Paul
I don't want to be the source of discouragement to anyone so feel free to
post this or not.
First up. Nice drawings. I was wondering how I was going to model it. Yes I
think we are pretty much in agreement now. A few differences in terms and
ID sizes. I happen to think a wee bit bigger ID is the way to go.
A press fit in my thinking doesn't necessarily mean a hydraulic press fit.
Of course distortion is to be avoided. If the hole and insert are round the
you can do a slip press fit with a small tolerances (.002"?) and a very cold
insert. I suspect even a good fit may even move a thousand of an inch
during heating and cooling cycles. This is a good thing I believe. Cary and
a few others have already done press fit with a tap of hammer. That is
most likely because it is difficult to get it to go straight in. A slight
bevel on the front edge would help. As Scallawag says if you get it cold
enough you shouldn't need to heat the housing. He recommends not to because
of warpage potential. How to get it real cold? Dry ice in a foam box, or
liquid nitrogen. The later is not available at your neighborhood supermarket
I know.
Yes all tubes and pipes are not completely round and so the insert needs
lathe work. I would machine a step on the end that holds the flange as well
to get a nice weld. The housing port will have to be finished off, ground
and polished in any case. It seems this is a given in P-ports. There are
ways to do this and precautions to take and the info is out there.
I do see where you are coming from design wise as it solves the gap
challenge and that you still have high regards for the JB Weld to act as
sealant. I don't think anyone can say how long it will hold up in an
airplane engine. That it works in auto racing engines is proven without a
doubt. These engines take a lot of short term abuse but don't endure
thousands of hours of hot cold cycles. I'm not trying to discourage the
P-port effort in any way. Au contraire. Safety is on my mind. Who wants to
rebuild engines even though they are easy to do so. I would rather be
flying with it. P-ports make a lot of sense for our airplanes. That and the
adjustable length manifold are great innovations.
Keeping the insert in place is not a design challenge. Finding the best
material to seal the inside housings but stay flexible is. Machine a step on
the insert to rest against the stubs and it won't be falling into the
engine. Counter sinking set screws drilled and installed in the remaining
two stubs on each side of the tube will hold it from coming out as the steel
bites into the soft aluminum. Look at how the exhaust port is kept in place
and you can see what I mean. Add to the holding force is the sealant.
You can pour the port full but why? Smeared around the insert and hole
before placement is adequate. Put some more around the pipe perimeter after
pipe insertion and then do a water test. Water leaks will be easy to see
where if indeed there are any with a tight fit. Is more sealing better not
necessarily. It is a mind set we do to make ourselves feel better.
O-rings are best for side sealing purposes but NG on our desired straight in
approach into a curved housing. I wonder what else is flexible but a
literal pain in the ass to remove from aluminum housings and comes in two
part liquid form as well with many hardness options to choose from. Hint you
use it to make molds for high temperature plastic forms with undercut
reliefs.
No picture came through about the potential leak area. I would be interested
to see that as I must have missed it.
I don't have access to the machine shop down the road now because they are
assembling some top secret industrial equipment for Epsom/Seiko. It looks
like a machine used in an assembly line plant for flat panel displays.
Seiko gets a little worried to see a non employee working in the factory and
threw their weight around. A-holes. Paranoid I might steal one of their
ideas. Actually they stole one of my research groups idea we brought to
them (our stupidity) to make 25 years ago. It was a wrist watch that had a
device in the band that sensed and displayed heart beat. They patented it.
Justice was done .... sort of. They spent a fortune trying to market it and
lost the fortune. Moral: Only let your rivals steal your bad ideas:)
That leaves me with a good drill press at the moment and a chopper circuit
to control the speed. The insert I will order out.
DougFir
Darn. Too bad! That machine shop was one hell of a resource for you.
Is this the 1990's SAE paper you referred to above.
Paul Lamar ...No rotor no motor.
Paul
About the SAE paper I think the one referred to is different. It is best you
refer to page 20 at the above mentioned RX-7 site. Posting the data here
will just confuse everyone. Again I concur racing ports shapes and aircraft
engine shapes have different design goals.
One question. When boring through the housing how much of the lower
bolt hole housing do you go through? None ? just graze it? Halfway?
Here is a post from the same site I thought you would enjoy.
"If you want to make a big precise hole in aluminum there is an easy way if
you have the tools.
1- center drill (no flexing in the tool that will determine the placement of
the port)
2- use your hole saw, a smaller one though, like 1/8" under what the final
hole should be.
