A discussion of coal loads on The Railwire prompted me to think about a smart way to easily create them for my hopper fleet. Because it’s 2024, of course I turned to 3D printing. Here’s what I did and how you can do the same thing.

I started with an Atlas 90 Ton Hopper (a terribly named model, since the prototype is actually a 100T car, but I digress).

First I measured up the inside of the hopper using my calipers and recorded the internal dimensions. I’ve stored them, and the other cars that I’ve done in a Google Drive spreadsheet, available here.

With those dimensions in hand, I headed over to Tinkercad to draw up both some loads and a useful device for covering them in coal.

The loads are pretty straight forward. I simply use a combination of parabolas and “mountains” to create a variety of coal lumps to fit inside the dimensions of a hopper then drawing a box with the inner dimensions of the hopper body to “cut” around them (like a cookie cutter).

Tinkercad isn’t good at providing a a “coal texture”, so covering the loads in real coal was going to be required. When I did this type of thing before I would just put the load in a car (maybe with some cling wrap to protect the car), paint it with glue and paint and then sprinkle on coal. I figured I could design something to make that job far easier and less messy while eliminating the chance for damage to the cars. I settled on a “box” sized to fit the load with an open bottom and sloped sides. I use Ultimaker Cura as a slicer when preparing objects for printing and enlarge the boxes 1% before slicing to provide a little clearance for the loads to drop in.

With the loads and “loader” printed, I paint the load with a mix of white glue and black paint and place it into the loader then sprinkle coal on top. I give it a minute or two to “tack up” then dump the remaining coal for future use.

Then, thanks to the generous open area on the bottom you can pop them out and let them dry. Easy peasy.

So, now you may be looking for the files.

The existing ones, along with new ones will be added to this Tinkercad collection. but here are the individual ones I have so far: