Paul,

Is there any merit to a .005" interference fit between an Al tube and
the rotor housing using LN2?

Joe Berki

You have to be careful you don't stretch or warp the housing. .005
inches would result in a major leak in the sides of the housing where
the water O rings are.
IMHO it is not worth it. The SS tube tig welded to the liner and the
conformal aluminum plate is straight forward and highly likely to work
with easy leak repairs in the remote chance you even get a leak in the
outer housing.

BTW a pound of Devcon pour came into today but I will probably use it to
make a casting pattern for the conformal aluminum plate. It was about
$56.
Larry has a new casting supplier he likes in Northern CA.

Paul Lamar

Paul,

Before you start please understand one point.  One of the main reasons
I went with a process of adding epoxy to the aluminum  housing was I
wanted the chemical bond between the two creating a homogeneous
epoxy/aluminum housing.  This was to ensure  that four M5 (3/16") studs
that will hold thethrottle assembly  had enough material to tap into.
If you examine the housing area on the lower part of your bore and
about seven to ten mm in from the edge  you can readily see that the
sloped housing profile is only about seven mm thick.  Not enough for a
blind tap unless you are going to pot the inside of the cavity as well.
However with a  epoxy material added on top of the housing you will
have added at least another six mm in thickness.  On the other hand
slapping on a cast epoxy wedge with screws and silicon sealer will
ensure that you lose the strength advantages of the composite as well as
needing to screw into something that is screwed on to the housing.  In
the end to have a perfect aligned fit you are going to have to machine
the housing  with an end mill.  Please don't tell me you are trying to
promote a quick and cheap drill press method  P-port:)

Doug in Japan

Well no. Here is the plan. Mill off some material off the housing down
to the outer wall with the housing in the mill at 90 degrees.
Same as if you were boring the final hole. Screw this aluminum casting
(3D 1) to the out side of the housing. Screw holes or screws not shown
yet. Then bore the 2 inch hole for the SS tube to be welded to the inner
liner.
Weld the tube. Unscrew the casting slip it off over the tube and cover
the inside with red RTV and the bore with red RTV.
Replace the casting. Your done. Expansion and contraction will not be a
problem as it is accommodated by the flexible nature of RTV.

I'll get a bunch of these casting made and sell them.

Paul Lamar



This thread has the feel of progress about it.
Decker, Michael



Paul,

Oh! you will cast an aluminum piece.  I see.  What about shrinkage of the
cast Al. piece?
Another consideration.  RTV does not function or seal in the same manner
as an O-ring.  Yes it flexible and will move but it may be expanding
against the steel machine screws that are trying to hold the cast piece
down.  Use O-rings if possible. The proper dimension and relationship
between O-ring size verses slot dimensions is a well known and
documented science.  The O-ring slot allows for thermal expansion.
Look what happens to steel housings when over size Teflon/silicon
O-rings are inserted.  Now where for the seal to expand to and so the
steel is cracked. You can still have proper gaskets or O-rings designed
into your conformal wedge or choose an epoxy with similar expansion
rates as the housing.

Doug in Japan

Yes I thought of that already therefore we are making a pattern on
a 3D NC machine that has the shrinkage calculated in. If it don't
fit your housing exactly a small bit of die grinder or mill work will put things
right. You fit it and screw it down before you bore the 2 inch hole.

There is room for the RTV to expand side ways out from under the block.
It is widely used to seal the water pump with no problems. I agree if silicone
is used in a closed  O-ring slot. Different situation.


Paul Lamar