I think this looks fantastic. I can't even tell that you're "bad" at drawing inorganic things — unlike what I often see when artists attempt a "machines practice" piece, yours blends nigh-seamlessly with your existing cartoon style. Nice work!
I do love this one... I'm quite impressed with the simple yet very effective dockyard background, giving the whole thing a great setting without competing with the awesome character in the foreground. Really wonderful work!
I think you should copy a picture of this [link] (for the car) and/or this [link] (for the Tommy gun) and redraw them several times until you get used to it, and then think of what it looks like in a different angle, and redraw. Results may vary from mood to ability.
Following the 'Sugar Cube Incident' which ended the life of the sole heir to the Griffin Throne; the Griffin Mafiosi in the ensuing chaos decided to move to Equestria, Pony-ville in particular, following the 'Neo-Bolshevist' Revolution, which caused the fall of the Griffin Empire and the death of the Basilius. One of the first Griffins who set foot in Equestria was simply known as 'Greyson Marcone.' He was well known for his sheer brutality and ruthlessness; as well as being one of the few things that kept Ponyville from collapsing further into Chaos, and has been immortalized into legend as a Robin-Hood kind of figure (to a extent). Today many Ponies doubt he even existed.
However, one cannot deny how much of a contribution this mysterious and complex figure made to the history of Ponyville.
You know, I really love this. When Gilda asked Rainbow if she was "out of gas" and later said to "give me a call," it made me wonder if the griffons had more tech than the ponies. I'd love to see Griffonland have a 30's America feel to it.