Paul

Welcome back.

I contacted IVO props recently to get some
info on their specs. for the twisting props.
A three blade paddle prop like the ones used
on Russian amphib. would weigh about 30 lbs.
I asked them how to be sure all of the props
are at the same 'pitch'.  I am still waiting
for the answer.

As I understand it the IVO props' outer
portion of the blade twists while in a
commonly configured variable pitch prop, the
whole blade revolves around its longitudinal
axis. Intuitively it seems the IVO props
seemed to be a compromise in efficiency as
only a small percent of the total blade is
creating greater lift. I am not actually sure
of this reasoning though. Could anyone
explain it better?

Another question.  I am working on the
landing gear design now. Do you have any idea
how much the steering drive motor and linkage
weigh on the RX-8?

Doug in Japan

No idea on the weight of the RX8 steering gear.
I guess it is unlikely your local dealer would
have one in stock. Surely there must be a few
crashed RX8's in Japan by now. The rack and
steel tie rods 50 inches long and .8 inches in
diameter would be about 7.5 pounds. Not
counting the motor or housing. If the aluminum
housings were 3 inches in diameter with a .1
wall and 30 inches long it would weigh about
2.8 pounds. Again not counting the motor. As a
wild ass guess the whole thing would be about
17 pounds plus or minus 3 pounds.

Paul Lamar

norm wrote:

Paul

Doug's comments regarding IVO prop's efficiency is
right on - the entire blade needs to rotate about
the blades axis while the IVO prop's twist is
created by a simple L shaped steel rod (about
5/16" diameter) that twists only the end (about
1.5" from the end) of the carbon blade so as to
increase the pitch angle.  The blade at the hub
position does not rotate (fixed) so it has poor
efficiency.    If the zero torsional position is
at maximum pitch then the inefficiency comes in
attempting to reduce pitch. He needs to publish
thrust versus hp data.  Of course the outer 25%
of the blade is 43% of the swept volume due to
the squared function of area versus radius.

Also, the delta twisted angle would  only be the
same if the torsional resistance of all blades
are equal.  I would be surprised if the layup of
the fibers are that accurate or if a selection
process is involved.

Norm

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