Bill mentioned a constant speed prop.
Here is something I saw at Aero.
Does away with the $1000 Woodward Governor
and drastically simplifies the PSRU nose.
No need for a Gov. gear driven mounting pad on the
nose of the PSRU.

A small electric pump controlled with a 555 PWM
could provide oil pressure to a stock constant speed
hydraulic prop. A high pressure positive displacement
fuel pump like the Walbro or the Airtex roller vane
pump could do the trick.

All you need is a rotating coupling to get the
oil pressure into the prop. There could be a way
of modifying Tracy gear box to do this.

Paul Lamar

Paul,
Do you remember the name of the company
Bill Jepson

No I don't Bill. They shared a booth and I could not
find
any info what so ever.

Paul Lamar


  I got this off the poster in the back gound. It looks
like the prop is
  only good to 115HP

  http://www.alisport.com/eu/eng/eliche.htm
  Kevin Bell

  It is the principle that is important and not the actual
device shown
  at the show.

  The principle will work with Hartzel and McCaully CS
props.
  Paul Lamar
-------------------------
Paul,
I was under the impression that the governor on a McCauley,
etc. prop was
actually a pump that was boosting the oil pressure to a
much higher value
than engine pressure. I am not sure that a Walbro or
similiar pump would
generate enough pressure.

I could be mistaken.

Bill Schertz
KIS Cruiser #4045
N343BS

Engine oil pressure can be as low as 30 psi.
Most fuel pumps can handle double that.
I don't know about a Walbro but a Airtex (MSD) can put
out 80 psi at 36 gph.
You don't need 36 gph for a prop so the max pressure
may be higher.
I have one of these things and it is powerful :) I'll
have to research what
a CS prop requires.

Yep you are right. 220 psi.
http://www.epi-eng.com/propeller_reduction_technology/governor_drive_issues.
htm

"Consider the fact that a standard, single-acting
governor such as found on
most light singles and twins (Woodward 210xxx series,
Hartzell and MT prop
governors) requires less than 3/8 HP to drive at 220 PSI
output pressure.
That is 12 pounds-inches of torque at 2000 governor RPM and
less than 9
pounds-inches of torque at 2700 governor RPM. If the pitch
diameter of the
driven gear in the governor drive mechanism is 1.25",
for example, then
12 pounds-inches of torque generates 19.2 pounds of contact
force at the
gear faces."

3/8 HP is 280 watts or 23 amps at 12 volts for an electric
motor.
The oil pump is easy to make from a couple of small spur
gears.
Here is a small one I made.

A small starter motor should work. A regular starter motor
is 3 HP or 2.2KW
or 185 amps at 12 volts.

Electric Starter For Briggs and Stratton
http://www.nationsautoelectric.com/Smallengine.html
The geared starters have a smaller, higher RPM motor so
they are lighter.
Also more expensive but you need to throw the gear box out
and use just the
motor.

Paul Lamar

Has this product been considered before?
http://www.variprop.com/products.html

C. Smith

I don't think so but there is not a lot of info on the
web site.
It is not clear if it is just ground adjustable or if it
is a constant speed type prop.

BTW on second thought the Airtex fuel pump might still work
if it is fed with engine oil pressure. The pump could add
to engine  oil pressure and get the prop oil pressure up
around 200 PSI.
Mazda engine oil pressures are in the region of 100 psi.


Paul Lamar

I looked at this [variprop] last year at Sun-n-fun, it is fully adjustable
in the air, constant speed. Little pot mounted on the panel.
I asked about failsafe and it reverts to climb pitch in failure
mode. Seemed like a good product. If you do sun-n-fun this year,
you might look them up.
C. Smith