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 though 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