<< the cost of making a rubber mold to shoot the waxes. >>
I made five rubber molds for the parts to build a oscillating engine
found in K.N. Harris book on stationary steam engines. The total cost for
the rubber (silicon two part mix) and the wax was less than $50.00. Making a
quality pattern is the most essential part of the process. After making the
patterns and the molds I discovered that making a well finished pattern is
essential. I did not finish mine well and I can see the grain lines, saw
marks, and flaws of the wood patterns in the wax castings. The flywheel has
given me a lot of trouble as I cannot seem to get a good wax casting no
matter what I do. I suspect that the web, (area between the hub and outer
rim) is too thin and not allowing the mold to fill completely. I have spent
a lot of time trying to add air vents, increasing the amount of pressure of
the hot wax and changed the point of injection of the wax. This has given me
some improved castings but they still have voids and air pockets. I have
taken to repairing the wheels as best I can and hope to have some wheels cast
in a brass alloy within a couple of weeks.
Making a rubber mold is not rocket science and providing one has a
quality pattern it can be done easily all that is required is time and
patience. A minimum of equipmemt is required to make molds of a reasonable
quality. I modified a small air pump made of brass to inject the wax. I
picked up an old hot plate at a Goodwill store along with a double boiler
that I use to melt the wax in. With the exception of the wheels the rest of
the castings came out with a reasonable quality.
The acid test will be if the parts can be investmemt casted and produce a
operating steam engine.
Salty (learning the hard way) CC&BW
