Paul.. thanks for your feedback (as well as everyone else).. This forum
is not the sole basis of my research. Thanks for wanting to ensure I
dont muck it up.

I agree it seems unusual to have an adjustable pitch prop SLOW you down
compared to a cruise pitched prop, but I have no reason to doubt the
veracity of my source on that.

The powerplant for this velocity WILL be a Mazda 13B (have a core and
mount already) or Renesis (if its available when we fly) so a hydraulic
CS is out of the question. Even with 200-250 HP normally aspirated, we
wont be dealing with the harsh vibration and power pulses of a 4 banger
(I)O-360.

I am a solid fan of having constant speed propellers, and would really
prefer to have one on this aircraft. However, until I made this post, I
had yet to hear ANY favorible feedback on the IVO. Now there is
something to go with. I CAN save my pennies for an MT, but if money was
no object, I'd probably be buying a PT6 engine or some crap like that.
So.. obviously.. safety and quality on a budget. I would really like to
get in contact with the folks who have used these props (ESPECIALLY with
the Mazda) to sit down and pick their brain.

Dave




Paul Lee wrote:
The main problem with the Ivo is extreme vibration - not the power
limitation. I never heard ANY inflight adjustable prop that would
reduce cruise from 213 down to 170 - inconceivable. Its usually the
other way around.

H-U-G-E four bangers like the Lyc. IO-360 need very ridgid props
because they induce oposing "bang" vibration and can shake the prop
out of alignment. Ivo will not sell a prop for Lyc IO-360. There is no
problem with 6's because they are MUCH smoother - about 120 degrees
out of phase compared to 180 degrees of a four banger. Just compare
any 4 cylinder car and 6 cylinder of similar size for smoothnes.

Smaller engines like 0-320 do not produce as much vibration because of
their smaller size. IVO props really like the 220HP Franklin because,
in addition to being a 6, it has a fluid vibration damper system built
into the flywheel - very smooth engine. Thats what I have in my plane.
A smoother engine has important benefits - longer parts life due to
less vibration. A lot of parts failures can be traced to vibration.

Here are a couple of Velocities with the Franklin 220HP and
IVO props:
http://www.ida.net/biz/arlfrd/ (sold)
http://www.lavoiegraphics.com/velocityrg/

If you don't fancy Franklin, the Continental IO-360 is also a 6
- but a little heavier.

----------------------------------------------------
Paul Lee, SQ2000 canard project: www.abri.com/sq2000

Dave S wrote in message link.net...

I am involved with the building of a velocity, and questions are flying
around about propeller choice. For in-flight adjustable, we are limited
at this time to an electric control, such as MT or IVO. Cost is pushing
our options in this area towards the IVO.

I have heard of some vibration/resonance probs with certified engines (i
believe it was a lycoming, but dont know specifics)..

And one emailer has mentioned when they used the engine on a mazda
powered a/c they were limited to 170 mph with the IVO but got 213 mph
with a cruise wood prop.

I am looking for any other experiences.. good bad or otherwise regarding
the IVO inflight adjustable props (particularly in the 200 hp range).

Experiences with any other electrically controlled props that can handle
200-220 hp would be welcome too.. but the MT is probably outside my
price range..

Dave