Ed
----- Original Message -----
Sent: Wednesday, December 20, 2006 12:44
PM
Subject: [FlyRotary] Re: hydraulic
constant speed prop for rotarys
Ed, The thing about props is that you can't really tell the difference
between one designed for A Rotary or a Lyc. Tip speed limits being
what they are we are all limited to a max prop RPM around 2700-3000 max
RPM. You know this of course, I'm preaching to the choir here. Weight is another mater, Eggenfellner
(Subaru FWF conversions if you're not familiar) is working with Senisich on a new lightweight composite
prop blade. They are doing multiple blade hubs with Egg's
-----Original Message-----
From:
eanderson@carolina.rr.com
To: flyrotary@lancaironline.net
Sent: Wed, 20
Dec 2006 8:03 AM
Subject: [FlyRotary] Re: hydraulic constant speed prop for
rotarys
Bill, I certainly do not question the likelihood
of demand for a rotary C/S increasing. Not having any experience
with a C/S prop other than a few hours behind one early (real early) in my
flying career, I'll certainly defer to those with more experience/knowledge
with the prop. For Lycoming and other big displacement piston engines, I
agree that the current arrangement is likely the best that could be developed
- at the time - and perhaps even now.
I am not as certain that technology in
many areas has not advanced considerably since the early 1950s that might lend
themselves to lighter C/S props for the rotary without the need for the
current incarnation of the prop governor. But, if I study the problem, I
might easily change that assessment.
My bird simple could not stand 50 lbs or so
stuck out on the end of the nose. 15 lbs additional -
perhaps.
Again, not knocking C/S props, just not certain
adopting the current configuration for Lycomings/Continentals is what we need
- just my opinion of course.
Ed
----- Original Message -----
Sent: Wednesday, December 20, 2006
10:37 AM
Subject: [FlyRotary] Re: hydraulic
constant speed prop for rotarys
Ed, I believe that there will be more and more requests for such a
system. All the reductions I suggested would allow a currently
available governor to work. Tracy could do a new prop shaft housing to
drive from helicals like Mistral, but it would be expensive. The
biggest advantage of this drive is that the reduction is already built in. I
think that is why Mistral went this way. Another fact is that you would be
hard pressed to come up with anything that is lighter for doing this job
than the current hyd/CS. I have seen a few inventive controls, but none that
work even close to as well as current hydraulics.
Bill
-----Original Message-----
From:
eanderson@carolina.rr.com
To: flyrotary@lancaironline.net
Sent: Wed,
20 Dec 2006 5:37 AM
Subject: [FlyRotary] Re: hydraulic constant speed
prop for rotarys
Hey, Bill, I think it would be great if a light
weight relatively inexpensive way could be found of providing the required
hydraulic pressure and speed control (adapting a lycoming governor is one
way). It wouldn't hurt my heavy RV-6A getting up quickly
out of short grass strips either.
I think had there been a large demand for Tracy's
gear box to have the provisions for it, it probably would have been
incorporated in the design - but the old chicken and egg
situation.
Perhaps the one that Lou referred to may be the answer as
its hydraulic control is apparently internal to the prop hub - if I
understood correctly. Wonder how much it weighs?
Ed
----- Original Message -----
Sent: Wednesday, December 20, 2006
12:19 AM
Subject: [FlyRotary] Re: hydraulic
constant speed prop for rotarys
Guess I did, Bill. I know the
governor has the pump to do this, its just I've not found a governor
suitable for a rotary engine.
OK Ed,
I kind of figured you understood about the pump in the governor. As
to the speed, I figured that the governor would require a reduction
identical (or really close) to the PSRU. This could be a toothed
belt/pulley system. With the reduction any standard governor would work.
Mistral uses a helical right angle drive to a pad on
the side of the prop shaft. I've also seen a v-belt driving off a pulley
at the front similar to the O-360 Lyc alternator drive.
Some movement is OK it needn't be timed. The reason I'm interested is the
RV-10 will probably benefit from a CS<
As you mentioned the RV-4 hardly needs a CS. Just
more complication. I am supprised Tracy didn't think about
the other planes that would or could be using the drive when going into
production though.
Bill Jepson
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