George,
You could put it back in the NC mill and pocket these out.
Simple set up. Only one set up. The hole NC program could be
the same for all and merely stepped around for each of the
ten holes. Same goes for the four pockets in the center plate.
Should save almost two pounds.
BTW please ask the machine shop people what PC programs they
are using to generate the NC G code. I might be able to
do it on this end for them. Also what kind of machine
is that as each machine manufacturer uses a sub set
of NC G codes?
The reason wall thickness is so important is
going from 5 mm wall down to 4 mm wall will save
20%. 20% of 13 pounds is 2.6 pounds.
It should also be easy to modify the pattern and cast in these
pockets and holes.
The 3D illustration shown here is not accurate in the sense of
the raised center section. It is really located behind the front face
and not in front as shown here as you well know.
Nor is it completely to scale.
Paul Lamar
Paul,
I understand what you are saying about the centre section and I'm already of
the same mind, however, as much as I'm looking for savings, I am a little
cautious about the cut outs ( good inspection holes however).
This area is one of the thinnest areas probably 5.5 mm, however my limited
engineering knowledge tells me stresses are carried through the surface and
removing a lot of surface MAY remove the ability to transfer all the
necessary stresses.
Then again the majority of stress may already be transferred by the
strengthening ribs (I'm unsure !).
What I was hoping for was that you would stress test the bellhousing as is -
do some weight saving exercise (probably some of what you have suggested)
and then some more, until we reach a maximum on weight savings.
Your suggestion that these holes may be produced by the foundry process may
not be possible, because of the thinness of the material and the restriction
in flow of the material, that these voids represent.
I feel that if the bellhousing is less strong with the holes yet more than
adequate for the 13b - the bellhousing without so many holes may be more
appropriate for a 20b application where the extra weight may not be as
critical.
I've got the bellhousing with a 'permanent mould' maker at the present time
for some costing, so will do those photos you requested when I get it back.
I will ask for the info on the CNC Program and ask for some suggestions from
the foundry.
Did you get the drawing of my proposed modification?
George (down under)
Yes I got it. Not to worry about the cutouts. With 5 mm wall thickness
it will be plenty strong enough. The ribs take all the load anyway.
Paul Lamar
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