George hit the nail right on the head. The issue isn't will the insert
move
or how strong the holding force of the epoxy is. The issue is will the
epoxy adhere to all surfaces well enough to make a waterproof sealing that
will last under the rigors an aircraft endures.
A press fit makes sense and if done like Cary suggested will seal. A
flange
welded onto the outer part of the insert held down to the housing with a
several screws ala Everett Hatch makes sense as well. I wonder if he had
any O rings or gasket material under the plate as well.
A screw in fitting should be easy to thread seal as well. Does Mazdatrix
tap
the inner liner only? If the inner and outer part of the pipe had proper
seals then JB Weld would not be an issue or even be needed.
I see the light on the hole shape as Aubrey rightly pointed out, aviation
needs would dictate a shape that is easiest on the seals. Thanks for
pointing that out.
More importantly concerning all the recent discussion is unless we know
and
use the R26B's port timing, port shape, manifold ID sizes, and lengths,
slide throttle hole shape, third plug etc. then the quest "to copy the
Lemans engine exactly" is counter productive and their data is only
ballpark
for us. Or we try to find our own way that fits aviation needs. In that
case Everett Hatch or Mistral Corp. is the role model we need to be
emulating not a Lemans engine.
Perhaps it finally dawned on me that the Lemans winning car didn't need to
fly more than a few inches AGL:)
Respectively yours
DougFir
You are now talking big bucks for a mill that can thread internal
holes. Not something you can do on a lathe. The simple system
will work fine if you pressure test the p-port tube before
you assemble the engine. However this is a free country
spend as much money as you like :)
"In that case Everett Hatch or Mistral Corp. is the role model
we need to be emulating not a Lemans engine."
Fine if you want to limit the HP to 200 HP in the case of Mistral
and 215 HP in the case of Power Sport. With slightly worse BSFC
I might add.
Intake systems are high speed aerodynamic devices. Why add drag?
Would you purposely add drag to your airplane for no reason?
Would you get lower MPG on your airplane if you added drag?
Paul Lamar ...No rotor no motor.
Doug,
I don't wish to put anyone off-side here, so please consider these as
suggestions only.
Considering your need for perfection I would suggest you follow Cary's
method - he quite obviously has skills in this area and you have the
resources to copy his methods.
O rings are out as far as I'm concerned as they are prone to fail, although
would be easy to replace.
Advice to me is that threaded intakes will eventually leak as well.
The areas of concern are the inside of the water jacket and how to best seal
that area. As recent events have proven - it doesn't take much to have a
small leak.
Cary's method is optimum - it does take more effort, maybe much more effort,
but worth the piece of mind IMHO.
Doug I would like you to follow Cary's method for your own piece of mind.
On the threaded housing my machinist buddy suggested to me that their
probably using a large tap to cut the thread into the housing and probably
cutting the tube thread on a lathe. I initially thought this was the best
way to go but was advised otherwise.
George ( down under)
---------------------------
Gee Doug you are going to fly an epoxy composite airplane.
Are you sure the wings won't fall off eventually? :)
You could always make that coupon sample I was describing.
Put it in the freezer for 24 hours. Take it out of the freezer
and bake it in the oven for 2 hours at 200 F and then repeat
500 times. Get back to me with the actual count :)
The fact is NOBODY knows how many cycles ANY particular configuration
is going to last. There is zero tensile load on the tube. If it fails
it will not be a catastrophic failure anyway. The first thing that
will happen... you will notice your antifreeze level going down slowly.
The next thing will happen the engine will over heat. Perry flew his
Long EZ several times with an internal leak after we thought we had
it fixed. You might also notice a difference in EGT.
Most cars today have a coolant level sensor. I suggest
everybody use one.
Paul Lamar
George
I concur. Double press fit it is. And yea I'm lucky to have a great machine
shop next door. It ain't cheap though. I'm still open to advice on a
perfect way to do it and I'll foot the cost of doing the two test housings.
They will look like Swiss cheese with the other holes I am putting in there
as well.
Paul my friend you have a habit of side stepping an issue you don't want
to address. You would make a good president:) The issue that has always
concern me IS NOT ABOUT EPOXY TENSILE STRENGTH or several different ways
(all satisfactory) for holding the inserted tube in. I repeat my concern
has always been about epoxy 's water sealing ability under the circumstances
we plan to use it. With a good interface fit then epoxy is non issue and we
have the advantage of warm water heating the intake manifold. Freeze plugs
in the blocks are only interface fits and they don't leak right?
Cary do you have any pictures of how you finished the outside of the
housing?
Cheers
DougFir
" You could always make that coupon sample I was describing.
Put it in the freezer for 24 hours. Take it out of the freezer
and bake it in the oven for 2 hours at 200 F and then repeat
500 times. Get back to me with the actual count :)"
"There is zero tensile load on the tube."
Notice I did not say anything about applying a load to the
sample. So boil it in antifreeze solution instead of sticking
it in the oven. The intent was to check the seal integrity and
not the strength.
BTW the radiator tubes you may have in your car are more likely
sealed with epoxy to the header flanges.
Sorry I should have been clearer. The bond to the aluminum was
exactly what I was talking about. If the bond fails it starts
leaking. I was not purposely side stepping the issue.
I am not against a press fit it is just difficult for the
average builder to accomplish. First the hole must be bored
to the EXACT size in the rotor housings +/- .001 and then
the aluminum trimmed to fit the inner trochoid surface exactly.
Not easy to do for the average fabricator.
In the beginning we used an NC punch to make all the slide
throttle parts. The flanges and all plates were punched out
square along with all the bolt holes. 3/16th thick with a 2 inch
hole was at the limits of the NC punch. The intent was to
mass produce the parts and keep the cost down.
If the tubes are cut first with the flange welded on them then
both flanges must be aligned so the holes in the flanges fit
the back plate of the slide throttle and the cut on the end
of the tube fits both trochoid surfaces. Are you going to
heat both rotor housings, cool the tubes and press fit
both tubes in simultaneously? Good luck.
That is why I used a slip fit for the tubes with square ends.
We placed both rotor housings side by side, inserted the tubes
with the flanges welded to them and bolted up the slide
throttle back plate to align the holes in the flanges
with the slide throttle back plate. The exact angular
position of the tubes was then marked on each rotor
housing. The back plate unbolted and the tubes bonded
in.
Think it through to final assemble. Perhaps you can
make a change in the design of the slide throttle that
can accommodate press fits with this alignment problem.
Sorry I did not explain all this stuff again when
the subject came up again. I assumed everybody had this
in their mind when I explained all this stuff way back when.
I'll dig it up. I will also add it to:
http://www.rotaryeng.net/fund-of-intake.txt
Paul Lamar ...No rotor no motor.
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