The P-port is the best way to go for rotary aircraft engines
as it is an easy and sure 250 HP at 7500 RPM take off with
a simple
to make intake manifold. Low cost Holley 2 brl carb or
expensive fuel
injection can be used.

I am trying to come up with a simple way of using
an O-ring for the outer p-port seal. This would be
replaceable
and less prone to error than bonding the tube in place with
JB-weld
or epoxy. It would also expand and contract as the relative
temperature
of the Mazda rotor housing and the SS intake tube changes.

We need a flat surface perpendicular to the tube to mount
the O-ring.

The goal was to use the same mill set up used for boring
the 2 inch hole for the SS tube welded to the steel rotor
housing liner.
A simple mill and a lathe are all that is required to do
this.

This is what I have come up with so far. A 2.5 inch
diameter aluminum
cylinder will be pre machined to slip into a hole in the
outer water
jacket wall. It will then be tig welded in before the final
two inch
hole is bored in the rotor housing.

A flat collar will slip over the tube and be held in place
by small machine
screws installed in drilled and taped holes in the rotor
housing.
This collar will compress the O-ring and hold it in place
around the SS tube.

I am open to other ideas. I would like to avoid the high
cost of an NC
mill and complications to make 3D surfaces to hold the
O-ring.

We are currently adding Al material to a junk rotor housing
using tig to see if
it warps the side sealing area. This might be the lowest
cost solution
if it does not warp the housing. A lot of heat is needed to
do this
however.


Paul Lamar

Paul,

Another idea.   I like your stainless TIG welded
straight-in approach but
agree the outer housing sealing technique is less than
stellar. Devecon
epoxy is not designed as an sealant.


I did the following, primarily as a can-it-be-done?
exercise.

  I bored the P-Port hole  at an exactly 12.5 degrees angle
above
horizontal. This is close to how the Lemans engine did it.
This is not
perpendicular to the inner housing per se, but I found with
this
particular angle  there is still enough material on the
inner housing to
have a proper step milled in. It also minimized the outer
epoxy
build-up.  Since the insert does not go all the way into
the inner
housing,  the port can have a larger radius edge over the
majority of
its perimeter.  My insert (is  ID is 51mm - OD 56mm. The
upper part of
the insert OD bore just grazes the upper hole boss.  The
insert is very
short  and only protrudes six mm outside the outer housing.
The insert
has machined in slots to accept an O-ring where it sits on
the inner
housing step as well as where contacts the inner part of
the outer
housing and inserts into the back of the slide throttle.

  The result is a removable insert. The advantage for a
research engine is
obvious as different port size and shapes can be tried.

After proper aluminum cleaning and two step alodizing, I
made a plastic
barrier and potted the outside of the housing with Devcon
aluminum
epoxy.  This is using the material where it can be
inspected and in the
manner it was designed for. The  wedge step is small in
comparison to
that needed for a similar epoxy build-up on the straight-in
approach
however. After I heat cured it for maximum strength it was
milled flat
and the insert hole as well as the outer casing  O-ring
step was
machined in. This epoxy  has very good compressive and
tensile strength
characteristics and can hold an O-ring and can be tapped to
hold a  bolt.

Port Notes: The entrance to the inner housing comes out
exactly the same
opening and closing locations as your straight-in approach
48.6 mm dia.
except the cross section area of the hole is obviously
bigger.

Now since we want a slide throttle up real close and
personal, I reasoned
  the inner plate should provide two functions, which are
accepting the
relatively short port tube and retaining the outer housing
O-ring. As
you stated the housing can be tapped but make them four
small studs
instead.  Place them around the inlet hole with dimensions
corresponding
to the outer perimeter holes on the slide throttle plate. I
found I had
to redesign the slide throttles (plural) to position them
in a compact
way and link them together.  The studs provide the mounting
mechanism
for the rest of the slide throttle as well. Again when
assembled the
inner slide throttle plate will accept the P-port tube as
well as press
against the port O-ring sealing the water jacket.

Advantages:  Allows the engine water jacket sealing to be
O-ringed on the
inside and double O-ringed on the outside.
The Insert is removable and can be changed to different IDs
or nozzle
profiles if desired.

Disadvantageous:
The angle requires milling off some of the top corner of
the intermediate
and front housing to clear the slide throttle IF
horizontally
orientated slide throttles are desired.

Unknowns. (I am using a boosted system)
Intake manifold routing may become more problematic
Air may have more resistance entering into the intake
chamber.

Pictures to follow

Doug in Japan

Remember, Crosley and Offenhauser engines were furnace
brazed together.
What's wrong with that method of insertions and sealing
on all pport
surfaces? Is there nothing out there right now that will do
that with
aluminum? What has been done in the vacuum brazing of
aluminum field?

Oh ye of much more knowledge than I? (That does cover
pretty much everyone, you know?)

jofarr, soddy tn

It would be nice if one were making a couple of dozen at a
time.
One off would be costly I suspect. As I recall it takes a
1000 to 1100 F furnace to braze aluminum.

Paul Lamar

If you decide to go batch process, count me in on a pair of P-Port intakes.
C. Smith