Steve:
There is no requirement for a large wheel. Clocks are all about energy. One wishes a clock to run for years on a single wind. Never happens, but thats what one wishes for.
So a clock design is always about energy and friction. "Keep it simple stupid" could have been written by the original clock designers, even though
at the time it was a wonder of the world due to their complexity, but underlying all that was the concept of energy conservation. Large wheels
keep the friction down and allow the spring or weight to be smaller, it allows for longer runtimes, and pisses you off when you have to make one.
BUT, as a hobbiest it doesnt have to be that way, youll just find it takes more wheels and pinions and it wont run as long on whatever energy you use. If you use a slow motor then it wouldnt matter at all other than wearing out earlier. Remember all such devices have friction points, mainly the bearing on the shafts as well as the tooth contact. Its why you dont typically use involutes as well, you use the cycloidal teeth, they barely touch
so they reduce friction. Hypocycloidic gears, when I finally get to them will allow much higher reductions with smaller gears, ( Google cycloidic planetaries for those).
But you know, building a clock or a ticker isnt always about doing it right, Im as proud of my old wooden clock that barely runs due
to friction as I am of my ticker that runs very well. I do it to learn and make a work of Art.. ( No pun intended.
)
So dont feel you HAVE to use large wheels, use whatever you CAN make, it will still work. Use cycloidic teeth or cage gears to their
best advantage, start with the escapement, its always the best place, then work backwards to the weight or spring, then again forwards from the escapement to your hands..feet..whatever will display the time, if indeed a display is necessary. I'm a huge proponent of gear works that just..well..run, they dont even need to do anything other than look good.
In fact, I just took down my first wood clock and will now ( at my wifes request) turn it into a plant holder. So never feel constrained
by convention..
( Heres a photo of my old wall clock as an example, Ill be adding a small table to the top to hold a plant..
)
Just my advice..
Art