OK thanks Charlie.
The lower cowl is still a couple of inches too deep in this 3D.
Looks
like
a water rad under the engine is not practical with the Schertz
beam
so
you will have to
use evap cores like Tracy and Bill Schertz used. There is room
of
course for the
oil cooler and people seem to have more trouble with that than
water
cooling.
Why cannot a 22/24 inch wide radiator be fitted, lying flat
under
the
engine. The Intake plenum above it has only to clear the 1.5
inch
beam. The beam may facilitate hanging the rad as it provides
something to attach to. I'm going to install a piece of hat
section
across the back of the engine so I can hang the other end of
the
rad
as well. The Tailwind firewall is only 25 inches from top to
bottom
and I have mocked up the rad/plenum installation before. It
seemed
to
be doable. Jerry
Once I corrected the lower cowl dimensions a good size rad and
stock
RX7 oil
cooler does fit side by side. The only problem is that 1-1/2 inch
high
Schertz beam gets in the way of the air coming in over the top of
the
rad.
20 inches wide by 1-1/2 inches high is a considerably area. 30
square
inches to be exact. This is about 30% of the area required to get
air
into the
rad and oil cooler. That space under the flywheel is critical real
estate.
Fortunately I have a solution. Yet another Schertz beam
configuration.
This one does double duty as a motor/PSRU plate spacer. It
utilizes
the two large
lower ten mm bolts that are used to hold the motor/PSRU plate to
the
end housing.
No clips are needed and no pan bolts are used. It is tricky to
make
however and it can only be this size and no larger. Still made out
of
4130 .065 sheet steel. The flywheel just fits in the slot on top
of
the beam.
Paul Lamar
Taking the path of least resistance, I think we should follow
Bill's
example and mount the oil cooler under the beam. It is a natural
location. Nothing wrong with cheek rads, either. They are proven.
I
forget how long the stock cooler is but it would be a good idea to
make
the Barry centers far enough apart that it could be hung between
them. Oil cooler mounting brackets can be part of the package.
Jerry
The problem with cheek rads is the need to open up the intake to
obscene
proportions :) This cause more drag than necessary.
More complicated plumbing. So far we have lost the vast majority
of rotary powered airplanes to plumbing failure.
There is just not enough room in there to get a proper diffuser.
They
are too
thick so it takes a lot of air speed (dynamic pressure = V^2) to
get the
air
to flow through them.
They work sort of but you must compromise your climb. In Florida
it is less of a problem because once you reach 500 feet you rarely
need to climb higher.
I don't like them. I think we need to move beyond evap cores.
Paul Lamar
Here is the square box Schertz beam. This opens up underneath the
flywheel
for more air to the rad.
Charlie lay out your side mounted rad. I think you will have trouble
ducting
enough air to it. the plumbing will be more complicated as well.
Paul Lamar
----------------------------
I think you will have trouble controlling the width of the beam to the
precise measurements that Tracy calls for with his spacers. He
cautions that
the surfaces of the spacer blocks should not be painted because it
can cause
tolerance changes.
Bill Schertz
KIS Cruiser # 4045>
I am glad you brought that up. I think Tracy is getting carried away
there as the spline and Mazda pilot bearing in the engine don't require
that kind of tolerance. Heck for years people had the Ross input
shaft moving back and fourth a 1/4 inch pounding the 13B e-shaft
thrust bearing :) Tracy also uses a spline and the Mazda pilot
bearing on his PSRU.
I agree. I am sure the sheet metal shop cannot hold tight tolerances.
I am shooting for three inches wide +/- .050 and shimming it to fit
the actual 3.050 dimension. Probably with mild steel sheet which
can be tack welded to the beam. Also the spacers where the 10 MM bolts
go through can be 3/4 wide small aluminum blocks.
This will feed the shear loads from the large bolts better into
the steel beam. There are some other things to like about this
version.
One: The reaction torque from the prop goes directly into
the beam.
Two: The vertical six 6 load is partially shared by all
the 10 MM bolts and spacers connecting the PSRU plate to the engine.
Three: This scheme stiffens up the torsional connection between the
PSRU
and the engine.
Four: It has considerably horizontal bending strength so no prop
gyro clips are needed.
All and all a very rugged way of doing it. Not to mention of
course the increased cooling air for a bottom mounted rad.
Paul Lamar
If 3.050 is required and you don't NAIL it, Tracy is going to drop his
guarantee like a hot potato. In this case I would agree with him.
If you are going to do it, then do it right whatever that entails.
Send the finished piece off to be ground to the final dimension.
Jerry
Tracy said the same thing about the motor plate and the bell housing.
Van Gruz said the same thing about RV's. Mazda USA would have a conniption
if you could prove in a court of law their engine was somehow
at fault in a crash. I don't see that stopping anybody.
Tracy is just covering his legal butt like everybody else thanks
to an over population of hungry lawyers.
The shims will work fine. Each 10 MM bolt will take about 12,000 pounds in
single shear at a stress level of 100,000 psi. Even if you halve those numbers
according to Butch criteria you still have a well over kill design.
You don't have to do this if you don't want to but it does allow
a larger rad in any given cowl because the rad can be higher by
about an 1-1/2".
Paul Lamar
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