I suspect that most of who run contemporary trains have one or more auto carrier cars. They have been available for some time from each of the major manufacturers. But, I also suspect that like mine, they all have a problem. In the real world, you see train loads of auto cars with autos filling them heading to their destinations and running empty only on the way back to the manufacturers.
But on my layout they are always empty and I can see right through them, particularly when they are backlit.
Unfortunately, I know of no source of cars that meet these criteria:
+ really cheap, since I will need dozens and dozens of them
+ light weight since a die cast car will add lots of weight to the car if it is filled
On the first criteria, the only manufacturer that makes really inexpensive cars is Menards, but they are die cast and thus heavy.
What we need is a very simple plastic body casting. It would have wheels, windows, etc all in the single "shell". Perhaps three body styles: a sedan, a SUV and a pickup. And if it were cast in clear plastic, when we paint them, the clear windows would be there. Even if clear plastic will not work, a neutral color still let's me paint them in different colors, and making the windows "black"
Would anybody else besides me be a customer?
