IVO prop dyn. balancing

On 8 Nov 2005 16:23:06 -0800, wrote:

When ground testing my auto engine with an old style 3 blade IVO prop, I
took several still photos. Some of the photos appeared to show the blades
advancing or retreating much like that of a helicopter.....not sure if this
was a trick of the camera or actually happening. After about 10 hours of
ground time I found damage to the base of the blades. Now that the engine
is flying with an MT prop I have been unable to duplicate that effect in any
of my photos.

The focal plane shutters used in many good cameras would give
that bent-prop effect. As the shutter gap moved across the plane,
either side-to-side or top-to-bottom, one side or edge of the film was
exposed before the other, so a rotating prop or rotor would be caught
over a rather long time, spread across the film, and would appear bent
or out of phase.

A rather extreme example:

http://www.bowersflybaby.com/takeoff.mpg

(Cheap digital video camera).

Ron Wanttaja

Hey Russ... what are you flying and where?

Dave
Houston (EFD), Rotary powered Velocity under construction..

R&R Sherwood wrote:
The blades, being held by only two bolts each, can move (or
swing) chordwise in the hub......
Even with those bolts torqued to spec we had blade movement between the
plates. Fretting was evident on the blade bushings and mating plate
surfaces. Scared us.




When ground testing my auto engine with an old style 3 blade IVO prop, I
took several still photos. Some of the photos appeared to show the blades
advancing or retreating much like that of a helicopter.....not sure if this
was a trick of the camera or actually happening. After about 10 hours of
ground time I found damage to the base of the blades. Now that the engine
is flying with an MT prop I have been unable to duplicate that effect in any
of my photos.
Russell Sherwood
Houston, TX

When ground testing my auto engine with an old style 3 blade IVO prop, I
took several still photos. Some of the photos appeared to show the
blades
advancing or retreating much like that of a helicopter.....not sure if
this
was a trick of the camera or actually happening. After about 10 hours
of
ground time I found damage to the base of the blades. Now that the
engine
is flying with an MT prop I have been unable to duplicate that effect in
any
of my photos.

The focal plane shutters used in many good cameras would give
that bent-prop effect. As the shutter gap moved across the plane,
either side-to-side or top-to-bottom, one side or edge of the film was
exposed before the other, so a rotating prop or rotor would be caught
over a rather long time, spread across the film, and would appear bent
or out of phase. I don't know that the IVO would move all that much,
unless it was flexing as well...........
The aperture shutters found in smaller, cheap cameras wouldn't
"bend" rotating stuff.. Were you using the same sort of camera both
times?

Dan


Same camera was used on both props. A Nikon single reflex, the shutter
moves from side-to-side. I bought it new in about 1985....before the
digitals came out.
Russell Sherwood