Low Melt Alloy Castings?

[kelticsylk]

I've been reading up on using low melt metals after stumbling across an article in the July 1954 issue of Model Railroader. From what I can ascertain some of these metals expand as they cool, capturing fine detail (or defects) in the mold. One article claims they can copy fingerprints! Some of these metals can be poured into molds used to make candles and the like. One has a melting point of 158 degrees Farenheit. This sounds high enough to take some abuse (like being left in the sunlight) while low enough to melt in hot water.

Anyway...I found out this stuff is still available, and now even in lead free variants. It occurred to me that this is a great alternative to resin for locomotive shells and car frames. I'm especially interested because of  the additional weight provided by the metal for traction and riding qualities. I have a couple of pewter kits and this would enable the average wonk like me to make my own metal parts. I could use RTV molds and hot water to cast any number of things in N scale. I'm thinking that this could also be used with the hydroshrink casting process I've seen discussed. The final casting could be done in metal in the naptha shrunk mold.

First question...Is anyone working with this stuff?

Second question...Regardless of what you use for the casting, how do you make a hollow shell for a locomotive or car (or even an automobile) without machining out the inside?

Frank Musick

[ElginLoco]

To do a hollow shell you'll need a two part mold. Picture casting a bathtub. You have one that molds the outside shape and a plug that molds the inside shape. They would meet around the rim. Now when you have windows you have to shut them off whether you are making the inside and outside molds at seperate times or at the same time as a single pour. So I use celofane tape on the inside of the shell. It is so thin it is almost not there when you do the casting. The flash would be easy to trim out later.
There are high temp RTVs that can cast pewter as well.
Good luck.

[SAH]

Probably 10 years ago (at least) there was a series of articles in N Scale magazine about casting with pewter.  Very good series if I recall correctly.

[kelticsylk]

Probably 10 years ago (at least) there was a series of articles in N Scale magazine about casting with pewter.  Very good series if I recall correctly.

I'll try to ind them...Thanks!

[PGE_Modeller]

A quick check of the index on the 2000-2004 N Scale magazine CD indicates that Greg Scott's 3-part "The Art of Steam" article on building an NP 4-6-0 in the May-June, July-August, and September-October 2001 issues discusses the building of the styrene master as well as the pewter and resin casting of various parts.

Cheers,
Greg Kennelly
Burnaby, BC