Paul -
I found the Barry bushing load ratings on-line at their website.
Looks
like
the 22002-15 is most common for a 200HP engine? (Rated static load
of 630
lbs per mount). If so, looks like 6000 lbs/in axial, and 9200 lbs/in
radial
should do it. I'll plug it into the model for vibration runs.
Dan-
I think the 6 G's will cover most airplanes. Now perhaps a Berkut with
a really stiff carbon fiber straight leg might be higher.
I think you want to rate that more like 150 pounds static load or half
the one G load. That will give max vibration isolation. When these
things
are subjected to 6 G's of course they bottom out but that only happens
once or twice which will not destroy them. Of course they go non
linear
when that happens. 2002-11
Paul Lamar
Dan Ruggirello wrote:
OK, the -11 is then 1333 lbs/in axial, and 1666 lbs /in radial and
used for
the 2 mount system for a ~300 lb static load. This is what I'll use
for the
spring contants. Probably not even required to use the mounts in the
dynamics model since the isolators isolate at a low12 Hz but it
wouldn't
hurt and actually makes the solution a little cleaner since you don't
have
to worry about the rigid body modes.
As far as a 2 barry mount system goes, if the mount in the back of the
engine does not have an isolator, there may be vibration loads
transmitted
here during climbs, (the 300 ft-lbs at 2500 rpm?). Also, this could
lower
the natural frequency of the PSRU/prop/MMP. Not sure what the
implications
would be since we don't know what the natural frequency is yet.
(Near 2500
rpm? 6500 rpm? )
I would like to find out more where the 4.5/6G number was from
though. But,
for now, maybe just calculate an acceleration based on energy to see
how it
compares? My mounts are bungee and since I havn't built them yet, I
cannot
test them for stiffness. How about your KIS crusier - got a solid
model of
the spring gear handy? Anyone have a model or drawings of the RV
gear legs?
Either one looks stiffer than my bungee gear anyhow and we could use
those
as estimates.
I would say that Bonanza landing and the F-18 drop test qualify as
hard
landings ;-) Can't design everything to those loads though 'cause we
ain't
Russian!
Dan
The Questair Venture successfully uses the two mount system with a
rigid
aft mount. Rigid only in the vertical direction of course. In the
horizontal plane
it is entirely free to move around so no forces are transmitted in
that plane.
The early RV gear's such as the 3's, 4's and 6TD's were copies of the
Tailwind design.
Jerry might have a dwg of the Tailwind in electronic form.
I doubt Vance has a solid model for the KIS Cruiser landing gear but
I could probably
do one in Rhino in a day or too. Any idea Vance what the spring rate
at the wheel is
for the main and nose gears? The nose gear uses an automotive shock
absorber
with die springs. That of course will bottom out at six G's. I am
redesigning
the joint where it connects to the firewall using Barry bushings.
KIS had small automotive shock absorber bushings in that location.
Paul Lamar
I have a good detailed drawing of the gear leg that I can scan later
today. Jerry
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