If I may ask, any tips for improving the Vityaz?
Sorry for late answer. Unfortunately, since Your drawing seems to be no longer available, I can give only rather imprecise suggestions, based on what I remember (so this may be not a complete list).
1) As Laforest mentioned - tracks were the weakest part of the drawing. They looked like they were cast in one piece. Also, what made them look even more awkward is that - if I remember correctly - around the drive wheels they took rather strange shapes (on rear wheels they seemed to even largely cover them from the viewer's perspective);
2) also the road wheels could be improved - especially their central (white) part, which looked somewhat square-ish;
3) I have a feeling that more detailing could be included in the coupling between both sections and of that carrier platform;
4) perhaps I'm wrong, but I have an impression, that generally the drawing was short on shading, also, I have a feeling that in some places the black lines could be replaced with simply dark shades of the colour of the part in question.