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Date: Sat, 29 Apr 2006 08:05:20 -0600
From: Bob White <rlwhite@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Engine Run and Static RPM Report
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Hi Ed,

Yes, it's the 2.85:1 so no secrets.  I have a "street" port and 9.7:1
rotors.  What I'm wondering now is what would I turn if I could get
some air to it, like by reducing my elevation 6000 ft.

If I might ask, who made the 74x88 and about how much was it?  I would
much rather have a cruise prop as the climb performance is pretty good
anyway.  I'll see what other molds Steve Hill has also. I can get this
prop to 76x78 but that's still somewhat short of your 74x88.  I do like
the appearance of Steve's props.  They are a beautiful carbon fiber.
He would make a new mold, but he needs to sell about 5 props to make it
cost effective.

BTW, congratulations on the new hanger.  It looks great.

Bob W.


On Sat, 29 Apr 2006 05:57:12 -0400
"Ed Anderson" <eanderson@carolina.rr.com> wrote:

> Bob, I presume you are using a 2.85:1 PSRU to get 6600 with your 68x78 prop 
> which would give you approx 2300 prop rpm.  I flew with a 68x72 and a static 
> of 5600 would give me a prop rpm of 2580.  At 7000 rpm your prop would be 
> swinging at 2456 rpm.  My point is that assuming your are using the 2.85 
> then I agree with your assessment,  you are a bit  "under propped", if you 
> are using a 2.17:1 then I want to know your secret {:>).
> 
>  I found that with a 2.85 gear box and going to a 74x88 prop, the take off 
> and climb out performance improved tremendously over using the 2.17 and my 
> 68x72 prop.
> 
> Also if my old 68x72 would turn 2580 at 5600 engine rpm and yours 2456 at 
> 7000 rpm then I think you will find that your fuel burn is going to be a bit 
> higher for the same prop rpm.
> 
> Ed
> 
> ----- Original Message ----- 
> From: "Bob White" <rlwhite@comcast.net>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Friday, April 28, 2006 9:24 PM
> Subject: [FlyRotary] Engine Run and Static RPM Report
> 
> 
> > I've been trying to finish up all the little nitpicking details and a
> > few big details so I haven't ran my engine for quite a while.  I made
> > up my mind to get some time on it today.  The weather was a bit nasty
> > today with the winds kicking up to 20-30 kts (it wasn't that bad when I
> > started).  I fired it up, and the first problem showed up - No
> > charging.  The new alternator mount from Pineapple racing is power
> > coated and insulating the alternator from the block.  I rigged up a
> > jumper to fix that problem, and started the engine again.  All was
> > well.  After taxiing around for 1/2 hour or so, I hit 4 hours run
> > time.  Bruce T.'s break in instructions was to run the engine 5 hours
> > below 4500, but I couldn't stand the suspense any longer.  I really
> > wanted to find out what my static RPM was.  So, I stopped it heading
> > into the wind and gave it full throttle.  I saw 6400 RPM and backed off.
> > The mixture was going a little lean, so I turned up the mixture and got
> > 6600 RPM.  Max manifold pressure was a little over 23.  (Don't forget
> > that I'm at 6000 ft.)  That's a little over the 6000 RPM limit Bruce has
> > for the 5 to 15 hour segment, but his regime seems quite a bit more
> > conservative that some of the other break-in schemes I've heard on
> > here.  :)  With this prop, I suspect I could exceed my RPM redline of
> > 7500.  If everything is looking OK, I may increase that to 7700.
> >
> > It seems like I'm a little under propped.  This prop is 68 in. dia, with
> > a 78 in. pitch.
> >
> > I also found out that a little air flowing over the rads is a good
> > thing.  As I mentioned earlier, the wind was kicking up to about 30
> > knots toward the end.  While taxiing downwind, the water temp started
> > climbing above 200 F.  I shut the engine down, got out and pushed the
> > plane around into the wind.  After starting the engine back up, the
> > temps dropped down to 160F.
> >
> > Now the next big question is how badly will my new cowling and cooling
> > plenum screw up the cooling.  I'm only about 1/2 done with the cowling
> > mods and getting ready to jump back into some more fiberglass work.
> > Apparently according to the checklist my DAR sent, I need to do a high
> > speed taxi test.  I'm not going to do that until I think the plane is
> > airworthy, even if I don't have the paperwork!!
> >
> > Bob W.
> >
> > -- 
> > http://www.bob-white.com
> > N93BD - Rotary Powered BD-4 (first engine start 1/7/06)
> > Custom Cables for your rotary installation -
> > http://www.roblinphoto.com/shop/
> >
> > --
> > Homepage:  http://www.flyrotary.com/
> > Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/
> > 
> 
> 
> 
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/


-- 
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (first engine start 1/7/06)
Custom Cables for your rotary installation -
http://www.roblinphoto.com/shop/