I just spent some time looking on the internet for negative comments
about JB Weld.  I did not find any.  One testimonial, a guy repaired
a gouged  cylinder  wall and ran the engine for several hundred
hours.  Tear down showed no change or deterioration  in the JB
Weld.   Also, JB weld claims the product is good to 500 degrees.
Based on what I  have learned today, I think my skepticism about JB
Weld was misplaced.   Jerry

Jerry,
If your considering manufacturing P-ports, you might consider a slightly
tapered shrink fit of the tube within the housing with some high temp epoxy
to take up and imperfections in the machining.i.e. heat-up the housing and
freeze the tube - his would take some experimentation to find the most
suitable size whereby you can still get the tube inside the housing and this
would all need to be done on a CNC for the accuracy needed.
This would be the most ideal method of sealing, but how practical it would
be I'm unsure!
Just a suggestion, as it's something I'm considering..
George ( down under)

Hi George;
I did my Pports as you are suggesting with the inserts all the way
through with
match tapered (smaller towards the inside of the housing) insert and
bored hole
and an interference (hot rotor-cold insert) press fit with epoxy on the
prepared insert
bored hole.
One advantage is that it should never fall into the engine.
One disadvantage is that the 2" ID is rounded to 2.125" on the rotor
surface - I am
not too concerned about the slightly reduced apex seal support as the
edges are
beveled to soften the apex seal landing back onto the rotor surface.
This measuring and fitting took significantly longer by hand using a
basic mill, lathe,
digitial calipers and sandpaper...and lots of measurements.
The interference can be figured out easily enough looking up the
material and
temperature differential  you plan to use between the housings and inserts.
One press fit did take a little more convincing with a mallet and wood
block ;)
I machined the inserts as well, finding the correct sized tubing could
save a lot of work.

Without starting an epoxy war...
One of my biggest concerns is the ability of any epoxy to bond to
aluminum with less than Boeing processes.
Any bond can fail for a variety of reasons - poor surface prep, surface
contamination, poor epoxy prep,
differential thermal expansion at temp, chemical resistance, vibration,
thermal stability at higher temp (say 300F),
epoxy cure shrinkage, and for northern residents - differential thermal
shrinkage over the winter months.
In any case, some sort of mechanical assistance/backup to the epoxy is
not a bad idea - threading, brazing,
welding, press fit, pins, extra mechanical bond area (grooves, etc...)
to insure the insert does not fall into the
engine catastrophically without warning.  A leak would be annoying, but
hopefully less dramatic and with warnings...

Take a look at an interesting article by Bill Husa regarding bonding:
   http://www.oriontechnologies.net/Documents/bonding.pdf

To summarize - sanding the aluminum surface with epoxy already on the
surface may help adhesion by removing
and preventing the oxide layer from reforming.

Cheers
Cary

Cary,
I was thinking of a slight taper on both ends with the tube being
mechanically locked into position and the thin high temp epoxy only being a
( surface imperfections) void filler, in the tapers and of course the water
cavity.
This would be extremely difficult to do as your measurements would need to
be exact AND you would get only one go at it.
The benefit would be that you would never have to worry about the tube
moving either way.
I have looked at the threaded inserts, as done by X-Treme Rotaries, but
others suggested that it wasn't optimum.
Is nothing ever easy!!
George ( down under)

Hi George,
I had the same anxiety you and Doug have in the "research" phase.
When doing interference press fits you are pretty much committed once
you start ;)
-stop early or keep going...
Removal of AL-AL press fits will cause some spalling? damage and require
a larger insert.
Measure lots, machine under-oversize and finish with 400 grit sandpaper
if you like.
Give yourself some margin based on temperature for the interference fit.
Not hard to do - just time consuming.  The epoxy will fill any
imperfections anyway.
Again, practice on a junk housing or whatever to verify your plan will
work and gain confidence.

Decide what you want and Just do it!
Cary


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