Hi again
Yes 18 teeth could be considered as standard. To quote this article again:
“For all standard needs, the driven wheel has 18 theeth, whether 10 pitch or 12 pitch.”
Note that there exists two pitches of theeth, of which 12 pitch has a smaller diameter. (No dimensions stated.)
They are obviously not comparable with each other.
I think that 49 theet sounds right for 12″ centre height.
I once had my Cowey serviced by an expert (of the old kind, that really where experts), he told me that they could be “fine tuned” to show exact speed. Sadly he passed away years ago, and I know nobody that can service them nowadays.
Again stating the article: “If the head works, leave it alone because the chances are that it won’t ever work again if you interfere with it. In my unfortunate experience, even professionals have got into a dreadful mess with Cowey heads.”
Good luck with your speedos!
Leif
