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 holeat 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 anglethere 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 (isID is 51mm - OD 56mm. The upper part of
the insert OD bore just grazes the upper hole boss.The insert is very
shortand 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. Thewedge 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 casingO-ring step was
machined in. This epoxyhas very good compressive and tensile strength
characteristics and can hold an O-ring and can be tapped to hold abolt.

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 IFhorizontally
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

Paul,

As you might remember about one year ago, I had planned to go down this
road of brazing an aluminum insert onto the engine housing for exactly
the same purpose as you describe.I purchased a torch and some rods
from an outfit in Texas but of course still found that I had to preheat
the sample to 600 degrees to get a good weld.I tried welding on an old
scrap bell housing and did not attempt a rotor housing however.
Perhaps if the rotor housing was tightly bolted and sandwiched between
two steel 12mm plates distortion may not happen.I couldn't get any
positive feedback on welding aluminum to the rotor housing so that is
when I went the DEVCON AL. epoxy route.


Doug in Japan


My son, a machinist, found this stuff (Durafix
(http://www.durafix.com/)) on the web the other day and decided to give
it a try. This stuff is amazing and may be a good solution to your
'brazing heat' problem. Anyone out there used this yet?

Barry


Barry,

There are about ten companies in USA that sell these brazing rods.For
small parts or fixes they work fine. I found a company in Texas that
claimed its rods were second generation and melted at a lower
temperature, 650F I believe.I ordered one packageand they sent me two
and of course charged me for them. Inever find a real person to speak
to when I called them and they never answered my email.

The technique:
Preheating a housing so it is hot enough to melt the rod on contact will
take a lot of heat and time. If 752F is the Durafix's rod melting
temp. that is getting pretty close to melting temp. of the casting
itself. That is one challenge.The others are containing the part so it
won't warp and then having an kiln, oven, or hot plate that is large
enough to cool it off gradually. Aluminum has more thermal creep
(expands)than steel increasing the chance of cracks adjacent to the
weld when it cools.

Best idea is to buy the P-port factory racing housings but I don't have
an idea how much they cost.

Doug in Japan