3.1- I make my own boring tools, It's easy as hell, take a 1" or greater
steel round
3.2- turn one end down so it fits in the chuck or collet of your machinery
3.3- cross drill a 3/8" hole in the other end of the 1" round
3.4- cross drill and tap another hole in the round that intersects the 3/8"
hole
3.5- take a broken 3/8" tap and walk to your bench grinder (it's a hard
metal and makes good cutters.
3.6- grind away until the thing is shorter than your hole dia (plenty of
clearance)
3.7- now grind a cutting edge into what's left of the tap (I know kind of
unclear)
It should look similar to a cutter for a lathe
3.8- stick your cutter into the 3/8" hole you drilled earlier and secure it
with a set screw in
the hole you tapped earlier.
3.9- chuck this boring bit into your machine and make a hole a few thou
under desired
so the final pass just cleans it up and makes a nice surface.
My dad is an old tool maker and he taught me this, we have a half dozen
different sizes lying around the shop.
The end result should be way more precise than the hole saw method and
should hold the sleeve a lot better. I can't imagine the surface is smooth
with a hole saw, the more rough the less surface area and less holding
force.
Making the tool might take an hour but it will make a perfect big damn
hole."
Doug Fir
That is funny. No mention of the required mill or lathe
rigid enough to hold the cutting tool and the rotor housing
in precise alignment due to the tremendous forces involved.
You want to know why a good mill weighs 7000 pounds?
It is because there is no substitute for lots of cast
iron when it comes to rigidity.
Heck if you own a mill or lathe you can afford a $60 Chinese
boring head. You are not going to do this on a drill press.
I should not say that as you might try and be successful :)
"One question. When boring through the housing how much of the
lower bolt hole housing do you go through?
None ? just graze it? Halfway?"
I am not sure I understand the question. OK I think I know
what you are saying. You are talking about the lower TENSION bolt
hole just below the p-port bore.
We go through quite a bit of it but we don't break through
the bolt hole. See the attached scale Mazda DWG.
We split the difference at 8.640 inches up from the
bottom. The Lemans engine uses the same tension bolt
pattern as the 13B and RX8 engines.
You have hit precisely on the problem of using a tube greater
than 2 inch OD. I think you just talked your way out of it:)
The problem did not occur to me until you just found it :)
Paul Lamar ...No rotor no motor.
Paul
Actually it was when I was doing the angles I noticed the conflict of
weakening the tension hole housing. Not a problem if you follow the angle of
the upper part of the intake port. If so now you are getting into the realm
of being able to use 0-rings. Ha Ha. You could also grind a flat spot on
the insert where it come close to the tension bolt housing as well.
Another approach no one has mentioned yet is to shape the housing and then
weld a flange to the outside of the housing effectively sealing it. THEN
bore through the plate it and cut a step in it as well.
Lemans housings were probably custom cast as they show a vertical flat
service where the inlet is. Ours are curved in this area and the cause of
misunderstanding when we are admonished to copy the Leman exactly:)
Using thin wall stainless sounds sexy but with the heated aluminum housing
expanding at a faster rate than the stainless steel why would you want to
use it? This would exaberate the sealing problem I would think.
No on the drill press use. Actually it could be done but the hole wouldn't
be round. A gig could be made to hold the housing in position firmly but the
common drill press has too much slop in its bearings. I have other
options. There is a lot of used equipment in the neighborhood that is
unused now as Japan's manufacturing ability has hollowed out and moved to
Thailand, Vietnam and China in the last 10 years. I'll order any aluminum
welding out as that is not my forte but I really like working on the
lathe. I'm looking to buy a nice used one now.
An additional thought on your slide throttle design mounted up close and
personal. If the pump is mounted remotely on the plugs lower side then
there is no outlet interference. Only one problem and that is you never
remember to actually send the remote pump to me:) Sooo....I'll be over in
Ca. next month and I'll fly the Puddle Jumper (C-150) down and look at it
first hand. I may go over to Copper State Fly-in as well after a business
meeting in Flagstaff and would look forward to seeing some of you there as
well.
Doug Fir
Yes the Lemans engine rotor housing were custom cast.
I took some pictures of one today at Mazdatrix. Sand cast
no less and the steel liner has no teeth. Go figure.
The tension bolt pattern is the same as the 13B however.
I would avoid welding on the rotor housings.
Remind me and I'll bring the pump with me to Copper State.
Or you can stop at SZP. We can put you up at the new house.
No need to sleep in the hangar :)
Bring your bathing suit if you want to go swiming in the ocean
with Mikey.
I have been so busy with the houses and moving I feel like I am working
24 hours a day.
Paul Lamar ...No rotor no motor.
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