On Jul 22, 1:47 pm, Gordon Airporte wrote:
Father Haskell wrote:
Cast iron is harder. It machines better. It's rich in graphite,
which helps moving parts move smoothly instead of sticking
and galling.

I recall hearing that another advantage is the extra weight/density of
cast iron, which gives the wheels more inertia, like flywheels.

Which dampens vibrations and helps machinery last longer.
Not sure why trunnions would need more inertia, though.