> Water & molten metal heap bad medicine.

I don't doubt that for a moment

If I were the OP, I might have a go at a cast polyester gear, as
polyester can stand a fairly high occassional operating temp

Usually I have a small can (1 litre) of encapsulating resin in the
workshop which comes in handy for all sorts of things. For a
series of castings I'll use silicone rubber molds but I have had
good results with plasticine smeared with vaseline. Plaster or
modelling clay would be OK as long as it's dry and/or has a
mold release like vaseline

If there's a fibreglassing workshop such as a boatyard, vanity
maker (eg bathroom, kitchen sinks) or panelbeater/repairer in
the area I'm sure they could spare a few mls of resin from a
job in progress if the mold was taken to them

Just a thought

Joe
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