I designed this trailer for the Peterbilt truck I made. unfortunately, I don't know the exact scale of the truck. it's about 1:32. so I modeled the low boy trailer after that. I would be happy the share the truck files to if I knew if it was legal. I'm not sure where it comes from. 

when printing the axels please use the step file of the combined axel and rims to test print before printing the real model. when printing the real axels for the trailer. do not glue or assemble till the rims are snapped in. place axel part on flat surface and gently tap the rims on. There is no way to remove the rims after their snapped on without breaking them. the STL files where the perfect tolerance for my Creality k2 printer. please feel free to make changes to the step files I provided if needed

update. After printing I realized if you place something on the trailer it buckles and the 2 back axels lift up. it works perfect for just a standalone trailer. I will beef it up once I find the time to do so.