George Lendich wrote:

Paul,
Had a talk to the foundry manager again to day, checking on things.
I took your drawings and he said he had no trouble pouring 4mm for short runs, but the run on the bellhousing  was such he would
recommend 5mm minimum.
(by 'run' he means the distance the liquid aluminium must travel)
He feels that the aluminium will start to cool too quickly in 4mm, he feels that by the time the 4mm got to the 13mm face it
would be too cool to fill the void. Even if it did manage to fill the void there could be range of problems, all of which
would result in rejects i.e. localised cracking, through uneven temperatures etc.

Considering this, I would be happier at 5mm as I don't want any weakness in this area.
He's happy with the stiffeners from 3mm to 5mm.
Lucky I checked !
George (down under)

I'll take what I can get :) 5 mm it is. 

My foundry claims 3.6 mm but occasionally they have problems. Sand casting is as
much an art as it is a science. A good foundry man knows from experience where to put the
risers, gates and sprues. You are lucky you have no core boxes to deal with.

My uneducated guess is he should fill that 13 MM face first. Is he talking about a green
sand or dry sand mold? I think you might be able to preheat a dry sand mold to
a several hundred degrees F with heat lamps to help the flow of the molten aluminum.
A green sand mold might fall apart. I don't really know.

Paul Lamar
 
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