should start by saying that about 10 years ago I produced some 7mm kits for both a P4 and a P5 coal hopper and R2 and R4 coke hoppers. These were resin with brass strapping over layed onto them. With the moulds dying last year I decided to see if I could upgrade them to be a one piece 3D print.
This was achieved pretty quickly. But then I had the idea to make them work ie make the bottom doors open and close automatically. Easier said than done.
So starting with the P5 hopper this is how far I have got.

The wagon body. The lugs on the bottom hold the doors in place and the lugs on bracing is for the door operating lever.


Bottom doors and door operating lever.


Body with doors attached. There is a bit of brass wire running through the lugs and the door hinges.

These are 7mm ones I'm hoping to have some in 4mm before EMGS spring in may.
Marc