Superb concept of designs. I was also in a stage at my time when I used to create rocking car designs but now my skills has gone away from me.
I don't know why, but I always have a hard time sketching cars. I envy you for having the talent to do so, and in an awesome way. The shading and the depth of your sketches make them even more attractive.
My brother used to sketch using paper and pen… Now that we have advanced technology, he uses his pc to sketch. He's made a lot of artwork with the help of his PC. Most of 'em are cars, btw. :D I guess you also have that talent.