have wheels in ones head

Dear teachers,

Would you be kind enough to give me your considered opinion concerning the interpretation of the expression in bold in the following sentence?

Such subtleties had no interest for these all known boys. When Jimmie persisted, they called him a “nut”, a “poor cheese”,; they told him that he was “cuckoo”, that “his trolley was twisted”; they made whirling motions with their hands to indicate that he “had wheels in his head”, they made flapping motions over him to signify that there were “bats in his belfry.” (U. Sinclair, “Jimmie Higgins’)

have wheels in ones head = he is not all there

V.

The index finger pointing to the temple and making a circular motion is a stereotypical sign to indicate that someone is "crazy", but it does not refer to "wheels turning" in the mind. In fact, wheels or gears turning in the mind usually refer to someone using logical/strategic thought.

NOT A TEACHER

If this is allowed I'd like to point out one subtle typo.

Quote:

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Such subtleties had no interest for these all-knowing boys.

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Thanks.