Re: Model brake component size comparison to prototype
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Schuyler Larrabee
Ralph, I believe that lost “was” is, except for unique individual items made by artists casing in silver or gold, no longer used for mass production of parts like model railroad brake gear. That has become a “lost plastic” process, where many plastic parts are glued together in a “tree< which is then inserted into a can of wet plaster. When dry the plaster cylinder is heated to get the plastic to run out, and then brass is poured into the middle of a spin casting machine, which forces by centrifugal force, the metal into all the voids in the plaster cylinder. After cooling (and shrinking) the plaster is broken away and the parts harvested.
I presume that the plastic used has a lower melting temperature than that used for injected molded parts from metal dies.
I have received lost plastic parts that still have plaster on them.
Schuyler
From: main@RealSTMFC.groups.io <main@RealSTMFC.groups.io> On Behalf Of Ralph W. Brown
Sent: Saturday, April 04, 2020 1:34 PM To: main@RealSTMFC.groups.io Subject: Re: [RealSTMFC] Model brake component size comparison to prototype
Hi Tim,
My understanding is that the sacrificial material used to make the molds for casting is, as the name of the process implies, wax, which melts and is absorbed by the mold when it is first heated leaving the void later filled with molten brass or other casting metal. I doubt plastic detail parts made by Cal-Scale or others would or could preform the same function, although I suppose they could be used as “masters” for casting the sacrificial wax patterns, copyright issues notwithstanding.
I suspect there are others here who are more familiar with the process and could provide a more detailed description of the process.
Pax,
Ralph Brown
From: Tim O'Connor Sent: Saturday, April 4, 2020 9:15 AM Subject: Re: [RealSTMFC] Model brake component size comparison to prototype
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