Me: Hubby, look it. Someone is talking about drawing robots. And they like Transformers and know Gundam.
Hubby: Oh? peeks.... my turn this time.
The artist speaking at this time.
Yo! First of all, I'd like to say that I actually really like the designs you showed us. The red robot in particular is pretty sweet. So don't sell your self too short ok?
Now, my advise would be REFERENCES. You've already got the right idea. Look at mech designs you like, mech designs you don't like, mech designs that you think are "just ok I guess", just look around and absorb ideas and concepts. I don't know how easy they are to get now a days, but I would recommend "How to Draw Manga: Giant Robots" and "How to Draw Manga: Mech. Design". These books give a lot of basic ideas on how to design and draw various kinds of robots.
Another handy book could be, and bare with me on this one, "Mark Kistler's Draw Squad". This book, while made for children, is great for teaching basic 3D drawing techniques. I've had the great fortune to actually meet the author on several occasions through out my life, and his lessons have stuck with me and I find my self using them ALL the time in my comic.
When you draw your bots, try breaking them down to simple 3D shapes, and go from there. For example, the build bots in my comic have arms made up of a sphere, slender, a cone, and then some boxes for the hands/fingers. Star simple, the build up from there.
Finally, and as cliche as this sounds, I would advise you to just keep practicing. Try challenging your self to drawing different kids of robots every day for a month (like March of Robots). If you want start drawing super detailed stuff, FORCE your self to do it. I have to do that my self sometimes. Just keep going, and don't let up.