I'm actually in the process of adding weight to my freight cars. Many use lead to add weight. I was particularly interested by auto adhesive wheel weights as described by Mike Confalone. However, lead weights are getting hard to find. Every auto parts shop I went turned me down, telling me to ask a repair man in a garage changing tires. I also found them on the Internet, but shipping dead weight is prohibitive, almost as costly as the item itself.
Thus, last Friday, I went with Louis-Marie to the local home improvement center to find the cheapest way to add weight to a car.
First, nuts and bolts. Costly, very costly, and most are from a cheap alloy that doesn't weight that much: chromed zinc.
Second, we checked steel rod. Less costly but not very fun to work with. Cutting the rod is labor intensive and leaves very little place to customization.
Third, steel pipes and accessories. Cheaper, but still costly, not very practical.
At this point, we were a little bit disappointed. Each car would cost at least 2 to 3$ to add sufficient weight. Then, Louis suggested we take a detour and check up tiles and grout...
BIG DEAL! Cheap glass mosaics were selling for $4.95 each. It weighted a lot and was customizable: you just cut the number of tiles you need with an X-Acto. Better, they stay together because of the supporting mesh. Let's do some maths!
A 12 inches x 12 inches mosaic tile cost 4.95$ and weight 52 onces. A tiles is made of 144 small 1" square tiles. Each little tile weight 0.36 oz and cost 3.4 cents.
Just for fun, I tried to weight up a Walthers FGE 50ft boxcar to reach about 11.1 oz just like Mike Confalone does (yep, that's a lot of weight, maybe too much, anyway I tried it on a few cars and it makes switching more realistic and less prone to derailment, not sure if I'll upgrade all the fleet). It took me 3 rows of 6 tiles and thus cost me 60 cents! Most people will strike to get the NMRA recommended weight. You only need one row of 6 tiles in most cases, costing you 20 cents. Now, try to beat this. And I guess you can find them at cheaper price if you find a dealer discounting tiles!
I recommend gluing the weight with hot glue. Strong enough but removeable if needed and glue instantly.
Glass mosaic tiles are cheap, readily available to most people, easy to work with, quite heavy and non toxic. They may not suit every type of cars, but for boxcars, reefers and many other enclosed cars, they should do the job. I had good results filling some cars with Plasteline or sand. Plasteline is particularly useful for hoppers as you can fill discharge bays.
Still, I need lead for my locomotives!