The engine/psru/prop CG is where it is. There is nothing you can do
about
it. The datum for the calculations of the CG of the engine can be
anywhere.
In an airplane CG calculation it is usually up near the prop flange. In
an engine situation it could be the front edge of the e-shaft pulley.
Let me put the whole thing in perspective. If the guy doing the
designing
really knew what he was doing he would not compromise the motor mount
and use four equal sized rubber bushing at the four corners the engine
oil pan. The rear two rubber bushings are carrying 90% of the load.
He would use two larger rubber bushing under the engine/psru/prop
CG!
He also would not start with a chunk of aluminum that was 18 by 14
by 3/4 of an inch thick. The weight of that chunk of aluminum alone is
19 pounds! At $3 a pound that is about $60 worth of aluminum. You are
paying for that and then some.
To machine it on an NC mill to cut the weight by half or 2/3 rd would
cost several hundred dollars. You are also paying for that. When
you are done the plate is going to weigh somewhere between six
and eight pounds.
Four or six pounds of that weight is totally unnecessary since
it supports the two front rubber bushing that carry little or no load.
A Schertz beam would be one tenth or less of the cost and weight.
Paul Lamar
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*
Paul;
This is all academic to most Budgeted Builders and those in the How To
Do
This circles, as we all know this is not the people who are targeted
by
suppliers of Bolt On installations, they happen to be a completely
different
breed.....I will admit though that there are a lot of us (ME included)
on
this list that would much prefer to buy a proven ready made component
or
better still complete Firewall forward, which is even supplied with the
crow
bar to open the crate with, installation, and would gladly pay good $$
for
it..Instead we are forced to wait, contribute whatever we can to
further the
happening of such a thing in the future....Why because we are all
enamored
and involved in an engine which has spent it's entire lifespan in the
shadows, casted with doubts and to boot labeled a lowly Pink
Elephant.....However, we have in the interim gained a lot of knowledge
from
a lot of talented subscribers so we are trapped by this and at the same
time
committed to use the Rotary only..There's a lot to be said about
Ignorance
being a blessing.
Here are the people who are the clients being targeted.....I know
personally
of 5 builders who are presently building an aircraft each...The
aircraft
costs range from low to mid SIX figures....All they did was select what
they
liked, attended a How to Build-This-Plane class and walked out with a
list to
Beat The Band With, of sub builders of Parts, Sub assemblies, Firewall
Forward Bolt on WITH PROP, ready to be Plugged in connectors, add oil
gas and
hit the starter.....Believe it or not their biggest job so far has been
selecting from a HUGE book of Avionics the Panel manufacturer sent them
:)
Now, I ask you, do you think these people would know or give a shit
about the
differences between a Shertz Beam mount, Paul mount versus a Bed mount
or the
fact that one is lighter than the other or cheaper to make?? Of course
not,
they want something that looks real nice, which they expect to pay more
for,
after all....They know it works nice already since it's being used out
there
by a lot of other people.
So again let's move on....Before I kick the Bucket without getting to
at
least fly a Half Ass Unfinished, Loud, Working Rotary :-)
We have a lot of work ahead of us.
Butch
So I am supposed to shut up about bad design because it is off the
shelf?
I also ask you, is anybody flying with this mount?
Paul Lamar
It's good to have an educated opinion on the mount design and know where
it's strong, weak, heavy, etc.
So far I hear:
1. The mount could be cheaper to build
2. It's got some extra parts that add weight but no strength
3. Two seals for the oilpan = more probability of leaks
4. The lower truss design causes increased compression stresses
5. There is little support for lateral movement
6. The CG picture is arguably confusing
While all of these are valid criticisms it's difficult for a novice like
myself
to tie any of these to the engine falling off my airplane in a hard landing.
The next question is whether this mount has ever been load tested and if so
under what conditions and with what results? Even is someone is flying with
this mount that doesn't mean it's safe.
While Butch's response was a bit over the top it did have a few valid
points,
including the fact that if you don't want to spend alot of your own time
designing and fabricating a mount there isn't a whole lot of choice out
there.
Just like the bellhousing that George is working on, until something better
comes along you either build it yourself or accept what's available.
Dave Wilenius
Jerry Hey builds a good mount. Ed Klepis will also build a mount to your
design. If you tell me what you have in mind Sheet Craft here in Santa
Paula will also build a mount. I can work closely with the owner
Bill Mensinger to answer any of his questions as he is a neighbor.
He has completed and flown a modified Pazmany aircraft design.
He also builds water drop tanks for fire fighting helicopters used
world wide. His prices are very reasonable indeed.
He also does some restoration work for the local antique
airplane community.
Paul Lamar
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