I've been in a drawing funk, and pushing through it I need to finish a mosaic long overdue, but here are some sketches of Prime I did.
Nice! But in the first picture it seems his right half is somehow missing, although we see his right arm, I think there should be a little more visible. The second line of his torso top is a bit too high from the angle (Hope you guess what I mean, don't know how to express it better. Guess I'm missing some vocabulary). If you draw it lower it is obvious that you could have drawn the rest of his right half. Apart from that I like Optimus' style in the first drawing best!
Yeah, I get what you mean, I just felt like making the "behind him lines" as I call them. haha Maybe the last one, I actually like that one best, I usually don't get the legs on Transformers right they always seem to long and square so I made his sweep forwards, and I kinda' like it.