Credit:
First off, credit where credit is due: Thanks to Kraftrains and their "HO Scale 45ft Flatbed train car" where I sourced the hardware from, they're great, couldn't have done this without them, their stuff has really gotten me into 3d printing and modeling by making it accessible so thanks! Also thanks to Firelightphotography's "Log Bunk for Logging Cars" that I used as the tipper cradles.

Story:
Anyway, so remember that cousin? Well anyway I wanted to give him some industry to play with (Aside from the calypso tonix) that was kinetic to engage him more, so that's what I did.

Assembly:
So, this is a really simple concept but it's hard to explain so imma do my best, I'll supply photos later to help.
Basically find the chassis half that is more angled than flat and glue the semicircle upright on the right edge with the long bit pointing away from you. it should be perpendicular with the edge of the car and as close to the edge of the car as possible. Then take the tipper so the rod is on the right and place it in the hole on the semicircle. Then, push the tipper all the way into the hole till it stops. After that, take the other half and hold it (not glue) to the other half so the short ends of the chassis align. Now, put the other semicircle on the other end of the tipper, and find the point to where you can move the tipper back and forth, and it tips outward in one position and in the other it won't tip. Mark the position of the not glued semicircle, take all the not glued parts off, and glue the semicircle on it. Then put the tipper back in like you had it and glue the two chassis parts together, with the thin parts touching. Finally, put the trucks on with the truck pins, add wheels (Not provided), put in couplers (Not provided), and put on the coupler plates. There! log car! Huzzah!

Operation:
You just press the little rod on the tipper until it's off its shelf and then tip the thing over. then you can flip it back and push it back onto its shelf. otherwise it's a normal rail car that does rail car things

P.S.: if you're lost on assembly, comment or something and I'll gladly walk you through it better. Again it's really easy just hard to explain.