Joseph M Berki wrote:
Paul,
Thanks for the input. The landing gear pivot bolt is a 1/2"
stud that
secures the main gear by trapping it between two bulkheads like the Cozy
MkIV. The rear hard point is boxed from the firewall to the rear landing
gear bulkhead. Exhaust: What is the space required for the tightest SS
tubing used for the exhaust? There is room. Rear mounts: What size
tubing
is used to support the isolators? It looks like 1" very short stub with
just enough length that the tubes have something to weld to. I am
assuming
that the arrangement in the pics for the rear mount will not work?
Generally speaking a 3 inch center line radius is about
the sharpest radius you can find. That makes fitting the
exhaust into this type mount rather difficult even using
two inch exhaust SS tubing. It is also not good to have
a sharp radius as soon as you exit the exhaust ports as
that is a good way to burn a hole in the bend.
Here is a 3D. I will see what I can do to fit in some exhaust
tubing tomorrow as I need to go pick up some manifolds from
the machine shop today. This could be a big waste of time unless
we plan ahead carefully and make sure everything fits.
What is the distance from the lower firewall hard point
to the upper firewall hard point?
Paul Lamar
Ok Joe a couple of 45 degree SS 2 inch pipe bends on a 3 inch center line
radius from RB Wagner will clear the motor mount tubes but you
will have trouble getting a muffler under the cowl.
Here is another way of doing it.
This is the P51 motor mount trick basically. You will still have to
brace it diagonally back to the spar. You will then have room
close to the engine for a simple hollow tangential muffler
made from .065 SS. This is about the only way to get a muffler
in a tandem pusher. Tom Jordan did something similar
in his Limo EZ.
Paul Lamar
Joseph Berki wrote:
Paul,
Thanks again for all you help. The distance between the upper
hard point and the lower hard point is about 20" ( at work now will measure
later) There is about 4 to 5" clearance between the block and the tubes,
the rear exhaust port is closer than the forward. The muffler will go
below the motor as the radiator is way in front of the motor. I have cut
more 1/2" 6061 T6 to make the holders you described and will order some
more 4130. Should I tie the rear buckets together with a cross member? It
will have to be bent. This would result in a box around the bottom of the
motor front and rear cross member and the Schertz beam. I would like to
make the diagonals to the spar removable so a plate at the bucket would
permit them to be bolted to the mount.
Joe
Where in front of the motor is the rad going? What are the rad dimensions?
I'll put it in the 3D.
Paul Lamar
I know you are interested in thrust augmentor so I added one to the
3D. With a 2.17:1 psru the optimum length for the tuned exhaust
pipes is about 32 inches into a collector and then one pipe
into the augumentor. I like the idea. Don't know how loud
it will be put the prop will chop up some of the noise.
The rad air intake duct shown is problematic in that it is probably unpredictable.
I suspect most of the air will stack up at the back of the duct.
Could be made to work with a lot of trial an error. Preferably
on the back of a pickup truck or on the top of a van at 80 MPH.
Perhaps if we are lucky we can talk Dan into doing a CFI on it.
I suggest you just mount it horizontally flush with the bottom of
the fuse and use a simple wedge shaped diffuser. We know they
work. That will also get it a bit further away from the oil
pan and increase the air flow through the rad in that area.
The motor mount tubes are still a problem for the exhaust
pipes. I would change the motor mount to the previous suggested
P51 configuration. What is your reasoning on putting the motor
mount brackets on the bell housing instead of just using the
PSRU plate? The brackets will be a little weaker fore and aft
and you might have to brace them. It will work of course
but it is also a bit heavier.
Paul Lamar
I recently saw a Beech Baron motor mount with the engine removed from
the plane. It was interesting in that it carries a relatively heavy
engine (Cont. IO-470) and used tubes in potentially more convenient
places. The Continental is a bed style mount, similar in concept to
Tracy's oil pan plate.
Horizontal tube under the motor, slightly larger than typical diameter.
Diagonal brace tube hits near mid span of the horizontal tube. The
cantelevered end of the horizontal tube is braced with C-channel tapered
from zero- height at the tip to several inches under the mid point, then
zero height again at the firewall end of the horizontal tube.
My thought is that for a small weight penalty, it might get the
diagonals back away from the intake & exhaust tubing. If anyone thinks
this has any merit, I'll try to get a picture if the engine is still off
the plane.
Charlie England
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