A comment on Ångström's article by Daniel Sieber
Concerning your article, I do miss tungsten (W) and its alloys (in particular W-Ni-Cu, aka "Densimet") in that list. The material intended to add weight, much more than with lead (Pb), and the materials designed for flywheels. Tungsten powder from golf supplies (or sintered tungsten pieces) give weight by filling empty rooms in a model. More weight brings better adhesion to a model loco and thus increases traction power, particularly important in small scales running on 6.5mm or even smaller gauge. Pure tungsten is (almost) not machinable, it's mostly sintered. But tungsten alloys like W-Ni-Cu are again machinable (with HSS tools; the rods of this alloy are also sintered). At little loss of weight, they're still 50% heavier than lead and have the strength of steel. Plansee and Mallory are just two manufacturers of dense metals. An internet search will find others.Added 30-9-05