Wheels is a new concept. Inflatable tires on the wheels is a new concept. Springs on the axle is a new concept. Steerable wheels is a new concept. That just about covers it. Most of the rest of the improvements around the wheel and axle are derivative, unworthy of a patent. They don't advance the state of the art enough to merit giving their creators exclusive control.
The differential drive weeps at you.
That's what patents are about, right? They're supposed to encourage leaps of brilliance by making it practical for their inventors to profit off them. If there's no genius, just plodding iterative improvement, there shouldn't be a patent.
Not at all. You want a reward for a leap of brilliance, go get a Nobel. Patents are - to use Jefferson's term - an "embarrassment". And bear in mind that he was not only the drafter of the first patent act, but the first patent examiner. Patents are a monopoly, grudgingly granted by society, in exchange for public disclosure of the invention. They aren't a reward - they're a payment offered to the inventor to encourage them to destroy trade secrets. Absent patents, inventors would keep their ideas as quiet as possible (this is business, not academia, after all). There would be (and have been in the past, and are in non-patent regimes) major non-disclosure agreements, intense security against corporate espionage, etc. Instead of all of that inter-corporate fighting, society has said "we'll give you a time-limited monopoly in exchange for destroying your trade secret". But it's certainly not a reward. You can make the greatest invention ever known to man, and if you don't disclose it, you deserve nothing.
With that in mind, plodding improvement is exactly what the patent system is about. Say a flash of genius comes about once every hundred years... we don't need to encourage public disclosure, because it's so rare and major that you'll get your damned Nobel prize and publish papers for the fame of it. But what about the invention that takes a mere hundred man-hours to make? Well, if you keep that secret, and you have a thousand competitors in your field, they have to spend a combined hundred-thousand man-hours duplicating what you've already done. That's a huge waste for society. If instead you reveal your invention and they pick up a simple license, then those 99,900 hours may be spent on new inventions, encouraging innovation.
Basically, if you're the only person who could ever come up with an idea, then giving you a patent is useless to society. On the other hand, if you're the first person to come up with an idea by a non-negligible time period, then giving you a patent in exchange for you telling everyone else how to make and use the invention is very beneficial to society. The value of the patent to society can almost be calculated in terms of hours-to-produce/rarity: the more hours something takes, the better, but only if it's not so rare that you're the only person who will ever spend those hours.