>
> BTW I just read about 28 pages of posts about building P-ports on
>> the RX-7 site along with pictures and comments. I suggest you refer
>> people
>> to read it as it will save you and them countless hours of
speculating
>> about
>> the what ifs:)
>>
>>
>> DougFir
>>
------------------------------------------------------------------------------
>> -------------------
>>
>> Doug,
>>
>> Which rx7 site had the p-port info.
>>
>> Thanks,Geir
>>
>> This is what I got from Doug. Perhaps you can make sense
>> of it :)
>>
>> RX-7 Owners Club - Building Per
>> --
>> Paul Lamar ...No rotor no motor.
>>
>> It appears to be an HTML file.
>>
>> What I can gather so far... it is about some guy by the name
>> of Scalliwag that built a P-port with a hole saw on a lathe.
>> Very clever. It was posted 12-29-2002. I swear I never saw it
>> before but great minds think alike :) He suggested pressure testing
>> it.
>>
>> A lot of the questions we have heard on here were asked then.
>> Perhaps some of you have read this before :)
>>
>> The last picture (port27) shows what you are up against with
>> various other schemes such as O-rings.
>>
>> Paul Lamar ...No rotor no motor.
>
> Paul
>
>
> Sorry about that. I saved one of the HTML files and thought that went
> through to you.
>
> It takes about 2 hours to read all of the RX-7 post and wade
through the
> garbage and the gems. Several racers weigh in with opinions on
P-port
> size,
> position and grinding techniques and by the time you get to post
page 28
> you
> will notice that almost every epoxy out there is bashed:) That's
life. I
> hear some people hate tofu also. Lots of good pictures and hints
about
> what
> shape the Leman port was.
>
> Start with this link and work your way forward..
>
>
>
> BTW the I have done a some drawings using an insert with 1.5mm
O-rings
> properly slotted in the insert. If the ID is about 48mm and the
OD 54mm
> then the port can punch through at the same place or open even a
little
> earlier (if you so desire) at the position Rolf indicated in his
Lemans P
> timing diagram.
>
>
> In USA use this size pipe for and angled insert with O rings. But
> probably
> not worth the effort if you do a nice press fit IMHO.
>
> McMaster Carr
> 4559T611
> 2" Pipe Sch 80
> OD - 2.375"
> ID - 1.939"
> Wall - .218"
>
>
> BTW Two seats inner and outer are possible. Outer just.
Unfortunately
> the
> insert will be angled up about 12 degrees up from level. May not
be a
> good
> thing for air entering the chamber in this manner. Also as Jerry
> correctly
> indicated the manifold would leave the housing about 15mm higher
than the
> Puerto Rican straight in style and by the time we want to turn it
back
> and
> over the engine the bends get severe or the height tall in
aluminum. From
> the slide throttle it would have to be composite to bend like GURU
> Racing's
> manifold.
>
> Thanks Cary for finding this and for the fine work on your housing.
> Double
> step and deep freeze then light tap or press is what I finally
decided on.
> Most space saving way. Perhaps a couple of screws to hold it in
place as
> well. Whew!! Port shape is top secret and I'll let you know when
I do. I
> notice one reference to a racer named Jesus that potted the
housing with
> silicon rubber??? Well if it good enough for Jesus its all right
by me:)
>
>
> Doug Fir
>
> I understand you can't get 500 degree F JB Weld in Japan. It must
> be on the d*e*f*e*n*s*e department's top s*e*c*r*e*t
not-for-export-list
> :)
>
> (apparently NSA is listening :))
>
> With all due respect Doug you using a sledge hammer where
> tweezers will work.
>
> The tolerance on pipe as opposed to tube is all over the lot.
> Quoting it to the nearest thou is not the real world.
>
> You will be surprised I am coming around to your way of thinking
> in a couple of regards. Press fit is not one of them. Any press fit
> requires precision measuring tools and is risky in regard
> distorting the rotor housing. I would like to keep this
> in the realm of the home builder and keep the cost down.
>
> I am thinking we can machine a .030" shoulder
> in the .065 wall tube. What this means is a is 1.940" ID final
> hole in the trochoid liner instead of 1.875" ID. .015 material
> is machined off the end of the 2 inch OD tube about 3/4 of an
> inch long. This should take less than about five minutes on a
> lathe. The OD of the end of the tube should then be 1.940".
> The wall thickness on the end of the tube .0325 more or less
> if my arithmetic is correct.
>
> This is easy to trim with aircraft snips. It is all still a slip
> fit. You bore the holes until the tube with the shoulder and flange
> welded on but no bolt holes drilled yet just slips in. You use a
> machinist level to check the flange orientation. Slip the tube in and
> mark around the outside to fit the trochoid surface. Remove
> the tube and trim with aircraft snips or any other means.
>
> Sand it all over and smooth it with additional trial fits.
> Smear it with JB Weld on the thin end and insert it checking the
> position with the machinist level to be sure none of the aluminum
> pokes beyond the trochoid surface and the flange is square.
> After the JB Weld cures around the thin portion of the tube go
> ahead and pot both sides with JB Weld. After that is done assemble
> the engine and match drill the flange bolt holes with the back
> plate of the slide throttle. This blocks the problem
> leak area in the rotor housing and by far the cheapest and
> easiest way of doing so with the least amount of work.
>
> Here is a shot from the RX7 list of the problem leak area.
>
> With 3000 psi JB Weld holding in the tubes... machine screws
> are totally redundant.
>
> Drawings shortly.
>
> BTW Scalliwag's way of using a lathe is ingenious. Many
> more people have lathes than have mills. I see no reason
> why a boring head can not be chucked in a lathe.
>
> Paul Lamar ...No rotor no motor.
>
>
> OK here are the 3D's dwg's. The first two illustrate the problem but
> are not entirely accurate. The hole is much smaller than shown.
> This is due to an approximate 3D model of the rotor housing.
> It is close enough however to illustrate the problem
>
> The rest are the simple fix.
>
> Paul Lamar ...No rotor no motor.
>Paul,
If JB Weld is machinable it may be easier to clean the water jacket
with a
die grinder, fill all spaces with JB Weld, and bore the hole for the
p port
tube straight down to the shoulder position. This should mean that
there are
no missing bits to fill after the tube is epoxied in.
Colin Smith
Yes that is a very good idea. I should add that to the instructions.
Good point. I did that when I hogged out the bad epoxy on Marks
engine. If you epoxy it quick the aluminum does not get time
to oxidize. Yes JB Weld is very machinable. They claim the main
ingredient, other than high temp epoxy, is steel dust.
That reminds me Doug you can make your own. Gather up some
aluminum or steel dust from you local machine shop and clean
the oil off some how. Bake it at 1000 F or some such.
Paul Lamar ...No rotor no motor.
----------------------------------------------------------------------
Grinding thru the above mentioned 28 pages, a post on pg 27 by PDF
indicated he makes his own filler. He uses Araldite and aluminuim
powder for the housings or steel grit for filling the original
ports, see attachment.
Joel
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