Adding weight to tank cars

My method for adding weight to tank cars you can't easily open is to carefully drill a 1/4" hole in the bottom and pour in enough liquid plaster to bring it up to weight.

I make the plaster very runny and use a postage scale to measure out the weight of plaster I will need. I have a tiny funnel that I got from a gourmet cooking supply store and I use it to assist pouring in the plaster.

After pouring the plaster in, plug the hole with some modeling clay and set the car upright to give the plaster as low a center of gravity as possible while it sets up. Let tyhe car sit for a couple of days.

I replace the modeling clay with a little putty, sand it smooth, and then paint it the color of the car.

Thanks, Joe.

I had never thought of using liquid plaster.  I'll pass the word on to him.  We were discussing using steel shot and epoxy, but it is difficult to control exactly where the shot would end up for weight distribution when the epoxy set up.  Do you just put tape over the hole after the first pour, to seal the tank so that you can turn it over and to settle the plaster to the bottom of the tank for a low center of gravity?

Oops! I just reread your post and saw your suggestion to use modeling clay to plug the hole while the plaster dries.  Somehow I missed that point on the first reading.

I have also used sand, it is

I have also used sand, it is easy to fill as much weight as required when done on a scale, it levels itself out when you turn it over, and similarly, I plug the hole with a glued in sprue and filed smooth. 

Steve

Weights

How is the Walthers car assembled? I was able to pry the ends off a similar Atlas car without any damage -- they were simply pressed on. Some assembled cars are very permanently stuck together but others re-kit themselves quite easily.

Joe: What happens to the moisture in the plaster as it cures?

Joe: What happens to the moisture in the plaster as it cures?

It's a tank car. That's its lading!

Joe: What happens to the moisture in the plaster as it cures?

While I like Alan's answer, the moisture stays sealed in the car as permanent internal humidity - no harm done.

Plaster curing is a chemical reaction, not an action of water evaporating (drying). The plaster sets up just fine, even if the mosture can't go anywhere.

But sand is a good option as well - with the advantage that you can close the hole immediately with a styrene plug and it's self-leveling when you turn the car back upright.