Replacement part for model railway wagon

[bkk-bkk]

HelloI am new to 3d printing (first filament arrived today, first printer - Creality Ender 3 Pro - due next week).The part I am trying to design is a railway wagon coupling mounting arm for a Hornby KFA container wagon. Four images are attached, the main one shows dimensions in mm. The measurements along the bottom are various features measured form the datum on the left. The 2 measurements on the upper edge are the centres of the red and blue rings measured from the datum. The 4 on the right are the inner and outer diameters of the rings.The red and blue rings were my attempt to start designing the shield-shaped part from two native rings, this was a failure. My first attempt was in Tinkercad, the second in Sketchup. I am mow using Mattercontrol which is more to my liking but I am still struggling to get past the first step on the very steep learning curve.My next thought was to prepare a 3rd angle projection and convert it to STL for slicing. Is this possible? and if so which app should I use? Failing that any hints on designing the shield shaped part of the item would be very welcome.After that it will be a case of designing and adding the remaining parts, plus figuring out how to add support structures, etcBest regards Brian (bkk-bkk)