David,
I have done all the design with Butch, who did all the FEA on it and I
made
the pattern.
The big problem is getting thin enough and strong enough with sand
casting -
mine is 5 to 6 mm.
Then there is the problem with getting the Al to flow over distance in
such
a thin section. Then there's the problem of porosity of such a thin
section.
The Al has to be heated beyond recommendations for it to retain sufficient
flow ( read heat) over distance in thin sections - this walled casting
which
aren't pressure cast are a nightmare!!
But there's more! the real problem is the machining, I can do the casting
at
a reasonable price, but the machining costs (especially CNC) are
outrageous.
Then there's the postage and handling cost to USA - ever posted something
to
the States -again outrageous.
Our design ( Butch and myself) is strong, is a reasonable weight, includes
3
positions for starters, allows for 2 different starters, but I can't
supply
them at a reasonable cost! It is also caters for engine mounting at the
sides, will accommodate 2 different PSRU ( Tracy's and my own design). has
additional supports for Aerobatic work
You will notice Tracy does his own machining in-house, I don't wonder why!
George ( down under)
---------------
George,
I worked on a foundry for a short while (3 months) a very long time ago,
from memory when there was something like the size of the bell housing or
bigger the way they used to get the alloy to flow all the way through was
to heat up the sand casting (lost wax system) to an applicable temperature
you need a big cooker for that, they did of course, when the whole cast is
that hot the alloy will keep flowing until the entire cast is full, did
you try it that way? Just a thought.
George why don't you contact me direct on the phone at 03 95480704 ex-711
Regards David Gaze
Also down under but further than George :)
David,
I worked in a foundry as well - first job!
The local foundry chap has many years of experience, so I leave it up to
him. The end result is pretty good. You will notice I don't need a two piece
pattern like many foundries insist on, he will do it with a one piece and
it's much easier making the pattern and no misalignment.
George (down under)
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