With a 2.85 psru and a "small" diameter prop, you are
turning the prop
slower than if you had a 2.17, so the tip speeds would
be relatively low
- good for noise reduction. To go fast with a "slow"
turning prop will
require a lot of pitch, which might tend to stall more
at the start of
takeoff roll. But you have lots of power so a prop can
be built that
will work. What is max RPM you want to operate the engine?
Perry
Perry,
I do not want to go much beyond 7500 RPM and would go lowest
at 5000
I have 48 " from the thrustline to the ground and the prop
flang is 41.5"
to
42" from the firewall. Right now this is theoretical as I
have not
purchased the PSRU because I am trying to decide on a ratio.
Thanks for any
input.
Joe Berki
I think mine measures about 48" from thrustline to ground at the
prop,
but I lowered the thrustline a couple inches because of the
ducted fan.
When I build the new engine mount I plan to raise it back up
where it
should be. And your prop is farther aft than mine and probably most
Long-EZs. So I don't think you can go larger in diameter than the
recommended 62 to 64 inches on the prop. Max. RPM on a 62" prop
is about
3000, exceed that and you start to go above 800 fps at the blade
tips.
3000 prop RPM is 6510 engine RPM with the 2.17 drive, which is
where I
run mine. My engine redlines at 7000. If you want to go higher
than 6500
engine RPM you would need the 2.85 drive. 7500 / 2.85 = 2630
prop RPM -
reasonable. But you will still be stuck with the small prop
diameter to
avoid prop strike with nose high attitude on landing or takeoff.
To go 220 mph with your 2630 RPM prop and your engine running at
7500
RPM you will need 88" of pitch, which might give you some grief
on takeoff.
Perry
Perry,
14" is a lot of clearance, is that because it's a pusher? I'm
working on 10"
for my tractor application with a minimum of 6". The more the better
is an
'understood', provided you have the capability to extend the
undercarriage
legs. Which is something I'm considering.
George (down under)
George,
I'm aware of at least one Velocity that overrotated on takeoff and
caught
the prop on the runway. Pilot couldn't figure out what happened
that would
cause the engine to run so rough.
Tom Parkes
Hey Tom,
We haven't heard from you in quite a while. How's the ES doing? I am
almost done with the 40 hour test phase with no serious issues. I
really love that rotary engine.
As I recall, you switched from a Ross gearbox to an RWS unit (RD2-C?).
How is it doing behind your turbo 20B? And how is the turbo holding
up? Have you been checking your motor mount for cracks? That is a
common problem for the ES.
Mark S.
37.5 hrs
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