George Lendich wrote:

Paul /Butch,
Considering Butch's concerns about cutting into the face of the
bellhousing causing stress risers and the fact that a area
is needed to be milled for the starter motor( to make it nice and
flat). I think what is needed is a raised pad of 2mm across
both areas which would accommodate the milling process.

 Even if  most of the 2mm were milled -off, it would make for
a better finish (more stress free). This would be off-set by
reducing the internal pad by the same amount and also the back
of the bellhousing, where the depth is currently marginal.

I think what we would end-up with is a front pad of approx .5mm,
reducing the depth of the internal housing .5mm, however
retaining the 90.9 mm overall depth.

Please consider these suggestions, when you get the housing.

There are also a number of other changes I'm considering
1. Reducing the front mounting pad thickness where it's not needed.
2. Reducing overall thickness of the walls to about 4.5mm.
3. Making the sides equal length.
4. Reducing the Draft of the walls to accommodate milling right
angle to the face. There will be some extra thickness at the
wall at the time of pouring the housing but this would, for the most

part, be milled-off.

5. Reducing the bulk of the internal mounting 'stand - offs'.
6. Reducing the excess depth of the strengthening ribs,
(the excess have been milled-off on the prototype).

I'm hoping for a target weight of 12 lbs, or less if possible.

I still believe that an 'Investment Casting' would be the best
alternative, it's a pity we don't have the numbers to make this
type of casting pay for itself. I believe we could get it to 9 lbs or

less.

Getting there !!
George (down under)

Paul,
I've spoken to 3 Investment casting foundries, one quote was $21,000 one was
$10,000 and one was $5,000 - rough estimates only.
These were for cast steel moulds and from talking to them I've worked out
how they do them, which is just a couple of more steps than what I've done
so far.
One - make a cast of the pattern
Two - make a sand mould then pour your steel.
Three -  clean up the steel mould.

Two steel moulds would be required one front face and one inside face.
Most of the cost is in the time - which I have.

It's something to think about, however finalisation of the design is
necessary and some more research !

These would be gravity castings and as such still require a minimum of 4 mm.
One draw- back with a steel mould for thin sections, the air tends to get
trapped.

George (down under)

 
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