Dan Ruggirello wrote:
Paul,
The deflection I get at 20" is .0687", or .0824" at 24". The results are
scalable, so .065/.0824*16ksi=12.6ksi max von Mises stress. But this
isn't
an apples to apples comparison....... I am not pleased with the model
displacement. I typicaly get an error <5% and this error is way too
high.
I was looking at the model vs the tested configuration and they are not
quite the same. I modeled up your mmplate4.gif plate - the ribs look
narrower and the bottom pockets taller than the tested configuration which
would mean higher displacement. Is there a dwg or sketch of what jerry
tested?
Dan
Hey I would settle for .0824. I think the correlation is amazing since
we did not talk about the depth of the pocket or the radius of the
mill used to cut the pockets. The angular deflection is still
inconsequential. 0.0687/20 works out to about .2 degrees.
The deflection shown in the jpg is exaggerated for clarity and
in no way is even near the actual deflection in case the people
not familiar with FEA were wondering.
BTW that is with a heavy metal prop. The gyro torque at one radian
per second yaw or pitch for a carbon or wood prop would be half that.
I am not sure if we have an actual drawing as
the guy that wrote the NC mill program just went on what I gave
him roughly. As I recall we made the ribs one inch wide instead
of whatever was shown on that drawing. Jerry, do we have a drawing
of the actual part Danny programed?
16 ksi is also well within the strength properties of 6061 T6.
If we get a chance we will redesign it slightly to improve
the design based on this work. Great work Dan. I am very pleased.
This is also just an interim solution. What we really need is a
light weight one piece cast aluminum PSRU case with rear loading like
the typical modern automatic transmission. We also need
a 2.85 gear ratio. If Tracy does not get on the stick
soon there will be others out there breathing down his marketing neck :)
Dan, can that FEA program accommodate some other simultaneously forces
such as what would happen if the gyro torque and the 6G landing
loads were applied to the plate simultaneously? In other
words 900 pound uploads at the apex of both motor mount ears.
Paul Lamar
I was just thinking more about the dynamics of the mount. We could also run
a frequency response and apply that torque as a dynamic sine load, say 600
ft-lbs at 6500 rpm, or 108 Hz and see what the stress and displacements are
like. That would really give an indication if there is any gain in the
system. Not very difficult to run either.
Dan
Dan Ruggirello wrote:
Oops....Must be getting late. I believe 6500 rpm is too fast for a prop
unless it's Perry's ;-) How about 2500 rpm?
Dan
Perry does not use the motor plate Dan. He uses direct drive.
Paul Lamar
The AirCraft Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/
Copyright 1998-2002 All world wide rights reserved.