SOLVED. Picture book: mouse (?) builds a flying machine with a secret key [s]

[Cassie]

There was a picture book from when I was a kid (so, published pre-2000) about a mouse (I THINK) who was creating a secret flying machine. I think it might have been a bicycle. No one believed he could do it, and at some point, the bad guys in the story tried to steal the machine to fly it for themselves, but there was a secret key it needed to make it work, which only the builder knew about.

The name Cornelius keeps bouncing around in my head, but that may be because I'm getting confused with Once Upon a Forest, which is NOT this book, despite involving animals building flying machines and possibly a character named Cornelius.

Any help would be appreciated! Thank you!

[Kit★]

Probably a way-off chance, but maybe one of the 'Bernard' books by Berniece Freschet? I've only read one of them, but in that one (Bernard Of Scotland Yard), Bernard the mouse built himself a hot air balloon. That's what reminded me, and its possible he builds other things in the other books about him :)

[Lobstergirl, au gratin]

Bumping since Cassie posted today.

[Cassie]

Thanks! But I forgot I ever made this post, and I found the book! It's Herbert Binns and the Flying Tricycle!

[Lobstergirl, au gratin]

Fantastic.