N scale 55 ton hopper car

OSTycoon's awesome HO 55 ton hopper car, scaled down to N scale.

The new version builds the whole car in OpenScad rather than just scaling the original STL. This allows a bit better control of the wall thickness which were a bit thin. Additionally there is now a version of the car with a buck in it to make it easier to fill with a load of your choice.

Added a HiRes version meant for resin printers. It has much thinner walls and floors as well as adding brake platforms, ladders and some detail to the ribs. Note that the HiRes version takes ~50 minutes to render on my machine, so if you hit F6 in OpenSCAD and nothing happens, it isn't broken, just super slow.