Personal car starting sketch 

The cartridge hole has to be made with fixing the sketch at the back turning it from an arc to a straight line since you cant carve out a arc back and cut extrude a hole into it. 

Car axels had to extrude so the tip would print properly, acting as a tip of a bullet allowing the car to go faster. 

Fillets went around the whole car and curves for more speed.

The designs on the bottom of the car. 

cut out extrudes on the sides of the car