As we are moving toward pouring metal castings for various weights.....Let's talk alloys and toxicity.
I am no expert by any means, but I have done a good bit of reading and prep for modeling.
Lead is a great substance because it is dense and soft.
But there are two problems with it.
1. It is toxic. If you ever melt it, do it outside. Also, always wash your hands when working with it in modeling.
2. It has a very high melting point. It is a whopping 621 degrees F. That by itself makes it a bit more difficult and dangerous to work with.
But people discovered that if you combine metals in various ways, you get alloys with very different properties.
The properties that I care about are: melting point, density and hardness, toxicity.
Here is a GREAT website for learning and studying alloys.
CS Alloys manufactures this stuff. I have never bought from them but they have a WONDERFUL chart of organized information.
Go to their website: http://www.csalloys.com/
Over on the right side you will see a chart.
Just under the chart you will see a link that says:Click Here to See Full Specification Table
Click on that (scripts must be enabled since a pop-up window opens).
THAT chart has a bunch of info.
The things I look at are:NAME- left edge
MELTING POINT - middle left
BRINELL HARDNESS - middle right
COMPOSITION - right edge
Now remember, water boils at 212 F. So that is a good reference point.
Hardness. If you are a math and physics guy, read this: http://en.wikipedia.org/wiki/Brinell_scale
I don't care why. I just need reference markers.
LEAD has a rating of 5.0 and of course is fairly soft.
BRASS is about 60 (and is pretty hard).
So bottom line..... when I go to the CS Alloys chart, I see a low of 9 and a high of 22.
For my purposes (like a gearbox) 9 is pretty soft.
Indium- fairly low
Lead- fairly high Cadmium- bad news
So for modeling, when I look at that chart, I want to stay away from Cadmium.
Now I have 2 weights. One is big and is over the gearbox and sits in the cab.
That weight is not a big deal.
For that one, I'm going to use Lo-136.
When searching to buy some, just search ALLOY 136.
I'm not certain, but I'm pretty sure this is the stuff Walthers used to sell years ago as "Temp-Lo". It melts in boiling water and is moderately hard.
But the other weight is a bit different. That smaller weight is right up next to the motor and will get pretty warm. I don't want a 136 alloy melting in my loco!
For that one, I'm going all the way down to TRU-ALLOY 281. Hopefully that is high enough to withstand the heat of the motor (300 degrees is cooking temp. If my loco gets 300, it would seriously burn my hand).
Also, it has low toxicity. And at Brinell 22, it is pretty hard. The density is not a whole lot different from all the others.
So those are my choices. I have bought both.
I have cast with good results already with Lo- 136. I made a gearbox for another Kumata loco (Trainmaster).
I have not cast with Tru- 281.
So I will be reporting my experience in the future.