Twenty years ago I replaced one of the gears in my Tangley with a gear
from Boston Gear.  They are the old type of gear tooth, but with the
little Boston Gear book and some time, you can calculate the specifi-
cations for replacements, assuming you have enough of the originals to
count the teeth and measure the diameters.  Sorry I can't be more
specific, but I am lucky to remember doing it at all!

Allan Merralls